I'm having trouble making a decision making the new 408 10.1:1 compression or lowering it and adding more boost. I currently run around 11lbs on the 6.0. I figure it would take around 3 lbs to make up for the power loss with the lower compression.
I wouldn't mind keeping the higher compression and same boost but I don't want to limit myself. I don't like doing anything that makes me loose power. How much boost could I run safely on a forged 408 with high compression and how much with lower CR?

Any help and input would be apreciated.
Thanks,
Mike

 

Thats not an easy question and really depends on the setup (especially the cam) and fuel used.

What you need to ask yourself is would you rather have less power out of boost and be able to run more boost, or have more power out of boost and run comparatively less boost?

The latter makes a much better DD in my opinion, while the former is a better race type scenario. Ultimately you will be limited by your fuel choice....if you decide to run e85 you could probably get away with your 10:1 and 20lbs.

 

Forgive me if I'm wrong(and please correct me if I am), but 408 stroker and big boost numbers don't play well together IIRC. Too much skirt below the hole @ BDC, with high boost won't it kill pistons relatively quickly?

 

How much boost are you running Atomic?

 

20-22lbs give or take

The short piston skirt is a known concern about stroker engines on gen 3 blocks, but matters more with high-rpm engines, not necessarily high boost.

 

If you use the LS2 Aluminum block your in a little better shape since it has longer skirts.

 

Thanks for the replies. It is a tough decision.
So the power loss out of boost would be pretty noticeable with the lower CR? I very rarely see boost daily driving. But, with all of the money I've spent over the years and now a new motor, I do want to see some good track times.
I would probably get a different cam, unless the one I have now would work.(in my sig below) I always use 93 octane.
Would the lower CR with higher boost be more durable than a higher CR with lower boost?
I wish it was an easier decision. I'm not a good decision maker LOL

 

My 402 is 9.5:1 and I never go into boost unless I want to....9:1 would probably be about the lowest I would go and still want good street manners....on gasoline. Like I said with e85 you can keep your 10:1 and have plenty of boost.

 

That seems like the best of both worlds. High CR and High boost.
What fuel do you use. I have done some reading on e85. Some people say you can just run it with no adjustments. I've also read you need different injectors, different tuning, etc. I think I was more confused after reading about it LOL.
Do you think the ls2 block is better than an iron block?

 

It is...trouble is you will need roughly 30% more fuel system to support it....so if you have 80lb injectors you need 115s and at least dual pumps.

No way you can run it without tuning.

Not for boost...its about 80lbs lighter, but the iron blocks are stronger...unless you mean a heavily worked ls2 block with pressed in iron sleeves.