View Full Version : Cylinder Head Surface Finish?


Deeavi
11-01-2007, 08:14 AM
What is the proper finish of the Aluminum cylinder head surface? The Patriot Performance LQ9 heads that I bought and put on my L92 short block have a real smooth finish, almost mirror like? I always thought that they should have a little rougher finish to seal properly, but I put them on as they were

The reason I am asking is my tuner says that I may be losing compression when my engine gets hot. I have the new FelPro head gaskets and the car runs decent, but it does not make good wot power. After I put the FAST 90/90 combo on, the car lost power. It went from 450 rwhp/470rwt to 420/440. The power really drops after 5,000 rpm. I am going to pull the heads and have them resurfaced. I am also going to change the cam to one that Patrick G recommended, but right now I am frustrated!

Anyone else ever have a similar problem?

Deeavi
11-01-2007, 08:40 AM
I just found an answer here: http://www.aa1car.com/library/ar996.htm

I guess I won't know unless I pull the heads and check them?

KCS
11-01-2007, 10:52 AM
What is the proper finish of the Aluminum cylinder head surface? The Patriot Performance LQ9 heads that I bought and put on my L92 short block have a real smooth finish, almost mirror like? I always thought that they should have a little rougher finish to seal properly, but I put them on as they were

The reason I am asking is my tuner says that I may be losing compression when my engine gets hot. I have the new FelPro head gaskets and the car runs decent, but it does not make good wot power. After I put the FAST 90/90 combo on, the car lost power. It went from 450 rwhp/470rwt to 420/440. The power really drops after 5,000 rpm. I am going to pull the heads and have them resurfaced. I am also going to change the cam to one that Patrick G recommended, but right now I am frustrated!

Anyone else ever have a similar problem?
Take the FAST 90/90 off and see if you pick that power back up. If you do too many changes at once, it's hard to pinpoint whats hurting and whats helping.

With the LQ9 heads, whats your compression ratio at? What size chambers did ya get?

Deeavi
11-01-2007, 01:52 PM
Take the FAST 90/90 off and see if you pick that power back up. If you do too many changes at once, it's hard to pinpoint whats hurting and whats helping.

With the LQ9 heads, whats your compression ratio at? What size chambers did ya get?

Most of my stats are in my signature!

compression should be 10.8 to 1. 72cc Combustion Chambers, 0 Piston Deck Height. .053" thick 4.1" bore head gaskets. This engine should be making close to 500 rwhp. I think the cam is hurting it now, but I am not going back. The FAST 90/90 stays. Besides, I don't have anyhing to go back too. Sold my old stuff to help pay for the new.

Beaflag VonRathburg
11-01-2007, 07:54 PM
Why such the low compression? You might have not installed the fast correctly and have a leak.