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View Full Version : what rpm can you spin a volvo and a 351w?



Moody Blu'
03-12-2012, 12:58 PM
what rpm can you spin a volvo 250 drive to and I need to know what you can spin a vovlo 275T or 280 T not sure what mdoel my hydraulic trima nd tilt volvo is, MOP said it was a early model 280T.. anyway I want to know what rpm you can spin these drives at as far as engine rpm goes...

both drives have 1:61 ratio

also, what rpms can you spin a 351 windsor to with stock internal bottom end. I was told 7k rpms is ok with stock bottom end.

also what rpms can you spin a 351 windsor top end to? Griz told me not to go past 5500rpm.. Ive had it to 5800 with a crappy prop.

last time the boat was in the water I was hitting 4800-4900rpm @ 62mph on the gps with a lunati 00110 cam-(1000-5000rpm), edelbrock rpm intake, edelbrock Tuned-750cfm carb, msd6t ignition, accel coil msd mech advanced distributor. Holley mech fuel pump up to 130 GPH , and a 24 1/2p x 15 brass elephant ear propeller which was freshly redone. drive was on last pin.(always is there)

So I know I'm in the ball park of what that cam can do, as far as performance the cam in it absolutely rips the boat out of the water and on plane in less then 3-4 seconds if I stomp on the gas.. So Im not lacking in bottom end at all. I am however lacking in top end. and everything ive done as far as mods here and there are for more top end, 1" carb spacer(added 100rpm), if I open the hood scoop front i get a added 100rpm, the gps run was with scoop plug out. when I added headers, went from 4300-4400 rpm(with new prop) to 4800-4900rpm, I may go with a 2" swirl torque spacer since I was really happy with the 100RPM gain with the 1"(pretty much creating a tunnel ram intake)

specs here for cam in the 351w now.
http://www.lunatipower.com/Product.aspx?id=2234&gid=245

Hydraulic, good Idle. Good cam for street performance applications with good low-end and mid-range torque and horsepower. Works well with dual exhaust.

Advertised Duration (Int/Exh): 284/284
Gross Valve Lift (Int/Exh): .488/.488
LSA: 112
RPM Range: 1500-5000
Includes: Cam Only

Part Number: 00110

Jobber Price: $116.47

i want to go to a roller lifter definitely not sure to go either solid or hydraulic? I read solid roller you have to adjust more but you dont have to worry about valve float if adjustment is checked. is it really necessary for a 351w I thought you didnt have to adjust the ford valve train? Or am I better off with a hydraulic roller to make maintenece minimal?

I plan on swapping the cam, springs and lifters and if possible do the push rods and rocker arms a little later on depending on cash flow and if its possible to do it in stages (I can do this with the boat back together). and just watch the throttle and rpms . I also have a spare set of 351w heads that at some point will have ported and polished. so going with a cam that will breath and give more power as I do the other mods is something I want you to know about so you can give a better opinion..

-----------------------------------------------------------

Im lookng at these 4 solid roller cams from lunati

http://www.lunatipower.com/ProductGroup.aspx?id=286&cid=68

here are the specs for all 4 solid roller cams.

Street Strip Solid Roller Cam - Ford 351W 302HO 278/285
Product Description

Updated to be based on Lunati's new camshaft profiles. If you are looking for that extra performance and
consistency needed to compete at the strip but you still want to be able to hit the local cruise-in,
this line of Lunati Street/Strip camshafts are just what you are looking for. These Solid Roller Tappet
camshafts have been computer designed to deliver added performance without being too harsh on valve train
components.Solid roller, rough idle. Excellent cam for high performance street or mild bracket racing
applications.

Needs 3000 RPM stall converter or 5-speed transmission, headers, 9.5:1 compression ratio or better and
3.73 gearing or better.

Advertised Duration (Int/Exh): 278/285
Duration @ .050 (Int/Exh): 244/250
Gross Valve Lift (Int/Exh): .593/.593
LSA/ICL: 110/106
RPM Range: 2500-7000
Includes: Cam Only

Part Number: 510B1LUN

Jobber Price: $337.16

Solid roller, rough idle. Good cam for hot street or bracket racing applications. Vey reliable on valve train
components. Needs 3500-4000 RPM stall converter or 4/5-speed transmission, headers, 10:1 compression ratio or

better and 3.90 gearing or better.

