Stock Merc Camshaft

[Rootsy]

I was thinking about it and i figured someone out there would know this. What is the lift and duration of the stock roller cam in a 1997 210 hp merc 350? Reckon someone out there has a book on the subject... maybe i can use one of those glorified engine software programs to ATTEMPT to see how much hp my mouse is putting out...

thanks eh!

[Forrest]

I believe the specs in Dennis Moore's book titled, Small-Block Marine Engine Performance. If I get a chance, I'll post the specs on this thread.

[Riley]

Jamie, where do you come up with that "eh", Eh? You're not a Yooper by chance, are you?
According to Dennis Moore's book on sbc marine performance, the roller cam used in all production 305 and 350 engines is as follows:

.430 intake lift (with 1.5 rockers)
.450 exhaust lift

Duration in degrees @ inches of lift
Intake
197 @ .050
249 @ ..006
258 @ >004

Exhaust
207 @ .050
264 @ .006
272 @ .004

Did the prop get there yet? Let me know.
By the way, I drove that Top Dragster on Monday..... Awesome! All 3 1/8 mile runs were at 5.14 seconds and 132-134 mph. Even with lifting at the 1/8th and coasting thru the 1/4 the e.t.'s were in the 9.3 second range. If you ever get the chance, sign up for the WIX course. It's by far the best $385 I've ever spent!

[Rootsy]

Riley,

those cam specs look awful big compared to what i got with a dial indicator for lift. is this the cam spec for vortec headed motors? i have the 87-95 version heads on my motor (canted center intake bolts). With 1.5 ratio rockers i indicated something like 385 intake and 410 exhaust or something around those numbers....

[Riley]

Jamie, are you sure you have the roller cam? I took those specs right out of the book, page #120. On page 118 they list the specs for the flat based hydraulic lifter cam used on production 305 and 350 Merc engines, .400 intake, and .410 exhaust.

One thing I'm curious about, you say your '97 350 was listed at 210 hp, while my '99 305 is listed at 220 hp. Do you think the difference could be roller vs. hyd. cam, as well as vortec vs. standard heads? I'd think a 350 would have 25-40 more hp than a 305, all else being equal.

[Rootsy]

Riley,

i'm about 250% sure i have a roller cam. Was there plain as day when i had the intake off, lifter tie bars and everything, only roller lifters need orientation. The 16 hull is rated at 220 hp max, before the vortec heads i am under the assumption that merc made a 210 hp version of the 350. I found the specs at mercruiser.tv, same rpm range, timing and everything. beginning in 1998 motors were rated at WOT 44 - 4800 rpm whereas mine is 4200 - 4600. There is a post about this in talk to the donzi factory section but it was never answered at least in a public forum. If my motor WAS a 250 hp version originally i should be getting close to the 275 - 300 hp range now and i would think i'd be needing more than a 21P prop. Makes sense since we are turnign about the same prop at the same rpms. I have noticed that with my 19 i can spin the motor right up to 4600 rpm with the snap of a finger (just bury the throttle and she is there) and then she slows town to drag out the other 400 rpm before i get to the rev limiter... 45 - 4600 must be my HP peak i'm thinking.

[RickSE]

The cam specs. are in the Merc. manual. They have specs. for both the flat tappet and roller cams. I'll check tonight and get back with you.

I went through a similar situation on my 96 350. The 2-barrel motor was advertised as 210 H.P. but when we ran some of the speed numbers and calculated H.P. it was acting more like 250 H.P. I never did figure it out and eventually said the Hell with it since I ended up changing the cam and carb anyway.

[Rootsy]

Rick,

what were some of these numbers and such? i'd like to estimate my hp... just right off hand i don't have those equations, etc etc... look if ya would though, i'd appreciate it.

Thank ya!

[RickSE]

Jaroot,
This always confused me but this is what my Mercruiser manual states.

Flat Lifter, Valve Lift
Intake .394"
Exhaust .404"
These seem close to what you measured.

Roller Lifter, Valve Lift
Intake .288
Exhaust .300

This seems strange since I would assume the roller cam would have more lift than the flat tappet cam, rollers usually have less duration and more lift. Maybe it's a typo. Also, the manual does not list duration.

