[JoeF]

I haven't seen much info here about 670 heads. Is there a lack of interest in them due to compression issues with pump gas? Anyone have any pros/cons, do's/don'ts or opinions on 670's.

[JoeF]

I haven't seen much info here about 670 heads. Is there a lack of interest in them due to compression issues with pump gas? Anyone have any pros/cons, do's/don'ts or opinions on 670's.

[urhere2]

I hope one of the knowledgable people answer this because I have these on my 400 and was wondering what kind of work I should have done to these, or if I should get different ones when my budget allows.

[Bruce Meyer]

The 670 head came on 67 GTO,s and 400 firebirds and maybe some others. They have big valves and small closed chambers around 72 cc,s. A good head for a 400 if you can stand 10:1 compression. A trick some guys do is open up the chambers to resemble an open chamber head. Drops the compression and improves breathing.

[b-man]

The 670 is an excellent head, as long as you use a dished piston to adjust compression for the fuel you plan to use they are great. Saw a test where the open-chamber mod enhanced flow on the bench but made no real noticeable increase in power, go figure!

Supposed to be one of the best if not THE best flowing head at low valve lifts (under .400") in stock form. I have set I'm saving for a 350 build-up someday, they will be right about 9:1 compression on a 350.

Let's go racing!
www.outlawpontiacs.com/members/B-Man2.php
www.outlawpontiacs.com/members/B-Man.php

[urhere2]

I knew the compression was high because I get a bit of knock under acceleration, even with 93 octane. I tried some octane boost and it still happens. I think I'll have to find a place that sells race gas to take care of it.

BTW, I am looking to change the carb. Would a 750 be enough or should I go with an 800?

[Bruce Meyer]

What kind of carb?

[urhere2]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Bruce Meyer:
What kind of carb?<HR></BLOCKQUOTE>

4-barrel. I'm not sure what brand. Not a Holley.

I've been thinking of the edelbrock for ease-of-use reasons, but if I can ge a properly set up (insert type here) that I can plug and play, it would be just as well. I'm looking to get into the high 12's, if possible, on a budget. I am not good with carb setups so I wanted an expert to do it. I will be redoing the valvetrain as well with a more agressive cam, perhaps a RA IV.

I have an edelbrock performer intake now with a 1411 carb, the current cam is unknown.


BTW, are the studs on the 670 heads screw-in or press-in?

[Bruce Meyer]

Yes the 670 have screw in studs. Cant help you on carb choice since I would recomend a Holley. Block off the heat risers to your manifold and try to run cold air to carb. This will help prevent pinging.

[urhere2]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Bruce Meyer:
Yes the 670 have screw in studs. Cant help you on carb choice since I would recomend a Holley. Block off the heat risers to your manifold and try to run cold air to carb. This will help prevent pinging.<HR></BLOCKQUOTE>


Why would you recomend a Holley? I really haven't made up my mind, I've just heard things about the Holleys leaking.

[budman]

The early, closed combustion chamber is more efficient in power production than the later open chamber heads. Tests done during the 50's show a 5% increase in power from a closed chamber to a fully open chamber. On the other hand, the airflow is enhanced slightly by getting that part of the chamber out of the way. The additional airflow raises the horsepower and the net result is pretty much a draw. The reason for the change in shape was mostly for pollution considerations. If you look at the aftermarket race heads, you find that they are produced with the minimal combustion chamber philosophy.

[Bruce Meyer]

urhere2- The main reason I like Holleys is their ease of tunning. The double pumpers that is. I dont like their vacume sec. carbs. To get in the 12,s with a 400 w/RA4 cam will take some tuning.

[herdsman]

Joe, I have a set of 1967, 428, 670 heads on a .030 over 400 with TRW forged flat top pistons 9.78cr. I use 93 unleaded gas with no problems. In my 65 GTO it runs 11.73 @ 117. The 400 heads are 72cc the 428 heads are 75cc.

Man, I'm pretty! WHOA MAMA!

[JoeF]

Herdsman,
Unfortuately, I don't have too many specifics on my CR since the engine rebuild was done by the prior owner. With 93 pump gas, I haven't had any pinging under load. I had a short spell of run-on which seemed to go away with the next tank of gas. Cam was described to me as a Ram Air III so I assume it's a 068 or 744 (not sure how I can tell without a tear down). Timing is set at 10 initial and I have yet to spec out the rest of the curve. Based on that I'm assuming that the pistons are dished. Factory advertised CR for the motor is 10.75 which makes me believe I'd be having problems if there weren't some sort of dish on the pistons.

[KK]

670 heads have a closed chamber design and behave differently than open chamber design heads. They generally require more timing than open chamber. I wouldn't be afraid to run them on a 400 with pump gas and performance cam. 455 would require some blend of fuel or race gas. Polishing the combustion chambers goes a long way to prevent detonation. 670's have a really good short turn radius and combine that with a little porting and you can make decent power.

[Skip Fix]

Just open them up to look like a Fast Burn chamber! Should drop the compression down some.

[Z Code 400]

The Keith Black KB346 is said to yield 9.6:1 compression with a 71cc head...Robert

http://www.kb-silvolite.com/kbpontiacpg.htm

[Black 65 GTO]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Lorin Budzinski:
The early, closed combustion chamber is more efficient in power production than the later open chamber heads. Tests done during the 50's show a 5% increase in power from a closed chamber to a fully open chamber. On the other hand, the airflow is enhanced slightly by getting that part of the chamber out of the way. The additional airflow raises the horsepower and the net result is pretty much a draw. The reason for the change in shape was mostly for pollution considerations. If you look at the aftermarket race heads, you find that they are produced with the minimal combustion chamber philosophy.<HR></BLOCKQUOTE>

I agree with Lorin's post!

With the closed chamber cylinder head, you have a much larger quench area than an open chamber head. When the air/fuel mixture is compressed with a closed chamber head, the air/fuel mixture becomes much more turbulent. The more turbulent the mixture, the quicker and more efficient the air/fuel mixture will burn.

An engine set up properly (Zero Deck) with closed chamber heads and all other parameters equal, will require LESS ignition lead than an open chamber head.

An added bonus! Closed chamber heads, again with a zero deck, are also more knock resistant than an open chamber head.

Lorin is also correct about the open chamber head and emmisions control. You will notice that all American V8's began to use open chamber heads starting in about 1968. The same approximate time that Federal Smog Laws were being put into place.

I also would not modify the factory 670 chamber. It is an efficient combustion chamber. By changing the shape, you also alter the mixture swirl patterns. Without extensive dyno testing, I personally would not touch the chambers.

If you want to lower compression, properly dish the pistons.

[img]http://groups.msn.com/_Secure/0PAAAABsTshS*JL3aL9Lt3DTWpiaZQYuTwADv04vUiCSGPh1UW kUzJcyoBHF!u5vkOCDRCP1bN46o1zkzqk3S2WcjuGbw2xV8/Black-65-2-1.JPG[/img]

[Skip Fix]

In a Hot Rod build up a few years ago Ken Crocie opened up some 670s kind of like I'm talking about. Dave Bisshop of SD performance said he has some also just partially opened up and they make good hp and take less timing than most other heads. Even most current designed small chamber quench/fast burn heads havc alot more unshrouding around the intake than the 670s do.

[dlw6767]

i hear a lot of good things about these heads. how come nobody wanted this set i have for 200.00?,,its ok though ,i put them in ebay,in less then 24 hrs they are at 267.00 with 6 days to go..

GTOCRAZY67.....ALWAYS LOOKIN FOR A GREEN LIGHT..