Author Topic: Mechanic to carry out top end rebuild - Glasgow Area  (Read 1630 times)

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Offline Allanchvet

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Mechanic to carry out top end rebuild - Glasgow Area
« on: Feb 17, 2017, 15:43:17 »
Hi,

Could someone recommend a good garage or someone to carry out a top end rebuild on my standard Chevy. Suspected inlet valve seal wear.

What would be a rough cost? Not sure but may be worthwhile doing the piston rings too if the head is off anyway.

Glasgow (Johnstone)
Cheers

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Offline Bill

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Re: Mechanic to carry out top end rebuild - Glasgow Area
« Reply #1 on: Feb 20, 2017, 11:59:34 »
hi,

I cannot answer the question sadly as down south, however the valves are usually pretty resilient on these and i do 1-2000 miles a month in mine.

What i do find is the tappet clearances do close up on some valves over time, most likely due to unavoidable seat recession in hard driven pre-unleaded engines. Setting them a bit wide delays this issue , something like 13 thou or so (0.3 mm) .

@Mad Max A.K.A. Mal is / was nearer you so may know some local engine shops though if that is no help.

Bill

Offline Bill

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Re: Mechanic to carry out top end rebuild - Glasgow Area
« Reply #2 on: Feb 20, 2017, 12:03:38 »
just re-read your message, you said valve seal :D , doh!

You may find a workshop with the kit that would mean they can change the valve stem seals without taking the head off.  i.e. able to compress the valve spring/hold the valve up via some means like an air bag through the plug hole or something.

would be a lot less hassle than having to take the head off. Although if the engine is old and the head gasket original then there is a good chance it will fail at some point anyway :(

Offline Allanchvet

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Re: Mechanic to carry out top end rebuild - Glasgow Area
« Reply #3 on: Feb 21, 2017, 09:13:01 »
Thanks Bill,

Scotty did mention the seals could be changed with the head in place but as I'm not certain the seals are the issue and following advice on here, I'm just going to take off the head, inspect it and go from there. I'll post up some pictures for yous knowledgeable guys to look at and advise once I have the head removed. If necessary I'll probably have a go at changing the seals myself.

Cheers
Allan

Offline Sambo

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Re: Mechanic to carry out top end rebuild - Glasgow Area
« Reply #4 on: Feb 21, 2017, 18:41:46 »
Hi. Do you have a compression tester /borrow one? Would be a good starting point before getting involved. Also if burning oil, generally if accelerating and you see smoke this normally means rings if none seen but as the engine slows (still needs to be driven to see) and you get smoke that would indicate valve stem oul seals. Hope this helps.

Offline Allanchvet

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Re: Mechanic to carry out top end rebuild - Glasgow Area
« Reply #5 on: Feb 22, 2017, 08:50:11 »
Hi Sambo,

Yes I've carried out a compression test, showed good results, Approx 130psi on 1&2 and 140 on 3&4 with no change adding oil to the cylinder. I haven't driven on the road as no MOT, only up and down the drive at low speed but just seems to smoke constantly idling or higher revs.

Think the next move is to get the head off.

Cheers

Offline scotty

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Re: Mechanic to carry out top end rebuild - Glasgow Area
« Reply #6 on: Feb 22, 2017, 11:40:00 »
If its smoking continuously and it doesn't vary with engine speed / throttle action its very odd!  I had something similar when I fitted a new exhaust to a motorbike once- it turned out to be a exhaust manifold air leak caused by a broken stud in the end.

 Is the smoke blue? Does it smell( of oil or fuel or antifreeze) Are you losing water?  Is it the same with the original carb on?  Does using the choke do anything? Is it the same hot and cold?

Offline Allanchvet

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Re: Mechanic to carry out top end rebuild - Glasgow Area
« Reply #7 on: Feb 22, 2017, 13:36:47 »
Hi Scotty,

Yes it smokes all the time, fine on initial cold start then it changes once its just getting warmed up. Using choke/revs don't make any difference. Also adjusting carb mix did nothing either. I tried to swop over the old manifold and carb to eliminate a possible leak at the intake but due to modding the connection for the servo to fit your manifold, I couldn't remove it from your manifold without cutting it again so no vacuum to draw the fuel through. I might have another go at swopping back to the original set up. I can maybe borrow the standard servo connection from my mates Chev. (He has just pulled it out of the barn after 20 years! Needing work!).

The smoke looks grey blue/cloudy. I think the water level had maybe dropped a little last time I checked but doesn't smell of antifreeze. It looks to me like oily water being emitted, now seems worse than it was initially.

