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timing the 248 buick straight 8


Guest TheRusch
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Guest TheRusch

I replaced the timing chain, but am having trouble setting up the ignition timing. When number one piston is at the top of it's stroke with valves closed, the timing mark on the flywheel is nowhere near the mark on the bell housing. I installed the timing chain according to the shop manual, but can the cam be 180 degrees off since the crank turns twice for every rotation of the cam? Am I missing something here?

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A very common problem with the Buick straight 8's is that the flywheel can be put on wrong if it is taken off for some reason. There are 6 bolts and 8 cylinders, so there is only one right way to install the flywheel. Done wrong, the timing marks will be nowhere to be seen.

If that happens to be the case with your engine, you'll have to rough in TDC on the firing stroke by putting something in the sparkplug hole and carefully turning the engine until you determine the TDC and then just time the engine by ear, adjusting the distributor so the the engine cranks without balking and then runs without pinging.

The flywheel error is very common

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Was engine running before you installed chain? Was engine at TDC #1(t-mark would have been in the window)and chain had 11 links (mark on crank gear to mark on cam gear) on your installation? And then you dropped the distributor in with rotor pointing to #1 plug wire, you could easily be off if dist. was not fully seated in to oil pump. I would pull the valve cover and #1 plug. With ign. "off" manually turn engine until T-mark shows in the window. At this point #1 and #8 are at TDC(one will be on intake stroke and the other will be on exhaust stroke), you can tell by the rocker arms. If #1 in on the exhaust stroke rotate engine 360deg. Then check if dist. is in correctly, rotor should pointing at #1 plug wire in dist. cap. If pointing to #8 plug wire your dist. is 180deg off. Good Luck

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Guest TheRusch

By the time I get this engine together, I will know just about everything there is about Buick straight 8s. I'm going to put a 1938 engine in my 1940 Buick Special because the original engine was partly disassembled and then left to rust. I purchased the 38 engine minus intake/exhaust and distributor. In order to put the 38 engine in my 40, I had to change the bell housing and the front motor mounting plate. That meant taking off the rear main bearing and removing flywheel, pressure plate and clutch plate to get at the two bolts on the inside of the bellhousing. It never occurred to me that the flywheel could go on six different ways. Thanks DonMicheletti for pointing that out. The engine is not in the car yet, but I don't like the thought of dismantling it again in order to change the flywheel position. I have the valve cover off and number one plug out so I can tell when the piston is at top dead center. Thanks pont35cpe for pointing out the position of #8 in relation to #1 piston. If I decide to relocate the flywheel, I'm guessing that I will have to have the engine turned so that #1 is ready to fire and then put the flywheel on with the timing mark showing in the timing window of the bellhousing. One other question. Is #1 plug wire to the right of the vacuum advance on the distributor? Thanks guys.

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Once you check out all the above, some oldtimers (older than us) set the timing with a vacumn gage. Get the engine running then rotate the distrubitor to get the highest vacumn at idle....

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Timing without a light wasnt that difficult when "high compression" engines came about in the early 50's. Once you got the engine running you'd advance the distributor until the engine pinged on hard acceleration, then you'd back it off a bit until it didnt. Harder to do with a 6.5:1 compression engine.

To reset the flywheel, just turn the engine via the bolt on the crank front pulley until the #1 piston is at the top of the stroke (poking through the sparkplug hole) and both intake and exhaust valves are closed. Then you'll be able to position the flywheel properly.

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As a temporary measure if you want to wait to swap the flywheel around, find exact TDC of #1 using the long screwdriver method or similar. Make sure it's in the firing position with both valves closed and distro rotor pointing to #1 wire. On the front of the engine on the generator side, take a look at the damper. Get some white paint and using a small artists brush paint a small line on the damper. Since there isn't a pointer you will have to find and mark a reference on the block. White touchup paint for a car that already has the small brush will work well. For 4 degrees advance, it's about 1/4" advanced from this line.

This way you can use a timing lite until you get around to switching the flywheel around. The paint can be removed with a small bit of chemical paint remover when you are done with it. I have a driver so I put the marks on the damper after trying to time it using the flywheel marks - couldn't see them very well! So I manually rotated the engine to the mark and painted marks on the damper. MUCH easier and the added advantage of seeing how well (or not!) the centrifugal and vac advances are working.

Cheers, Dave

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Guest TheRusch

I still have the 38 front engine mount Jenz. I also have the 38 bellhousing, flywheel, pressure plate and clutch plate. I also have a 38 transmission without the shifter. The guy I bought the engine from kept the shifter and mounted it on the GM automatic trans he put in the 38 coupe he is building. Dave, I like your idea about putting the timing mark on the damper.

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Rusch, My dist. is set with the v-advance pointing toward the firewall, almost parallel with the block. In this position #1 plug wire is just to the left of the upper cap clip. "If" you have an original distributor cap, the number for each cylinder, is on the top of the cap at the base of each plug wire tower. I marked my flywheel at 90, 180 and 270deg from the TDC mark, these marks are for valve adjustment. I warm the engine up, kill it, pull the valve cover and starting with #1 TDC, work thru the firing order turning the engine manually 90deg(or my marks)and adjust both valves and repeat this thru complete firing order. Takes two complete revolutions, and done... No big oily mess..

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  • 2 weeks later...
Guest TheRusch

I decided to bite the bullet and remove the flywheel. I have it located correctly now. And I had the timing chain one tooth off. So, now I need to get everything back on and see if I can spin the engine with the starter. It will be some time before I actually try to fire it up.

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