Advertised Duration (Int/Exh): 290/300
Duration @ .050 (Int/Exh): 257/266
Gross Valve Lift (Int/Exh): .593/.593
LSA/ICL: 108/102
RPM Range: 3500-7500
Includes: Cam Only

Part Number: 510B2LUN

Jobber Price: $337.16

Solid roller, rough idle. Good cam for hifgh performance street applications with single turbo charger and
moderate boost. Needs 2500 RPM stall converter, headers and 3.73 gearing or better.

Advertised Duration (Int/Exh): 287/295
Duration @ .050 (Int/Exh): 256/244
Gross Valve Lift (Int/Exh): .621/.593
LSA/ICL: 110/106
RPM Range: 2500-7000
Includes: Cam Only

Part Number: 510B3LUN

Jobber Price: $337.16



Solid roller, rough idle. Good cam for hot street or bracket racing applications that you can drive to the track.
Needs 3500-4000 RPM stall converter or 4/5-speed transmission, headers, 10:1 compression ratio or better
and 3.90 gearing or better.

Advertised Duration (Int/Exh): 287/295
Duration @ .050 (Int/Exh): 256/264
Gross Valve Lift (Int/Exh): .621/.621
LSA/ICL: 106/100
RPM Range: 3500-7500
Includes: Cam Only

Part Number: 510B4LUN

Jobber Price: $337.16

thatgirl
03-12-2012, 08:23 PM
[ QUOTE=$originalposter]{$pagetext}[/QUOTE]go with a hydraulic cam much more forgiving for the gain

MOP
03-12-2012, 08:44 PM
I had a buddy with a well worked 383 that spun his Volvo to 6500 on a regular basis did it for quite a few years, don't try that with a MERC!

f_inscreenname
03-12-2012, 09:44 PM
Mark IV (454ci) fully rollered and stroked to a 496ci, 280T transom Shield, 40 year old Volvo 270. Itry to keep it under 5500rpms and shooting for around 5200 with new prop this year. I would rather have a faster cruise speed the all top end. Just works for me.

Conquistador_del_mar
03-12-2012, 10:27 PM
My 1971 18' Donzi came originally with a 350/350HP Lt-1 engine that I ran at 6300RPM quite often through the original 270 Volvo outdrive. No problem until it finally let go at about 400 hours since I was too young and ignorant to know that I should have been changing the fluid. Tough drives! Bill

mattyboy
03-13-2012, 08:36 AM
Bill, Kenny has the same motor in the 72 cig with a 270 we ran it in two poker runs one for about 60 miles and one for about 70 miles at wot 5200 rpm. I told him I would never have run my ford that hard for that long.( both of those runs have me with bruised kidneys and tinitis but we didn't finish last)
My benchmark so to say would be to build a motor that can turn 5000-5200 day in day out with a volvo aq 270 or up with a 1.3 gear set turning a big solas the volvo can take more but that would be my limits.

my benchmark would have an 18 in the low 80's would probably need a nosecone though and I guess the motor would need to be 475hp or more. Again I guess it would be more economical to built a chevy sb than a ford sb in the marine world to get that kind of HP. not quite sure how my benchmark will plane? can a small block be built that delivers close to 500 hp and still have good low end torque to plane a 24 ish pitch prop on 1.3 gears and would reliability be effected?

pipnit
03-13-2012, 09:11 AM
[ QUOTE=$originalposter]{$pagetext}[/QUOTE]



Unless it's a TRS! :yes:

silverghost
03-13-2012, 12:49 PM
Pipnit~~~
I agree on the old Merc TRS outdrive.

In my opinion it was the most robust & bulletproof & inexpensive outdrive that Mercruiser ever built for 400HP; & up..
A bit heavier & longer than a Bravo & Alpha drive~~~ but no cheap inside clutch & waterpump.

Add a #2 streamlined speedmaster racing lower unit & you have the very best high-power, & high-speed, racing Mercruiser drive going for the best possible low price.

I was very disappointed when this TRS package was dropped by Mercruiser.
Used units can easily be bought for very fair money.

There are still lots on NOS & good used parts around for these old TRS drives also.

mattyboy
03-13-2012, 01:14 PM
here's the recipe I was given for a 350hp 351w with 400lbs of torque, your hi teks should fit as the exhaust, also not sure how the components meet your salt water needs just some info to help you make a decision.


