tr4a Cylinder head airline cracks

[Geko]

Seems opinion divides into the pesimists who say scrap it, and the optimists (like me) who are of the "never throw it away- it may be useable" train of thought who have actually been running their cars on bits they found on the garaage floor over the years

So definitely don't scrap the head, it is almost certainly useable and the rewards of TRing is that you can have fun making it work and it at the end of the day it doesn't then you will know a whole lot more about heads and what will work.-- and share it with us!

Michael

 

Michael, brought the head to the machine shop today: No problem. They performed the compression test in front of me and it's all good. They will shave it by 0.10 thou for a start and see what's comes out. Anyway I won't change the head until it pops off the bonnet. I kept this 4A on the road for the past 8 years (1 of the 5 registered TR4 left in this country) through sourcing parts in the last messy/dusty British car parts shop with only NOS since 30 years and handle my grinder and calliper better than fork and spoon. Will keep you all posed.

[Geko]

Get the head to a good machine shop - I'd be very surprised if they can't rescue it for you, from your photos it should be possible without too much difficulty.

 

When you rebuild the engine, take it steadily, and from perhaps 70 pounds keep going round the head studs in the correct order, raising the torque by 5 pounds each time. Tedious, but should avoid undue stress to repaired cracks. And use only a minimum amount of sealant.

 

Cheers, and good luck,

 

Alec

Alec, as above. Also the machine shop guy advised against soldering the crack as the heat spread might weaken some other area of the head. I then specifically asked about brazing - limited heat diffusion with less heat stress to the rest of the head - but they don't do that.

Edited January 9, 2014 by Geko

[Alec Pringle]

Hi Michael,

 

something like this might be needed, perhaps ? - http://www.peterburgessshop.co.uk/QuiksteelXtreme.html

 

It may be worth sending your photos to Peter with a plea for his thoughts, he's a good man and knows more than most about TR heads, and about the need to 'make do and mend' on occasion.

 

Cheers

 

Alec

[roy53]

 

 

Sorry Geko but that photo must be in bad taste. 9 / 11

 

ROY

[Motorsport Mickey]

Hi Steph,

 

Just returned to this thread from your other regarding cam follower wear, now given that you are attending to the head, and now probably changing cam and followers, maybe you should just check the liners protrusion above the block face. You are now starting to get to the " maybe I should pull the engine and rebuild stage".

 

You need between 3-5 thou across all the liners, 3 3 3 3 is fine as is 5 5 5 5 across the 4 liners, what you don't want is 5 5 3 5 which would comprise the clamping effect on the gasket.. The liners need measuring at 4 positions around the circumference measuring down to the cylinder block surface. You could machine and replace liners with the engine in situ if needed to remedy any misalignment of the liners, but if they need doing machining for another 2 hours work you can pull the engine and gearbox and crack on with any remedial work.

 

Mick Richards

[Guest ntc]

You actually only compromise the fo8 using the std head

[Geko]

Hi Steph,

 

Just returned to this thread from your other regarding cam follower wear, now given that you are attending to the head, and now probably changing cam and followers, maybe you should just check the liners protrusion above the block face. You are now starting to get to the " maybe I should pull the engine and rebuild stage".

 

You need between 3-5 thou across all the liners, 3 3 3 3 is fine as is 5 5 5 5 across the 4 liners, what you don't want is 5 5 3 5 which would comprise the clamping effect on the gasket.. The liners need measuring at 4 positions around the circumference measuring down to the cylinder block surface. You could machine and replace liners with the engine in situ if needed to remedy any misalignment of the liners, but if they need doing machining for another 2 hours work you can pull the engine and gearbox and crack on with any remedial work.

 

Mick Richards

Thanks Mick, just checked the liners protrusion using my calliper as a straight edge but didn't expected this type of reading ! Now what is the verdict ?

Could the head crack next to the waterway of cyl 1 be related to the .006 protrusion?

 

And the head gasket with another sensible application for a fridge magnet.

The liners are 87 mm bore and in intended to refit a new standard copper gasket whose diameter is exactly 87mm. Considering the above findings, maybe should I consider an oversized one steel or copper? I have no idea

 

Edited January 14, 2014 by Geko

[MichaelH]

I suspect with those readings from 6/5 thou on the pushrod side and 3 thou on the other that I would take the liners out- this does mean taking the pistons and pushrods out - which inevitably means you will check the bearings and have a look at the crank etc etc - will it never stop?

