1969 Mach1 351W Hood Clearance With RPM Air Gap

[Lemon Owner 11]

Thank god it fit....otherwise the airgap I just bought will make a very expensive ashtray! :eek:

[BigDuke6 17]

BigDuke6:

You mentioned the air cleaner *just* fits under the hood with the RPM Air Gap-4150 Carb-Air Cleaner combo you have. Do you know how much clearance there is? I spoke to Edelbrock Tech Support and the tech told me from personal experience there is not enough room to adequately fit an air cleaner under the hood. I'd like to make the change but just trying to get more info first.

 

sorry for not replying but I was gone over the weekend. I see that you already answered your own question but in my case, it is tight. We are talking not more than 1/8 of an inch at the most.

[Cruzzar 22]

FYI, for you guys that are getting tight clearances when using the 3" tall filter you can always go to a little shorter air filter. K&N for example has several slightly shorter 14"dia. filters available. For example, in a 14'dia. you can get these different height air filters.

3.000

2.813

2.500

2.313

Edited September 6, 2011 by Cruzzar

[Lemon Owner 11]

I think the main problem is drop. After some measuring the carb will be nearly rubbing on the hood. Plenty of room around the sides for a 4 inch filter.

[1969 Mach1 14]

Whats frustrating with the RPM Air Gap is it looks like the huge 'air gap' below the plenum could easily be reduced by 1/2" or so. I don't know how that would effect the function or performance of it but it would solve fit issues on alot of vehicles.

[BuckeyeDemon 211]

Whats frustrating with the RPM Air Gap is it looks like the huge 'air gap' below the plenum could easily be reduced by 1/2" or so. I don't know how that would effect the function or performance of it but it would solve fit issues on alot of vehicles.

 

i've read somewhere where the Performer RPM and Performer Air Gap had the same runner cross sections. The only difference being the Air Gap lifts the runners for "cooling". Have you ever read this? It's probably false, but would be funny if they were actually the same.

[BuckeyeDemon 211]

actually i just did some checking. the main page for the manifolds seems to indicate they are the same with one just be the "air gap".

 

http://www.edelbrock.com/automotive_new/mc/manifolds/ford/ford.shtml

 

also the port exits are almost identical (Performer RPM vs Performer Air Gap).

[Lemon Owner 11]

It's hard to say from just looking at it but it is sure alot taller than it needs to be. One would think the runners would be slightly longer for that reason alone but IDK. It is a monstrous manifold in the flesh, much larger than I expected from the pics.

[1969 Mach1 14]

I did alot of research before I purchased the Air Gap. Every article I read where the RPM Air Gap and RPM non-air gap were compared them side by side stated the RPM Air Gap's runners have a larger cross sectional area than the RPM non-air gap. Also, the RPM Air Gap was designed to handle larger CID stroker motors. The Weiand Stealth, which I use to run, is a nice looking manifold. But its runners have a smaller cross sectional area than both the RPM and RPM Air Gap. I hope the RPM Air Gap's performance makes up for the headaches the height causes.

[BigDuke6 17]

I did alot of research before I purchased the Air Gap. Every article I read where the RPM Air Gap and RPM non-air gap were compared them side by side stated the RPM Air Gap's runners have a larger cross sectional area than the RPM non-air gap. Also, the RPM Air Gap was designed to handle larger CID stroker motors. The Weiand Stealth, which I use to run, is a nice looking manifold. But its runners have a smaller cross sectional area than both the RPM and RPM Air Gap. I hope the RPM Air Gap's performance makes up for the headaches the height causes.

 

have a look the video at the 6:18 mark where the guys milled the plenum divider on the Performer RPM to mimic the Air Gap. The dyno results for the modified Performer RPM almost equaled the results for the Air Gap.

 

[1969 Mach1 14]

I watched that before I decided to go with the Air Gap. Keep in mind, that testing was on a small block Chevrolet. For the 351W, both the regular RPM and the RPM Air Gap have full height (unmilled) plenum dividers. Also, I am not a 100% believer in what works on Chevrolets will work on Fords. It would be nice if more shops did comparison testing of performance parts on a 351w and posted their results. I have used a regular RPM on a 351W and I wasn't very happy with it. It was a bit lazy at lower rpm's and it had very uneven fuel distribution. When checking the spark plugs for color, numbers 6 and 7 were always white as new while the others had some color to them. I am hoping the RPM Air Gap won't be like that.