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MG MGB GT V8 Factory Originals Technical - bonnet bulge/hood scoop?

How many of you have a modified hood? How many have a hood/bonnet that closes with out mods?
It would be intersting to know the year of the car and which engine.

Interesting subject. How some can do a conversion without a hood bump/scoop has amazed me. I got my motor mounts from Cleve Wheatly and am using an Edelbrock intake manifold and Holly carb. I have found that the K&N cast air box will fit and plan to route the air pipe to the front to the left of the radiator. It looks like it will work but a hood bump/scoop is still mandatory. There is a little Nissan that has a hood bump that I have heard of people cutting out and insering in their hoods but it does not look right. Something about the shape looks wrong. A possible way out is to use a fiberglass scoop for a Cobra Replica. I got one but it still does not have the right shape but it will fit. One of the Miata web sites describes making a hood bump from clay and using it to make a mold for your own fiberglass scoop. An old thread said that the bump on the RV8 is not deep enough to work even if it were avaidable in the US.
Richard Porter

CB car with a rover 4.2, edelbrock 500 carb w/elec choke, 'stock conversion' motor position, don't know what the source of the motor mounts was, Mr. Gasket Competition air cleaner w/2" element. Edelbrock manifold angle-milled on top. Stock CB crossmember, mounted to body with 1/8" shims. Whole thing clears the stock hood -- and I mean just barely -- maybe 1/16 to 1/8 of an inch. Hood brace wasn't moved -- the point of closest proximity hood to air cleaner is about 2" behind it, at the air cleaner's center nut.

I am not happy with the 2" air filter on a drop base. It is so low that I am practically certain that induction is severely compromised. I am going to put a C hood on there (probably with the small C carb-specific bulge removed) because doing so should allow a slightly higher air cleaner. I am unwilling to run without a choke, as some have done. It may be useful to devise a way of sealing the top of the radiator surround to the hood, as is done on MGCs, and I am trying to think up a neat way to do that.

Richard, the K&N air box sounds like a good idea at first ... I had looked into it ... I can relate that K&N specifically warns that this is only for small motors up to about 200ci -- you are likely going to strangle your motor unless perhaps it's a fully stock 3500 or BOP215. OTOH, if you do it, tell it how it goes. At least the air that you do get will be cold.

Sometimes I am tempted to just take the 'Sweet Home Alabama' route and cut a big old hole in the hood, put on a 5" air cleaner and be done with it! That'll get ya plenty of cold air (and a lot of other stuff when it rains!!).
Harry M. Peeters

I have about 3/16" clearance between my bonnet and air cleaner with the bonnet brace removed. I used mounts from Dave Vale (V8 Conversions, Kent, UK), an Offy dual port manifold with Holley 390cfm and a Mr Gasket Daytona 2" Low Rider air cleaner. If you set the engine back an extra inch then there should be even more clearance and if you use a Carter 400 or edelbrock 500 there will be even more clearance. My car is a 79 MGBLE and Inhave no bonnet bulges. You can see pictures at:

There is another alternative. I am in the process of building a '72B with a '94 Chevy 3.4L V-6. The fuel injection intake comes out right at the top of the radiator and won't clear the hood. I've decided to use a hood bulge from a Mitsubishi Eclipse. I got the idea from a RB car that Tim McCracken built in Kansas City. You can see his car at the site "Stuffing a V-8 in a British Sports Car" at "". To me it looks very much like the RV8 bulge. I've seen a video of his car, showing both outside moving pictures and inside from the passengers seat and it looks great IMHO. Check it out.

Harry I worry about restriction too with the K&N but my engine is bog stock Rover SD1 so I may be able to get away with it. I ordered a drop air cleaner from Ram Air of Canada but it was huge, no way it would fit. I think my motor mounts must raise the engine more than most. I did set the engine back as far as I could and still use the stock heater. I like you do not want to lose the choke, it gets cold in Indiana.
Richard Porter

I specifically put a bulge in the bonnet of my car to allow me to use a 3 inch filter on a lowrider. Additionaly I milled off the horn of the Holley 390 double pumper and threw away the choke assy. It flows very nicely, over 200 hp at the wheels on Sigma Engineerings rolling road from a 3500 cc, fully balanced motor with a cam, David Eales heads and RV8 headers. The point is, if the inside face of the filter cover is too close to the barrels and emulsion tubes the signal gets screwed up. Auto Techniques in Luton told me they had on many occasions improved peoples cars by removing the Horn. You can see a pic of my carS bulge on the V8 conversions website.
or e-mail me
bob p

Interestingly, when I had my car on the dyno, we tested it with the 2" air cleaner on and with it completely off. We found no significant difference and produced 174HP at the rear wheels regardless. We lost several HP (5, I think) by closing the bonnet (hood)!