If you take the liners out and then take the FO8 gaskets out (you can clean the inside of the block ) but also get a bit of lapping paste on the end of the reversed liner and lap the base of the block where the FO8 go then with new/cleaned FO8gaskets you can rotate/change/swop the liners until you have a consistent deck clearance. then seal the FO8 & liners in with welseal.

I would be interested to see if any others would just put the head back with a new copper gasket?

Michael Hunter

[Guest ntc]

Somebody has been there before and not built it up right, you are in for a full strip down

[Geko]

 

I would be interested to see if any others would just put the head back with a new copper gasket?

Michael Hunter

or two ?

[Ashley James]

In my opinion what has been shaved from the head is only part of the problem. I suspect that a lot of corrosion has occurred in the water jacket and eaten through the metal making it very thin. I believe the cracks in the photo show this because I've seen it before on old Bentley and R-R engines when this has happened, so I agree with Alec that a machine shop needs to look at it, but you'll probably need a new head.

[Ian Vincent]

With engines it's all about the correct repair to suit the circumstances, unless a good cylinder head is available a reasonable running repair like this is fine. From the days of TR man where the TR was the only car he had, and almost full engine rebuilds including crank replacement were carried out at the side of the road, we've regressed to being wimps and carrying out full rebuilds at the drop of a hat.

 

What Mickey says is so true.

 

In days of yore, my friends and I were driving around in old cars that we bought for a tenner and kept running on a shoestring. There is no way we would have scrapped this head until we had exhausted all possibilities. This engine is not far removed from a tractor engine, it is not an F1 unit. Unless you are going racing, I would go with giving it a skim.

 

Rgds Ian

[Motorsport Mickey]

Hi Steph,

 

Sorry I've been a while getting back to you. Your latest information now moves the chess piece into a far more serious position. From the readings shown, their consistency of 5-6 thou on one side and 3 thou on the other makes me suspect a partly skilled Auto machinist.

I think he' s plonked the engine block on his table, not bothered clocking it up and wiped the top of it with a minimum skim. Hence the block was either distorted or the machines bed was off by 3 thou, I would suspect if the engine was put on a jig borer and the liner alignment checked in both planes through 90 deg it would show the blocks top surface with a 3 thou " lean" from the high side on the passenger to the lower drivers side.

Any good machine shop could offset the top of the liners and grind 3 thou off one side to nowt on the other which would correct the lean and hopefully give a consistent 3 thou clamping height around all the liners ...BUT Any work you do on the liners to correct the lean is only hiding the real problem which is I believe a top block surface that has been misaligned in a previous machining excercise, this is bad practice and sometimes comes back to bite you.

 

Time to bite the bullet, go the whole hog.

 

Pull the engine and gearbox and split the units apart.

Strip the engine to component parts

Extract the liners from the block, use a threaded bar and a puller

Dig out all the rust around the liners and the inside of the engine

Fit new FO8 gaskets before going any further (dry no sealant)

Refit the existing head ( no head gasket) and torque down to about 80lb, ( this to check what liner heights will exist with new FO8 gaskets). I would continue with this head until use proves it's suitability or not.

If the liners still show a lean ( no matter what the dimensions ) give it to a respected machine shop and ask him to skim the top of the block AFTER clocking the liners in both planes ensuring that the top of the block is both parralell and square to the plane of the crankshaft. (Remove liners before skimming).

Then recommence the engine build by machining the liners so a consistent clamping height from 3-5 thou exists after clamping the liners down with the head to 105lb ft

Strip the engine and rebuild using Wellseal or your choice of sealant around the FO8 gaskets following the Workshop manual instructions, incorporate the new camshaft and cam followers into the build.

Because you are now down to the bare bones a crankshaft check is of course stupid to ignore and to rectify the easiest way possible.

 

Mick Richards

Edited January 14, 2014 by Motorsport Mickey

[MichaelH]

Not much to do then! be finished by lunch time!

 

 

But worth it in the end

 

 

Michael

[Geko]

Thanks all - especially Mick- for your comprehensive explanations and advices.

