MG Sports Cars

engine swaps and other performance upgrades, plus "factory" and Costello V8s

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Michael Williams
Kent, UK
(1 posts)

04/10/2020 06:17PM

Main British Car:
MGB GT - V8 Conversion Rover 3500 V8

MGB GT V8 conversion
Posted by: MJW16
Date: April 11, 2020 04:08AM

Morning all

Iím in the UK, new to the forum., and hoping the wealth of knowledge here will help steer me down the right path.

I have a 79 GT thatís being converted to V8 and chrome bumper.

This weekend Iíve stripped down the engine which was an eBay purchase a while back. Hereís what I know;

Engine number starts 10A, which I believe means itís from a manual SD1. Compression ratio is 9.35:1. I have a JWR Offy dual port manifold and Edelbrock 1404 500cfm ready to go. Gearbox is 5-speed LT77.

The engine had been stripped and Ďpartially rebuiltí by the previous owner. However Iíve stripped it back to a bare block to start again - partly because Iím not taking any chances on someone elseís work, but also because heíd done something wrong as the engine wouldnít turn over even with a socket and bar on the pulley. As I dismantled I expected to find a seized piston or stuck valve, but all were fine. I suspect heíd used old mismatched bearing shells tightened incorrectly and with no assembly compound, so it had all pinched down tight. Hopefully thatís all it was(?)

Two questions have come up so far;

Valves - I seem to have a bit of a mismatch. Inlets are all 614088 VL, except for one which is a 614088 B.C. and looks slightly different. Exhaust are all 614089, but one has a V after it and the others donít. I donít know what the V/VL/B.C suffixes mean.
The exhaust valves are fairly pitted after a clean up, and one is really bad. That, combined with the apparent assortment of types is steering me towards replacing the whole lot (inlet and exhaust). Does that sound sensible?

Camshaft - on removal Iíve found it stamped BP285, which I believe makes it a Piper ĎUltimate Roadí. After initial excitement at this discovery (the inner kid!) itís occurred this needs some careful consideration. A lively Cam might be great for enthusiastic drives, but I wonder if the idle will be annoyingly lumpy and the drive not so good if cruising around normally. Also, more importantly, the heads have standard single valve springs, and Iíve read conflicting opinions about whether that Cam can be run without upgrading to double springs and machining the head to suit?

Has anyone got experience of a similar set up to the above? Any thoughts and guidance would be very welcome.

Iím not aiming for a racing machine here, but if I can get the old girl to nudge over the 200bhp mark that would be great.

Many thanks

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