Race X-flow small chamber head options - Burton? Alloy?

[Monkfish]

It looks like the head on my 1700 race x-flow is cracked.
The head chamber size and shape appear to be original spec but with larger valves. Burton list a full-race cast iron chambered head - does anyone have an opinion on the Burton race heads? Or could a big-valve alloy head be machined to suit?

Cheers

[Monkfish]

This is the head I've been running

[Monkfish]

[racing escort]

Chamber and shape are not std in my opinion, very big valves also ! Can't it be repaired ?

[Monkfish]

Agreed, I think the chambers on my head have been modified a bit from the standard head, like the one in this picture.
I don't know where it's cracked, it's a bit of a mystery. The head pressure tested fine, I get 200psi on all 4 cylinders on the starter when cold, but after running it for maybe a minute or so, 3 & 4 drop to 100 & 125 psi

[HonkyWhiteTrash]

Those chambers look pretty standard to me - I've got 3 in the garage and I can't tell the difference between yours and mine! There certainly not anything ground-breaking in terms of performance - by that I mean it's not going to be expensive to re-produce a head to that spec if need be.

As for whether it's cracked or not - it needs pressure testing to see if the head is cracked. But, I can't see that a crack that you can't locate would cause that much pressure loss!

[Graham]

Those chambers look pretty standard to me - I've got 3 in the garage and I can't tell the difference between yours and mine! There certainly not anything ground-breaking in terms of performance - by that I mean it's not going to be expensive to re-produce a head to that spec if need be.

As for whether it's cracked or not - it needs pressure testing to see if the head is cracked. But, I can't see that a crack that you can't locate would cause that much pressure loss!

i agree to me it looks like an early shallow chamber head as opposed to something aftermarket with a "proper" chamber

i also agree i cant see a crack in the head doing what you describe

[Monkfish]

Thanks for the replies - the top 2 pics are of my head and the 3rd is a pic of a stock head I grabbed from an old thread. I agree, looks like mine has had a little smoothing work done on the chambers but mostly just the big valves and porting work.

I had the head pressure tested and they found nothing wrong with it. When I got the all clear on the head I looked elsewhere for the problem, I ground the valves, had the block honed and renewed the rings, tried different types of head gasket - but after it's been running the compression still drops on 3 & 4 to the exact same readings I was getting before. I can take the head off and put it back on again without changing anything and I get full compression on all cylinders... until I start it and run it for a minute, then it's low on 3 & 4 again. I don't know what else to try?

The problem started with a misfire during the last race of the weekend, I assumed that as the compression was low in adjacent cylinders that it was a head gasket failure - when I got the head off there didn't seem to be anything obviously wrong with the gasket.

[Graham]

is it on twin carbs? are you doing compression tests with throttle open? if the answers are yes and no in that order you might have a carb balance issue

[katana]

Is that a crack in the exhaust seat? Are the seats machined in the CI or are they pressed in seats? It is a big drop in psi for a little crack though...... maybe more cracks in the head elsewhere?

[Graham]

assuming you have access to compressed air a cylinder leakage tester can give you a better idea where the compression is going to

[Monkfish]

Thanks Graham - you might be on to something there. It runs twin 48's and no I wasn't opening the throttle when testing the compression when it was hot. You know, after messing with the head gaskets etc. I would check the compression when cold without the carbs attached!!!

[Monkfish]

I'll be home from work in about an hour or so - I'm going to test it again...
I'll be over the moon if this is all that's wrong!...
I'll also feel like a bit of an idiot

[Monkfish]

Ran the engine for a few mins last night to get it warm and checked the compression again:

Throttle closed pressures = 200, 200, 100, 125 psi
Throttle open = 200, 200, 200, 200 psi

Graham, you were spot on with the carb balance issue. I can't thank you enough. It was a stupid mistake
I was looking for an issue with the head as this is what I found when I opened it up. On closer inspection of the gasket I see a bit of corrosion on the sealing ring so that's likely where the water got in.

[rallyrob]

I'll also feel like a bit of an idiot

No need to feel like an idiot. Everyones here for advice in one form or another.