Like to say sorry to everyone for clogging up the forum with this annoying issue! Really need to get it sorted  :wallbang:

Offline scotty

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Re: Mechanic to carry out top end rebuild - Glasgow Area
« Reply #8 on: Feb 22, 2017, 14:08:44 »
Just put the original msnifold on and blank off temporarily the vacuum connections and just connect up fuel to get the engine started.  All thats needed is to eliminate the new carb / manifold as the source of the problem.

 From what you have said today about the smoke I think its likely that all you need to do is change the head gasket after decoking the head and pistons. Don't bother with skimming as being a cast iron head it is unlikely to be warped. No need to grind the valves either. - Scotty

Offline Sambo

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Re: Mechanic to carry out top end rebuild - Glasgow Area
« Reply #9 on: Feb 22, 2017, 21:11:37 »
You could maybe try the test again when hot as this would maybe show up any coolant getting into the cylinder. The colour doesn't sound oil more like the h-gasket or bad fuelling. The joys of cars!!

Offline Allanchvet

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Re: Mechanic to carry out top end rebuild - Glasgow Area
« Reply #10 on: Feb 23, 2017, 08:51:21 »
Cheers guys,

I'll fit the original set up back on tonight, at least the manifold and weber can be ruled out then. I should get vaccum this time (nicked the servo connection off mates Chev). Couldn't find anything suitable to blank it off last time.

Update later.

Offline Bill

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Re: Mechanic to carry out top end rebuild - Glasgow Area
« Reply #11 on: Feb 23, 2017, 11:23:19 »
hi,

i think i put a video up of when this happened to my chevette. you get what looks like smoke out the exhaust but is fairly white.   It is water vapour basically.

The most common failure on the 1256 is the head gasket , especially between cylinder 4 and the water jacket.  As a high mileage driver of these beasts i have had that happen three times now .

They also fail from age as the gasket thins, the head tension reduces and coolant seeps into the gasket, rotting it. the combustion chamber gasket rings also rot away, exposing the gasket to the full force of compression.

The last HG change i did i took heed of some advice i found on google and before fitting the new gasket, i brush painted it with wellseal, a liquid gasket compound. far better and easier to use than hylomar.

you brush it on both sides like paint (use a good paint brush or non fluffy sponge etc..) , let it evaporate its solvent a while then fit it to the car.  It is sticky stuff so avoid getting dirt and crap on it before fitting too.

I used one of those household paint / paper removal scrapers that you can drag backwards (has a rigid handle/blade) to clean up the head and block surfaces too prior to fitting.

so far so good some 10k miles+ later  :)

Interestingly the original replacement GM gaskets for the chevette were also coated in a sticky stuff so it seems this was the done thing .

the wellseal should keep the corrosive/damaging coolant and oil away from the gasket and as it is non hardening should keep the head sealed nicely .

I also initially torqued the head evenly in stages from 60nm to the recommended 76nm (i think) and went past that to 80 as a final.

Make sure the head bolt holes are clear and the head bolts threads are clean too.  brake / clutch cleaner aerosol helps here as does pressurised air :)

Also make sure no bits of old gasket fall into the oil way that goes from block to head . stuff some rag or kitchen roll in that hole while working on it.

if crap in there gets pushed into the head it will block the small oil ways that lube the rockers.

Bill

Offline Bill

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Re: Mechanic to carry out top end rebuild - Glasgow Area
« Reply #12 on: Feb 23, 2017, 11:30:50 »
cylinder 4 to water jacket failure on my yellow hatch.

https://goo.gl/photos/9PqmP37EmMBgVxYU9

it was a generally unwell gasket.

https://goo.gl/photos/HNAE9uWFnn4MZ3aTA

« Last Edit: Feb 23, 2017, 11:48:17 by Bill »

Offline Allanchvet

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Re: Mechanic to carry out top end rebuild - Glasgow Area
« Reply #13 on: Feb 23, 2017, 13:39:08 »
Hi Bill,

That gasket has seen better days! Intrigued to see what mine looks like! I'll follow your step by step for changing the head gasket.

Cheers

Offline VanneVette

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Re: Mechanic to carry out top end rebuild - Glasgow Area
« Reply #14 on: Feb 23, 2017, 18:21:05 »
Before you take the head off, just run the engine and spray WD40 around the inlet manifold and see if you get any bubbles or patches where air getting in. I had this problem when i fitted my manifold first time i did it. The bolt are pretty long and the silly middle bolt that's inside the manifold i locate it in just in case?? I think the original manifold needed a skimming to make it perfectly flat again. If the car be sat for 20 years the water pump may be rusted up. A new waterpump and a few flushes with a dishwasher tablet will do a great job cleaning it all up.

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