Opinions on an engine rebuild - Broken Pushrod guide

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Opinions on an engine rebuild

Post by peter freeman » Wed Jul 26, 2017 6:38 pm

The two types below.
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Opinions on an engine rebuild

Post by Oldconn » Thu Jul 27, 2017 12:07 pm

Those bores don't look as though they have been run-in at all! All my previuos experience tells me that the piston/bore clearance is excessive . Who did the rebore, and how many miles has it done since? I think that it needs at least a new set of rings, and running-in thoroughly.


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Opinions on an engine rebuild

Post by French Coupé » Fri Jul 28, 2017 11:43 am

Oldconn wrote:
Thu Jul 27, 2017 12:07 pm
Who did the rebore, and how many miles has it done since?
Bit of an unknown really, as it was all done before I bought the car and there are no invoices to go on. The garage which looked after the car thought the previous owner had the engine rebuilt by Specialised Engines, but not everyone has good things to say about them... :w I've done 12000 miles with the car since I bought her.


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Opinions on an engine rebuild

Post by Oldconn » Fri Jul 28, 2017 12:36 pm

Well, after 12,000 miles it should be thoroughly run-in; but the cross-hatch honing marks are still there, which more or less confirms that the pistons are too sloppy in the bores, or you could say the bores are too large. Your pistons appear to be in good 'nick 'with negligable scuffing; but the ring gaps were not properly staggered. I'm with Jim , the ring-gaps are too wide, and all the evidence is that the re-bore was intended to be +.030 but they took too much out.


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Opinions on an engine rebuild

Post by gtcse8 » Fri Jul 28, 2017 12:52 pm

James are there any markings on either the piston crowns or on the rings near the gaps??.

Also what is the total height of the pistons from crown to lowest part of skirt?

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Opinions on an engine rebuild

Post by gtcse8 » Fri Jul 28, 2017 12:59 pm

You could also carefully remove a top ring and push it down into the bore using the upturned piston till the rings prevented any more movement, then with feeler gauges measure the ring gap.

If the rings ARE worn it will be obvious


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Opinions on an engine rebuild

Post by Oldconn » Fri Jul 28, 2017 5:03 pm

James you have a PM.
Ian.


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Opinions on an engine rebuild

Post by scimjim » Sat Jul 29, 2017 1:20 am

French Coupé wrote:
Fri Jul 28, 2017 11:43 am
The garage which looked after the car thought the previous owner had the engine rebuilt by Specialised Engines, but not everyone has good things to say about them... :w
That would explain it :-)


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Opinions on an engine rebuild

Post by French Coupé » Sun Jul 30, 2017 8:43 am

gtcse8 wrote:
Fri Jul 28, 2017 12:52 pm
James are there any markings on either the piston crowns or on the rings near the gaps??. Also what is the total height of the pistons from crown to lowest part of skirt?
The total height of the pistons is 95mm. I couldn't find any markings on the rings, but each piston is marked as being +030, preceded by the letters BRF, LQF, or JRF.
The ring gaps vary between 22 and 29 thou on the compression rings, so they're definitely worn or to small for the bores.


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Post by gtcse8 » Sun Jul 30, 2017 12:56 pm

Ok James
That rules out the earlier type of piston that was fitted to the Zephyr 6 Mk1V as they are slightly longer at 101.1 and they were +30 as standard so would not have been stamped as OS.
Just sounds like someone has set the boring bar to +40 and fitted +30.

I think I have a few old and used +40, I could measure them and see if the results compare with your bores.

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Opinions on an engine rebuild

Post by French Coupé » Mon Jul 31, 2017 8:01 pm

Thanks Mark, I like little snippets of info like that!
I did wonder myself if the engine had been bored too big... If you could measure a +40 next time you have one to hand that would be great. No hurry though, I won't be able to make any more progress on the rebuild for a couple of months now.


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Opinions on an engine rebuild

Post by French Coupé » Tue Jan 02, 2018 11:29 am

Right, time to revive this thread as after a busy few months moving house and setting up a business, I've finally gotten round to working on the Coupe's engine again.
Before splashing out on a set of new pistons I got my local engine specialist to check all the measurements on his equipment. It turns out all the bores and pistons are within tolerance, so the moral of this story is don't trust cheap tools for precision measurements! :roll: So a quick deglaze and new rings is all that will be needed.

With the block away, I turned my attention to the heads. Burton's have supplied new valve stem seals but they're different to the old ones (new on the left, old on the right):
Stem Seals.jpg
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There's no way they'll fit over the castings in the head, so I guess they're the wrong type and won't do the job properly. Unless they're meant to just sit on top like that? Any thoughts?

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Post by ScimmyMike » Tue Jan 02, 2018 1:02 pm

There are two types avaiable, you have them both there and looking at your head the current are the right ones, I may have some in head gasket sets I have on the sehlf happy to look if you'd like them.
BTW something looks odd on left valve guide against the seat, is the seat damaged?


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Opinions on an engine rebuild

Post by BusaPhill » Tue Jan 02, 2018 3:39 pm

French Coupé wrote:
Fri Jul 28, 2017 11:43 am
Oldconn wrote:
Thu Jul 27, 2017 12:07 pm
Who did the rebore, and how many miles has it done since?
Bit of an unknown really, as it was all done before I bought the car and there are no invoices to go on. The garage which looked after the car thought the previous owner had the engine rebuilt by Specialised Engines, but not everyone has good things to say about them... :w I've done 12000 miles with the car since I bought her.

If you phone Specialised Engines
Give them the engine number they can confirm if it's been rebuilt by themselves.

My 3.1 is marked SE7547
Old engine number is no longer visible..

Valve stems seals.
Will they not tap down over the casting.
Socket or tube over the edge of seal.

I'll much prefer to use the ones of the left.
Better sealing with the wire ring.


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Post by gtcse8 » Tue Jan 02, 2018 6:49 pm

James you have "K" liners in the guides.
And the left one does look damaged.

Shame SE did not bore out the original castings to take proper replacements as they are turned down at the top to accept the much better later type.


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