[pontiac_boy]

Little bit of a noob here when it comes to boosted Pontiac but I wanted to get a general understanding on y’all’s experience and opinions on cranks.

I’m in the initial process of collecting parts for a Boosted drag and drive motor. A couple months ago I called Frank at All Pontiac and made a deposit on an aftermarket iron block. While talking to him, he recommended a 4.25 bore and 4.25 stroke Billet crank.

I’ve seen previous threads from a couple years back where people have stated keeping the stroke shorter would be ideal and even some have said 4.00 and under, but I’ve also seen a few guys successfully running a longer stroke successfully. What’s the current consensus in stroke?

I’m looking to build something capable of mid nines initially with room to grow as I gain more experience with the combo. So I’m figuring in a 3600lb car I probably need to be in the 1k-1200hp range?
Am I crazy?

[performerrpm]

have you received your block? i put my deposit down 2 months ago as well and hoping it gets here soon.

frank rec'd me to go with a 4.35 bore with my roots blown build and at the time i was gonna use my 4.0 crank . i instead used that crank in my 400 and going to run a 4.250 crank in the ia2 block with a procharger. seams like 4.0 and 4.250 is the general consensus on boosted apps even using a new block

[charlie66]

IMO the smallest stroke is the way to go. I go mid nines with a 3.75" stroke with a 198ci motor . More stroke will just make it harder to get down the track ..

[pontiac_boy]

Originally Posted by performerrpm

have you received your block? i put my deposit down 2 months ago as well and hoping it gets here soon.

frank rec'd me to go with a 4.35 bore with my roots blown build and at the time i was gonna use my 4.0 crank . i instead used that crank in my 400 and going to run a 4.250 crank in the ia2 block with a procharger. seams like 4.0 and 4.250 is the general consensus on boosted apps even using a new block

So I talked to him in mid February and he said I was 9 or 10 on the list. He said he wasn’t sure but he was expecting them to be done at the foundry in a couple weeks but we’d then be at the mercy of the machine shop after that. I hope to hear something this month but I’m not expecting anything as I’m not in a rush.

It seems like a decent amount of guy’s suggest the shorter stroke I’m just trying to better understand why. And those billet cranks are a big purchase.

[charlie66]

The reason why is that with a turbo torque becomes so multiplied it becomes a problem to get traction. So a short stroke will help you in that respect.. You still will have more torque then you will need with the shorter stroke. Im building a motor now with 3.330 stroke because even with 3.750 stroke it was too much imo...

[performerrpm]

Originally Posted by pontiac_boy

So I talked to him in mid February and he said I was 9 or 10 on the list. He said he wasn’t sure but he was expecting them to be done at the foundry in a couple weeks but we’d then be at the mercy of the machine shop after that. I hope to hear something this month but I’m not expecting anything as I’m not in a rush.

It seems like a decent amount of guy’s suggest the shorter stroke I’m just trying to better understand why. And those billet cranks are a big purchase.

dang we must have ordered within days of each other lol. i ordetrd around the 16th of feb and was number 8. i hit him uo yesterday and he said its at the machine shop.. im not really in a hurry either...i think my 434 will be plenty while i piece together the new one

[Dragncar]

Lots of big power boosted Pontiacs with 4 inch strokes out there. Its what Chief ran.

[Tom Vaught]

Originally Posted by pontiac_boy

Little bit of a noob here when it comes to boosted Pontiac but I wanted to get a general understanding on y’all’s experience and opinions on cranks.

I’m looking to build something capable of mid nines initially with room to grow as I gain more experience with the combo. So I’m figuring in a 3600lb car I probably need to be in the 1k-1200hp range?
Am I crazy?

John Meany had a 1000 hp Small Block Chevy STREET engine in a Corvette 25 years ago that he drove everywhere at low boost (less than 15 psi of boost) John Lingerfeller was involved in the project.

A YSi Vortech Supercharger would make 1200 in a street car with a basic BB Chevy engine years ago. A Procharger supercharger can easily make the same power.

A boosted Pontiac Turbo Engine (one turbo) would require a Large turbo (or 2 turbos ) and would be very soft on the bottom unless paired with a 400+ cid engine.

Tom V.

[blueghoast]

Mine is a 400 ci 60-over make's a ton of power no dyno numbers.
I just bump the cam a bit to a solid roller I'm hoping for 1-1200hp
with iron heads, When I get the 77-firebird done I'm going to install
it in that might be a while unless I just have to know and put it one of
my other cars. I might dyno it this time too.

GT

[blueghoast]

Originally Posted by blueghoast

Mine is a 400 ci 60-over make's a ton of power no dyno numbers.
I just bump the cam a bit to a solid roller I'm hoping for 1-1200hp
with iron heads, When I get the 77-firebird done I'm going to install
it in that might be a while unless I just have to know and put it one of
my other cars. I might dyno it this time too.

GT

I meant 1000-1200 and that would be spraying it too.

GT

[opeliac]

I ended up with a 4.250 x 4.250...Its been a durable combo for Chief's car...ANY car that is being built for power, should be able to deal with the traction that is needed...

[mgarblik]

At the power levels you are considering, I don't feel any Billet crankshaft from a quality vendor like Moldex, Crower, Wynberg, Bryant will be any issue at all. Honestly, a Molnar forging would be fine as well. I have used all the ones mentioned personally other than Bryant and Wynberg. As far as stroke, we ran 4.50" stroke in IA and IA 2 blocks for years @ up to 1500 HP and never had a crankshaft or bearing failure. That was nitrous boosted. The long stroke was pretty hard on piston skirts with lack of support at the bottom. I prefer 4.25" stroke if given the choice. A square engine, 4.25"X4.25" is a nice compromise with 482 inches for excellent torque, better skirt support, more cylinder wall material and sealing area. I feel that's the sweet spot for these engines. Not sure what the attraction would be for a shorter stroke in a Pontiac race engine? Rules requiring a smaller displacement? The desire to run it at very high RPM's? We ran our 482 Cu In engine at 8400 RPM's without issues. That was with a roots blower.

[R 70 Judge]

Originally Posted by mgarblik

At the power levels you are considering, I don't feel any Billet crankshaft from a quality vendor like Moldex, Crower, Wynberg, Bryant will be any issue at all. Honestly, a Molnar forging would be fine as well. I have used all the ones mentioned personally other than Bryant and Wynberg. As far as stroke, we ran 4.50" stroke in IA and IA 2 blocks for years @ up to 1500 HP and never had a crankshaft or bearing failure. That was nitrous boosted. The long stroke was pretty hard on piston skirts with lack of support at the bottom. I prefer 4.25" stroke if given the choice. A square engine, 4.25"X4.25" is a nice compromise with 482 inches for excellent torque, better skirt support, more cylinder wall material and sealing area. I feel that's the sweet spot for these engines. Not sure what the attraction would be for a shorter stroke in a Pontiac race engine? Rules requiring a smaller displacement? The desire to run it at very high RPM's? We ran our 482 Cu In engine at 8400 RPM's without issues. That was with a roots blower.

Curious, is there a preferred rod length with that stroke?

[mgarblik]

Originally Posted by R 70 Judge

Curious, is there a preferred rod length with that stroke?

To get the compression height we wanted and provide room for the large pins, {1.031"), we used 6.7" aluminum connecting rods. I don't really know if they were optimal. We had Bill Miller as a consultant on the roots blower engine and that's what he felt comfortable with. No issues.