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MG MGB GT V8 Factory Originals Technical - Acceleration

I was just looking at the MGC section and read through a posting regarding acceleration.
Since I haven't finished my conversion, this is interesting to me and I'd like to see what others are getting, even if the measurements are not that accurate.
How about some feedback on how your cars accelerate? List rear end ratio, engine size/tweeks, gearbox, wheel/tire size and a 0-60 figure plus any other inputs (like wheelspin).
Erich Hovley

I've been using a car test program I found on the internet. See write up on my website

www.mgbv8.co.uk

This program comes in DOS and windows versions, but I think I prefer the DOS version as it handles the presentation better.

There is a link to the site where you can download a shareware copy from.

I found it a little optomistic, but everything if changeable, down to gearchange times, humitity and drivetrain losses etc for each car.

Nick

Nick Smallwood

I have been trying to get some accurate figures for my car and intend to take it up the Santa Pod sometime soon. In the meantime my home measured figure is 6 seconds 0 - 60. The engine is a 3.5l SD1 with 9.75 CR, standard cam and SU carbs, it produces around 160 bhp at the wheels at 4000rpm. The rear axle is 3.3 to 1 ex MGC shod with 185/70 14" tyres. The car is not lightened. I can get wheelspin in 1st, 2nd and 3rd, but fastest times are recorded by pushing the pedal down fairly steadily rather than flooring it all at once.
Chris

Chris,
What fuel are you running with those 9.75:1 pistons, and do you have any problems with detonation? I've put those pistons in my GT V-8 engine during my full rebuild, and I am curious what the outcome will be.

Cheers,
Paul Kile
Paul Kile

I run it on 97 octane unleaded fuel and 6 degrees BTDC ignition timing. I get no detonation at all, but then I wouldn't expect it with ally heads. I had the engine set up on a rolling road intitially with BAK needles in the carbs which were then filed down as necessary to get the right fuelling troughout the range.
Chris

Paul I ran 9.75:1 pistons in a Rover 3500s engine instead of the 10.2:1 that come as standard in the first V8 conversion I did here in the States. Timing static at 8 deg BTDC. No problem using 93. My two cars in England both use 9.75:1 pistons. With Lumenition ignition, and modified primary advance springs in the dist.I get no pinking (pinging) under light or heavy loads on 4 star or Super unleaded. The 3.5 Roadster gives 182 bhp at the wheels. The 3.9 "factory" GT about 215. I wont bore you with the engine spec!
tess D'Urberville

I don't have 0 - 60 times at present but I do have a lot of 20 - 60+ data from a logger in the car ( it just doesn't see the wheels start moving!).

A good 20 - 60 run is in 4.2 seconds, the software mentioned in an earlier post sugggests a 0 - 60 of about 5.5 for the same 20 - 60.

Spec is SD1 gearbox, mgc 3.3:1 diff and 195/60/14 tyres (road/race yokohama 032r and warmed up) driven by a 3.9l on carbs giving about 165 hp at the wheels. CR is not certain but should be a little over 9:1, unfortunately I don't know what the pistons are intended to give or with which head gaskets and changing from tin to composite gaskets can lower the CR by nearly half a ratio.(However I will check with the supplier)

Roger Parker might have some figures, I suspect his car has been tested more than most and a injected car should have a better induction system than the carb setup.

Dave

Dave Brooke

I don't have official figures, but my car(73 MG roadster) can out accelerate a 91 and a 93 camaro Z28(only fast cars I have raced), starting in second gear. I need to install traction bars as a hard first gear start will produce VIOLENT wheel hop. I can spin the tires in 1, 2, and 3rd from a standstill.(3rd requires 2000 rpm launch).
Top speed over 130 (too scary to take it over this speed as front end starts to lift causing car to drift, windows REALLY start to shake) but would estimate 140 -150 top speed with top down.

Engine block is 4.6
heads RPI stage 3
295 deg. cam
Offy 360 intake, Carter AFB carb
home made full length headers
BW 5 speed tranny
3.08 rear end. (3.9 rear was GREAT for acceleration, gas mileage sucked)
15 inch rear wheels

Supercharger comming soon :)
joaquin

Eric, Check out this web site http://members.aol.com/danmas4/mgv8conv.htm#dragstrip
for some drag strip times posted from the 1999 NAMGAR V8 meet Champaign, Illinois.
One MGB V8 302cid broke 100mph in the quarter mile! Regards, Jack Renaud
John Renaud

This thread was discussed between 03/02/2000 and 08/02/2000

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