85 Mustang GT OEM Aluminum Intake Manifold Help

[Mikey]

Hello all,
I put an 85 Mustang GT OEM aluminum intake manifold with a Holley 4160 on my 74 Bronco with the stock EGR plate with a block off plate where the valve goes.. It's been on for a while but now I get between 10-14" vacuum. Did all the usual checks and can only see a slight increase in rpm if I spray carb cleaner around the choke side of the primaries. At this point I think it could be a leak through the primary throttle shaft, something with the EGR plate, intake gaskets or a cracked intake.

Where can I get a nice high quality plate to completely eliminate the OEM EGR plate? I need specific info so I can order one and try it out before I go the intake gaskets or carb shaft routes.

Thoughts?
Thanks,
Mike

[bwguardian]

Any reason not to replace it with a non EGR unit...that stock unit is so restrictive...

[Mikey]

Hood clearance is a huge issue on the Bronco. Not willing to put on an aftermarket hood or hood scoop. I do have an old cast iron 4V intake if this one is cracked, which I doubt. Problem with cast iron is it's freaking heavy to install and, of course, adds weight on the front end. Also, Broncos need lots of low RPM torque....not so much top end.

[Supersonic G.T.350]

A standard Edelbrock Performer will fit under the hood I imagine. They aren't a high rise and it's still an improvement over the stock 5.0 junk.

[FB71]

Remove the egr spacer plate entirely, and replace it with an aluminum four-hole carb spacer. That will eliminate the possibility of leaks there. Be sure you haven't sucked an intake gasket, or slipped it during install. Do you have power brakes? I've had leaking boosters before. Verify your base timing, as that can greatly affect vacuum as well.

[Mikey]

Will any aluminum four-hole spacer work? I thought the standard spacers would be too narrow.

I did unhook and cap off the brake booster and the C4 vacuum modulator...no luck. Timing is good unless the harmonic balancer outer band slipped.

[cb650]

I bought a plastic one off ebay. was called some fancy name but it works.

[mcfairmont]

Because of the EGR slot on the stock 83-85 4V intake, I have yet to see a carb spacer that cover that opening, and will have a terrible exhaust leak. Years ago, I had a thin aluminum spacer from an old Mr. Gasket heat isolator kit that was wide enough to cover the EGR slot, and that allowed using a common carb spacer. Should be fairly simple to make such a thin spacer to cover the slot, if you can not find something else.
As mentioned, the stock 83-85 intake is quite a turd, I had to run that intake manifold on my 85 Mustang NHRA Stock Eliminator 302, but on a test weekend, I swapped the E4 intake for a Edelbrock Performer RPM, and the car picked up considerably, from a 12.4 ET, down to 11.8 ET., with no other changes.

[Mikey]

I figured the standard spacers wouldn't work. Any problems sealing up the original plate using a block off plate at the EGR valve port? I have the entire stock set up including the heat shield...was the gasket between the carb and heat shield a thin one or a thicker insulator type?

[cb650]

I bought mine so I could keep the heat shield. Without it the shield sat to low with out flattening it out.

[FB71]

I bought a plastic one off ebay. was called some fancy name but it works.

phenolic; fiber impregnated with polyester resin

[FB71]

I figured the standard spacers wouldn't work. Any problems sealing up the original plate using a block off plate at the EGR valve port? I have the entire stock set up including the heat shield...was the gasket between the carb and heat shield a thin one or a thicker insulator type?

I hadn't considered the pad footprint being that much larger. A steel or thick aluminum plate would be needed under the spacer to cover the egr port in the manifold. The heat shield shouldn't be needed without the egr valve, but can't hurt. I checked my old Edelbrock Performer intake (not the RPM version), it's only slightly (maybe 1/4") taller than the stock intake. Switching to that would yield a better breathing intake, even at low rpms, and a short (1/2") spacer under the carb would put everything at roughly stock height.

Otherwise, yes, a thick (1/4" steel, 3/8" aluminum) block plate on the egr spacer would work just fine.

[dagenham]

I recently discovered the Mr Gasket carb gaskets don't work under the factory spacers. Their gaskets have two mounting holes at each corner and the inner holes cause a vacuum leak under factory spacers because of the underside of the spacer being hollow.

[tiptopss]

Throw all that EGR stuff under the carb away, and get a 4 hole spacer

[erratic50]

Ok.... had some thoughts on the stock mustang intake discussion.

One thing to consider when discussing performance aspects......... 12.40's are actually quite quick if you put it into the context of any other car's intake parts from the same time period or cars from that period. Granted -- picking up 0.4 simply by adding a better intake is INCREDIBLE. That's added some boost from a supercharger territory usually. Or a 75 shot of giggle juice.

Lots of guys with cars technically faster would get their butts handed to them lining up with a four eyed fox then getting that 12.40 driving lesson. Heck, a lot of guys roaming the streets get stomped if you run mid-to-low 13's even. Its even more slanted in favor of the old four eyed fox when sitting at a stoplight if you've been driving yours anywhere near as long as I've been driving mine.

Granted -- there are a lot more 10 and even 9 or 8 second rides around than there used to be and some of them can run something close to their number on the street.

I do enjoy watching those guys in my rear view mirror if they go up in smoke. They'll ultimately come flying around hauling tail but by then there's no saving face on it for them, that's for sure.

I guess what I'm saying is that I really can't fault a guy for running an intake that produces good torque down low and has somewhat decent midrange on a Bronco. That's where a Bronco usually gets run.

[BaconB8]

Heres one thats built for this purpose. Its sold by Edelbrock. I don't have the part number.

[Mikey]

It's an Edelbrock 8714 and can be found on eBay for around $56.....I got it and it helped. Problem ended up being a problem with the Holley carb....worn primary throttle shaft and incorrect, damaged idle mixture needles. Had another great condition old Holley 6919 laying around. Something very important...the 6919 idle needles control air and are different than the usual Holleys that meter fuel. The air control needles are larger diameter and blunter.

[RazorbackGT]

Yep, I run the Eddiie EGR block off spacer, works great, no problems. I will eventually get rid of the factory manifold.

[Mikey]

Thought I'd give an update. I never could get the emissions Holley 6919 idle to work right; it's just too lean. I changed to the newer Holley Truck Avenger 670 cfm and WOW! what an improvement. Running the 85 GT intake and Hooker comps made for the classic Bronco. Lots of torque. Runs 20 in vacuum at idle.