View Full Version : Block talk

joseph m. hahnl
12-02-2012, 10:15 AM
I have to replace the block in the Minx due to a score in the jug from a failed spark plug ,I have an another 4.0 bore DIA stock block and rotating assembly .This would be the most economical way for me to fix it.

Buttttttttt. I don't think that will due. I.m thinking more on the lines of a big bore dart block.

That parts pretty straight forward, it's just a matter if you want to punch it out .030.
I'm a little skeptical on the oversize 4.156" bore,as if something should happen like a score. There would only be one more time i could resize the block, or if the score was deeper than .030" it would be scrap.

Does piston displacment add torque or horsepower? Both?:confused:

So now were at stroke. and there are alot to choose from. I'm thinking full all out 3.875"
This set up would require modified pistons to keep the compession ratio down.
Merc runs there 380 hp scorpion in the 9's most all Mercruiser stuff is.I'm assumming there runnig 72cc heads. at the moment I have 64cc heads. With a 15cc piston the 4.155 x 3.875 would be in the 10.3. Deck height i'm sure would play a roll. The Dart I'm lookig at is .205.
Where does a higher compression ratio change the torque curve?:confused:

The other option is to go a little milder with the same block at the stock bore of 4.125 and a 3.75 stroke macking a nice small block 400 and would also lower the compression ratio.

Any Input is greatly apprieciated:biggrin:

12-02-2012, 10:24 AM
Joe, rule of thumb says the largest bore will give the greatest HP, longest stroke will offer greatest torque.

One of the main reasons for multi-cylinder engines in Formula racing (10-12 cylinders) is they will produce the maximum piston surface area for a given displacement, and therefore more HP.

12-02-2012, 10:27 AM
BTW, Dart blocks are beautiful things to behold.
A very good investment.

12-02-2012, 10:50 AM
I have always been partial to the 383 over the 400, I like the larger journals.

Compression adds quite a bit of power, many years back I was running a 302 Jimmy out to 320 trip two barrels and a Schaller 1/4 speed cam. I popped a head gasket and while it was apart I had the head shaved .080, the Jimmy was in a very lightened 38 Chevy coup which was running very consistent 14.3 14.5. With the shave job and a little better tire I could on a good day pop into the upper 13's, but more of a kick was beating a buddy who had stuffed 265 in a 52 Chevy. He was the first to beat the krap out of his firewall to stuff a SBC in his car, A month later with some massaging to the 265 he blew me away getting into the lower 13's.


12-02-2012, 12:59 PM
Joseph ~
Have you ever considered getting your old block's scored cylinder wall bored-out & a cylinder repair sleeve chilled & pressed-in ?

This is great, and very successful way to save the old engine block.

I have had a number of very rare, & almost irreplacable, very early Brass Era "Antique" auto engines successfully repaired in this manner.

Diesel engine rebuilders use this cylinder sleeve repair method all the time.

The cost to do such a cylinder re-sleeve repair is very nominal at most engine machine shops.
And the sleeved cylinders will then be just like new.

12-02-2012, 01:05 PM
now your talking...

I turned a 3.625 x 4.155 to 8400 :kingme:


I just happen to have a 400 block and 3.875 crank and rods and cam and solid lifters too :)

and the trick heads, the whole package was in my stock appearing Nova that at one time was the fastest stock appearing small block Chevy anywhere..

it's a 2 piece seal block and crank though, so all you need is an early flywheel and flat top pistons and rebalance the asembly since the crank has mallory metal in it now

12-02-2012, 08:18 PM
I think you have to be very careful with rod choice on a 3.875 crank with regards to clearance. H-beam might even need a reduced base circle cam. That being said I used a Scat 3.750 I beam combo in a stock block and have tons of room.

