jsetzer

Well I spun a bearing a few weeks back. Decided to do it right and someone showed me a deal I couldn't pass up.

Eagle 4340 3.5 Crank, srp forged pistons -5cc, eagle h beams 5.7"

My cam is probably toast so heres my plan....

I have a set of alum lt1 castings (heads) that are decked .020, have 2.02/1.57 valves with 3 angle job to match. The intake ports have been gasket matched (intake also). I have a set of Impy (thinner) headgaskets I was planning on running. GM847 cam will be going back in.

What kind of additional work can be done to the heads without spending much money? What kind of compression would I be looking at? More interested in dynamic. Have to keep it on pump gas.

Can this setup make 375+ to the wheels with full bolt ons + EWP etc?

89385formula

How much are you looking to spend on the heads? If you already have heads with larger valves....I know LE will do porting pretty reasonably. I think its about $400 for the porting since you won't need new parts in the heads. Probably a little more for a good valve job, etc. If not that, You can try your luck at porting them...or maybe a local speed shop could do some porting for you for a decent price.

jsetzer

Thanks. I think I will just let the machine shop look at them and get an estimate on what a little porting will cost.

fast 93 z

Pm Sent

jsetzer

Thanks.

What will the compression ratio be with the 847? Static/dynamic?

The Engineer

Does anyone know the "exact" LT1 compressed head gasket thickness (stock factory gasket)? I've seen some conflicting information on this subject. I'm planning on a head upgrade this winter and want to increase the compression to about 11.1 to 1, by using both head surfacing (.025) and thin gaskets (.030). However, I need to know the baseline (stock gasket thickness) for a starting point to compute the change in compression. I believe .006 = 1cc. When I tear-down my engine, I'll measure the gasket thickness, although, I would like to know in advance.

jsetzer

I have read .008 = 1cc. I am sure that its not entirely linear though. I have some .029 Impy gaskets that I need to decied if I am keeping......

Anyone do calculations for me?

The more I look at it I may keep the cc306 (or replace it) so I won't have to buy new springs and possibly different length push rods. How do a figure his dynamic junk so I don't get too small of a cam. I know my static will be fairly high for pump/street.

Mindgame

Don't understand the problem.

Stock CR is 10.4:1 so let's just back into it with what we know...

bore = 4.0"
stroke = 3.48
gasket bore = 4.1
piston volume = 7cc

the rest is not exactly "critical" as we are calculating a ratio, so let's assume....

comb chmbr = 58cc
deck height = .020
compressed gasket height = .051

= 10.4:1

Brodix states ".006 per cc" flat milling combustion chambers. So let's mill the heads .018 and change the gasket to .030...

= 11.4:1

-Mindgame