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MG MGB GT V8 Factory Originals Technical - Chopping a hole for a hood scoop

I'm resigned to the fact that I have to have a hood scoop to clear the plenum chamber of the EFI.I've already got the scoop from a hot rod shop. It's a nice looking one in my opinion, but now I have to cut the hole for it. But how ? The electric can opener is definately out. One friend suggested I take it to someone who has a Plasma cutter. Another one said don't. I thought of drilling a hole in each corner & cutting the rest out with a blade in an angle grinder or possibly an electric jig saw. The hole is approx. 8" x 15". I do not want to distort the hood at any cost & I hope to save the paintwork. The scoop bolts on from underneath, so I'm hoping this will provide some strength & stabilise the hood structure a bit. Any suggestions are welcome. Barrie E
Barrie Egerton

Plasma cutter will work quickly but if you want to keep your paint, forego that option. I would cut it with an pneumatic cutting wheel, or a cut off wheel on an angle grinder.

Why not simply have a bulge English-wheeled into the bonnet, kinda like an RV8?
Bill Withum

The "Razor Blade" (TM) on an angle grinder is great for straight cuts but a real challenge on the corners. A good pneumatic shear is quick, easy, and does corners well and cutting from the bottom would leave a clean edge. I think that would be my choice but you have to watch it closely on the straights.

Jim Blackwood

Use a sheet-metal nibbler. It's a manual, hand-operated tool that cuts neat straight lines and curves, without distortion. Available from Eastwood and some auto-body supply shops. best, Joe
Joe Ullman

The bulge sure sounds good but I agree with Joe's nibbler or Jim's shear if you really must cut it. I have an air powered nibbler that works great and cost $16.95 on sale at Harbor Freight. Use masking tape to prevent scratching the paint and a straight edge to stay true. Don't rush the air nibbler or the kerf will be saw-toothed. Speaking of bulges, a friend of mine has a hood that has a bulge from a Mitsubishi of some sort grafted on and it looks slick.

Is yours a Rover conversion ?

Thanks guys for the tips.
RMW yes
Barrie E
Barrie Egerton

How about an MGC hood. I have just fitted a 4.2L Rover with Hot wire EFI. Took out 27.3mm from the plenum assembly and it clears the "C" hood by about 1/8". The extra height of the "C" hood at the front also allowed me to fit a taller radiator from a 1965 falcon/mustand.
Tony Bates

Here's my first take at solving the problem...paint is just rattle can playing around with schemes..&, we're even modifying this hood for more clearance
anthony barnhill

ooops, sorry...just go to
anthony barnhill


Are you sure you can't get your EFI to clear? Mine clears after machining, Glenn Towery has done several that clear the hood. I started with Roger Parker's advice on machining, then when I still did not have enough room- the hood closed but was right on the plenam- I hammered the fuel rail down & took another 3/8" off the bottom of the trumpet section.

Is it possible to get the engine any lower? After my engine is in place, I leave the puck to body bolts loose & then smack the top edge of the puck with a bar & hammer. Usually good for 1/4" plus it prolongs the life of the rubber mounts by keeping them compressed.

Another solution I have seen is to machine the top of the plenham flat & weld a piece of 1/4" aluminum plate to cover. The trumpets need to be shortened, but that is a simple job.

If you must do a scoop, the air nibbler & masking tape is the best way to go. Drill your starting hole a good way inside your cut line. A bit of practice is not a bad idea.
Jim Stuart

Thanks for the advice Jim. I can't lower the plenum any more. The fuel rails are the problem. I've trimmed the injectors so the rail is as low as possible. The system I'm using is an airflow one ,not the hotwire one ,although it looks like a hotwire apart from the fuel rails. If I lower the engine, the steering column would foul on he headers.I've seen pictures of the plenum with the top replaced & it looks like serious machine work to me. I think the scoop was the easiest way out . Believe me ,I didn't arrive at this decision lightly. Regards Barrie E
PS I hope to meet up with you again in GR this year.
Barrie Egerton

Barrie - there are enormous variations in the rocker covers - I suppose you have the smallest ?


Somewhere on another thread, Glen Towery discusses his method of "adjusting" the fuel rail with a hammer to gain enough clearance 'without' machining the plenum. Claims it works for all the cars he has built. Might be worth searching the archives before cutting your hood. In my case, the plenum is machined and it obtained enough clearance, except when you leave a wrench on top of the plenum. I think the car looks better without the scoop, but others may prefer the more aggressive look. Good luck.
Edd Weninger

I don't see any advantage whatsoever to an MGC bonnet because the extra height is way up front. There is emphatically not one RCH more height to it where your plenum goes. ;-) . Plus a C bonnet has that little side bulge which is great on a C because it implies what's underneath, but is totally random on a V8. Again, I'd say, just get an RV8 bonnet or have it's equivalent made up. Given that you're using an EFI setup, the RV8 bonnet should be just perfect (the bulge is slightly too narrow for a 14" air cleaner on top of a carb) and they look great. There was a guy on this BBS who'd had an RV8-style bonnet made up out of a stock alloy bonnet and it looked screamingly great, though I know he said it cost a fortune.
Bill Withum

All I can say is the two B bonnets I have (one steel, one ally) both touch the top of the plenum, the C bonnet doesn't. For reference, the high point on the plenum is 15" from the back of the bonnet.
I agree an RV8 hood would be nice but the C bonnet cost me $80, more the cost of shipping an RV8 hood to California, let alone the cost of the hood itself.
Tony Bates

Barrie - you get the drift don't you ? We think you can get it under a conventional bonnet and that you won't be happy unless you do.

e-mail if you think you might have missed some of the lowering tricks.



I thought you had RV8 headers? I don't have them, but am surprised there is a steering column clearance with that style.

I carefully 'creased' my block huggers to keep the engine very low. This combined with thinner rubber mounts may help.

I am sure I read somewhere you can get thinner mounts?

Ian Buckley

" am sure I read somewhere you can get thinner mounts?"

Clive Wheatley or the Club.


Thanks everyone for the advise. I can't lower the engine anymore because the car is a '71 rdstr. & I've retained the CB crossmember & original steering although the shaft has been lengthened to move the U/J further back.It has blockhugger headers. This set up was an achievement in it's self for which I was quite proud of. The EFI is the last type of airflow system. The maximum amount of metal has been removed from the plenum, trumpet section etc. The fuel rails have been lowered to the lowest possible point & the front half of the plenum is still about 10 mm too high. I not concerned about the hood scoop. It looks good & will be a means of evacuating hot air from the engine bay whilst stopped in traffic. The original post was how to cut the hole without distorting or damaging the hood/bonnet. One other point I should mention is, in Australia very few MGs ever get scrapped. so ,used parts or panels are very rare & generally not cheap.Thanks again everyone . Barrie E
Barrie Egerton

One other thing to remember, be sure to leave a radius in the corners. If you cut the corners square it is more likely to start a crack. Could perhaps use a 50 mm hole saw at each corner of the hole, going tangent to the outline.

Good luck.
David Walworth

The deed has now been done ! I cut 35mm holes in each corner & found a really thin (1mm) cut off disc for my angle grinder. There is no distortion in the hood & the paint didn't get damaged. The scoop is now fitted & I'm looking for some flames to adorn the front of the car. Barrie E
Barrie Egerton

Good show Barrie. Sounds like the perfect approach. Glad you're happy with the results.

Jim Blackwood

Dont forget the Studebaker fins for the back end.

This thread was discussed between 03/02/2004 and 12/02/2004

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