Awhile back I blew a head gasket, since then the car has sat on stands under a cover till school was over, well it's over. I want to put a 408 fully forged short block in place of my 355. I've seen LT1 forged short blocks that can be had in 383, 385, 396 and 408. I assume it will fit without a problem. My question is, which platform will give me a ratio of performance and reliability (which ever setup, it'll be forged and balanced.)? and what's needed with that setup? As far as my top end, I assume I can still use the intake. My stock heads are already P/P and 3 way'd, gold 1.6 rockers and dual springs. I'm going to have then bench flowed to see if they have decent cfm's and are worth keeping. Also, what are your thoughts on the Comp Cams "Extreme" LT1 Camshaft, 230 / 236, .510 / .520 112 LSA? If I'm only going to see a marginal gain using a 408 over a 383, I'd rather go 383? Thanks for your opinons.

 

First...I would not get a cam until you know your flow #'s, cubes and intended purpose.

Second, 383 will be the easiest to put together in regard to clearancing.

Third, you bump those cubes up, your heads might not do what you want anymore.

And those are just a few of the many things to think about.

 

Thanks for the reply, I was wondering how far I would still be able to use the heads. Do you know the average numbers of a NA 383 to a NA 408?

 

The 408 requires 4" stroke which is more piston speed so it wont be rpm happy as the 383. All the stroker require clearencing, the more the stroke the more clearnecing is required and the more the chance of breaking into the water jacket. This will also depend on the brand of rods used, some are stroker specific and requires less clearencing.
The heads should flow well to support the cubic inches or you can go with a cam that has more overlap.
This cam will work but it wont be ideal, like a custom one.

 

To many variables to guess averages...but a decently built 383 can run 11's with medicore heads. From there, who knows.

 

This is going to required more planning than I first thought. As far as the short blocks, they come balanced with either Eagle forged steel cranks or Cola forged steel. with the corresponding parts as well. Clearance issues, shouldn't be a problem.

 

Stick to the 383 and concentrate your effort$ on cylinder head, valvetrain and induction. The power is there... you just have to pull it out.

I'm doing better than 550rwhp from a NA 383 if that's any inspiration for you. That Comp Cam is a bit of a dog IMO, work with someone on putting together a valvetrain/camshaft combination and you'll be miles ahead on this project.

-Mindgame

 

Thank you. Your 383, LT1 or LS1? If LT1, would you mind sharing your combo?

 

If I share any more than I already have people are likely to get a little nauseated.

Besides, I have a new book coming out... How to Build a 9-second F-body on a Wine Budget.

Other than that... there's a thread floating around where I pretty much laid out the whole build. Lots of stuff has changed but that's the jist of it so do a search for "Mindgame tell us" and you'll find the thread.

*kidding about the book*

-Mindgame