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MG MGB GT V8 Factory Originals Technical - Wow! Rolling road and upgrade result.

Had my Gt 4.6 Rolling road tuned yesterday with surprising results.
Engine spec before recent mods:-
4.6 crossbolted with tophat liners, Burgess econotune heads, Piper 285 cam, RV8 ehhaust, Edelbrock 500 carb on JWR manifold, 10:1 compression, Standard valves, mallory dual point dist.
The upgrades:
Fully ported heads with large valves and chambers matched, modified guides (DJE), Edelbrock performer inlet port matched to heads, 10.8:1 comp ratio.
Before 210hp at wheels
Now 247hp at wheels.

Electrifying to drive in the dry, very scary in the wet!

One problem highlighted on the RR was an intermittent missfire above 5200rpm. Have been advised that I need to upgrade my ignition system to cope with the high compression.

The Extra height of the inlet manifold has resulted in the 14" filter protruding up through the bonnet"C" about an inch. Cant seem to find a scoop/bulge big enough to cover it. Thought about a rear facing scoop.
Any thoughts.

Mark

Mark

Mark,
Does the Costello bonnet not fit ?

I understood that he designed it for this type of carburettor. I'm surprised that it's taller than the EFi plenum, which (just) fits under the RV8 bonnet (I'm assuming you've tried one of these ?)

If not I can give you approximate measurements from mine.


Mike
M Barnfather

Mike
I dont think the RV8 bonnet will fit at the airfilter is 14 inches diameter.
Havent considered the costello bonnet, anyone got pics and where could I get one?

Thanks
Mark

Mark,

I use K&N X st 14x3 dropbase with Holley which is marginally taller than Edle under RV8.

Which RR as a have an Edle in garage to fit at ssome time. What breather set up are you using?

Nick Smallward has RV8 dimensions on his site.

Paul
Paul

Paul
I too have the Xstream filter top. Have decided to try and make my own bulge just to be different.
The RR I used was Circuit motors at Castle Combe, Wilts. I think it was quite an old machine made by Bosch.
Which ignition system are you using?

Mark
Mark

Paul
I am using a Jazz mini catch tank which has a small filter. Pipes run to it from each rocker cover.
Originally I ran the pipes to the air filter but this made a lot of mess on the Xstream top.

Mark
Mark

Mark

Mallory Magnetic.

Just moved mine for that reason, but no catch tank as yet. Where did you obtain your catch tank and where fitted? I've still retained a small pipe to filter.

Paul
Paul

Bought my catch tank from Rally design, it is very small. I mounted it near where the servo used to be.
Think I will get a larger one eventually.
http://www.rallydesign.co.uk/catalog/index.php?manufacturers_id=32&sort=2a&page=2

Mark
Mark

I picked up a 1.5" drop-base, 14" filter assembly from a shop in the States on E-bay to use on my 3.5 Rover. Using the X-treme filter top and K&N's shortest filter, I can just get the assembly to fit under the hood but I did add a scoop for better cooling (looks like the '67 GTO scoop). This allows the hold-down screw to fit under the hood as well.

I've got the Edelbrock 500 sitting on a Performer intake which is taller than the JWR or Offenhauser.

Pictures and part numbers available if you like.

Great numbers off the dyno, Mark. I had my car done last fall. Stock 3.5, RV8 headers, carb as mentioned = 143 hp at the wheels @ 4750 rpm and 190 ft/lbs at 2500 rpm. I've since added an MSD ignition to clean things up a bit so have to get it back to the dyno.

Cheers
Simon
Simon Austin

Simon
Some pictures would be good especially the scoop.
What exactly is the MSD ignition?
My email is v8mg@blueyonder.co.uk
Thanks

Mark
Mark

Mark

Perry, also with a bonnet issue is using MSD available from Real Steel

http://www.jimmcglynn.pwp.blueyonder.co.uk/perrycar/index.html

Paul
Paul

Mark,

Interesting set of results and suggests about 280-285 flywheel BHP, sounds about as far as you can go without extreme measures and a large cheque book.The standard Rover casting of the exhaust port being the biggest restiction and the only way forward from there is a set of Wildcat Engineering heads VERY EXPENSIVE. A pair of their heads sold on ebay recently and the heads inc. roller rockers and throttle bodies sold for in excess of 2750.00 if I remember correctly.
A few more BHP will probably be found by improving the ignition system and an occasional misfire above 5200RPM suggests that you are getting less than perfect ignition in the higher rev band, a decent electronic ditributor should give you what you are looking for. I'll leave the recommendations to others as there are many choices available and I am still running a Lucas 35DLM8 which I'm sure is far from perfect.

Kevin Jackson.
Kevin Jackson

This thread was discussed between 12/02/2006 and 14/02/2006

MG MGB GT V8 Factory Originals Technical index

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