Block
Bored and honed with torque plate
1pc seal design non roller
Premium core max .040 bore. No repairs. No sleeves

Cylinder Heads
World 200 CC cast heads 2.02/1.60 60cc
ARP Head Bolts
3 angle competition valve job

Valve Train
Comp cam 226/234 512/531 111 requires performance exhaust
High Intensity lifters
Cloyes True Double Roller timing chain
Scorpion Aluminum Roller Rockers 1.6 ratio
Screw in studs and Hardened guide plates
Manley .080 wall pushrods
7 deg hardened locks and retainers
2.02 int 1.60 exh Stainless valves
Performance springs

Rotating Assembly
Speed Pro Coated Hypereutectic pistons 9.0:1 CR
OE rods w ARP rod bolts
OE crank 10/10
Balanced rotating assembly within 1 Gram
Speed Pro File Fit Moly Rings
28oz Balance

Intake and Tinware
Professional Products Dual plane Manifold
Professional Products Damper 28oz
New OEM Front sump Pan
Tall Chrome Valve Covers
New Aluminum universal timing cover
New OE Flywheel
Assembled with all grade 8 hardware.

Moody Blu'
03-13-2012, 01:18 PM
"i have been winding mine up to 6200 for years..the cams youe looking at are way to big for what your looking to do..you want a strong midrange cam and thats what i use..mine is only a 480 i 489 e .050 226/236 on a 112 LSA. flat tappet hyd...call bob mandara in ny and see if he can custom grind you a cam,,marine kinetics 585-654-8583..he is the cam guru..stay away from the lunati stuff,dont care what headers you have and with the advertised lsa on those cams you will revert water..look into comp cams also xtreme marine cams,they will rev.. " mr fix all

seems the edit with quote is not working properly

Thanks everyone for the drive part of the question, I could use more feedback on the cams though. suggestions as far as cams?

thanks mrfixall.. I know i have to watch for reverberation, I appreciate you bringing it up though! I def want to make sure I dont get reverberation... how can I tell from cam specs if they will reverberate?

I want a cam that can spin 6-6500rpm and if I want to go up to 7k I am sure my motor wont go to 6500-7000rpm until I get port work done on my heads.. but I want the cam in place so when i do port the heads the advantage is two fold.

Moody Blu'
03-13-2012, 01:26 PM
thanks matty, my engine is already built with hyperutectic pistons, double roller timing chain. etc... im just swaping cams out. ive read a bunch of articles about how high you can spin a stock 351w bottom end and they say around 7k Ive gotten tons of input on what the drive can do... Id like to hear some stories of what the 351w can do regardless if i read articles. I trust you guys.

Im not doing an all out engine rebuild, my motor only has 150 hours on it.. just swapping cams... and drives to gain that MPH I want ever so bad.

mattyboy
03-13-2012, 01:31 PM
if you plan on running over 6k on the drive make sure you are in a 270 or higher drive the internals got stronger as they progressed. my 250 didn't hold up all that well after 35 years of normal use and 3 season of me at high rpm

Fixx and the other motor guys would Know more but I have been told lsa of no lower than 112 with stock wet exhaust and no lower than 110 even with a good hi po exhaust unless you use dry pipes ,


what prop to you plan on spinning to 6500-7k??????

mattyboy
03-13-2012, 01:39 PM
the really fast volvo boats I know of are all chevies. Fixx,maddad,brian73 are all running in the 70s and near 80. Maddad gave up on the fords I think.

Magicbill has a warmed up ford in his 16 might be worth researching his project.


I'll add if you plan on getting into that range steering would be something I would add to the list.

Moody Blu'
03-13-2012, 01:40 PM
Matty I bought a drive from one of MOP's freinds art a while back, supposedly its an early volvo 275T trim and tilt...

I found this really cool vovlo penta model line up and no where in there is a 275T

http://www.volvopenta.com/SiteCollectionDocuments/Penta/Misc/drive_2_oil_rec_7745608.pdf

as far as the prop... the one I have on it right now should push the boat nicely, I can always have it reworked for more slip or less. All i know is this prop bites real good and when you slow down its like the boat has brakes. which I like. for evasive manuvering if it arises. I also have a right hand volvo ultra 25p(which I would have to reverse the cable to use...

Moody Blu'
03-13-2012, 01:51 PM
not sure why they gave up on the fords? All i know is I dont have any exhaust restrictions to get power output and thats a major factor.

I know the hydrodynamics of the drive don't help but im working on that....