12-02-2012, 08:24 PM
massaging it would be a chore for sure.. probably be more trouble than it's worth

12-02-2012, 10:15 PM
The engine in my Minx was tired when I purchased it. I opted to go with a mercruiser crate motor. It is a 377 cu 325 hp and gives me 68 consistantly with a spinelly prop. I will have to check my records but I think it was just under 4k. I wanted reliability, and it has all the modern parts-center mount valve covers, roller cam, good flowing heads, the latest electronic ignition with knock sensors along with a new carb. Not to mention a 1 year warranty.

Keep in mind if you are looking to add alot more power, you still have to worry about the alpha drive. Then there is the steering safety issues. I am adding full hydraulic now.


joseph m. hahnl
02-24-2013, 11:29 AM
Here goes:tongue:

4.155 bore x 3.750 x 6.0 rods 64 cc cnc combustion chamber with a static CR 10.7 : 1

The cam is XM270HR / LSA 112*, lift with 1.5:1 rocker I .495/ E .503
Intake event: open 25* BTDC, close 65* ABDC,
Exhaust event: close 24* ATDC open 72*BBDC


intake closes 65* leaving 8.53 :1 Dynamic CR.

02-24-2013, 04:53 PM
interesting... :cool:

is that with flat top pistons and zero deck?

joseph m. hahnl
02-24-2013, 05:43 PM
interesting... :cool:

is that with flat top pistons and zero deck?

-16cc or -21cc Dish 9.7 or 10.3 compression ratio I think a .030 deck height.

10.3 comes out to 8.22 with the cam. My understanding is 8.5 is optimal dynamic compression ratio. What do you think?


02-24-2013, 07:52 PM
Static and Dynamic Compression Ratio

(Considers Cam Timing and Rod Ratio)


Cylinder Head Volume (cc)

Cylinder Head Vol (cubic in.)

Piston Head Volume (cc)

Piston Head Vol (cubic in.)

Gasket Thickness (in.)

Swept Volume (cubic in.)

Gasket Bore (in.)

T.D.C. Volume (cubic in.)

Cylinder Bore Diameter (in.)

Gasket Volume (cubic in.)

Deck Clearance (in.)Note: Neg. nubmer above deck, Pos. number below deck

Deck Volume (cubic in.)

Stroke (in.)




Rod Length (in.)

Adjusted Stroke (in.)

Intake Closing Point (degrees)ABDC @ 0.050 lift plus 15 degrees



Return to United Engine & Machine Calculator Listing (http://www.donzi.net/forums/calc.php)

joseph m. hahnl
03-01-2013, 10:52 AM


I've been reading alot on this principle of dynamic compression related to octane rating, and how compression and duration with lift effects cylinder pressure.It's almost worth buying a pre-engineered motor, butttttttttt.NOOOOO!! IT Isn't:biggrin.:

I'm at the point where I got the hammer back and my fingers on the saftey.
I just need to figure where I,m going to ship the block, home or work.

Some things I've found: To run 89 to 93 octane the dynamic compression ratio needs to be between 7.5 to 8.5. This value is governed by the intake closure angle. By adding duration( the intake valve stays open longer ABDC) decreasing dynamic compression ratio. Because Merc stuff has such a low Static compression and the use dish pistons and iron heads, high duration is counter productive to engine performance.For instance if you look at a 377 scorpion the static compression is 9.5:1 with low duration and high lift achived by a 1.6:1 rocker ratio.The key was the added lift with rocker ratio ,but kept the duration realativly the same to keep the dynamic compression low enough to run on 89 octane. As the overall static compression is low, cylinder presure would also be lower. The higher lift helps create more pressure but the cam has modified architecture to prevent reversion.

By the way reversion is a loose term, as there is water reversion and exhaust reversion, meaning a land motor can also suffer from reversion. Reversion is mainly caused by low cylinder pressure with a late closing exhaust valve, closing further past ATDC. exhaust reversion is the culprit and water ingestion is the by- product. So remember the vacume break theory in the riser :rlol:. This is because that factory gm stuff is old technology used for more than 50 years, that rides on the edge of detonation right at the get go, cam modications are limited, because cylinder pressure is low causing reversion.

