CID heads, chambers hit pistons
 

Ok, so as many on here know I had a set of CID heads that had Greg Goods Small chamber program on them. Well once I got the car fired up and went to back out of my garage I heard a weird “knocking” sound. Immediately thought great, bottom end is toast. Pull it back into the garage and get out to listen to where it’s coming from and notice that it’s coming from the top end. So I shut the car off, pull the valve covers and everything checked out there. So I figured I’m already here, might as well just pull the plugs and put a camera in there and saw that the dome on the piston looked odd in one spot. So I pull the heads and to my surprise the pistons were hitting the chambers. It wasn’t much, but it was enough to hear. I ended up sending them out to my good buddy at CTporting since he offered to fix them for me. At that time he had his own port program for CID heads, so I decided to sell the ones I had once he fixed them after seeing the work and flow numbers with a smaller port. Also wanted to spend money with a friends business. Received the heads and just waiting on my exhaust valves from him(we ended up doing a 55* seat on the exhaust side)they were in a separate box and forgot to send them. But he did his SBE program on them and made sure to clearance the chambers enough for me to be able to run the .028 gasket. So if anybody is doing a big N/A build and milling quite a bit and running a .028 or .040 headgasket, double check the clearance even if you check the first time. But needless to say I’m pretty happy with how they turned out and ready to get them bolted on and run/drive the car.

referring to "old" heads

quench was a little tight, eh. was that the cid small chamber option i read about on their website? how much did you mill the cyl heads?

I think pray did a psa on this last week

When we checked before dropping it down in he car all looked to be fine as far as quench goes with the old heads. But yes it was the Greg Good Small Chamber program and they were only milled.030 at the time. The new ones are milled .060.

Yea, I actually talked with him about mine. I figured I would make a post here for the ones who don’t do Facebook as well

Ah nice. The timing makes more sense now
Facebook sucks

Even with undecked GM heads, you are likely to hit the head with a .028 head gasket. I would advise running a minimum of .040 quench or else you will run into the same issues.

A .028 inch gasket will still have contact on undecked GM heads? Hmmm...guess I need to order the .040's...thanks, Katech!

I’ve ran .028 gasket on multiple different SBE 6th gens with milled stock heads and didn’t hit. The factory piston sits down in the hole at TDC(at least all of the ones I’ve done do). With a drop in rod/piston(even any other aftermarket rod/piston setup) setup I could see the potential for pistons hitting the chambers while running a .028 gasket with an unmilled factory head. Only time I’ve ever seen it happen SBE while running a .028 gasket with the factory head is when you get aggressive with the milling on them.

I’ve seen CID heads hit just like mine with a .040 gasket as well. I’ve got mine bolted down with a .028 gasket since the post was made. I honestly don’t see it being an issue anymore. Plenty of guys out there running the .028 gasket like myself after having the chambers worked on and having no issues, Brandon Hill being one of them.

Quench is as outdated as a 23 degree small block Chevy.

What

It looks like I had 0.079-0.065 in in that area on mine, I think the spark plug quench/squish pad thing comes into contact there looking at the impression in the clay, I just can't remember which side its on on the GEN V combustion chambers?:

Attachment 1103953

Attachment 1103954

I have stock heads with a supposedly 0.015 in mill and I am running 0.028 Cometic head gaskets with a 226/238 .635/.630 114 Cam Motion cam.

What do you think your compression is at now? I calculate mine at about 12.95:1, I wish I was at 14 or 15:1, I run E85 100% of the time. I really haven't even tried to run 93 and see if it runs without knock.

Looks like I measured the quench at about 0.010 using the clay, which is a little difficult but should be accurate just by resting the caliper/depth gauge on the top of the clay and then smashing it into the clay until it hits metal.

I really want to cut reliefs in my piston and go with a bigger cam and maybe sacrifice some low end with a wider LSA to help balance out the idle and get a higher stall. Looks like I had about between 0.072 and 0.062 in for PTV for the exhaust valve.

I assume the discrepancy in quench between the top and bottom of the piston (0.010 and 0.022) is mostly due to the piston rocking in the bore, although that would be a pretty big rock?

Running super tight quench on most of the modern engine is not only pointless it can also lead to some serious failures. 30-40 years ago when dealing with SBC’s and especially BBC’s you had to deal with it and manage it to make compression because typically a 11.5:1 or 12:1 setup would require a massive dome on the piston so to try and cut back on some of that you ran it tight just to make compression. The bigger the dome the harder it was to get the flame front around the piston and clean burn. Modern engines with way smaller chambers don’t require such a thing and you can run a more normal head gasket, smaller valve reliefs in the piston and less of a risk of damage from either the head and piston hitting or bending a rod from hydro locking on high volume fuels (E85 or meth injected setups).

So unless it just has to be done, running a super thin gasket for “quench” is pointless.

My compression is 14.5:1. I’ve got .180 flycuts. But I’ve ran 13:1 setups on 93 without any knock. Just depends on the tuner and how well they can tune.