I see Pro Comp heads advertised with 69cc combustion chambers. They're calling it a 403 head. Has anyone measured one of these heads for accuracy?

 

Yes, I measured one set and they were 74cc iirc. Others have commented on the same.
In addition their springs suck, I’d replace them asap.

 

Holy hell, I believe the other guy on here that measured them found 71 or 72cc. That isn't great but 74 is 5cc larger, really will throw off your actual compression. They charge $200 for that milling service. They must base it off 77cc, probably remove somewhere around 10cc. Mark and others have measured the heads stock and found the stock Procomp at 81+cc. Why Speedmaster advertises 77 and it is actually about the same as the stock BBO head, is beyond me.

 

Its because its a Chinese manufacturer, and they stole the design from Edelbrock(after Edelbrock didnt renew the patent because they upgraded their design to version II, then III). they arent measuring anything, just assuming Edelbrocks numbers are the same as theirs.

 

Yeah, it's a shame. If old Junior actually measured them like his Chinese manufacturers, I would want a set. A set that were actually 69cc for only $250 over what Jegs charges would be a deal. Alas like most things, it is too good to be true.

 

Junior has no machinery, he doesnt re-box anything, just ships it out of his garage exactly as he receives it. No inspection, no quality control. He learned a lot from Lyn, buy junk, mark it up, re-sell, and give ypur customer a hard time if they complain

 

In addition he advertises, “call for tech help”. I’m not sure he’s ever even changed the spark plug in his lawnmower.

 

🤣🤣.
I think he should stick to his other job, selling BBQ grilles

 

I’ll cc a set for free , all 8 chambers if someone needs them done. they’ll be done correct and I’ll post the findings here.

I have a set of their bigger chamber heads coming next week. I’ll do them and post what I find.

since we can’t get a straight answer on ether version.

 

can you post the pro comp link to the heads? not the link from Rocketparts.

 

Everything currently listed on the Speedmaster site says 77cc's

Speedmaster Oldsmobile Heads.

 

They’ve always advertised them as 77cc’s.
You can measure the head thickness from the surface to the valve cover rail to get a baseline, and they’re fairly consistent there.
My bet is if Jr is cutting them to a certain distance, he’s not taking into account that they’re not 77 to begin with. I’ve seen them as high as 83 right out of the box.

 

That makes sense to me as well. Oh, they are 77cc, minus 8cc would equal 75cc, dam close to the set Mark measured. Their was a set measured was 71 and 72cc. Probably on the lower side of what has been found on these heads, say 81cc. Yes, Dale measure them. If old Junior actually measured the heads before him sent them off, these would be a good alternative, only $250 more than a single Edelbrock head, for a pair. As Mark pointed out, the cost of new valve springs at minimum on top of that. If Edelbrock releases their SBO head, it will be a great but will be $1000 more.