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Re-torque after rebuild


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Is there a set distance at which the cylinder head needs re-torquing after a major re-build? I've done 222 miles since a major re-build in 2016.I know I should get out more but some stuff got in the way (including a house) but I plan to put a few more miles on starting soon.

 

Thanks in advance

 

Keith

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Hi Keith,

 

Tom is of course correct.

However I'd be tempted to think that a couple of years without use after an initial 200+ miles will have relaxed the torque somewhat, so I'd hit it immediately with a retorque which should make it good to go and then after another 500 miles (hope that's done in a year) give it another retorque. It won't hurt the engine and prevent a possible blown gasket in the interim.

 

Mick Richards

 

PS: remember to relax the torque first by "undoing" the cylinder fastenings by 1 flat, it removes any sticking of the fastening and then retorque it back up to the correct setting in one smooth pull according to the torqueing sequence.

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Hi Keith,

 

Tom is of course correct.

However I'd be tempted to think that a couple of years without use after an initial 200+ miles will have relaxed the torque somewhat, so I'd hit it immediately with a retorque which should make it good to go and then after another 500 miles (hope that's done in a year) give it another retorque. It won't hurt the engine and prevent a possible blown gasket in the interim.

 

Mick Richards

 

PS: remember to relax the torque first by "undoing" the cylinder fastenings by 1 flat, it removes any sticking of the fastening and then retorque it back up to the correct setting in one smooth pull according to the torqueing sequence.

+1 - start again

 

Roger

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Is there a set distance at which the cylinder head needs re-torquing after a major re-build? I've done 222 miles since a major re-build in 2016.I know I should get out more but some stuff got in the way (including a house) but I plan to put a few more miles on starting soon.

 

Thanks in advance

 

Keith

 

Keith:

 

Just to stir the pot a little bit; I think the 500 mile rule was intended to insure that you had a decent number of heat/cool cycles on the motor. I suspect if you drove the car 500 miles in one pass after the rebuild, it might be a little too soon. But that is me.

 

Me, I just overtighten the bolts by about 5 lb-feet, and say "job done". But then, I am running a 0.060" overbore on my TR8, so I like living dangerously. :blink:

 

Vance

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Hi Keith,

 

200 miles in 2 years and not retorqued . . . . . ?

 

From my past experience, if it's an SD1 engine then it would be wise to have a head set ready on the shelf, there's at least a sporting chance one or other head gasket will let go . . . . . but if it's a P5/P6 engine or a slant-4 then I'd lay odds on the head gasket letting go sooner rather than later.

 

Cheers

 

Alec

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Ah.Thanks for the above gents. I forgot to say this my four pot I was talking about. The Grinnall hasn't progressed much since last May either but having moved house and largely sorted the new one, I'm hoping to get back onto both cars this spring. Thinking about it, the four pot has probably had five outings in all that time. As I said, I really must get out more. And if the worst happens at least the head should come off fairly easily.

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"at least the head should come off fairly easily".

 

If you smeared the fastenings with Coppaslip on the shanks (not threads) before refitting it will.

 

Mick Richards

Edited by Motorsport Mickey
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  • 4 weeks later...

Now the snow has gone away and the temperature is up to a tropical 8 degrees, I got back in the garage and re-torqued the head and checked the valve clearances. The clearances are all way higher than the Haynes manual figures so I'm in for a spot of shimming. With the clearances being greater than specified, what effect would this have on the performance? I'm guessing the valves would be open for a shorter time than required so less fuel gets in and similarly less burnt gas gets out, sort of proportional maybe? The car is running well enough as it is but it would be good to know.

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Now the snow has gone away and the temperature is up to a tropical 8 degrees, I got back in the garage and re-torqued the head and checked the valve clearances. The clearances are all way higher than the Haynes manual figures so I'm in for a spot of shimming. With the clearances being greater than specified, what effect would this have on the performance? I'm guessing the valves would be open for a shorter time than required so less fuel gets in and similarly less burnt gas gets out, sort of proportional maybe? The car is running well enough as it is but it would be good to know.

You will have a smoother idle, lower emissions, better economy, and less power all other things being equal. Oh yeah, valve train clatter might pick up a bit.

 

Vance

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  • 4 weeks later...

Thanks to all who have replied to date. I'm back on this now, re-shimming the tappets.

 

I notice that with the camshaft and crankshaft in alignment (sort-of) that the crank timing marks are 4 degrees BTC. Before I try to align these exactly, is it that critical? I counted the teeth on the cam sprocket as best I can and I suspect one tooth adjustment could give me 8 degrees movement so there wouldn't be any significant improvement. Is this indeed the case or is it worthwhile taking down the front of the engine to jump the timing chain one link or so?

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