I have done V-8 M.G.B.s for 18 years with 3500, 4200, 4900 & with Rover hot wire F.I. & 4 barrel carter & holly carbs & have yet to mess up the fine bonnet lines on a M.G. & on my cars I use the alu. bonnet witch has 1/2" less bow & yes it is tight, but it all clears. There is motor mts. that bolt to the motor that make the motor sit higher in the eng. bay were the bonnet will not close & the moss motors rubber motor mts. are taller & thay make the motor sit taller yet! I am welding up my mts. to sit the motor as low as it can be set were I have as much room for the F.I. up top. I have a 6sp. trans (borg warner T56) in my 72 roadster & that trans sits taller than the rover 5sp., so I had to lower the eng. & trans. to get it all in with NO hood scoop! I have had NO problems with the trans to rear set up were I were out u-joints. I have gone to car shows with my M.G and a 3,000 lbs + trailer full of M.G. bits from N.H. to Fla. to Kas. & in 600,000 miles I have had 1 U- joint go out (no grease fitting) If you do your home work & with the right parts it will all fit.
Glenn Towery

There is a post someplace (not sure where right now) by Roger Parker regarding mods to a FI unit to make it fit under the hood. Machining material off top and bottom of the center casting, shortening plenum to ram bolts and, other work, some of which I don't even understand.
Do you make these changes to get FI to fit under a CB bonnet?

I did Roger's suggested mods as you describe them. Search the archives for his explanation and my questions to him. Try "hot wire" --I think it's in a couple of threads. I simply printed the info and took it and the bits to my local machinist. He had no problems lowering things and I was pleasantly surprized at the price. My '71 GT is still under construction, but with Glen's "A/C" mounts, stock RB brackets and V8 rubbers the hood closes with about 1/4" clearance. I did shave a bit off the "legs" of the brackets to let the engine fall a little lower. I've been reassured that the rubbers settle a bit age.

I have detailed Roger's FI lowering at the following address.


Nick Smallwood

Angus, I did print out the info and, did take it to a machinist. I was not pleasently surprised. He quoted me $500.00 to do the work.

Yipes!! Do try a different place! The guy I used is not automotive--he does more industrial type stuff like making bits for saw mills and such. He even shortened the trumpets without desroying them. Good luck.

I just found my old post under "engine mounts settling" I couldn't remember what I paid for the work. Turns out it was $200 Canadian.
Angus Davies

I have used the bonnet bulge from a jaguar xj8(x300)
the middle section cut out and welded in to the mgb bonnet,the lenght of the bulge is almost good and looks are clean and classy...

Regards Nico
nico Bourgois

I'm going to try the buldge from a dodge intrepid,it's kind of big and not all that tall but has almost the exact taper as the "b" hood so it should blend in pretty good with the design of the car.

To answer your question about making modifications to the plenum; I have succesfully installed my 3.9L Hotwire EFi engine in my B without any modifications to the plenum or a hood scoop. To accomplish this, I had to set the engine in SO low that I had to re-locate the steering rack down about an inch and a half. I also have a rubber bumper ft crossmember (which has that extra inch of clearance) And then I made my own mounts and rubbers and it then fits. I have very little clearance from plenum to hood. But it works.
Wally Jonker

Wally, thanks for the post. It contains some of the details I am looking for. You state that your car has a RB front cross member. I assume that your car is CB as is mine but, I am hoping to retain my original cross meber so, it may be neccesary for me to do the EFI mods after all.