I could possibly raise my X up I have found a shorty lower unit with nose cone for the volvo...

I always planned on being the ford to make the chevy guys with 18 classics to watch out for hehe. I now have my trailer etc and things are looking up! so perhaps everyone will be able to meet the mysterious and elusive person that is me haha

mattyboy
03-13-2012, 02:21 PM
Moody,

If your using the same prop 24 pitch and you spin it to 4900 and 62 mph on a 1.6 you are at 12% slip or so. now you want to spin that prop to 6500-7k ????

a cam alone is going to give 1600 to 2100 increase in RPM???

I don't care how good you think your exhaust is if there is water in the jacket there is a chance for reversion and even with dry pipes hung over the side it could be an issue.


what do you figure your engine is putting out now in the way of hp?

just a thought if you motor is strong enuff to spin a 23 solas to 4900 you would be at 64 ish I doubt you would be able to turn 4900 with the 23 maybe 4500 or so

blackboat
03-13-2012, 02:33 PM
I used to have a 10:1 comp. 351 windsor with a Hydraulic 292 Magnum Comp cam,.The motor made good power and could run all day at 5200 rpm. I had a 270 volvo drive with a Hydromotive nose cone and a 14.5x 24 and14.5 x26 Spinelli s/s props,
these were reworked several times by Spinelli to get more lift and blades thinned and pitch changes.
I also added a single cylinder external steering which really helped out with handling.
The props and the steering were 2 of the best changes I made to the boat.
It was an 18 foot Donzi Corsican with the original Holman Moody exhaust.
I ran this boat several years before selling it and all I ever did was change the drive oil every season.
The only thing I ever saw hurt these drives was too much torque as a friend has one on a 21 foot Donzi with a big Block and he has had issues keeping the drive from breaking.
Also ,there was an x18 turning his 270 as high as 6800 rpm with a 400 small block which occasionally had some problems breaking his drive,but he likes to take things to the extreme.
The 351w Ford semed like one of those motors that would last forever!
The only way you could run those Lunati cams would be with dry exhaust. Reversion on the bigger ones would be an issue.The hot rod street cams dont like water in the exhaust.

Just Say N20
03-13-2012, 03:09 PM
Moody, that "short" Volvo drive isn't short. It is a standard drive with a nose cone.

Moody Blu'
03-13-2012, 03:40 PM
Its possible for me to modify my exhaust to make it dry, since my outer diameter is 4" and 3" for exhaust. I could weld 3" pipes inside all the way to the exhaust tips.. but then the transom water could be a problem... Im sure ill find what im looking for cam wise.

I am definately going to find a cam that can rev out to 7k without reverberation. if its possible. like I said I know its not going to rev to 7k just by dropping in the cam. I know I will need head work to get there and possibly a different manifold at some point(doubt it). I have the carb to fuel it (750 cfm) fuel pump, and the headers so whatever gain i get will be capped by the heads and im ok with that for now.


I would think the engine is around the 340-360hp mark however I have no idea without a dyno. and I know the prop im using can be reworked for more speed and higher rpm. I like using the prop i have as a basis to judge the mods I do. so for the time being the prop is staying the way it is for baseline tests. and once I can spin the prop to 7k thats when I will re work it to tone down the rpms to around 6300-6500 and gain even more speed. I want to hit 75-80+mph and so far, trim and tilt will give me 4-5 MAYBE 6mph. bottom paint off the boat????? 5-10mph ???????? ive seen dramatic speed increases with a clean smooth hull compared to a painted hull...(when I first used peel away and got all the paint off(years of paint) the boat was definately faster but i knew since i didnt have a trailer and kept it in i had to paint it... not anymore!!! so yes choosing the right cam is a huge deal for me. and I already know when the boat goes in its gonna be at least 5-7MPH faster just from the bottom being smooth and trim from the drive.

I already know I will need hydraulic steering So I appreciate bringing that up as a reminder..

the cam AND the roller lifters matty, those rollers will free up some power as well. heres a link to some ford dyno numbers with a mild cam in it. which is close to the cam I have but i don't have ported heads.

http://books.google.com/books?id=-kdA-TcHz_QC&pg=PA121&lpg=PA121&dq=351w+max+valve+train+rpm&source=bl&ots=65eo4HR0Tb&sig=moZNmgJIAbuXNHY5OioWY652ZNQ&hl=en&sa=X&ei=MYJdT6b3JMre0QHl_YWeDw&ved=0CFMQ6AEwBQ#v=onepage&q&f=false

and heres the cam they used

http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=877&sb=2


Id be more then happy to try out a solas to gauge power, but i already have a baseline prop. as far as my testing goes.

