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MG MGB GT V8 Factory Originals Technical - Need help with Buick tuning, Rich
|OK, New thread! Engine is a '63 HiComp Buick 215, used bottom end with rebuilt top end. This is the way I bought it... Carb is a downjetted Edelbrock 1404 from D&D out of the box. Stock cam and lower end, dual exhaust. Stock dizzy w/pertronix ignition, timed by vacuum gauge to peak reading. I ran the engine for about two total hours and checked the plugs/compression (three hits each) to get a feel for the state of tune.|
Cylinder 1=140psi, black sooty plug. 2=143psi, black sooty plug. 3=124psi, black sooty plug. 4=142, black sooty plug. 5=120psi, decent plug. 6=135psi, black sooty plug. 7=129psi, black plug. 8=120psi, black plug.
It has new gas, starts and runs pretty good but has some blowby out the oil fill cap. The exhaust smells a little rich. The manual choke is adjusted and functions correctly. Runs about 190F.
What is the normal compression, and where do I go from here to get it tuned better? Please advise. Thanks, Scott('58 MGA 215/T5, MGB brakes)
The whole thing apart from no.5 looks rich. If it's not flooding up at idle the carb needs setting up with an exhaust gas analyzer. As for no.5 check for a vac. leak. Could be an unused vac port on the manifold sucking air or maybee the inlet manifold gasket not sealing oroperly. Willy.
|D & D should know the corrects jets and rods for the 215/3.5L engine but probably worth checking what is fitted, it may be as stock.|
The recommended rods and jets fitted to the primaries of my 3.5 are rods1441 and jets 1421 with the secondaries as per stock setting.
The car runs well and will return up to 27MPG (imperial) on a run of mixed motorway (freeway) and cross country roads including a bit of spirited driving.
The engine is lightly modified with stage 1 heads and a fast road cam for approx 200BHP
I would be a little concerned about the cylinder pressures especially if it's 10.5/1 compression but if the engine has only done a few miles since installaton and the engine stood for some time prior to starting the rings may be a little sticky and not sealing properly.
You could try spraying some releasind fluid or carb cleaner through the plugs holes, turn the engine over gently and leave it for a few days then give a start up and take it out and give a bit of hard use to help the rings bed in to the cylider walls and then recheck the pressures. It could be that if the bottom end has never had a rebuild that that as good a your going to get, but certainly worth a try.
|If it's a used bottom end, I assume that included the pistons and rings. That being the case they should already be seated.|
I am also assuming that the cam and lifters were not changed.
Making a lot of assumptions here, I assume that the two hours running was mostly idling while you watched, listened and smelled.
Two questions: are the spark plugs the correct heat range, and, did you adjust the carburetor with the idle set at about 600-700 rpm?
This thread was discussed between 30/10/2008 and 03/11/2008
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