 

The head is back from the machine shop and the cracks have gone after the 1st shaving of 10 thou. Push rod tubes have been replaced (except one which they screwed up on assembly - BTW ordered from RB and needed to be re-machined to fit in). Now I'm going to sharpen the edges of the waterways, smoothen the edges of the compression chambers and put some Loctite around the flare of the tubes just to be on the safe side.

 

Re protrusion issue, I like to drive my 4A a little bit. After reading the comments I believe that the issue has ballooned. It's just a solid and reliable tractor engine which could go on for ages with minimum maintenance. IMO If the constructor gives a .002 tolerance that's to allow the head gasket to mitigate the variations under load and correcting these variations around the same liner as well, otherwise no point having a gasket. So a thorough cleanup of the face of the block and liners, a good copper gasket, a good dose of Locite and proper progressive torque should do the trick for now and until the full engine strip scheduled for her 50th birthday. Let's see how it goes. If the crack cyl 1- which I suspect relates to liner 1 high protrusion- comes back or other leaks appear, that would prove me wrong. Will keep you posted.

 

 

Edited January 15, 2014 by Geko

[Motorsport Mickey]

Steph,

 

Glad the head looks to have cleaned up, you might think that a propriety leaks sealer added to the engine from start up might help seal any undisclosed edges, Good luck with it and let us know how it fares.

 

Mick Richards

[Geko]

Ok, the head is back on

[RogerH]

fingers crossed.

 

Roger

[Geko]

Ok, the head is back on since this weekend and I took it for a ride. Everything seems ok: no leaks, no overheating (temp gauge solidly stuck at 2/3), no tappet noise, better pickup at low rev, etc... BUT now that the compression is higher - 80 thou taken off the head from stock thickness- there's much more blow-bys pressure in the crankcase resulting in a permanent stinky and smoky engine bay. So, I added a home-made vent/breather connected to the blanking plate of the fuel pump made of copper connector, stainless pipe 15 mm and Austin air filter found in my garage with the cone-shaped base of the filter acting as catch tank for oil residues. Problem is that it doesn't seems to make much difference as the pressure coming out from the rocker cover is still very high and not much blow-by seems to come from the home-made vent.

 

Question: Any tip/advice to provide further relief to the pressure in the crankcase ? Increasing the diameter of the pipe seems an obvious option but by how much (i know the wider the better)?

 

BTW: PCV is a no-no.

 

Thanks, Stef

 

Edited January 27, 2014 by Geko

[ctc77965o]

Stef,

 

If PCV is off the menu, then you've no chance to use reduced pressure to vent the crankcase, so its just the overpressure vs atmosphere.

Only option is the biggest possible hole in the block quite low down. Can't use the rocker cover as the flow of fumes up there is restricted by the pushrod tubes. Only chance is to stuff a fat pipe on that fuel pump flange, as short & as straight as possible..

[TR NIALL]

Why do Folks insist on using that Filter on the Rocker Cover,do they not realise what's happening.

[RogerH]

Hi Stef,

you seem to be creating one problem from another. Can youi not use a thicker solid head gasket. That may lower the comp ratio.

 

The rocker cover filter is venting some of the fumes into the engine bay. Why not duct the rocker vent into the carbs as per the TR4 design.

 

Roger

[Geko]

Thanks Dave & Roger for the positive comments, Actually I would like to solve the issue as close as possible to the source (Roger, heard you loud and clear re gasket) which in the current state of affairs is the block, for 2 reasons: 1/ As Dave pointed out the pressure under the rocker cover is residual due to the narrow passage of the blow-bys through the pushrod tubes hence the core pressure remains in the crankcase; 2/ I'd like to keep the carb system out of the way as there are too many negative interferences with the air/fuel mixture in using any form of emission control system for the purpose of crankcase vent albeit labelled "PCV". To be sure, the main goal is to relieve the pressure to avoid blowing the seals and splashing oil all over and if it would help getting rid of the stinky fumes at the same time that would be a perk.

 

PS: Incidentally wondered if playing with the advance/retard would help ?

 

XX, s

Edited January 27, 2014 by Geko

[Guest ntc]

You have no chance with what you have now,oil splash from the cam alone makes the bottom mod us

[Geko]

You have no chance with what you have now,oil splash from the cam alone makes the bottom mod us

you mean "usELESS" right ?