Moody Blu'
03-13-2012, 03:41 PM
bill, which shorty are you talking about? the one in the for sale section? should i just do my own?

Moody Blu'
03-13-2012, 04:11 PM
black boat, what speeds were you seeing with that cam?

Just Say N20
03-13-2012, 04:49 PM
bill, which shorty are you talking about? the one in the for sale section? should i just do my own?

That's the one. I'm not saying you should or shouldn't buy it. I just wanted to clarify for you what it was, so you didn't purchase it under a misconception, receive it, and find out it wasn't what you were expecting.

Just Say N20
03-13-2012, 04:57 PM
Its possible for me to modify my exhaust to make it dry, since my outer diameter is 4" and 3" for exhaust. I could weld 3" pipes inside all the way to the exhaust tips.. but then the transom water could be a problem... Im sure ill find what im looking for cam wise.

I would be very careful in considering such a modification to make the exhaust dry. Dry exhaust becomes a significant heat hazard in an engine compartment like we have. The water does a whole lot of cooling of the exhaust parts.

Perhaps someone more knowledgable than I will speak up, but my understanding is that reversion (water flowing backwards into the exhaust, then into the headers and heads/valves) is really only a problem when backing down quickly, or the boat is a rest in the water with waves hitting the transom. When running at anything above idle, there is enough exhaust gas flow to keep the water going the right way. Risers with good height, and downward slope are designed to make it hard for any water to get far enough to make it into the "header" portion of the exhaust.

blackboat
03-13-2012, 08:16 PM
N2o

When I say dry exhaust,I mean dry exhaust stream but manifolds and pipes are still double walled and cooled to the tips.Water is expelled at the tips or from a rear fitting on the risers. No heat issues with this setup,

Moody

My Donzi Corsican ran 71 mph 30 years ago. Cam technology today is much better for boats, X2 on what Fixx said about talking to Bob Madeira
You should be able to run 74-75 mph turning 5400 to 5700 rpm with the right stainless prop.
If you want to go 80 to 85,start thinking 400ci to 454 small block chevy and 6000 to 6400 rpm .

I guess the old saying still goes, you can go fast just keep your wallet open !

Moody Blu'
03-13-2012, 09:08 PM
yea with the dry exhaust I was going to do double wall to the tail pipes. right now its single wall after about 4-5" on the headers themselves.all I would have to do is weld a 3" pipe and seal it around the exhaust and the water will be in between the new 3" pipe and the 4" outer that goes to the tail pipes now....

I have internal flappers on my 4" tail pipes and they seem to work really well.. so i am only partially worried about the reverberation....

going to a big block with a 18 is not my choice. I think they weigh too much and going to a big block after all the work ive done and the custom headers on the ford is not in the cards.

I re read some articles and it looks like with a good valve train you can rev these motors to 7k intermittently until you have a built bottom end. the way im going about this... I plan on doing a cam that will rev to 7k if i want to go there but keep it to around 6000 rpm. the motor probably wont even hit 6500 until i get the proper head work done. then once the head work is done and I test and see the motor can rev to 7k rpm I will start saving up for a bottom end, that will be able to rev out that high. (all the while making sure I never go up to 7k for more then 5-10 seconds and more then likely staying away from that area until the bottom end is built.

then at that point I will re work this brass prop some more or test out some solas props and get it tamed to 6500.

Im not to sure if im going to be sucking down more gas because im shooting for 6500 with a cam that wants to spin to 7k.

Hopefully some of the gurus can chime in on here where are you guys?!

blackboat
03-13-2012, 09:52 PM
Moody

I was talking about a 454 small block not a big block 454. You are right the big block chevy would be too much weight.
If you are staying normally aspired the extra cubes helps out a lot.

