Why are Fel pro's poor?

I built my engine around a 1mm gasket (felpro) a little while later we had to strip the head off (inducted a rivet from the air box into number 6 and bent a valve) I decided to put a 1mm HKS on for a trial and from that moment on had issues of water leaks, poor compression and loss of power. I stripped the head off after a few meets to fit new springs (a set doesn’t last long at 7500 rpm and measured the HKS, using a dial gauge on the valve it was 1.18 mm and using a calliper on the bore yielded 90.5 where as the Felpro was a true 1mm and 88.5 mm bore, all of this equated to about 1.6 cc increase (about .5 of a compression point). Also when we designed the engine, the compression was specified at 11:1 and the squish area was engineered to 48 thou (pistons 8 thou under deck and a gasket of 40 thou or 1mm = 48 thou) altering this with the HKS completely changed the characteristics of the engine.

Whilst we had the HKS on we never achieved better that 13.8 on the quarter (20 runs)

Now we have a fel pro back on, we are back on form again running 13.4 quarters, 4.72 seconds 0-60 and in excess of 250 at the fly with no leaks, plus they are a damn sight cheaper than a steel which is more suited to forced induction or really big compression blocks engines.

Why are Fel pro's poor?

Hard to say for certain. There are plenty of people here and elsewhere who have had, or know someone who has had a bad experience with Fel-pro. But ask around a bit and you can find plenty of people who have NOT had any problems with Fel-pro and continue to use them all the time.

So I don't know. I can't imagine that I will need a steel head gasket for the stock L24 I'm starting to rebuild, so no way I'll pay for an HKS. Will I use Fel-pro? Maybe. Depends on what I can find affordably. I strongly suspect that most any normal gasket will work for my uses, if given proper preparation and installation.

Sorry I missed this thread earlier when the topic of metric conversions and calculations came up but I thought I would point out how useful Google is for things like this. No, I'm not talking about searching for a calculator. I'm talking about using Google as the calculator. Simply go to Google and in the search box type whatever you need. Here are some examples:

.030mm in inches

2+2

70mph in kph

3.5 USD in GBP

150000 JPY in USD