I used the cb crossmember in my 73B. I located the engine chasis mounts (Clive Wheatly) to the frame rails 2 3/4" behind the front crossmember mounting bolt, measured from the center of the bolt to center of the motor mount slot. This sets the engine back and down low. Good for hood clearance, great for handling!
I had to cut the rack mounts and rotate the pinon of rack the down and deepen the notch in the x member for pinon housing clearance. Be sure to mount the rack vertically and horizontlly as close to the factory location as possible so you wont have bump steer problems. I also used a RB steering coloumn,shorted the rack pinon shaft and made an intermidiate steering shaft. Borgenson makes U joints and shaft stock to do this. Fire wall widing and lower coloumn mounting area mods are also required. As you can see its more work to use a CB X member but you dont have to lower the front end to get back to the CB ride hight. However I did use a hood scoop from a 67 pontiac GTO,(shortened 6"),(off a wrecked hood) because I like the way it looks! Bill
bill jacobson

Just the information I needed for my 73BGT conversion.
Did you use the RB rack and pinion when shortening the shaft?
Andrew Worman

I used the CB rack. The intermidiate shaft is 3/4" "double D type". The upper end of the shortened pinon shaft was also machined to a 3/4" double D. (Easy to do) Borgenson makes a u joint that is splined to match the MGB steering coloumn on one end, and a double D on the other. I can e mail you a photo of the install if you want to see it.

Bill bill_jacobson@hotmail,com
bill jacobson

Bill Jacobson has, perhaps the prettiest MGBV8 conversion I have ever seen, & I have been driving & looking at V8 conversions for 15 years now. Technically outstanding, as well.

The Clive Wheatly mounts set the engine much too high, & are far too expensive. They are well made & nice to look at, but I wouldn't use them if they were a gift. Glenn Towery makes the best mounts- the "A/C" version- as far as engine location is concerned. I have seen nicer finished pieces, but not better locators, if that is a word.

By all means, use the CB cross member. It will not interfere with the oil pan, & maintains the correct ride height.

The Carter/Edelbrock carbs are lower than the 390 Holley. The stock 215 intake is lower than any aftermarket intake I know of. K & N makes a 2 1/4" element that fits the low rider air cleaners. I have almost an inch of clearance with this combo in my 1974 GT & the roadster I am building- C/B crossmemmber, 215 intake, Carter 500, Federal Mogul air cleaner, K & N element. Both these have max engine set back in RB bodies & clear the hood brace.

Richard Porter has the worst combo for height- not saying bad things about the quality or performance of the parts, just the height- with an Edelbrock intake, 390 carb & Clive's mounts. I would guess 2" difference between his setup & mine.
Jim Stuart

Bill, by "intermediate shaft", are you alluding to a 3-piece steering column? If so, does it work OK? ... and if so, how the heck do you hold the intermediate shaft in position? ... I don't get it.

Otherwise, I was hoping to pull off a setup in my chrome car where I use a 3.0 lock-to-lock RB/v8 steering rack, and keep my CB steering column. I was told it was possible to do just exactly that by simply sliding the bottom u-joint on the steering column up the shaft & securing it there (with a detent/ pin/ bolt/ what have you). I want the 'classic' setup -- if it can be obtained -- where there's just a 2-piece shaft with a single u-joint in roughly the plane of the firewall and inside the steering cone. Most of the installations of that type that I've seen give you half an inch or so to the rear-most LHS header bolt, which looks to me like the best way to pull it off.

Anyone who has successfully rigged a CB car with a CB x-member and a single u-joint in the steering shaft, please say the best way to do this!

Jim, don't the A/C mounts set the motor awfully far back? Where does your shift stick come out? Is the motor right up against the firewall? How much rearward of the regular position do they cause things to be?
Pat Pitpon

I plan to resolve any hood clearance problems by using a MGC hood for my '79 B. I just purchased a fiberglass one today on eBay for $91.10 (and shipping). I saw a picture of it and it looks to be in good condition and since a new aluminum one will cost you arround $500.00 from Moss how can I go wrong? I met another V8er a month or so ago who used a C hood skin on a B frame. It looked good and saved him the hassel of hunting for a bulge/scoop off of some junkyard Honda/Mitsubishi/Toyota/Nissan...etc. I personally think it's a better alternative in that it utilizes a MG part to solve the problem. Then again we are talking about converting the car to something that we feel it should have been so I guess whatever you like you should do. To each his own.

