It looks like finding a good ring pack for the stock 4.46 bore is a pita, so may as well punch it out to 4.5 bore, and my biggest question is upping my CR a good idea for 91 pump gas? I’m switching out the ZZ502 cam for the 168731 can which should bleed off a little more pressure, and SRP makes a -10cc piston that was made for the Edelbrock heads. It looks even if I deck the block .010 I should be at 10.25:1 at most, and that’s not including the bore notching and the fact that the Edelbrock heads tend to measure out closer 113cc according to the internet. Thoughts?

stock GM 4bolt 9.8 block
edelbrock Rpm Performer oval heads (advertised 110cc chambers)
Victor Jr intake
QF850m carb
Crane 731 cam
SRP pistons w/moly too ring
https://www.summitracing.com/parts/srp-212161-8

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Bore notch is about 1 cc give or take. I'm on way out the door but shouldn't you have not used -neg for piston volume. Just put in 10?

If you can find the cam card valve (timing events) for the zz cam post it. Also I may have mis read your first post with your piston being dome or dish. I can ck comp calculator also when I get back.

The Summit calc considers the area displaced by the dome, so a dish would be a + number. The stock piston a 1cc done and the replacements that I’m looking at are 10cc domes.

Adding a cc for the bore notch and the .051 brings it down to a fair enough level. What is a general rule of thumb for the highest CR that you’d be comfortable with on a N/A engine w/Al heads?
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Looking through the old threads of the same question it looks to be prudent to keep it 9.8:1 and 34* max timing.

I get where your at now just most piston manufacturers consider domes a +cc so in original post I assumed dish. No biggy. What is the part number on your heads? #60479? Also you are you leaving heads untouched. A little work on those would make your engine happy and would increase CC's if you did some chamber work and a little unshrouding. GM oval ports flow similar with not a lot of effort with 2.19/1.88 valves. Regardless your gonna have a nice reliable build.

Some good points.

i did a little reading on that also.

Be sure to match and intake to heads. Depends on what gaskets you have whether to gasket match or not. Also blend back a good 1/2-3/4". Over the years I've seen a lot of so called gasket matching and is completely pointless. I like to use cardboard for reference btwn intake and heads. Just bolt down and remove. Open and closed chamber is basically what it says. Years ago prior to octane concerns I do believe many heads were closed chamber. Open chamber just came into place to lower compression ratio. There can be benefits to both. There is power to be made or lost with chamber work. You can spend a lot of time and gain nothing if your not familiar with porting heads. Might be worth sending them off to a recommended head porter unless you just plan to do a little polishing and blending.

Look ok on the net for pics of open chamber and closed chamber heads. Closed can come in handy so you don't have to run big domes. All depends on what the build is for. As far as I'm concerned a flat top piston is ideal but I won't go into that however I think most outdated agree for the same reason. The explosion that takes place so to speak is more equal across the piston top and helps eliminating piston rock etc. But im by no means I'm no expert rather just years of experience.

hope I explained that ok in a way that made sense. Lol...

Btw those flow numbers are better than the ones I looked at. I apologize for that. I must have looked at a different eddy head. Might have been sbc? Not sure.

I see what snap is saying however I'd be getting after that intake big time. You can actually loose some velocity. Look at it like a funnel effect. It will be fine as is just power to be made. Been down that road. Many intakes are manufactured to be ported to match up to heads rather the other way around. I use to play around with a lot of that stuff and even ran an rec port intake up against raised dart floors. That's a whole other story but anyway will gain power opening up the intake ports. That can actually be an easy 35-50 hp gain depending on build. I wouldn't say it i didn't see it on the dyno. Just an FYI.

You Tube

Not always. Depends on build. I've seen it on the flow bench and dyno both. Along with actual boat speed and rpm. Good example and test was 5/16" raised floor dart rec port heads done by Valako in 89 as well as intake. Intake manifold floors raised to to match. Engine made great power. Removed the expoxy from intake as I was having another one done by Jim and prior to being complete I put the other on with NO raised floors to get by for a weekend and made ZERO difference in boat speed and rpm. We called it the tumble effect. Air tumbling into intake port perhaps even helping fuel atomization.
Who knows but it's been done as well by others with using a rec port intake manifold bolted up to oval port heads.

never tried an oval port intake with rec port heads. Although i have witnessed 502/540 builds ported by Jim and dynoed with stock dart intake and were no happy with the dyno results as customer didn't want to spend the extra money on intake work. To make a long story short after getting port matching along with other manifold work there was a 55-57 hp gain. True story.
Its amazing how far off out of the box dart heads can be off with out of the box dart intake. I've seen a port here or there with one side or the other being off up .060.

So not always is very true statement.

I did it once, not sure how it affected power but the intake would condensate a ton near the plenum on the outside so I’m guessing there was quite a bit of air speed.