I think I need to lower my compression

[shownshine55]

I am running a 355 with flat tops. This was going into another project that had 76cc heads on it. Now I want to put on a set of reman vortec 350 heads and use it in my '96. Gas in our area is rated at 87, 89 with 10% ethanol blend, and 91. I always run the 89 because it is the cheapest. With doing some research I'm guesstimating that I would be running around 10:1 compression. I'm thinking that if I run a thicker head gasket maybe I can get the comperssion down to where I can run the 91. Any suggestions?

 

[stubnosebrock]

What pistons are in it? Cast, Hyper, Forged? The problem with running a real thick head gasket, is that you start to loose quench and are prone to detonation. Thats a big problem with cast pistons and even worse with hypers. Are the heads aluminum? If you have aluminum heads you can generally get away with a half point or so more compression. So 10 to 1 actual compression with aluminum heads on 93 gas isnt too bad. But you really need to figure out what your real compression will be. Guessing wont work. Look up an online calculator and see what things you need to know, and start pushing in numbers. Brandon

 

[shownshine55]

They are forged pistons. the heads are iron. I will have to look it up to see if I can get come up with something closer than a guess. Beings this 355 started out as a tbi engine (it is sporting a lt1 roller cam), there are a couple of other things that I need to switch over. May just be easier to start over with an actual vortec engine. What about the 350s that came in the caprices? What year did they start making the blocks roller cam compatible? Would any of these be compatable for a vortec build?

 

[shownshine55]

Problem solved. Of course money solves everything, right? Just agreed to buy a '97 350 shortblock for $150 and a 4l80e for $250. Both are coming out of a running and driving '97 2500. The motor has a lower end knock so I'll be looking at a rebuild. The tranny I will save for a future project.