2013 brings alot of development break throughs for combating detonation. Higher Static and Dynamic compression ratio's can be achieved with the same octane ratings as the yester year motors.

For instance by the use of aluiminum heads the transfer of heat to the coolant is greater. This alone alows .5:1 more dynamic compression ratio or 1:1 in static compression ratio. This equals more cylinder pressure

Piston development has also contributed to the reduction. by eliminating a full dish piston and incorperating zero deck with a pocket under the cumbustion chamber and leaving a flat top where the head is flat .reduces detonation dramtically. Meaning more more dynamic compression ratio /static compression ratio. This equals more cylinder pressure.

Now that we have all this static compression we can throw more duration into it to put the dynamic compression into the range of the fuel octane we want to run with. As we add lift , the higher the volume moving through the intake and exhaust evacuating the the chamber and cylinder faster. Greatly reducing any chance of detonation.

SOOO!!!! after all of this with 64cc head my Static CR will be 10.3 (flat top piston with a 16CC pocket) the Comp cam XM270HR with a 65* ABDC leaves 8.22:1 which is high for an iron head but should just be right for an aluminum head running 90 octane. I think this will be a great running 406ci..
if i keep my:crossfing:

03-03-2013, 07:56 AM
I like your thinking... :yes:

the chart I did above was with 72cc alum heads, zero deck, and flat top pistons using 1.6 rockers too.... it just didn't post like I wanted it to when I pasted the work sheet... this *might* work better against detonation, instead of a 64cc head and the slug .030 in the hole,, to keep the flame travel more even and the bang in the chamber, not in the hole

just my .02 of course

03-03-2013, 08:19 AM
Unless you deck the block the pistons are usually not at .000 so cr will be less

joseph m. hahnl
03-03-2013, 09:50 AM
Thanks guys:worthy: Buiz: I allready have the heads , I'll have to work with the 64 ,cc heads. JW :I Found a short block with all forged internals. But I have some questions for the builder, specifically regarding your's/Buiz's post. If he can't provide a zero deck with a cnc pocketed piston I will have to go else where. But in the event I did have .030 in the hole,It would create such a stumbling stone. It would lower DCR wich would allow lower octane, yet then probably detinate in the hole so you couldn't:frown:

I have an issue with the fly wheel. I can use my style coupler (3.0"BC) for my drive on old 3.5" BC , but Merc doesn't seem to have made a 14"DIA (168) tooth in a 3.5"BC, only a 12 3/4". " Mop are you out there?"

I would think that a Merc fly wheel is a standard (manual transmission)
fly wheel. Any one Know?:confused:

Maybe:shocker: a lighter fly wheel :hi5:

Come to think of it:
I don't even know if a 2pc RMS Scat crank is on a 3.5 BC. couldn't really find it in any literature.

03-03-2013, 12:16 PM
On my block (010 GM 350) the machinist ~ a crusty old timer ~ said not to worry, he would deck it to 9.300 (don't quote me) and we would end up with zero deck. All of the piston heights ended up at .000" to -.001" perfect. Mahle / Scat forged rods and crank / everything new. Your mileage may vary...

joseph m. hahnl
03-09-2013, 09:08 AM
I pulled the trigger:hyper:

Pro star
400 CID, 4.125 std bore , .005 deck
forged 3.75 crank with forged 6.0 rods
15.2 cc half dish forged piston.
Arp 400 windage main studs:cards:
head gasket 4.125 x .038 " NO steam holes:propeller:"

Comp Cam xm270hr cam and Comp Cam lifters and timing chain, full roller 1.5 SS rockers
Eddlebrock, duel plane,spread bore, performer intake,with Edelbrock 750"electric choke:wink:"
aluminum:tongue: cnc 64 cc heads 210 cc runner with 2.02 1.6 +.100 PCM valve .600 max lift.

