RPM Manifold Fit out of the box
 

Ken Crocie put me in contact with one of his friends at Edelbrock about the RPM manifold fitment issues I've experienced. I took the opportunity to mention that the RPM has always been too large as delivered and approximately .060" has to be removed to achieve proper port and bolt alignment with the heads. Edelbrock doesn't have any complaints on file, so I contacted Butler for his experience, but he stated that they really haven't noticed alignment problems with the manifold. So his company's experience didn't support my asking for a change in the specs. I was hoping that we might finally have a shot at not having to mill these out of the box, but that is fading away.

So I'm requesting that you to post personal experiences below with your results on the RPM lining up with the heads. If you could limit responses to the RPM it would make for a stronger case. Please post both positive and negative responses for the RPM manifold only on fitment.

I'll include some photos taken over the weekend. First photo is a new RPM manifold from Butler out of the box, new Edelbrock D-port heads, and a stock deck height 455 block and no intake gaskets. Bolt holes align before the .060" gasket, so of course it will be off that amount when the gaskets are in place. So this new manifold will be going in for milling adding another $110 to the final cost of the manifold. The far engine in pic #3 also has an RPM on it and that manifold needed to be milled .060" to align properly.

Never had a problem with any I've used.. I have had the RPM on both milled and un-milled heads. Worked both ways

"... proper port and bolt alignment with the heads."

Presume you mean Edelbrock cylinder heads. In the 1999 Edelbrock instruction sheet it states their Performer RPM cylinder heads are matched in size and operating range with the Edelbrock Performer RPM intake manifold.

I've noted milling the intake in conjunction with their cylinder heads modified with taller ports.


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No, any cylinder head. Just happen to have a set of new Edlebrock round ports and Edelbrock D-ports on hand. I've had the same problem with stock iron heads, but the argument could be made with them that they might have been milled sometime in their life.

Mick,
I'm sure the reason there aren't any reported problems is because the average person will just install the manifold without checking alignment mismatch and not realize the bolts turn hard because they are rubbing. Just my 2¢.

RPM intake in a d port engine, a light surfacing (.005-007) on the engine and head, the intake bolts wouldn’t even thread in.

.040” off the intake manifold surface to make it fit decent.

I bought mine second hand and already ported by PaulK. Mine fit fine, but its possible it was already milled before I got it?

Interesting. I'm guessing this has just recently happened to you?

I've used 2 new ones out of the box and they fit fine.

I've never had a problem, and I've used both the Performer and Performer RPM, on stock and E-heads.

Mine never fit great on three different engine combos.... a little off on all of them albeit iron or aluminum d port heads. Not wanting to take the time and effort to have it milled I hogged out the bolt holes to get it to fit. Also ground a lot of material off the bottom runners to clear the valley pan.

Mick, I've had three Edlebrock RPM manifolds that did not fit out of the box. Each one had to be milled .060. The first was in 2004, and I've had two more since then with the same figment problem. That's $300 extra in machining costs.

My RPM intake bolt holes did barely lined up with the holes in the D-Port e-heads.

I had to open up some of the bolt holes in mine. I wasn’t impressed at all. I hope it works better than it fit.

had to mill plenty rpm intakes to get to fit i have seen a lot of people oblong holes to fit them correctly i always mill them

Late to the party, but here are some pics. The RPM is about 20 years old. Started out on a stock 350. Pics are on a 69 400, zero decked for 8 VR pistons, so probably .025 or so taken off the deck. 6X-4 heads that I asked the machinist to cut to 90 cc, but I have not double checked. The fourth pic is with a gasket, the fifth without. In the fifth, if I push the baseplate back, it makes contact, pushing forward it just clears.

I bought a RPM used, so I don't know if it was milled before I got it. I don't think so, since it was not port matched or anything. I ran it on a 350 with 17 heads that had a mild cleanup and stock d-port intake gaskets. No issues with bolt holes that i remember.
I also ran it on a 670/ '67 400 block combo. Deck was at 10.225," no issues that I remember. The worst part was getting it lined up with those orange gasket locators, those want to slide this way and that.

For this 434 stroker build, I had the same 400 block decked to 10.215" and the heads surfaced again, the bolts didn't want to line up. I had .060" milled off the intake, but I had to trim the lower edges of the ports and massage the valley pan to make it fit. I separated the water crossover and it did NOT want to fit after it was milled. I had to go with a KRE crossover and slot the holes to get it to fit and seal on a 1233 gasket.

Using the E-brock RPM better make sure the opening for Quadrajet secondary 2.25" throttle blades are big enough.

It's not just the RPMs, it's all of them these days. It's a crap-shoot. I hear some say it's better now than it used to be, which may be true, since I didn't have to surface the last two.

Iron heads seem to do fine with opening up the bolt holes, or at least most of the time. I know on other's cars I've run across a lot of leaks along the bottom surface that faces the valley. I've had to skim-coat the gaskets on a few just to be sure there were no future leaks, because I had some stubborn ones, and they didn't want the hassle of having them milled.

I got lucky with the last RPM I did, OE 400 block, round port E-heads. The bolt holes were a little tight when I tried to pull it forward to seal at the cover, but it didn't leak, so went with it.

The Super Victor EFI I just did, I should have opened up the bolt holes, it barely lines up with the ports, and some of the port openings were off even on the same bank. Had to gasket/port match grind the drivers side enough to where I was cussin' up a storm. I had to 'settle' with minor mismatch, there was no way around it. Had to trim the cover passage some to get it a little more forward too.

Now that I think about it, I've had to trim the cover passage area as far back as I can remember.

I agree, most don't check and that's why most don't know. Many just bolt and go.

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I had an RPM that didn't fit right on a 400 with a small surface cut on the iron heads and new Fel-Pro intake gaskets. Bolt holes didn't line up right, and I can't imagine the ports did either.

I got rid of that intake, and put on a Crosswind intake (Performer RPM imitation). No issues with fit at all.

Edelbrocks are classic for poor fitment - I think especially the RPM.

Going through it right now w/ my local machine shop.

Its a bonus if you get one used that's been milled.