Calling all opionated engine builders

[nheller76]

Ok guys hear is what i got; so i have a 350 that is bored .30 over (so 355) and its got a oil leak in the timing cover so its needing to be pulled to get at it. So i figure while im there i will do a few things. Hear is my dilemma, its got dished pistons that i know need to go so I'm thinking of going with one of these flat top or a domed pistons.

http://www.summitracing.com/parts/uem-9902hc-030

http://www.summitracing.com/parts/uem-9904hc-std

Also I have some cast iron head choices, i have a set of 202 160 valve 882's or a set of 195 150 487x's.

Im not 100% positive but i think i have a stock lower rotating assembly not including the dished pistons. I plan on using a steel shim head gasket that is 0.015 thick.

This truck is my daily driver but its more of a future hot rod so im not worried about gas millage to much but i do need "some" street driveability. but i do likey the HP and would love to suck a few more ponies out of the engine. down the road (long way down) it will get a set of vortech heads but that is a long way off.

So you pro builders out there if i could get your help in deciding what is the best combo for me it would be great! The guys on hear have never steered me wrong so I'm up for any help i can get. Thanks all

[craig113]

I have a 91 block and changed the pistons to a flat top, upgraded the cam, roller rockers, headers etc.... did not have to use a thin metal head gasket. By the time its built and running i can average 3 mpg and the front of the vehicle wants to pick up off the ground.

[nheller76]

So my question is should I do dome or flat top.

[Desert1957]

Originally Posted by nheller76

So my question is should I do dome or flat top.

It depends on the CC rating of the cylinder heads , 64cc , 72cc , 76 cc.

Years ago I ran .018 thin gaskets with a liquid compound on a race 327. I do not recommend that thin a gasket on a street engine, block and head surface would need to be perfect to prevent a blowout.

Felpro composite , multi layer gasket were invented to seal the first time.

Pic your target compression ratio for pump gas , then compute your cylinder head cc and piston choice to obtain that number.

You don't want to wind up with anymore ten say 10.5 to 1 compression ratio if your going to run pump gas on the street , especially on a daily driver.

Desert

[kalbert]

You are going to need machine work to use new pistons. You can't just buy .030 slugs and put them in your holes. They should be fitted to the holes properly. Your holes have been fitted to your pistons and over time have worn in to be perfect mates. They are slightly out of round where the new pistons will be darn near perfect. At worst it will rattle cold, the rings won't have enough support to stay put and the skirts will wear prematurely. At best it will use oil.

That said, I'd use off the shelf gaskets designed for longevity over a few thousandths of thickness. Compresson ratio and how to achieve a good one is most dependent on what heads you have. You want to be right near the 9.75:1 mark for a street driven pump gas NA motor. Check out the specs on the GMPP crates, those are pretty standard fool proof formulas .