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MG MGB GT V8 Factory Originals Technical - Intake manifold, Offenhauser or Edelbrock?

Well, It's time to buy the intake manifold! The question is; which one? I'm building a stock Rover 3.5 and would like it to fit neatly in place with out any bonnet mods. Which is the shortest? Any problems with either of these?
I will be using a Holley 390 .
The chassis is a 78 RB.

Thanks, Kelly
Kelly Combes

The Offy 360 is the lowest - and you can skim a bit more off the flange and mounting plate if you need it.

The Offy is also about the best candidate for a supercharger mount, and perhaps the injectors as well.
Jim Blackwood

Interesting, sounds like perhaps I mis-measured, but the Edelbrock Performer turned out to be a shade lower than the Offy. And thank heaven, we're talking _close_ fit! (Also, I had to have the flange milled at a slight angle to get the bonnet to shut ... seems like that would in theory affect fuel/air distribution but didn't have a lot of choice.)

Thanks for the info. Offy it is.


I recently purchased the Offenhauser and Edelbrock, putting both on the floor, the Edelbrock appears to be taller, but it is very close (3-4 mm). Depending on what air cleaner you use, you may need to move the centre bonnet support to clear the air filter. Depending on angle of engine, you may need to fit the leveling plate, so this may also increase the overall height of your carbs.
Ian Sanders

What is the leveling plate?

And the Edelbrock is suppossedly about 3/4" taller than the stock Buick 215 4bbl manifold.

Carl, 3/4"??? That's fantastic! For G*d sake, I'm going to start looking around for one of those pronto. Even with the lowest possible air cleaner on there, the hood clearance is literally about 1mm with the Edelbrock. Two steady bars hold the engine pretty well in place, but there is still a witness mark in the paint right over the center-stud for the air cleaner lid.

Would the stock Buick 215 model yield materially worse performance than the Edelbrock Performer currently installed (this would be on a 4.2 Rover)? If not, any idea where to score one of these Buick models?


A levelling plate is a wedge shaped plate that bolts on under the carb to get it level if the engine is at other than the usual angle.

If you are tight for space then you can get the manifold milled to the correct angle instead.

The lowest available 4 bbl intake for the 215/Rover V7 is the stock Buick/Olds factory piece. The shortest carb is the Carter or Edelbeock 500, & it is a lot less trouble than the Holley, also it doesn't leak. Performance-wise, the factory piece is the equal of any aftermarket manifold I know of up to around 4-4500 rpm. Not many of us make routine visits to the 6000 & up range, where the aftermarket manifolds really do outperform the old stock one.

If you are located outside the US, you may wish to try E-bay, as there is usually at least 1 at auction. Several US V8 suppliers deal in used parts. You may wish to contact Glenn Towery who frequently contributes to this forum, or TSI imports.

If everyone would stop reading the "How to" book & move the engine an inch or so to the rear, you would have plenty of clearance. The previously mentioned Mr. Towery sells an excellent set of mounts for this purpose, identified as A/C mounts. By moving the engine rearward, you gain bonnet height. By snugging the rubber biscuit nuts, then pounding on the steel base with a drift & BFH, you can lower the engine around 3/8" depending on the size of your hammer. Be sure to tighten the nuts when you get through.

Jim Stuart

Guys, how difficult is it to change out the intake manifold on a V8? Will the stock Buick unit fit on a Rover motor? I assume you are threading some of the bolts right into the aluminum block ... anyone know the torque settings for the same? If not that difficult, I am going to get a regular Buick 215 intake and scrap my Edelbrock. Might as well change over and try to get a halfway realistic air cleaner on there.

Question: swapping intakes would seem to entail emptying the cooling system. When you re-fill the radiator, is there some special "burping" procedure you have to follow with the Rover? ... everyone seems to be hinting, careful dummy, you'll get an air bubble in the top hose and all hell will break loose!

Please advise. I am not the greatest mechanic, but I am not totally incompetent either. Just want to be sure it is realistic to do this myself.

