ok im getting ready to order a new set of keith blacks for my camaro. on their web site they have quite a few different options for the 305's. the set i was looking at was kb-143. its a 10.0 comp piston with a 58 cc head. its a flat top piston with only 2 valve reliefs. where as the stock pistons have 4 valve releifs. what the differnce between the stock 4 and the kb 2. is it dish volume. less dish volume means a higher comp ratio right? should i order these pistons for my car. will it be ok with the 2 valve reliefs over the stock 4. why did the stocks have 4? putting the kb's with only 2 valve reliefs isnt going to cause any clearance problems right? can somebody please help me

 

Most aftermarket pistons have deeper valve reliefs. This is to help w/ valve to piston clearance. It is possible for a flattop 2 valve piston to have the same volume cc's as a 4 valve. These questions can be answered perfectly from kb. The can tell you every possible compression possible with different heads, gasket thickness' etc.

 

my main ques is will the kb pistons work in my motor without any special modifications because they only have 2 valve reliefs instead of the stock 4.

 

The pistons likely will work fine. The 4 valve pistons allow them to be used on either side of motor.

 

oh really. i had no idea. thats for your help floor guy. now i also have some ques on head gaskets. does anyone know what the compressed cc is on a stock felpro head gasket. i was looking at a set of mr gaskets's #1134. it isnt the thinnest head gasket out there but it seemed to be a decent choice for my application. should i get a thinner head gasket to get the most out of my compression or will i be asking for trouble. i was looking at a set of fel pro #1094 and it gives me a 3.2 compressed cc. what does everyone think. im still learning so if anyone can add some input it would be apreciated. thanks

 

Yeah, you would need something that thin to get up to 10:1. If you were to use a thicker composite head gasket like the GMPP .028" compressed thickness one (6.5cc) you would be down at 9.6:1

I am not a fan of steel shim-type or copper head gaskets on rebuilt motors- they tend to have more leakage problems than composite gaskets do. However, if you need the compression then that's about what you're left with. Some of the newer ones have built-in rubber o-rings around water ports and such which should help them seal up better, but I have not tried them yet myself.

 

well the pistons say they will give me a 10.0 compression ratio with a 58cc head. that was calculated with a .030 overbore though. im going stock bore. so there i lose a little. ok say with that im now at 9.70 compression. im gonna have the heads milled about 10 thousands so i gain a little there. that might put me back up to about 9.90 then i add the mr gasket head gaskets that are thinner than stock those gaskets give me a .028 compressed thickness and a 6.147 compressed volume so that should just about put me back up to 10.0 im not sure any insite?

 

Look on the KB-Silvolite webpage.. They have a calculator that will allow you to check...

 

Shaving 10 off the deck (.015" piston deck height) with stock bore (3.736"), 58cc chambers and 6.1cc for a head gasket you will be at 9.71:1.

It will take a 3.8cc head gasket to put you at exactly 10:1 with that combo.

OR.... you could shave the heads down a little (56cc) and again be at 10:1 with the thicker 6.1cc head gaskets.