The H.P. numbers I have were calculated by the Process Engineering Group at Donzi last summer. My 96 18 came with a 350 2-barrel engine which I was told was rated at 210 propshaft H.P. but the calculations run by Donzi seemed to suggest the motor made 250 H.P. With the 2-barrel the boat would run 53-54 MPH @ 4600 RPM's, this was at 3700 ft. elevation. Donzi's calculations showed an 18-Classic would run 53.5 MPH @ 4595 RPM's with a 19P Vengence prop, 60% Trim Up, 1.47 Drive Ratio, Full Tank of Fuel, making 232 P.S.H.P. So if I have a 210 P.S.H.P. motor why was it making 232 P.S.H.P at 3700 ft. From that day on I assumed I had a 250 H.P. motor.

Well I can't help you with the calculations but I can give you some of my data.

18-Classic
Stock 350 2-Barrel, Alpha-1 1.47 Ratio
19P/14" Diameter Vengence Prop
P.S.H.P @ 3700 ft. elevetion estimated 232 H.P.
Weight with full fuel and driver 3374 lbs.

3000 RPM's 33.8 MPH 12.5% Slip 20% Up Drive
3500 RPM's 39.0 MPH 11.5% Slip 30% Up
4000 RPM's 46.0 MPH 10.8% Slip 40% Up
4500 RPM's 52.0 MPH 10.4% Slip 50% Up
4595 RPM's 53.5 MPH 9.7% Slip 60% Up

Same engine "estimated" to make 269 P.S.H.P after adding a 4-barrel & alum. intake, running a 21P Revolution-4 Prop, I know the prop was a mistake.

3000 RPM's 37.2 MPH 12.6% Slip 20% Up Drive
3500 RPM's 43.9 MPH 11.4% Slip 30% Up
4000 RPM's 50.6 MPH 10.8% Slip 40% Up
4500 RPM's 57.6 MPH 9.7% Slip 50% Up

After adding a Holley 650cfm 4-barrel and Edlebrock Performer intake I got the following "actual" results with the 21P Revolution.

3000 RPM's 38.0 MPH 12.5% Slip 0% Up Drive
3500 RPM's 45.0 MPH 11.3% Slip 25% Up
4000 RPM's 51.8 MPH 10.7% Slip 50% Up
4200 RPM's 56.0 MPH 8.0% Slip 80% Up

4200 RPM's was WOT and the calculation now estimated 250 P.S.H.P at 3700 ft.

At this point I decided the stock camshaft was hurting me and it needed to be changed so I switched it out for a Crane 272(I)/284(E) Deg. Duration, 454"(I)/480"(E) Lift Cam. I've also added a 1" spacer under the carb and bumped the initial advance up to 10 deg. The boat now runs close to the 269 H.P. numbers with 57-58 MPH WOT speeds. So I assume now I'm making close to 270 propshaft H.P. again at 3700ft. Hope this helpes.

[Rootsy]

Thanks Rick,

with the 2V setup i was getting around 53 or 54 mph in my 16 @ 4400 rpm with a 19 P Vengence (old tach was 200 rpm low also). The camshaft is a roller and the lift is close to the flat tappet camshaft specs. So i don't know what merc did. Maybe it was a transition thing? the roller specs you listed are the lift @ the cam lobe, the flat tappet specs are the lift @ the valve, you need to multiply the roller's lift X rocker arm ratio... and that comes out close to what chris riley posted. The idea behind a roller cam is a lot of duration and lift because the roller is able to follow the profile unlike a flat tappet where the ramp angle cannot get to be too much or you'll end up riding on the edge of the lifter... I've never really looked at marine camshafts, would assume less overlap for torque and a shorter exhaust duration to help eliminate reversion? Anyone care to point me toward any good grinds?

I've added 1.6 ratio roller rockers so i net about 0.030 more valve lift plus an edelbrock performer and a 600 cfm holley and i have my initial timing at 10 BTDC (now if i could only get more total advance!). Now with the 19P Vengence at 12% slip @ 5000 rpm i'm GPS'd at 57.1 mph with some trim.... might be a bit more i ran out of lake! Gonna try the 21 Mirage this week or weekend so we'll see what we get... I'd swap camshafts but i REALLY don't want to have to remove my whole damn motor to do it... it's TIGHT... guess i could cut a hole behind the rear seat to feed it through *GULP* if i can get 60 out of the girl i'll be more than happy...

