I have an opportunity to pick up a brand new in the box set of Edelbrock heads, part number 60929, which are the 84CC heads for a very reasonable price. I am likely not going to touch my shortblock as it ran fine prior to my restoration and was rebuilt by a shop about 5 years prior to pulling it off the road. The motor was built to stock specs for a 69/70 six pack engine, pistons, rods, etc. Here is my question, I dont really know the actual compression ratio, but since it was built to stock specs, Im assuming its stock so Im wondering if this is the appropriate head for this motor, or should I be looking for a different CC head? I know Im giving sort of vague information, but I never calculated the compression ratio..Thoughts anyone?

The Edelbrock heads may increase your CR by about 1/2 a point. Not a problem since the more efficient chambers will have actual quench. The 1969 Six Pack/6 Barrel had an advertised ratio of 10.5 right? Most people feel that the CR was actually less when you calculate the specs. I have a 440 short block and the pistons sit .017 in the hole with double valve reliefs. A 906 head with 88-90 cc chambers, a .020 steel head gasket and pistons ( with 12ccs of valve reliefs) sitting .017 in the hole puts actual compression in the low 9.2 range anyway.

#1 is will the DCR with those heads/your cam support the fuel you intend to use. KB silvolite has a good easy to use CR calculator for SCR but is reportedly inaccurate for DCR which DCR includes cam timing in the formula but SCR is a good start & I like KB's calculator. Use Wallace racings' calculator for DCR. You'd need to know the deck height in the hole amount #1 to get a close answer and in addition the gasket thickness/piston valve relief CC's to get a dead on accurate number for what you'd end up with.

JUMP on that opportunity. There are only a few reasons not to: 1, You don't like the color of the heads. 2. You don't like the way the ends of the heads look. 3. You don't want a higher performance engine than you already have.

On a more serious note, if the engine isn't pinging with the stock cast iron heads it won't ping with the Edelbrocks. Also, the angled plugs on these heads give some people who run headers fits. And it may be useful to have a cylinder head pro go through the heads to check things like valve stem clearance, although I'm sure there are hundreds that went on the motor right out of the box.

You will, IIRC, need a new set of head bolts because some of the lengths are different. You can use the stock rockers, regardless of what Edelbrock says. You may need to change pushrod length, but I doubt it. Anyway, pushrods are a lot less expensive than rockers!

Good Luck,
R.

If you have zero decked pistons with 4cc valve reliefs, 84cc heads and a .04 in think head gasket you would end up with a compression ratio of 10.34:1. If your pistons have 4 valve reliefs you'll be closer to 10:1. So I say go far it, you should be able to play with head gasket thickness some to get the compression where you want it.

Only problem I see is t hey are ugly, painting them orange helps a little. But for the performance pay off I'd grab them. Then grab a set of 1.6 rollers and let it rip.

Thanks guys, excellent feedback and information, much appreciated. I do remember the pistons having 4 valve reliefs in them and only time it pinged is when I had crappy gas in it with the iron heads which were late 90's Muscle motors street killer heads. I had no problem when using Sunoco 94 (that was when it was running last though) I was already running Hughes 1.6 roller rockers so they will be going right back in. Hopefully the plug angles will be ok with my CPPA/TTI 2" headers.

I really want these heads, Im not worried about the look of them, I went a different direction with this car then before it was restored, it used to have manual everything, glass hood, no swaybar, etc, now its going back together with AC, power brakes/steering so the reduced weight of the heads should help me a bit. The car was low 12's at the track with 4:10s and an Auto, I now have a 4 speed and 3:54 rear and will be keeping the same cam, six pack carbs and not touching the shortblock so Im hoping the performance will still be at least in the 12's despite me adding hundreds of pounds with the steel hood, power steering, etc.

the spark plugs clear the 2" tti headers quit nicely on my set up; actually better than stock iron heads.

yes, they are butt ugly.

as far as power increase goes; they are only as better as the old heads are bad. in my case I consider them a power loss.

I think some of the hype surrounding the the edelbrock rpm heads may be exaggerated. I don't consider the ones have as anything marvelous.

You need to get out more often. Mopar engines were listed at one compression ratio, but were actually BUILT with a compression ratio around one whole point less. The six pack engine calculates out at about 9.25:1 using an actual cylinder head volume of 93cc.

R.

That engine does not need 2" headers.With the drop in gear ratio it is more likely to be less snappy at pert throttle(At least that was my experience anyway).Not saying you should change them as it will still be a heckuva motor and fun!Just an observation.1 7/8 were where mine was happy for part throttle and mid range at anything less than full throttle.

Heads?ABSOLUTELY!!

Have the heads cleaned up by a competent machine shop. The valve job OOTB is marginal at best. A good multi angle valve job will get you a few/several extra CFM. Check and correct guide clearance and chamber CC's.

Kevin