[Monkfish]

Thanks, I really appreciate everyone who contributes here - this forum has helped me out a lot with my foray into racing, with both the pinto and xflow engines.

[Monkfish]

*update*

Had a race this past weekend but sadly didn't turn a lap.
When up to race temperature it started to misfire and push water out the exhaust. Compression checked out fine across all cylinders (throttle open), no overpressure in the radiator and it wasn't overheating. Took the head off and there was about 30mm of water in number 3 cylinder; the old head gasket looked fine but I fitted a new one just in case and tried again. This time I left the rad cap loose and ran it up to temperature, everything seemed fine. I tightened the cap and ran it once more, the misfire came back and we had water in number 3 again.

My guess is that the head must be cracked somewhere upstream of the number 3 exhaust valve (see photo above)? I did have this head pressure tested so the crack seems to only show up when hot.
Any thoughts? could it be repaired?

Cheers

[Erikmex]

How do you know its not the block/cylinder?

[katana]

How do you know its not the block/cylinder?

Wouldn't push water into exhaust - would pressurise the system but there is no connection to exhaust unless via cracked port or duff head gasket.

[Erikmex]

Unless the cylinder is filling with coolant and it’s pushing it past and open exhaust valve into the exhaust when engine is hot and switched off although less likely than a cracked exhaust port

[Monkfish]

Compression is good on all 4 cylinders when hot - the block has liners and is out to 84mm, but would it not show low compression if a liner was cracked?
It would still pull ok at WOT above 4k rpm, misfired below that. Water seemed only to enter the cylinder either at idle or when stopped - if that much water was getting in while running it would likely have hydrauliced?

[Graham]

a cracked or a slipped liner could allow coolant in without a noticeable effect on a compression test.

if you have a cylinder leakage tester, or even compressed air you could try pressurizing the effected cylinder and looking for air bubbles appearing in the radiator

[Forest_rallying]

In the very early 80's we ran an Escort with a Twink fitted for Road Rallies. The engine had a 711M bottom end that was bored to 85mm giving a cc of 1760. We had the block pressure tested after it was bored and all seemed okay and all compressions were te same when the engine was built.

When the car was driven round on the road there was never a problem with the cooling system but halfway through an event when holding a good position the engine would suddenly throw out all it's water. We changed head gasket after head gasket in order to solve the problem but all to no avail. We eventually decided to investigate the cylinder bores only to find a very small hairline crack that must have been opening up under very hard driving conditions. We decided punch a hole in the side of cylinder when the block was stripped out to see the thickness of the wall. It could only be described as resembling an Ice Cream wafer. A hard and expensive lesson learnt on not trying to be too greedy on bore size.

[Monkfish]

*Update

Got back into this over the weekend:

- Cold compression check: 200, 200, 175, 200 (no3 lower than last time)

- Brought no3 to the top on the firing stroke (valves closed) and pressurised the cooling system to 15psi

- Within about 20 seconds water emerged from no3 plughole

- Removed the head again, cleaned it up and noticed this:



The casting is thin underneath what I think is a crack - it's probably < 8mm thick.

I have pictures from when I last had the head off - the was no visible crack or marking in that location

Any thoughts - should I have it magnafluxed or dye-tested? I need to be 100% sure the head is the failure point before I move forward.

[Erikmex]

Pressure test it and use dye pen

[Monkfish]

Thanks - head has now been pressure tested again, magnafluxed and dye-tested. Can't find anything wrong with it.

We're going to try to rig up something to pressure test test the block..

[HonkyWhiteTrash]

What type of cylinder liners do you have ie straight / flange top / stepped bottom? Has one of them slipped? What does the mating surface look like?

[Monkfish]

I made up a device using wood and an old head gasket to seal off the water jacket, leaving cyl 3 open so I could inspect for water ingress - managed to pressure up the block to about 10psi with not a drop of water entering the cylinder

Liner looks and feels flush with the deck, they look to be straight, wet liners - I'll post a pic

[Monkfish]

Looks like this crack between the water jacket and liner may be the culprit?

Is this block scrap or should I be able to get a head gasket to seal on the liner if it was located properly?

[Forest_rallying]

Is that crack on the same cylinder that you have had all the trouble with?

[Monkfish]

Yes