McLeod, 21lbs, billet steel, neutral balance fly wheel and new GLM coupler

Melling Select, Std Vol/ High Performance oil pump./GLM water pump

HGE Aluminum stock style exhaust manifold with my original 1988 4" exhaust Merc riser "no superceeded risers here:cool:"

A build :worthy: of a Donzi:drive:

:):):):):):):):):):):):):):):):):):):):):):):):):) :):):):):):):):):):)

03-09-2013, 03:48 PM
Long rod / long stroke lots 'o torque!
Which cylinder heads chamber / runner cc?
Sounds like a great plan.

joseph m. hahnl
03-09-2013, 04:40 PM
64cc chamber 210cc runner:wink:

joseph m. hahnl
05-04-2013, 08:42 AM
:hyper: Today the 400 goes in!:hyper:

05-04-2013, 10:28 AM
That's awesome! :party: Make sure you have enough beer (1.5x as much as you think you'll need), some tunes, and get that distributor hold-down wrench back from your neighbor.

Something must be wrong with my computer though, because none of the pictures of your new mill showed up on here? :lookaroun:

joseph m. hahnl
05-04-2013, 08:52 PM
That's awesome! :party: Make sure you have enough beer (1.5x as much as you think you'll need), some tunes, and get that distributor hold-down wrench back from your neighbor.

Something must be wrong with my computer though, because none of the pictures of your new mill showed up on here? :lookaroun:

:checkered::checkered::checkered: pictures come on race day :checkered::checkered::checkered: engine in:worthy: ,exhaust manifolds and out drive tomorrow:biggrin:.

joseph m. hahnl
05-11-2013, 07:47 AM
Finally :propeller:. I had little trouble with the starter solenoid, So I decided to put a high torque mini starter in, I had to wait 3 days on 2 day shipping:boggled:. Fed Ex must use the Chinese calendar :tongue:. Any way, splashed her yesterday. So far so good, what a difference in power:hyper:, I see more pitch is in the future:cards: ,we'll see, just how much after the break in.:D I'm going to try to get some video today weather permitting :umbrella:

joseph m. hahnl
05-11-2013, 09:05 PM

05-11-2013, 10:11 PM
Finally :propeller:. I had little trouble with the starter solenoid, So I decided to put a high torque mini starter in, I had to wait 3 days on 2 day shipping:boggled:. Fed Ex must use the Chinese calendar :tongue:. Any way, splashed her yesterday. So far so good, what a difference in power:hyper:, I see more pitch is in the future:cards: ,we'll see, just how much after the break in.:D I'm going to try to get some video today weather permitting :umbrella:

The Minx sounds great! Gotta be a good feeling to finally get her back out on the water. Roger on the shipping woes, it is kicking my butt right now. Mostly paying more for shipping than the little odds and ends I'm ordering. Glad to see you're happy with all of the work you put in this winter. Now start saying prayers over chicken bones or whatever black magic it takes to find a good prop!

05-12-2013, 06:01 AM
Now enjoy the hell out of it!

joseph m. hahnl
05-12-2013, 07:41 AM
Thanks JW, I went to start her yesterday and no luck. I had trouble with the Thunder Bolt CDI "so I thought" replaced with my spare and back and fourth. I started jiggling the interrupter switch and I could get it to spark:lightning. So I thought it might be the switch. Then I noticed a spark sound coming from the white green distributor wire. retightened it and it started. The distributor pick up coil seems to have a bad electrical post. I have a spare pick up coil :biggrin.: and it will go in today:wrench:. Boy do I know what you mean about the "missile - anus" stuff blowing a hole in your wallet. By going with the 2 piece RMS Dart block , it added cost that wouldn't be associated to a 383 one piece RMS. "flywheel, oil pan, Dip stick. Can you hear the lighter flywheel:wink: ? The throttle response is incredible :drive:

05-12-2013, 06:01 PM
Well done Joe!
Have a good summer.

05-12-2013, 11:16 PM
Dang I've had my new motor since January and it's still not wired up