[Thumpin455_GTO]

Have a set of JBP ported 670s and either a 455 or a 400 I would like to run them on with pump gas around 89 octane. Last time I ran them on a 400 and pump gas I lost all the upper rod bearings. I want to open the chambers to lower the static CR to run cheap gas and maybe not need 40 degrees total timing for max power.

How far can you go before you find water? Anyone have a template or information with pics of where you can safely remove metal from? right now they are disassembled so nows the time to open the chambers...

I know I could go E85, but that isnt available up here quite yet.. hopefully next year and I can dig out the 13,12, and other set of 670s I been hoarding..

[BILTIT]

A search should find some pics i posted of my chambers, i will try to find them.

Here it is:

http://forums.maxperformanceinc.com/...d.php?t=499475

I don't think you can run them with 87 gas even when opened (although i did run them on a 400 with 91 gas but had the RAIV cam to help, kept timing to 32 degrees and carb alittle rich). Mine only gained 3-4cc being opened up. Might wanna dish the piston alittle, i have a 30cc dish for 9.5:1 in a 455.

[janderson]

You may want to contact Mr. P-Body on this forum, Jim is a machinist and has done some interesting mod's on the 670 chambers to open them up.

[tc]

I cnc'd mine. Went fron 67cc's to 79cc's, but I took some off the floor because the valves were sunk. I can get some dimensions from the program. Also, a dish shape on the piston, of the new chamber shape would be slick.

You would probably need close to 13 to 1 for a high performance engine with E85. Gas milage would be worse, but the gas is cheaper.

[Thumpin455_GTO]

I could yank the TRWs in the 400 chuck them in a lathe and hog out a dish the easy way. It wont be a race machine, just a fun toy for the summer. Since the 455 has Ross slugs and eagle 6.8s in it, I think it will get some KRE heads instead. If I dont get that set of HOs that were offered in the sleeper thread. Have time to mess with it, since the snow wont be gone untill May.

Just thinking I could do something with them while I cant do anything else with them.. lol

[*67firebird*]

TC, is that a 670 head?

Did you just take metal off from the inside of the chamber?
Can one make the chamber bigger via scraping the walls? Or will it just screw up the head?
What i mean by that is : could i just take some metal off of the walls of the chamber? or is there a certain shape it needs to retain? not that im going to do this, but if i wanted to could i just shave some metal off of the chamber? and smoothen it out? or is it much more complicated than that? Hope this make sense. Osvaldo

[GRX]

Originally Posted by tc

I cnc'd mine. Went fron 67cc's to 79cc's, but I took some off the floor because the valves were sunk. I can get some dimensions from the program. Also, a dish shape on the piston, of the new chamber shape would be slick.

You would probably need close to 13 to 1 for a high performance engine with E85. Gas milage would be worse, but the gas is cheaper.

Looks like nice work. I know why the chambers are modded, but are the ports in the 670s that much better to warrent the extra work involved?

Not to derail this thread. What I would like to discussed is why the eyebrows on the cylinders are at a different location on factory equipped 670 blocks as opposed to all others from '68 up. And how that can effect valve shrouding when 670 are used on later blocks.

[242177P]

Originally Posted by GRX

What I would like to discussed is why the eyebrows on the cylinders are at a different location on factory equipped 670 blocks as opposed to all others from '68 up.

Pete McCarthy said it was a mistake. Valve inclination angle changed that year, maybe somebody missed it??

[tc]

67firebird. Yes those are 670 heads. I needed more cc's. After looking at alum heads, I figured it must not make a huge difference in what shape to make these. I did put some thought into, though. Even the 061's are very different and some say they work great.

GRX. These heads were sitting for 20+ years, I did not want to spend any money on another set and I have read that they are the best low lift flowing D-port. I ported these using Pete M's video. A 1.72 shaping valve, which is 1.58 window width. Quite a bit smaller than Jim H's 1.69 dimension at the short turn. The flowed 164@.200,214@.300, 240@.400,250@.500. So yes, I think they were worth the time.

[GRX]

Yeah, I can understand that TC. No need to buy more heads when you can machine the chambers yourself. Wish I had a brideport in my garage. Maybe someday.

What I was thinking is that many seem to buy 670s then mod the chamber.

[GRX]

Originally Posted by 242177P

Pete McCarthy said it was a mistake. Valve inclination angle changed that year, maybe somebody missed it??

Very interesting. Kind of makes sense since the 400HO that the 670 came on were early in 67, if my memory serves anyway. Which brings one to wonder if the 67 400HO was running to peak efficiency with the eyebrows like that.

Also, at one time I had considered that the eyebrows were that way since the 67 heads are unique in that they have the exhaust passage across the outside of the head like the 389. My thinking was that changed the valve position in relation to the cylinder. But that doesn't seem right when you look and measure the heads compared to later styles.

All points to ponder.

[tc]

GRX, one more thing about the 670 heads, the roof is about 1/16 taller than other d-ports.

[GRX]

Originally Posted by tc

GRX, one more thing about the 670 heads, the roof is about 1/16 taller than other d-ports.

Yes I know. The 061s are that way too unless mistaken. The 061s do have the nice shallow open combustion chamber much like the RA4 heads.