Thanks for the help!!!!

[RickSE]

Jaroot,

I agree with you about the total timing issue. I run 38 deg. in my SBC 400 drag car and would like to run more advance in the Donzi. Last time I had the car at the track I picked up quite a bit of top end just switching from 36 to 38 deg.

Look into the Crane Powermax Roller Cams. They have some nice dual-pattern cams for late model roller motors. Jegs has them for $300.

One question though, whose 1.6 roller rockers did you use? Did you have to buy the self-aligning type?

[Rootsy]

I bought Comp Cams Magnum Rollers 1.6 Ratio, the ball fulcrums with roller tips so they'd fit under the low valve covers. I had to get the self aligning tips (post 87, pre vortec heads) so they cost more... if i could get taller valve covers on it i would have gone full roller. only reason i did it was to get more valve lift without swapping cams... i dont know HOW many people i had tell me i needed to replace the cam if i was going 4V... i don't know why there have been plenty of motors in the past with less camshaft than these motors that came from the factory with 4V's. Think i am going to look into getting a Thunderbolt IV module and replace my V on the distributor... wonder how much those go for?????

[RickSE]

Sorry one more question, did you have to modify the heads (push rod slot length) with the new rockers? As you may know I was thinking about using the same rockers and was hoping the push rod clearance slot would not have to be elongated.

I may consider adding a Mallory Unilite and MSD Ignition box if I can't get anymore timing out of my distributor. I relly don't need any of the other features of the Thunderbolt V. The only useful feature of the T-V ignition is the knock sensor and my setup doesn't even have it.

[Rootsy]

Rick,

According to a fax i received from Chris Emerson from the Perfomance Big Block Chevy Marine book the 3rd generation thunderbolt IV modules will attach to the same location as the TBolt V module and plug right in, just unhook the knock sensor. The book even has ignition curves and part numbers for each of the 6 V8 modules... 2 for 20 degrees, 2 for 22 and 2 for 24, solid curves @ rpms, no hunting like the TBolt V does. I am going to check into this.

With the stock cam, adding the rockers i DID NOT have to elongate the pushrod slots, i was wary about having to do this and i paid attention when i assembled everything and i was in the clear, with any performance camshaft you'd probably need to do this.. and if you are gonna go that route, might as well go full rollers if you can get valve covers to fit behind the merc manifolds.

As for aftermarket ignition, i'd go with something with a larger cap diameter to prevent crossfiring.. have a mallory unilite in my 289 and i used to get crossfiring especially in damp conditions... and i don't care for the female plug cap... i like the HEI snap on style better and i am a fan of the MSD pro billet... she withstands 9000 rpm's in the camaro, no hickups or crossfiring or loose wires... been in there about 5 years now and only thing she needs is a new cap and rotor every season. I'd love to put a pro billet and 6AL box in... maybe next year.. we;ll try the Tbolt IV modules first...

anyone have the part number for the TBOLT IV module for the old 350 Mag Carbed, preferable? how bout the early 90's 260's?

Thanks

Jamie

[RickR]

Thunderbolt IV @Doug Russell Marine 350Mag (http://216.37.204.204/mercruiser_oem/mercruiser.asp?type=13&subtype=111&a=88&b=10) $171 :eek:

[BigGrizzly]

Your Idea of what a marine camis is incorrect so is the idea that rollars are faster than flat tappets.The maijor cam designers will tell you if yoy son't need rollers ( rpn' poor oiling etc) than don't use them. My Ford in the Corsican has flat tappis, and rollar rockers(to prevent valve guide wear). My supercharged 502 uses a rollor cam because the wear out cams due to a poor design oiling system inhearent to 454->502 Chevies. Which is why Merc went that route. I run close lobe centerd and long durations, and put torque up high. Most people think my boats run fairly strong with broad opwerbans. On the durability point the Corsican has been together for four years, and no problems as of yet.
I wouldn't wast my money on the thunderbolt, its not that good. The MSD or the unilite work great I have one of each.

Randy