Doing some calculations on the compression ratio of what I have with FLOTEK Small Block Chevy Cylinder Heads 102-505FT I get the following results.
Cylinder diameter 4.030"
Stroke 3.480"
Cylinder Displacement 727.4cc
Deck 0.025"
Deck Volume 5.2cc
Cylinder Head Chamber 64cc

Using a Fel-Pro Performance Head Gaskets 1003 with a 4.166 in. Bore, .041 in. Compressed Thickness
Gasket Volume 9.16cc
Compressed Volume 84.38cc
Compression Ratio 9.62:1

Using a Fel-Pro Head Gaskets 7733 PT-2 with a 4.125 in. Bore, .039 in. Compressed Thickness
Gasket Volume 9.16cc
Compressed Volume 84.38cc
Compression Ratio 9.68:1

There seems to be a lot of head gaskets to choose from, is there some way to know what to pick?

It looks like the above setup would need to run 91 octane which is not a problem.

If the cast iron 76cc heads are OK then that will give me 8.59:1 compression ratio.

JT

 

I finally uncovered the casting number of the block and it's 1410207 which is the correct casting number for the 82 C3.

JT

 

Reading your initial post, Compression is fine. Don't think your motor is bad. I would have looked at valve seals, weak ignition and carb being too rich. But I can see you are knee deep in engine overhaul. Good luck with the rebuild!

 

I don't think the lower end needs anything but cleaning up and new seals and gaskets but that's easier to do outside the car. I've replaced all the components on the HEI distributor as well as wires and plugs and have a new Holley 600 carburetor. While I could have checked and replaced the valve seals in the car it's a whole lot easier to do on the bench. If the valve guides are OK then I'll replace the seals and put the heads back on the block.

I was really surprised at the compression test numbers... that made me feel a whole lot better about this motor.

Also I have some Bubba items to correct in the engine bay that just can't be done with the engine in the car so I'll kill a few birds with one engine hoist

JT

 

JT
Previously you told us how, at TDC, you'd measured how far Your pistons are below deck. You wrote 0.025". That's a fair and reasonable number. When OE, they should also be 0.025". We also know Your pistons have been replaced by 4VR flattops And that you've measured those to be 0.025" down in the hole at TDC.

When you add 0.025 + 0.039 or 0.041 that'll yield a Quench Height about 0.064" to 0.066" --- that's too much, that's garbage and will yield little if any quench effect benefit.

if IF block's decks AND heads' surfaces are reasonably straight, true, level , smooth and not corroded/eroded/gouged, they can accept and be sealed by thin, embossed-bead, shim steel gaskets (typically about 0.015" thick (when compressed).

two common examples from Fel-Pro are: P/N 7733SH1 (uncoated) OR P/N 1094 (already coated). Both have volume approx 3.245cc. I've run countless numbers of these or equivalent. Very affordable as well.

combine your 0.025" below deck with shim gasket's 0.015" yield a very good and effective Quench Height = 0.040"

One of the most notable benefits of a good quench is its known ability to reliably dampen spark rattle in motors with otherwise too-high compression. May seem counter-intuitive but it is so.

I see under 10:1 w/ shims and your OE iron heads. That's where I'd be looking to end up. Many OE sbc did have OE thin steel shim gaskets.

There are affordable composite gaskets in the compressed 0.028" range as well. But .028 + .025 still too tall; will not yield much if any quench benefit.
Mahle-Clevite aka Victor P/N 5746
GM P/N 10105117
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OTOH, if you insist on 64cc chambers, Perhaps it might be practical to deck Your block an appropriate amount to accommodate one of the composite gaskets thicknesses; while yielding a nominal quench height 0.035" to 0.040" ?
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don't poo poo quench; it can be an important benefit.

and, lots of SELLERS listings of gaskets display incorrect thicknesses / volumes. Suggest Verify direct w/ manufacturers tech lines. T shirts. It pays dividends to get this right, it'll cost ya otherwise.

 

One thing on the HEI, get a GM module , even if it's a used one out of a junkyard, they are better than the new chinese junk. A new GM HEI module might be hard to come by.

