Gaskets

[Matt306]

I think I sort of know the answer here....

I am swapping my TR7 engine, I have had an ebay purchase of a cheap engine. Stripped it had it bored, +20 piston +10 crank regrind, the crank balanced top of block skimmed, flywheel skimmed and balanced. On the head head had it skimmed fitted fast road cam, new valve springs.

 

Swapped the engine over , turned it over on the starter, no oil pressure. Whipped off the dizzy (for those who know my TR7 its for a secondary cam signal and doesn't do spark stuff), spun the oil pump with drill and oil pressure came back. Refitted dizzy crank and we have oil pressure.

So on to refitting bits... on to the spark plugs fit wind them in my by hand as per usual. 1 2 and 4 tighten nicely, number 3... oh no its stripped, never noticed on the rebuild. Well it doesn't matter too much as i have a spare head on the old engine although the springs are weak and has the standard cam.

So I now have to helicoil the aluminium plug hole, its a little annoying as the engine hasnt started yet. 

 

So the question.... can i get away with reusing the head gasket? I have only filled the engine with oil no water as yet and it hasnt started.

 

 

 

[mikeyb]

My guess is not as it will already have been compressed

[Matt306]

20 minutes ago, mikeyb said:

My guess is not as it will already have been compressed

I was thinking that just wanted to gauge opinion

[Amy Wade]

There's no need to take the head off to repair the spark plug thread, when I was doing engine reconditioning as my day job I would just have the engine positioned so the piston is down the bore enough to be safe and the valves are closed. Keep plenty of grease packed into the flutes of the tap and the swarf will stick to it.

I  personally wouldn't use a Helicoil, my choice would be a Würth Time Sert, the kits are expensive & I'd suggest seeing if your engine reconditioner has them.

[glang]

Certainly you dont want the tang of a helicoil falling inside when you finish and snap it off! However a small vacuum cleaner modified with a flexible piece of plastic hose taped on the end could be used to suck out any debris in the combustion chamber...

[Amy Wade]

20 minutes ago, glang said:

Certainly you dont want the tang of a helicoil falling inside when you finish and snap it off! However a small vacuum cleaner modified with a flexible piece of plastic hose taped on the end could be used to suck out any debris in the combustion chamber...

If you're using a Helicoil (Personally I would never use one for a spark plug thread) break the tang off with pliers. 

[glang]

One thing with the solid type inserts: what stops them from unscrewing Amy, are they reverse thread?

[Amy Wade]

They have a shoulder on the top & expand at the bottom. 

Here's their promotional video 

the spark plug ones come with a stepped tap that uses the remains of the original thread as a guide to ensure the insert will be perfectly in line with where it should be.

[Matt306]

Thanks for the replies. I think for ease I will take the head off. I can properly assess the other spark plug holes. 

The problem with the TR7 head is it Aluminium and quite soft. How I miss a herald cylinder head. 

 

I also was a bit unsure on the exhaust mounting holes one seemed a bit iffy. My old head had all the exhaust holes helocoiled before I had it so perhaps common.

[Matt306]

On 05/11/2023 at 09:15, Amy Wade said:

They have a shoulder on the top & expand at the bottom. 

Here's their promotional video 

the spark plug ones come with a stepped tap that uses the remains of the original thread as a guide to ensure the insert will be perfectly in line with where it should be.

Got this done one all 4 plug holes.