Yes the original Buick intake manifold fits on to the Rover3.5 liter engine. This is the set up I have. It's a direct bolt on.I used the Carter/Weber AFB 500cfm carb.
werner van clapdurp

I bought my motor mounts from Glenn but I had to put a hood scoop in for clearance Olds 215 with the stock Carter 400 4 bbl and stock Olds intake manifold. But I don't believe the BFH was used which may have been the problem although I actually needed about 1.5 inches above the carb and low profile (1.5 inch) air cleaner (which was modified to sit lower on the carb yet still clear the linkage. The hood would close and latch without the air cleaner but would not latch with the air cleaner on until the scoop was installed.
Michael S. Domanowski

Michael, that seems awfully high. Two questions: (i) how high above the steering rack is the sump?; (ii) where did the air cleaner hit the hood? I guess hood scoops are OK, but they certainly should not be _necessary_ even on a CB car. Especially so if you are running the OE 215 manifold. If the front of the air cleaner fouled the hood, you could just move the hood cross-brace forward or have your intake milled at more of an angle (I believe they are 5 degrees stock; that might not be enough).

Terrence, I have a book on the SD1 3.5 that states 25 to 30 lbs on the manifold bolts, 10 to 15 lbs on the gasket clamp bolts.

With the scoop there is no longer a cross brace, the metal scoop makes the hood more rigid then with with brace (it is made up with 20 guage steel and 1/8 inch wire on the edges all welded to form a solid structure.

I don't know the exact hight above the rack that the sump sits, I'll have to measure that when I get home tonight and get back to you on that.

The air filter (12 inch diameter low profile moidified as I said in an eairlier post) hit the hood from about 6 inches forward of dead center to 6 inches rearward of dead center (in other words, the entire air filter) of course as you close the hood the rear touched down first.

I'm actually quite happy with the look the hood scoop gives my 1978 MGB V8, slightly aggressive, but subtle and the ram air affect at speed has to be good for a couple HP.

From everyone I've spoken to, 1.5 inches is real close to fitting. This seems to be a common problem (if you want to keep the hood completly stock) in the conversion, but then if I wanted stock I wouldn't have put in a V8.
Michael S. Domanowski

Your engine does seem like it is in high and perhaps forward. My V8 is nearing completion. With a stock hood and engine mounts (body is a 77) the engine gave enough clearance for a 2.5 inch air cleaner on a 3/4 inch drop base (14 inch diameter). The forward edge of the air cleaner is just behind the hood cross base.
James Johanski

whoops! Forgot to mention. Engine is a 63 buick with stock 4V manifold and an Edelbrock 500 CFM carb.
James Johanski

Wow , leave for a week and you miss all kinds of things. From what everyone is saying, it looks like the stock Buick manifold would be better for clearance. I have one sitting in the garage already. I also have a Holley 390. Would adding the carb adapter plate make it too high? Or, does anyone want to trade a Holley 390 for a Carter 400? I think a 500 would be too much carb for my stock 3.5.


From what I have seen and heard I would agree that a 500 is to much carb. Kurt B had a 500 on his tuned-out 215 and it would not run well. After a rolling Road tuning and switch to 390 it runs like a champ..
Larry Embrey

The Edelbrock 1404 isn't to much carb for the 3.5 & it's lot less dangerous than the 390. I just changed from the Holly 390 to the Edelbrock 500 CFM & it was a bigtime improvement. NO LEAKS!!!!!!!!!!!

I don't if any of you have seen gasoline an inch or so deep perculating on top of your hot intake, I have & it's real buzzkill, what's worse is when it torches.

The 1404 is a better design than the 390, no power control valves to blow when the engine backfires, no side hung floatbowls to leak, no sticky gaskets & no little F*****G O-rings that allow gasoline to spray all over the top or your hot motor so it can catch on FIRE.

Holly carbs are a defective product & if any of you keep running them chances are that your car will catch
on fire like mine & many others have.

Dwight McClain

Thanks Dwight, Safety should always be the main factor in any project. I've heard about the Holley's leakage problems from several people now. I to am in a hot climate and that could be a problem.

Keep talking folks! This sounds like a very important issue.


Who is Kurt B. and what kind of engine and size is he running with this poor functioning Edelbrock?
James Johanski

E-mail me and I'll send you photos and give you the dimensions.
Michael S. Domanowski

Guys, just dealt with this exact issue: of all the manifolds listed the Edelbrock comes with _noticeably_ bigger ports. While the stock 215 intake might work fine on a 3.5, for a big Rover (3.9 up) with ported heads, I don't see how the stocker is going to keep up flow-wise. And the stock 215 intake doesn't have all that much material to take away around the ports. I agree that the lower height is a bonus, but I think you'll be choking anything other than a stock 215/3.5L with the stock manifold. I'd go with the Edelbrock unit and try to figure out a way to get it in there. Not sure you want to go milling it, etc.; they are technologically pretty advanced castings, leave as is if you can. Good heavens, as stated above, stick with the Carter/Edelbrock/Weber/whatever you call it. I am not convinced that even a really low drop-base air cleaner hurts you too much; sure, as far as the primaries, the choke tower surely fouls things up a little, but the secondaries will still have plenty of room to flow properly, and that's what counts.
Phil Barnes


Has anyone tried one of those K&N Filter tops (round, 14") that is actually a filter in itself - ie not a chrome top? I wonder how much of an improvement that would make to space limited filters installations? Summit racing sells the ones I've seen.

