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MG MGB GT V8 Factory Originals Technical - loosing power?
|I have owned a v8 converted B since 1993. |
I have often though that the power has dropped off quite a bit over the years, despite 6 monthly service intervals despite lowish mileage. Full use of engine is made when driving car.
Spec I beleive is standard SD1 9.75CR, mileage approx 70k (60+ on clock but reads slow)
Starts fine, runs fine burns no oil, quiet runner
Comperssions are level and dont seem to have dropped since milage was 30K.
Run on plain unleaded, tried octane booster/ lead free adative and hi octance fuel
still pulls very well but I really do think she is down on power
Any suggestions on best way to check?? or what else to check??
Gearbox is past its best now, noisy, hard to get some gears now and then so its on list to get replaced but would like to make sure engine is up to scratch before pulling it all out!
|One possible source of decreased performance is stretch in the timing chain which will retard the cam. I found this on my V6. It totaled 15 degrees, which was the amount of retart found when a new chain was installed and the distributor reset. I picked up 5 mph in top speed after just that change.|
Lots of people have reported heavy wear on cam lobes after taking their engines to pieces, I'm guessing that's your problem, 70k is a fair mileage, particulary if previous owners have not been too consciencious about oil & filter changes.
I replaced mine at about 60k with the standard Vitesse cam, metal timing gears, and offset keyway to give more torque.... it made a tremendous improvement to initial pick up without ruining fuel consumption.
|A mechanic friend who helped with my first V8 conversion raced TR8's, & told me that his experience was that the Rover cams were soft & wore the lobes down. He recommended new cam & lifters at 50,000 miles. He changed all the motors he built to aftermarket double row timing chains, & for street cars, an aftermarket single row timing chain, replaced at around 50-60,000 miles.|
Aftermarket cams & lifters seemed to last longer, but should be checked at around 75,000 miles. I am not a mechanic, but it seems to me that you could measure the amount of lift by turning the engine with the valve cover removed, without an engine tear down.
|...and double check your vacuum advance.|
This thread was discussed between 14/05/2004 and 15/05/2004
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