Thinking about Doing Up Iron Heads

I know some people have issues with the Eddys and 3/8 pushrods, more so when running 1.6:1 rockers. You might make it with 1.5:1. Maybe not. I just apply Murphy's Law with my own stuff and assume either would need clearancing. I can tell you that you will definitely need to clearance the Stealths from my own experience with 3/8 pushrods.

I believe the EZs are a great bang for the buck aluminum head, they just happen to be the more bucks than RPMs/Stealths. You may lose a little bit of low end, particularly with a smaller cam. They also appear to have a more modern closed chamber than the Eddys/Stealths, which are more similar to a 915 closed chamber. However I have never had a set of EZs in my hands.

And yes, there are a lot of hidden expenses associated with aluminum heads. No one mentions these when spending your money and advising the the cost difference of aluminum vs iron is so close that you are money ahead buying aluminum heads. It can snowball easily. If you don't have rockers yet and intend to buy a set of roller rockers don't overlook a set of Victors either. Hughes offset rockers are literally 5 dollars more for the offset kit, and apparently they're decent quality.

Dawyne Porter may be a good guy to talk to also.

Hey 67satty, I run Eddy RPM's on my 512 and have 0 issues with clearance with 3/8" pushrods and 1.5 adjustable rockers. Eddy claims up to .600 lift with the assembled RPM performer heads, but I still changed to COMP locks and retainers. Springs checked out good at the head shop, while they were getting ported, and i've had no issue running my .520/.540 lift cam.

I run 632HP/696TQ with these heads and could easily jump that up with a different cam type/selection, harder springs or slapping on a single plane intake.


Hope it helps..

67Satty said:

Another question I have on the subject of how much work needs to be done to the "bolt on" aluminum heads before you can bolt them on, I was reading about a guy on another forum who flowed all the different intake ports on his new RPMs and found one that was at 257 cfm vs. the 290 or so cfm on all the others. So then he had to straighten that out. IQ52, maybe you can answer this, how common is that kind of problem on the RPMs?

I starting to seem like the price difference between these fully checked out 906s I can get done and fully checked out aluminum heads might be more like $750-$1000.

I've heard of people buying Indy EZs all done up and gone over by an Indy dealer/head porter for just a few hundred more than the $1600 RPMs. If that's the case, then maybe the EZs are the best bang for the buck with the most potential for future upgrades?

Just a little leery of the 75cc chamber giving me too high a compression for pump gas and that they might be overkill and/or have poor low lift flow for my cam.

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It's common with all OOTB cylinder heads.

I've tested two sets of CNC'd Indy 440-1 cylinder heads that flow 30 cfm difference in the exhaust and they were always the same two ports in all four heads. You'd think CNC heads would at least be the same, but no.

It takes quite a bit of work to balance the flows in each port.

As far as pushrod clearance, I always recommend you buy a cam that has the lift you need with a 1.5 rocker unless you plan on grinding some clearance for the pushrods. Do this even if you are running stock iron heads because Pop's engine with the 346 heads needed extensive clearancing with the 1.6 rockers and 3/8 pushrods.

Man we gotta get Pop's back on the dyno with the EZ heads and the XE285HL.

To OP, what you are suggesting is not at all crazy. The allure of cheap aluminum heads I believe is far from cheap. You may get lucky and bolt a set on OOTB and have them work, but can you do that with 10 sets of heads? But if you take a set of iron heads and have them worked by a reputable shop you will truly get a set of heads that you can bolt on and go. Even if you don't do any major port work, you will still have a good running street car if you choose the right cam. Remember, the cam's job is to fix an otherwise restrictive port by altering the valve events to more completely fill the cylinders.

You don't HAVE to port the heads if you just want a hot street car. I knew of a 69 RR with a hot 440 that ran low 12's. My buddy was to end up with the engine and when we pulled it out an apart, we were shocked. It was as basic, and in some ways as wrong, as you can get if you were to ask for opinions. Old TRW pop ups (the short dome kind); something like a Crane .520 / 320 cam; Eddy performer intake - and not the RPM type. This was the Performer that you would find on a motorhome or a replacement for stock iron intake. 1-7/8" headers; 750 vac secondary Holley; MSD box with a points type distributor (maybe an old Mallory). And the best part were the heads. Completely untouched 906's - aside from guides and proper springs with good retainers. That's right. Not even pocket ported. I will say it again. This car ran consistent 12.20's with slicks and all was done to the body was a basic removal of seats and stuff. The rear end, which I have to this day, was a Dana 60 with 4.88 gears. Slicks were 10x30's I think.

I will also like to add that I recently received a set of 906 heads done by our very own IQ52. Total price was under $1400.00 and they look fantastic. Big valves and some port work included with flow numbers, springs set for cam, etc... These are for another member's 451 I'm building and when it comes time to bolt on the heads - that is all I will have to do - blow them off and bolt them on. One more benefit of iron heads is you can use a regular head gasket. So if you have a good set of 906 heads that can be saved with basic machine work, I say use them!

Meep-Meep said:

You don't HAVE to port the heads if you just want a hot street car. I knew of a 69 RR with a hot 440 that ran low 12's.

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I hear ya on that. My 452s are unported, just a valve job and my car does 7.90s like clockwork in the 1/8 mile. That would be like 12.20s - 12.50s in the 1/4 according to calculators. I'll find out for sure when I take it to the reopened Fontana later.

But I'm running out of steam around 5,000 and have to short shift it to make it down the track. I'd like to get closer to the mid 7s in the 1/8 or high 11s in the quarter and told myself to stop spending any more money on little things and put that money into a fund for better breathing heads.

Propwash said:

Hey 67satty, I run Eddy RPM's on my 512 and have 0 issues with clearance with 3/8" pushrods and 1.5 adjustable rockers. Eddy claims up to .600 lift with the assembled RPM performer heads, but I still changed to COMP locks and retainers. Springs checked out good at the head shop, while they were getting ported, and i've had no issue running my .520/.540 lift cam.

I run 632HP/696TQ with these heads and could easily jump that up with a different cam type/selection, harder springs or slapping on a single plane intake.


Hope it helps..

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I too have very similar Eddy/RPM's set-up with full roller valve-train/cam & 1.6:1 Crane Super Gold Roller Rockers have no clearance issues at all, it's always a good idea to check anyway....