Moody Blu'
03-13-2012, 09:57 PM
if i were to do that I would go with a stroker 408 0r 418 ci short block from FPS performance

http://www.f-p-s.com/?p=231

maddad
03-13-2012, 10:36 PM
Broque, I'm not a motor expert, but I've learned over the past 10 years or so that in a boat with an old AQ drive, it's much cheaper and more productive to twist the motor harder, not faster. You may want to shelve your old style prop and get a more modern design like the Solas, then work on building the torque to spin it at 5000- 5500 rpm. Those rpms with a 23" Solas will get you high 60's to mid 70's, and also convince you you need external hydraulic steering. Take a look at Comp's X4 270 for a flat tappet, or their XE 276 HR for a roller setup to make power that will let your motor live a long life. Engine speeds over that will quickly kill everything, mostly the valvetrain. I use a 406 sbc and a 23" Solas, can cruise at 60 all day, can do 70 whenever I want, and have more in the well to scare myself silly if I want. I'm working on an external steering set up now to see how fast an old AQ can really go. Best so far was a bit over 76 on the GPS, but that only happened once and even with my internal hydraulic steering, I felt I had 0 control.

mattyboy
03-14-2012, 10:11 AM
Maddad,
that is well said that was the point I was trying to make. Especially with most volvo props the faster you spin them the less efficient they are. The speeds you are running are right up there with the top volvos I can recall. In a perfect world a cross reference would be great as each setup is slightly different as an example.

Brian 73 runs big chevy power thru an edrive no trim ( i think) to around 78-80 mph

Grizz (RIP) ran a strong 351C with a 290 with trim in the low 70's

your setup and Fixx's very similar setup run mid high 70's do you have trim?

Magicalbill with big ford power and no trim runs mid high 60's with a ton left

Mario runs very strong ford power thru a merc and his boat runs very well high 60 low 70's from what I have been told.
so while close each setup is just a little different

e drives have their own props,some boats have trim others don't, I would love to see you and Fixx prop swap as your rigs seem to be similar


let's not forget that mighty mouse before it was a arneson boat was a 90 mph volvo e-drive boat

Moody Blu'
03-14-2012, 11:08 AM
WHOA>...... when did Randy pass??????????????

maddad
03-14-2012, 06:15 PM
:(http://www.donzi.net/forums/showthread.php?63611-Keep-Grizz-in-your-prayers

Moody Blu'
03-14-2012, 07:36 PM
thanks madad just posted. ****, I really wanted to have a prop session with randy like we talked about :(

Here's to you Randy, may the heavens have the perfect race courses, conditions and power you can handle. May the boats be tsunami proof and may the calm dusk bays be refuge to relax in.

rest in peace Randy.

Now, im sure he would say the post must go on!


So, you guys are saying make it more powerful down low instead of revving it out. I understand that however I want to stay on regular unleaded not 93.. I know i can raise compression to get more torque but stay on regular gas? Do they make cams that are brutally strong in between 1-6k?

I was under the thought of, make it rev more for a wider power band and always have that extra RPM if i need it to pull on another donzi... if most donzi owner are capping their rpms an advantage would be to have a higher rpm to go to in case of that. Of course just more speed in general without even racing someone.

why do you all think going with a high rpm setup is not smart when Ihave said how I will watch my rpms until the bottom is built?

I know garvey racers that throw in insane cams on there stock 302 and 351w bottom ends with just girdles arp main bolts and a good valve train and they rev them to 8-9k Ive watched these motors race and was amazed what the right cam can do. So im really scratching my head as to why u guys think its a bad idea... especially if I re work the prop or try a new prop to get it to around 6500 rpm.. it seems like the drive will take the rpm I understand the whole efficency of the volvo drive in terms of propeller bite. Ive already thought about that and the larger the prop diameter the more bite the prop will have. obviously a larger prop is needed to bite because of the large diameter of the lower unit.

If your telling me youve done it and it wont work or you know people who tried it and it didnt work I dont see the point?

Moody Blu'
03-14-2012, 08:50 PM
I understand the crappy bottom end performance part, but seriously, the boat would get on plane with a 40hp outboard with the 351w inside. Ive already brought up that I will be porting the heads later on and will gain even more power doing that and just dealing with the crappy lower rpm until the heads are done. I didnt mention it but im also contemplating a super charger AFTER the bottom end is built... I will never use nitrous, thats one reason I want it to be able to rev out so high without using it.

my biggest concern with the cam choice is reversion and if i can even get a cam that wil makepower up to 7k without reversion... two of the cams I looked at have a 110 lobe separation and thats on the borderline for reversion. I'm sure I'll get it right. its almost like you guys dont want me to try it since you didnt, or you dont want me to have the fastest ford donzi hehe just joking.. Anyway to sum it all up, i really want to find a cam that I can get that will rev to 7k and make power without reversion. if its possible thats the route im going.

