Small block stroker: 408 vs 426 kits?

Small block stroker: 408 vs 426 kits? - 04/04/11 07:14 PM

Having a devil of a time deciding which to go with (and yes, I'm aware most the 426 kits are actually around 418ci w/ .030 pistons as I'll likely be using).

It seems that they are almost a wash price wise...after you factor in the balancing, clearencing for the block, and upgrading to H beam rods that is required to make everything "equal" for comparisons sake with the 426 kits.

Which would you go with?

BTW, this is a magnum block and using ported eddy al magnum heads w/ 2.05 valves and a moderate roller cam 218/228 @ .050, .567/.567 lift, 106 lsa. This will be going in a truck with mild 3.55 gears and 2500rpm stall torque converter.

Posted By: chargincharles

Re: Small block stroker: 408 vs 426 kits? - 04/04/11 07:34 PM

All costs the same?

Well- There is no Replacement for Displacement.....

CC

Posted By: HotRodDave

Re: Small block stroker: 408 vs 426 kits? - 04/04/11 07:54 PM

Why not get one of the BPE 4.25 cranks and have an honest 434 ?

No replacement for displacement and with that small of a cam you are not gonna turn enough RPM to have any accelerated wear issues. It should do a very good impression of a cummins

Posted By: POS Dakota

Re: Small block stroker: 408 vs 426 kits? - 04/04/11 08:51 PM

Quote:

Why not get one of the BPE 4.25 cranks and have an honest 434 ?

No replacement for displacement and with that small of a cam you are not gonna turn enough RPM to have any accelerated wear issues. It should do a very good impression of a cummins

hehe Yeah, I would definitely look into some more cam.
The extra stroke will be wasted without more duration.

Posted By: DJVCuda

Re: Small block stroker: 408 vs 426 kits? - 04/05/11 12:45 AM

You should definitely call Rod @ BPE - I got one of his 4.125 kits ( 430 Cubes @ 4.080) and I could not beat the price even for a 4" kit with the quality of parts I got with the kit.

Here is a link to my build if your interested.

https://board.moparts.org/ubbthreads/show...part=1&vc=1

Posted By: Prince_Valiant

Re: Small block stroker: 408 vs 426 kits? - 04/05/11 05:36 AM

Thanks for the recommendation for BPE...will definitely consider their kits.

Quote:

Quote:

and with that small of a cam you are not gonna turn enough RPM to have any accelerated wear issues. It should do a very good impression of a cummins

hehe Yeah, I would definitely look into some more cam.
The extra stroke will be wasted without more duration.

The plan is in the future to go ahead with a bigger cam, but not too worried about the one going in there...first reason is the head flow and port volume are huge, so even with a small cam, it should make pretty decent power.

Secondly, hyd roller cams don't quite compare directly to flat tappet cams...for a given duration @ .050 might be the same, the head flows little to nothing at .050. However, compare the duration at points that the heads are flowing real cfm, such as .200, .300, and .400....as well as the .500 duration numbers, you'll see a decided edge for the roller cam. And again, that was assuming the same duration at .050 numbers. That's not to say I've got a big cam...it's still smaller than I'd otherwise really want.

But case in point...the LS7 out of a Z06 'vette? 427ci with a slight flow advantage (330cfm vs 310cfm) over my engine and revs up to 7,000 rpm w/ peak HP at 505hp. What are it's cam specs? A measely 211/230 @ .050 w/ 116 LSA. Again, not saying I'm building an engine comparable to an LS7...

I'd like to swap to a hyd roller from huges...236/242 with similarly narrow LSA. We'll see...not too worried either way

thanks for the input though....

Posted By: patrick

Re: Small block stroker: 408 vs 426 kits? - 04/05/11 01:41 PM

personally, I'd go with the 4" crank and 6.2-6.3" rods to minimize side loading if you want this to be something that's going to last 100k miles. the only heads out there with enough port volume and cross section for a 420+ inch small block are the big CNC indy's and the W7-8-9 IMHO.

for a street driver with the truck's weight and stall your cam choice doesn't sound too far off the mark, you're right, your .200" lift duration is probably more comparable to a flat tappet in the 230@.050 duration cam...I'd widen the LSA from 106. you'll sacrafice a bit of midrange torque, but flatten the torque curve out and extend it higher in the RPM range....something like a 112-114, installed on a 108ICL is what I'd do. should give you great power from near idle to 5500 RPM or so. I'd guess the narrow LSA cam you chose is going to nose over a little under 5k.

Posted By: HotRodDave

Re: Small block stroker: 408 vs 426 kits? - 04/05/11 03:32 PM

Quote:

Thanks for the recommendation for BPE...will definitely consider their kits.

Quote:

Quote:

and with that small of a cam you are not gonna turn enough RPM to have any accelerated wear issues. It should do a very good impression of a cummins

hehe Yeah, I would definitely look into some more cam.
The extra stroke will be wasted without more duration.

The plan is in the future to go ahead with a bigger cam, but not too worried about the one going in there...first reason is the head flow and port volume are huge, so even with a small cam, it should make pretty decent power.

Secondly, hyd roller cams don't quite compare directly to flat tappet cams...for a given duration @ .050 might be the same, the head flows little to nothing at .050. However, compare the duration at points that the heads are flowing real cfm, such as .200, .300, and .400....as well as the .500 duration numbers, you'll see a decided edge for the roller cam. And again, that was assuming the same duration at .050 numbers. That's not to say I've got a big cam...it's still smaller than I'd otherwise really want.

But case in point...the LS7 out of a Z06 'vette? 427ci with a slight flow advantage (330cfm vs 310cfm) over my engine and revs up to 7,000 rpm w/ peak HP at 505hp. What are it's cam specs? A measely 211/230 @ .050 w/ 116 LSA. Again, not saying I'm building an engine comparable to an LS7...

I'd like to swap to a hyd roller from huges...236/242 with similarly narrow LSA. We'll see...not too worried either way

thanks for the input though....

310 CFM? Who the heck did your port work?