 

Here's another clue to the engine, I changed the oil but have only idled the engine a few times and when I drained the oil out it was black like it was old oil. I really expected the oil to look new when I drained it... any thoughts on this?

JT

 

Got the bolts out of the flex plate and it took a 1/2" breaker bar to break them loose... after I got the first one out I could see why, the holes are no longer round. Adding a flex plate to the list.

JT

 

Suggest Expedite sample of that ugly oil to blackstone lab or equivalent. Local CAT dealer may have an alternate route.

Any crack(s) in that flexplate ? suggest fresh fp bolts as well.

 

With modern chamber aluminum heads I would use steel .15 shim gaskets (I did actually with the same pistons and 66cc (64 advertised) heads and a .24 deck height ) to get your quench down to a smaller number which will allow to to run 89 without any detonation issues.

 

I didn't see any cracks but didn't look for any either.

I may have contaminated the oil but that's a good idea to send a sample to Blackstone.

JT

 

You may have had a bad experience ( have yet to actually find any threads with data on these failures here but lots of warning to stay away because they are cheap and chinese) Maybe you can share what was wrong with the unit you had issues with to help the rest of us understand what to look for?

Theres a lot of us who stabbed a $50 HEI off amazon or ebay in and had zero issues also. I needed the tach drive and replaced my points distributor when I swapped engine 14 years ago. I did tune the curve by changing the springs and adjusting the vac can but you want to do that with a stock hei as well. I pulled the hei to put a melonized gear a few years back when I swapped in a comp roller cam and there was no additional play or wear issues I did a little research and found there are at least 2 different chinese manufacturers selling online and they sell the same units as summit and jegs brand and others. I have a new accel non tach drive HEI and thats also a generic chinese clone just branded and sold by Holley/ accel. Again Im not stating these are all fine with no issues but I did look for more data and searched this forum as well as other hot rod forums and found all but one of the mentions of issues I read about were anecdotal third party or from folks who had no idea how to change springs or weights or adjust the allen screw in the vac can to make the curve work with their engine configuration. these arent a bolt on and go with best results thing.

The one thread I did find with actual first hand reports of issues from chinese HEIs was from a guy who had a side business rebuilding OEM heis so theres kinda a bias and conflict of interest when they were costing him business.

Im no crusader for chinese good but I Do like to research and know when I do buy something due to budget if its actually poor quality and /or if its the same stuff being rebranded and sold under the big performance part brand umbrellas for much more $$ So often with car parts its all about the marketing and not so much who and where its made anymore. case in point are the head castings... Many are chinese now and the same castings are rebranded and sold at drastically different prices. cam shafts and lifters are another area where only a few manufacturers make and sell to all the other brands (if those brands arent already a sister company like edelbrock/comp/lunati and the like.)

 

I'll have to see what I have to work with when I get the short block out, still need to check the heads to see what they are like.

But gotta design and make an engine leveler... most of the design work is done in my head so it won't take me long to do a 3-D model of it in SolidWorks.

JT

 

My experience with Blackstone labs was water contamination hoist oil from a machine with water in the hydraulic system. The hoist oil looked like a milkshake. The results came back good with no mention of contamination. Go figure?

 

I did manage to remove the springs from the #7 exhaust valve and the valve guide is good, I didn't have time to put my test indicator on it but I could not feel any movement at all.

JT

 

Just put your finger over the valve guide as your pulling the valve out. If it has suction it's good.

 

Now for the other 15
Was the spring assembly comprised of a single (round cross-section) wire-wound coil + an inner damper made of thin flat steel ?
Was the square-sided rubber O-ring (stem seal) in place (groove just below key groove) And Viable ?

 

I got my best test indicator out and the valve guide has 0.002" clearance and the service limit is 0.0037".

Yes, that accurately describes the spring.



The square O-ring looked OK but the seal was loose on the valve stem.



JT

 

Those black umbrellas are aftermarket seals added later during service.

 

Something didn't seem correct so I read the service manual again and sure enough I measured the clearance the wrong direction. Measuring from the side the clearance is 0.0032" so that's close enough to the service limit of 0.0037" that I'm not wanting to bother with the OEM heads now and just get a set of 64cc aluminum heads.

JT