Just on here searchin around, was actually curious in the boring of the 4G69, but found some previous posts, and changed my mind on that. As far as raising compression on these cars, what is max limit on pump gas, such as 94 that you be legit for street. My plan was: If parts would be availible Forged 10.5:1 pistons, or to octane limit with being tuned properly *timing/ A/F, and rod set, bearing set for the main, and rods, some type of Cometic head gasket, RPW cam, with cam gear, and trying to research maybe a stronger valve spring set-up, as not to float valves with the higher lobed cam. and with the rrm pulley exhaust the whole nine yards... Just a half decent all motor... Post for thoughts... thanks guys

 

You can go 11.5:1 maybe 12 with 93 oct, WELL WELL tuned

not that good for dailydriven car but sure you can go from 11 to 11.5:1 on 93 oct.

Is that what youre asking?

 

Yea man, thats all I needed to know thanks a lot for answering that question

 

How would this be easily accomplished? Thicker head gasket? Different pistons? Head porting?

 

There are different ways to raise the compression. One way is to go to a thinner head gasket...if that is an option with the application. Another way is to mill the head. A more popular method is the change the pistons to ones that have a higher dome.

 

I get it...you decrease the area in the head/compression chamber which will raise compression. Thanks!

 

youre really asking thaT? or thats sarcasm??

 

for the newbs sake, cause im not or anything :-), just hypotheticly.
some explain this "boring stuff" to mee... them..

 

sure...
Borig out a engine (over-bore) is nothing new, engine builders have been doing it for a long time.

-One reason it is done is if there are deep scratches in the cylinder bore. Common overbore amounts are .010" .030" etc.

-Another reason to over bore a cylinder is to increase the overall displacement of the motor. If the cylinder is bored out to larger than stock size, you need a larger piston. If you tried to use the stock piston, it would be far too loose in the cylinder.

Hope that helps !

 

i mean what is "boaring". making more room in the cylender?

 

yes, you "bore" out the cylinders. Which means you make them a larger diameter. Which means you have to run a piston with a larger diameter.