Chris Mowris

Yes there are 2 u joints in the system. Its the same princable as the drive shaft. There is a support bearing on the upper end of the pinion shaft to eliminate any pinion shaft flexing. But when you use only one u joint on each end of the intermediate shaft (2 u joints total) a support bearing is not required on the intermediate shaft. The most important thing to remember is to keep your shaft/u joint angles to u joint manufacture recomendations.
I went with this system to give me greater freedom to locate the engine as far back and low as possible! The steering is smooth and responsive.
For what its worth almost all new cars and trucks currently use some type of intermediate steering shaft with out support bearings when only two u joints are used!
I used the RB coloumn because it is shorter Than a CB one, and it places the upper u joint further back for reduced steering shaft angles and better exhaust header clearance.


bill jacobson

Bill, thanks for the info. Makes me re-think a couple of things. For one, I had always thought that having a V8 conversion with an intermediate shaft was the very definition of Bodge -- i.e. that it was a half-assed way and 'cheating' way to solve the problem. I had no idea that modern cars do this all the time ... you learn something every day. What I don't get, though, unless I am missing something, is how the whole column/int. shaft/pinion assembly stays in one place without some sort of brace or support ... it just doesn't seem physically possible. Are there photos of your setup some place online? For one thing, how long is the int. shaft? I reckon you'd have to shorten the rack pinion by that amount, correct? Terribly interested. This mickey mouse yahoo mailbox unfortunately doesn't really allow much in the way of attachments.

If any one is interested in different shafts, Check Flaming River,They manufacture steering racks for MG's, steering shafts, Support Bearing Etc.
also Tony Barnhill is using some Motor mounts from England that are lower I believe. This might be some of the Parts discussed above. mike
mike childress

Jim I agree that I have ended up with a higher set up than I planned. Sometimes you just listen to advice and do the best you can and still have problems. I have the engine in and the mounts welded and I don't really want to start all over again. You are right, the Wheatly mounts look great and who would have thought they would end up so high. I moved the engine as far back as I could and it still is high. Other things have worked very well. I used two Borgeson u-joints on the steering and they fit perfectly. Someone in Colorado suggested a Ford Falcon radiator and it fit with almost no problems. I plan to live with the need for a hood bump and maybe if I have to take the engine out later I will redo the mounts. Also fuel injection in the future may be lower.
Bill You used the Wheatly mounts. Did you need the hood scoop to clear or just because you wanted a scoop?
Dick Porter
Richard Porter

The intermediate shaft on my car is 5 1/2" long. I do not remember how much I shortened the pinion. It was different than 5 1/2" though, due to u joint length and coloumn to pinion offset. The intermediate shaft stays in its proper place because the upper pinion support and lower coloumn bearings do not allow vertical or horizontal movement only rotational (turning) movement.
Make sure the nylon inserts in the telescoping coloumn shaft are not broken from accident damage. you don't want the coloumn shaft sliding in and out changing the u joint angles. I don't have a photo on line. I am new to computers and have not figured how to do photos on the web yet! You may want to get a copy of Borgeson's catalog it has excellent tech info on steering system design, strengh requirements, and parts. There # is (860)482-8283. Bill
bill jacobson

A hood scoop was not required on my car. I used one for looks to match up with the flared (Huffaker)fenders. I did make my own engine to motor mount brackets which may be allowing the engine to sit lower with the Clive Wheatly chasis mounts. I bought aluminum mounting brackets only to find they would not work on a Buick 215 (their for a Rover 3.9).

bill jacobson

Managed to get my V8 under the bonnet by machineing about 37 thou from the fuel injector. Just fits and no change in the body lines

Mare, are you CB or RB?

Glenn hits the core subject on the head, which is the final mounting position of the engine. This has so many knock on effects with other parts that you have to design your conversion around the engine mount position.

My choice has been to use the stock chrome bumper V8 mountings and modify my injection castings to suit. If the early Federal spec Lucas injection system is used (Rover SD1 and TR8) then clearance should not present any real difficulties as this is so much lower. Power is not that different to the later Range Rover style induction system as this was designed for torque rather than max power.

Incidentally there was a development twin plenum system quite a few years ago that operated with separate inlet manifolds rather like the multple Weber carb set ups that produced a huge wad of extra power and torque on the standard engine. It also was quite fuel efficient and those who were involved in the development still can't understand why this was not productionised. A custom twin plenum injection system could be desigend to overcome clearance problems and provide that extra power as well.

Roger Parker


Apart from the MGC option for those who have a high mounted motor, another option usin "MG" parts is to use an RV8 bonnet. I have seen fibreglass copies of these for sale in Australia for MGB V8 Conversions.
Phil Stafford

This thread was discussed between 05/11/2000 and 26/11/2000

MG MGB GT V8 Factory Originals Technical index

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