maddad
03-14-2012, 10:51 PM
Broque, while there's a lot of talk about LSA, it's not a stand alone number that decides if a motor will have issues with reversion. What really affects a motors ultimate power is the valve overlap, the time when both the intake valve(begining to open)and exhaust valve(finishing closing)are open. Less overlap creates a lot of intake vacuum and less chance of reversion, more overlap lowers intake vacuum and can cause reversion. As an example, the cam I run, Comps XM276HR, given the duration of the intake and exhaust, and how far the lobe centers are spaced, has 55 degrees of overlap. In the car world, that kind of overlap is barely into the performance picture, but with a water in the exhaust boat motor, much more overlap will cause reversion problems. If I had less duration, I could have a tighter LSA, the same overlap and no issue. More duration and you need a wider LSA to keep the overlap down. All of these things(duration, LSA and how the cam is installed)close the intake valve at a specific place during it's compression stroke. Where the valve closes combined with the motors compression ratio gives a specific cranking pressure in the cylinder. To low, not the power you want. To high, forget about buying gas at the dock, you need race fuel. You need to decide what kind of power you want to make and at what rpm, and put together a package that does it. Just adding a cam with more duration, or a different LSA to a motor with a C/R that was meant to make good cylinder pressure with something else will only dissapoint you with it's performance. As an example of a motor that made AWSOME power, but had no business in a boat, my 351C had 13.5 to 1 C/R, a Lunati solid lifter cam with 300/310 I/E duration and an overlap of 89 degrees. It needed 110 octane with lead and still killed exhaust valves as fast as I could replace them. It would also spin a 24" ultra to 7000 rpms and make a wicked sound, while not really going that fast because the prop became very inefficient.
The bottom line is this, be happy with what you have, or decide what you want, and build to get it.

mattyboy
03-15-2012, 07:49 AM
Moody ,
i see the high rpm cam you want but will the motor idle at 600-800 rpm? with a 24-25 pitch wheel it's going to be a real pleasure around the docks if it needs to idle at 1200 or more and the volvo while tough is not going to like that.

5500 on a solas 23 gets you to 70 with a 1.6
4900 on a solas 21 gets you to 64 that's 2 mph over what you have now the key being if your motor can turn a 21 to 4900 as it sits now. they are for sale for under 400 bucks I think I have seen them for around 300. would be money well spent as it could be used all thru your build. My 310 hp 351 could get a 21 to like 4800 maybe 4900 on a good day

mattyboy
03-15-2012, 10:34 AM
Moody,
another thing I forgot to mention keep an eye out for justsay n20 his 16 restoration will be getting new chevy power this spring. his boat is a 16 with a volvo 290trim and when repowered will be a good benchmark on how to build a faster volvo boat, just like Maddad and Fixx

silverghost
03-15-2012, 01:45 PM
From what I have been reading on your engine posts here you seem to be confusing performance pleasure boats, full out special-class race boats, and performance/race car engines & cams vs marine pleasure performance engines.

Sure race cars turn 6000-8000+++ RPM and have very agressive high overlap & long duration cams.
So do some classes of race boats~~~
But these engines are typically re-built afer each race event ; and do not run very long hours between rebuilds.

But for high performance pleasure performance boats you cannot turn these ultra high RPS you seek ; nor can you use these sorts of performance camshafts in a boat engine with water cooled manifolds & riser elbows..

These high overlap & duration cams you talk about can cause real water reversion & engine water exhaust injestion issues.
The end result a totally trashed engine.

These types of cams as Matty stated wil not allow very slow speed marina, docking, and no-wake-zone operating speeds.

Outdrives were also never designed for these ultra high RPM ranges you speak about.
The old Volvo Aquamatics are said to be very tough~~~But Not That tough.

When you use any marine engine in a boat it is under a tremendous load at all speeds.
Much more than an automobile with a multi speed gearbox transmission.

You not only need horsepower in a boat ; you also need lots of low speed torque.

Many engine builders who typically build engines for performance cars, & race cars, do not have any idea how to build a marine performance engine that will work ,or hold up..

If you spin a marine engine at these very high speeds ~~~te engine, and your marine outdrive, will not last very long at all.

Read through past forum posts here to see what engines others have successfully built that work very well; & push a Donzi to 80+ MPH .and actually hold-up to the abuse of a performance pleasure boat.

Good Luck on your Donzi restoration & repower !