Are 99 LS1 (not sure of the casting number but I think its 853) worth porting and polishing and putting bigger valves in or not?

 

Thats what I'm doing right now. I think with a competition port/polish/valve from LS1 casting to LS6 is only a 10-12 hp difference.

The heads 853 and 241 are the same things, just different numbers.

I'm porting a used set of 241's and have them at the machine shop right now doing a valvejob for 2.02/1.60's. After I'm good and done (in a couple more weeks) I'm going to have them flow benched. I'll post pics and results when I'm done of course. Then when i swap them on my car and put in my F13 112 then I'll post my dyno results.

 

The '99 heads are sand cast and the first year for center-bolts. The '01 and '02 cars go semi-permanent mold cast heads that came out better. These are the 241 heads. If they're getting ported, it doesn't matter. Once fully ported there will be no difference. Many do not know this.

Ben T.

 

What do you mean there will be no difference. In performance or between a ported set of 853 and 241's. Or will I be better off with some 5.3l heads ported?

 

853/241 won't be a difference when fully ported. Put all of the other goodies the '01 & '02 LS1 cars got, and there will be a 5hp advantage to the 241 heads. So, basically nothing is gained from ONLY the heads. When both are fully ported, the "slight" advantage is then gone.

862 heads you ask? If they're CNC ported you could do those too. You'll have similar free drop to the heads you currently have, but chambers will be smaller requiring less head milling which would reduce piston-to-valve clearance.

Ben T.

 

What he's saying is that an 853 head is sand cast and that a 241 head is a semi-permanent mold cast.

So you would have slightly better performance out of a 241 head stock as opposed to stock 853 head. Because the insides of an 853 head would be rougher due to using the sand casting technique.

Now if you were to port either head it wouldn’t matter which one you used because, due to the porting all the roughness in an 853 head would be gone.

So if you can find some 853 heads cheaper than 241 heads and you’re going to port them, just get the 853’s and save yourself some money.

 

Bingo.

Ben T.