Wear/failure pattern in a Big Valve engine ?

[Canuck]

Not quite "how long is a piece of string ?" but what wears out first in a thrashed/hard driven engine ? Most engines follow a pattern of wear. One part more frequently wears or fails eg crank on a 356.

I am about to start a restoration on a 69' +2 with a Big Valve head fitted to the original engine. Nothing is known of it's history ( 48 thou. miles ? and I have not been able to drive it on the road nor under load - yet.)

The compression is excellent 10.6 : 1 measured. No smoke. The 'mechanical sound' has a hint of piston slap and maybe some little-end noise. Same general mechanical sound when any of the 4 plugs disconnected.

So what wears/breaks most frequently on these engines ? Any audible symptoms ?

i will be doing a full mechanical restoration but it would be nice to know from other Big Valve owners , what to expect in my first twin cam.

Cheers Canuck

[elan_fan]

A little piston slap when cold in classic "large bore" fords is normal. I would say that if the water pump (which is probably the highest wear part) has no free play when you rock the pulley, and you are showing above 180psi on the compression tester with all four at about the same reading, and you have more than 1/2 inch of timing chain adjuster screw showing above the nut and the chain is not trying to grind its way out of the cam cover then you are good to go. These engines aren't modern but in my experience when they are cared for they don't overheat, they do start easily and they are reliable. Normal wear areas are bores, corrosion in water ways especially in the head, valve guide wear (there are no oil seals on the guides remember), slack cam chain, water pump and then on to the usual engine problems that effect all engines such as worn bearings and so on. These are old technology and as such it is usual to use oil and make strange noises. Have a look at the forums though and see how many threads start "my engine was proffessionally rebuilt 1000 miles ago and has now developed a problem/seized/exploded/caught fire/etc. Like all engines, if they need rebuilding then don't do a half measure but if it's not broke then don't try to fix it.

regards
Mark

[Canuck]

Thanks for your reply Mark,

I tend to have a similar approach to old sports car engines as you do.

Your message confirms the general mechanical noise levels that the engine produces. They all have their own distinctve rattles and taps and the Twin Cam is a new one for me to interpret.

I will be checking out the wear levels on bearings etc but I definately believe in " if it aint...etc".

My compression readings hot and dry were betweem 160 and 155 psi which at the ambient atmospheric pressure indicate about 10.6 : 1 (ok for a Big Valve) and good enough for me - it won't be a track car.

Cheers, Canuck