74 V8
Neil Cotty

Neil, you mean a K&N X-Stream: tried it, but they are pretty thick and they come down to close to the choke tower. Unless you're running, say, a 3" filter, can't really use an X-Stream, at least on a dropped base.

using offy intake with carter carb and 1 inch spacer. The only reason I would not recommend the offy is because of the uneven fuel distribution caused by 360 design. edelbrock's 180 deg probably flows fuel a heck of alot better, but just speculating.

I have an Offenhauser manifold but it is a Dual Port not a 360. Has anyone compared these to the Edelbrock? I can't find any info on this manifold on the Web but it seems to perform ok. It is said to be a lot lower than the Edelbrock, but better performing than the 360. The Edelbrock being best over 4500rpm.

Neil Cotty

I forgot to add the Offenhauser manifold is also marked 'JWR'. I have bundles of clearance with this manifold, and Edelbrock 500 & 14" chrome pancake aircleaner. Over 2" - my car is a Factory V8.

Harry - Yes, I looked in the Summit catalog an X-tream it is. But did you go for the complete filter assembly or just the top plate? If you use a low filter assembly like say the one I use at and a std K&N filter and add this top, would that improve breathing in a limited space? I doubt adding just the top would increase height? Or was that what happened with yours?

74 V8
Neil Cotty


I'm not sure if you know this but the Offy 360 and the JWR manifolds are completely different. The 360 is a dual plane manifold that feeds one primary and one secondary venturi to each bank of cylinders independently.
On the other manifold the JWR stands for John Wolfe Racing which was developed in the UK from the original design. The JWR is a dual port as you say which feeds all the fuel air mixture from the primaries to all the cylinders via the lower port. The secondaries use the upper port to all the cylinders.
I went for the JWR as it had good recommendations for torque. (have not fitted it to the car yet). As to which is better I think the Edelbrock would have a slightly better top end but I leave it up to the individual church goer as to what sort of performance they're after.


Kurt is a local V8 conversion owner. he has a beautifull car and has spent much time tuning and tweaking it. I believe it is a true 215 with edlebrock intake. I do not know which 500cfm he had on it, only that it ran poorly and/or unevenly. Not sure which 390 he ended up with, but he said it was a 180deg improvement, he got 225hp at wheels, so must be doing something right...

His car is featured on the Danmas site. It is the Yellow rubber bumper BRUMBLE license plate..
Larry Embrey

Phil Barnes-

I run a stock Buick intake with a Carter 500 on a 4.2 Rover, & I guarantee you that it works fine. Several 5.0 Mustang owners will also agree. Plenty of power to 6000 rpm. It is still pulling at 6500 when the valves start to float.


the 500 Carter or Edelbrock can be jetted up or down to work very effectively with a 215/3500 or a small block Chevy. It is a very forgiving piece. I run the same carb on a 215 & a 4.2, with some tuning help from Dan Lagru @ D & D. Dan claims the NEW Edelbrock is now better than the Carter.
Jim Stuart

Well, after all the talk, I sold my Holley and bought a Carter 400. I was able to sell the Holley for what I bought the Carter for so I thought that worked out well. Since I already had the stock Buick manifold, this seems to be the best setup for my 3.5 according to the advice and the numbers I ran on a carb selector program. This also seems to be the shortest setup. Thanks for all of the input.


Stock 4bbl manifold with the "low profile" ROCHESTER of 1961, '62. I have three and one I use on
a 4bbl. manifold for my slant six (225 dodge). That is the lowest profile I have seen. Of course
you could manifold some S. U. CARBS ???? OR JUST GO FUEL INJECTION (PRO-JECTION) $$$$

This thread was discussed between 20/04/2001 and 23/05/2001

MG MGB GT V8 Factory Originals Technical index

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