Thread: engine swap
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Old 04-06-2017, 09:55 AM
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Luva65wagon Luva65wagon is offline
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I'd prefer pulling a transmission, personally, but something you said just now seems to push me further on the side of a non-weight related issue. If this imbalance doesn't get worse with engine speed, then it's probably not an imbalance after all. Things flinging out of balance tend to get more intense with speed. Anything will seem to run better once you've reached speed. Most effort to accelerate behind you, weight and momentum carry you along. But increasing engine speed should intensify a weighted vibration.

So I would focus on the low compression issue to begin with. The one thing you can do to check for an ultra loose timing chain is to put a socket on the crank bolt in the front and rotate the engine, by hand, to the left and right. You may have to loosen the fan belt so you are not fighting the fan. The cam and valves will resist turning more than the crank does, so you will feel a definite amount of resistance as the chain tightens in one direction and the the other when it is trying to move both crank and cam. Where the crank moves forth and back with the most ease will be when you are only taking up chain slop and only the crank is moving - and not the cam also. If, when you feel this increased resistance, you make a mark on the balancer (in one direction) and then reversing you make a mark using the same pointer mark (when going in the other direction), you can then surmise roughly how many degrees the crank can move without also moving the cam. If this is excessive, like more than 20 degrees, then the chain can be stretched enough to skip over a worn cam or crank gear.

This is really the only external test for a loose timing chain.

Note 1: A new chain will stretch very quickly to allow a few degrees of forth and back slop, but the total slop is really half that as seen by the cam. The engine only spins in one direction normally, so my test for total slop is not what the total number of degrees the engine is running off of. As chains loosen over time the running condition worsens, but an engine will run with a lot of cam degreeing. Racers sometimes do this on purpose.

Note 2: Though I'm not certain all of what motors Ford did this to, it was common in the 60's to have a nylon cam gear, which was added to an aluminum cam gear blank to make the thing quieter. You know how annoying that cam chain noise is. Yeah, right. The problem was that the nylon could fail leaving an aluminum set of gears, but way smaller. This is a common reason old, revived, Fords fail when brought back to life. These gears were one of Fords better ideas. Not.

If the chain doesn't seem too loose, there is still the potential for it having been installed wrong - if this is a recent rebuild. I'm still unclear from reading your posts whether you still hold to this notion of newness or not.

And yes, a motor can run with a timing chain jumped. But too many teeth off and all the valves open and close at the wrong point for optimum air intake and compression will suffer.

Good luck.
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