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MG MGB GT V8 Factory Originals Technical - What is it?

Hi

I'm trying to work out what spec. the engine in my V8 is so that I have a clue what springs and needles to put in the new HIF6 carbs (cheers, Philip) when I install them.

It's an old block (rope seal on the front cover, engine number on the rear face), the donor car probably had HS6 carbs (as that's what's currently fitted) and the stated compression ratio is 10.5:1.

The engine has been rebuilt at some stage, so even identifying the donor vehicle may not yield the answer - I don't think a 10.5:1 engine would be happy on regular unleaded.

Any ideas?

Alternatively, do HS6 and HIF6 needles have the same codes?

Thanks,

Nick

Nick Wilson

You don't give us much to go on ! If identifying the donor car via the engine number is not of any help, what else can we do for you ? telepathy perhaps ? (sorry, couldn't resist...)
Seriously I would expect any competent carburettor specialist to be able to translate the HS6 needles across to HIF6 for you...
HTH
David Smith

David,

You're right. I didn't really phrase the question very well. What I meant to ask is: Is it possible for me to determine the (approximate) spec. of the motor without taking it apart?

And also, is it likely to still be 10.5:1? (given that it seems to run OK)

Nick

Nick Wilson

Old block
Rope seal
10.5 compression ratio

Sounds like Rover P6 to me!

Nick
Nick Smallwood

Yes I agree it sounds like P6. I t's unlikely that the previous owner has gone to the trouble of lowering the comp ratio - if he had then he'd be the sort of person to have kept records and passed them on to you, surely. I don't think you can find out the spec without a strip down. Remember what our US friends say - if it ain't broke, don't fix it'.
David Smith

A rebuild would probably have included plus 20 or plus 40 pistons which should have by default reeduced the compression to about 10.2 to 1. This was a standard feature as 5 star petrol had disappeared and so the replacement piston market adjusted the dish to compensate.

However my own pre production engine which was built during early 1967 before any cars were produced. Test engine) has had two rebuilds in its life. Once when it was still on a test rig during the 1970's and then after it came into my hands during 1985. I have retained the high compression, 10.2 to 1 with plus 40 pistons and added Pete Burgess modified heads, which significantly increases volumetric efficiency.

Even so I have had no problem running standard unleaded since it first appeared and the engine has in the same period gone from strength to strength in increased power output, which was last recorded at just under 190bhp at the rear wheels.

A recent head removal for simple examination (as th opportunity presented itself) showed only one problem and that was related to the outer four short head bolts causing the heads to pivot and introduce signs of compression leakage into the vee. This is another issue and one of the reasons that since the introduction of 4.0 and 4.6 litre engine specs only ten head bolts are used.

Rog
Roger Parker

Roger,

Thanks, that's good news about regular unleaded, as super U/L is hard to find out in the sticks.

Your car is 'injected, IIRC. Is the ignition timing under the ECU's control too? I'm just a bit paranoid about pinking as the car is so noisy I don't think I'd hear it.

Cheers,

Nick
Nick Wilson

This thread was discussed between 18/08/2000 and 30/08/2000

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