What stroke to use for my new SBC combo?

[FastBuick]

Hello everyone,

I had to buy a new block, so I am possibly looking at changing my engine combo also. I just bought a Dart Iron Eagle block with a .434" raised cam, .905" lifter bores, spread pan rails, a 60mm babbitt cam journal, 9.025" deck, and will most likely be a 4.165" bore to start.

Right now I have a 3.625" stroke crank, 6.00" rods, and a set of CFE 268cc intake runner 18 degree heads with 2.200" intake and 1.600" exhaust titanium valves. I will also be using an Edelbrock Victor Glidden Spyder Intake manifold that has been ported, and a Pro Systems 1100 Dominator.

It is a 3100# car with a 7000 stall converter, and a TH400 with all lightweight internals and a 2.10/1.40/1.00 gear set.

My 398 combo ran a best of 9.25 @145 with a powerglide in it, turning 9000 RPM. The TH400 is new and hasn't been used yet.

My question is what bore stroke combination would work best with the heads, car, and drivetrain I have? I'm looking for the most gains and I am not afraid to turn RPM. So far my idea was a 3.750" stroke, but was looking for more info before I make the decision. Or should I keep the stroke the same?

Any help is greatly appreciated.

Thanks
John

[jason snyder]

I would PERSONALLY go 3.875 stroke , and sell the converter for something that will fit your new LOWER powerband ...Its a WIN win SITUATION !and you will make alot more power everywhere !

[CNC BLOCKS]

With a 9 inch deck i would go with a 3.875 with a 6 inch rod, better rod ratiio over the 4 inch stroke.

With the 60MM cam tunnel did you get the DRCE-3 oiling option?

[FastBuick]

I would PERSONALLY go 3.875 stroke , and sell the converter for something that will fit your new LOWER powerband ...Its a WIN win SITUATION !and you will make alot more power everywhere !

Do you think I will still gain more horsepower using the same heads? Or will I just shift the RPM range to lower RPMs?

[FastBuick]

With a 9 inch deck i would go with a 3.875 with a 6 inch rod, better rod ratiio over the 4 inch stroke.

With the 60MM cam tunnel did you get the DRCE-3 oiling option?

Yes all that was done at Dart. The oiling, cam tunnel, lifter bores with special bushings, and the .434" raised cam were all options that I ordered.

And as far as rod ratio, has the optimum rod ratio changed over the years? It used to be 1.7-1.8 was optimum. Recently I've heard Pro Stock was using 1.5-1.6. Is rod ratio still a concern or doesn't it really matter much? That's one of the reasons I was concerned about changing the stroke. The rod ratio and bore/stroke ratio are still good with the 3.625 stroke but obviously get worse with more stroke. What effects will this have? I'm thinking cylinder wear is one.

[CNC BLOCKS]

With a 9 inch deck i would go with a 3.875 with a 6 inch rod, better rod ratiio over the 4 inch stroke.

With the 60MM cam tunnel did you get the DRCE-3 oiling option?

Yes all that was done at Dart. The oiling, cam tunnel, lifter bores with special bushings, and the .434" raised cam were all options that I ordered.

And as far as rod ratio, has the optimum rod ratio changed over the years? It used to be 1.7-1.8 was optimum. Recently I've heard Pro Stock was using 1.5-1.6. Is rod ratio still a concern or doesn't it really matter much? That's one of the reasons I was concerned about changing the stroke. The rod ratio and bore/stroke ratio are still good with the 3.625 stroke but obviously get worse with more stroke. What effects will this have? I'm thinking cylinder wear is one.

Do search on rod ratio see what you come up with.

[FastBuick]

With a 9 inch deck i would go with a 3.875 with a 6 inch rod, better rod ratiio over the 4 inch stroke.

With the 60MM cam tunnel did you get the DRCE-3 oiling option?

Yes all that was done at Dart. The oiling, cam tunnel, lifter bores with special bushings, and the .434" raised cam were all options that I ordered.

And as far as rod ratio, has the optimum rod ratio changed over the years? It used to be 1.7-1.8 was optimum. Recently I've heard Pro Stock was using 1.5-1.6. Is rod ratio still a concern or doesn't it really matter much? That's one of the reasons I was concerned about changing the stroke. The rod ratio and bore/stroke ratio are still good with the 3.625 stroke but obviously get worse with more stroke. What effects will this have? I'm thinking cylinder wear is one.

Do search on rod ratio see what you come up with.

Ok no problem. I was just hoping to get some real world recent theories instead of ones in a book or online that may be 10 years old and outdated.

[62ChevyII]

Ok no problem. I was just hoping to get some real world recent theories instead of ones in a book or online that may be 10 years old and outdated.

I think he meant search here on Speedtalk for rod ratio, I think it has been a hot topic in the not too distant past.

[FastBuick]

Ok will do. I guess I took that wrong. That happens with text lol.

I guess my main question is will there be significant gains with more stroke and the heads I have? I just don't want to waste money. Looking for good bang for the buck so I can utilize my money wisely and use it in another area if there's a better option.

[rookie]

Here is a good thread in the advanced section that has side load calculations. viewtopic.php?f=15&t=32153

[levisnteeshirt]

a long stroke motor can wind , my friends shop did a 421 for a super late , the driver had a SB2 in it before ,, they wound it to 8800 for 3 races , not the best idea , but its still together ,, if it had a cam that would pull that high , it would be a monster

[sjvalleydave]

We have a 421" SB2.2 in a DLM and run it 8400 all the time...

[bigjoe1]

Rod ratio is all bull shit. You can make anything work. Dont loose any sleep over it.


JOE SHERMAN RACING

[jmarkaudio]

I'd use a 4'" stroke.

[BigBro74]

Rod ratio is all bull shit. You can make anything work. Dont loose any sleep over it.


JOE SHERMAN RACING

^^^^^^^Yes! ilike the way Big Joe Tells it.