Head gasket question
Discussion
From experience I would go for a genuine manufacturer gasket because (as you have seen) cheaper ones can be a little (or a lot) less than accurate.
It'll work for a while then it'll start to burn due to the amount of "face" of the metal part of the gasket thats in the firing line.
Don't do the job twice when you can do it once
It'll work for a while then it'll start to burn due to the amount of "face" of the metal part of the gasket thats in the firing line.
Don't do the job twice when you can do it once
Suppose it would depend on the state of tune but I'd be concerned about the potential for that to become a hotspot if lots of compression/advance was being used and, thus, a possible cause of preignition/detonation...
But, if the pistons are not up near the deck at TDC, I guess the static compression is not going to be that high?
But, if the pistons are not up near the deck at TDC, I guess the static compression is not going to be that high?
kenmorton said:
Little project on the go at the moment and the fire ring on the head gasket is protruding into the cylinder about 1mm for about a quater of the circumference on two outside cylinders. The pistons don't come anywhere near the top of the bore so is this likely to cause any problems?
The sealing area of the gasket needs to be properly clamped - this will be be slightly inboard of where you are seeing protrusion but with tolerance stack it may be a problem. The gasket protruding into the cylinder is at risk of causing detonation. You don't say whether the gasket is genuine parts or A.N.Other
From personal experience I never use other than genuine parts headgaskets - sourced franchised dealer even though I often get only 10% trade discount - unless the GP is completely unobtainable.
Same goes for many other critical parts. Just too many dreadful pattern items around.
From personal experience I never use other than genuine parts headgaskets - sourced franchised dealer even though I often get only 10% trade discount - unless the GP is completely unobtainable.
Same goes for many other critical parts. Just too many dreadful pattern items around.
Edited by paintman on Thursday 17th December 14:35
It's a frankenstien engine. 1275 mini A+ bottom end with BMW K100 bike head. It is the BMW K1100/1200 hg that slightly protrudes. The new head stud pattern, water passage holes and lack of push rod holes make it a bit awkward to use A+ gasket. Only bespoke gasket I know of for this conversion is £150.00 + V.A.T. Another possibility would be to make my own copper gasket and 'o' ring the block.
Or even Frankenstein, however.
A) You might want to speak to Mike at Ferriday Engineering. Tell him Dave Baker says hi.
B) I've seen many instances of gaskets overlapping bores slightly in the past and it's caused no problem as long as the engine is running well away from detonation conditions of high compression ratio and/or over advanced ignition timing. There are all sorts of things in combustion chambers anyway that can be termed "hot spots" such as exhaust valve edges and the spark plugs but clearly they don't stop engines running. The nicely rounded edge of a gasket fire ring shouldn't hurt either by that logic and nor does it seem to. You'd want the piston to be at closest 1mm to the gasket though because of rod stretch and thermal expansion of components. If necessary you can chamfer the piston crown edges in a lathe.
I used to build a highly tuned 1700cc variant of the Ford CVH 1600cc engine that had a 2.5mm bigger bore than standard and hence a slightly too small OE head gasket, by about the same 1mm as in your own case as I recall. I had to make a small machining mod to the piston crown edges to clear that safely and I've had engines to that spec running happily for many tens of thousands of miles in both road and track day use. In fact it was one of the most popular, torquey and reliable engine specs I ever built. The gasket overlap never caused a single issue.
If my mate Garry Muir ever posts on here he'll tell you about one car with one of those engines I built for a guy in the Aberdeen area that was such a giant killer at Knockhill track days, and road use, that it had a queue of people waiting to buy it whenever it came up for sale just because of the engine in it. I think it got owned by 4 people in the same circle of friends over the years and some 40,000 miles of "cane the arse off it" thrashing day in day out.
So been there, done that, got the T shirt and I think you'll be fine. Block and head surface finish is always critical though and needs to be finer than most machinists seem to be able to manage with their crap equipment. Most head gasket failures are actually caused by poor machining rather than the gasket itself.
A) You might want to speak to Mike at Ferriday Engineering. Tell him Dave Baker says hi.
B) I've seen many instances of gaskets overlapping bores slightly in the past and it's caused no problem as long as the engine is running well away from detonation conditions of high compression ratio and/or over advanced ignition timing. There are all sorts of things in combustion chambers anyway that can be termed "hot spots" such as exhaust valve edges and the spark plugs but clearly they don't stop engines running. The nicely rounded edge of a gasket fire ring shouldn't hurt either by that logic and nor does it seem to. You'd want the piston to be at closest 1mm to the gasket though because of rod stretch and thermal expansion of components. If necessary you can chamfer the piston crown edges in a lathe.
I used to build a highly tuned 1700cc variant of the Ford CVH 1600cc engine that had a 2.5mm bigger bore than standard and hence a slightly too small OE head gasket, by about the same 1mm as in your own case as I recall. I had to make a small machining mod to the piston crown edges to clear that safely and I've had engines to that spec running happily for many tens of thousands of miles in both road and track day use. In fact it was one of the most popular, torquey and reliable engine specs I ever built. The gasket overlap never caused a single issue.
If my mate Garry Muir ever posts on here he'll tell you about one car with one of those engines I built for a guy in the Aberdeen area that was such a giant killer at Knockhill track days, and road use, that it had a queue of people waiting to buy it whenever it came up for sale just because of the engine in it. I think it got owned by 4 people in the same circle of friends over the years and some 40,000 miles of "cane the arse off it" thrashing day in day out.
So been there, done that, got the T shirt and I think you'll be fine. Block and head surface finish is always critical though and needs to be finer than most machinists seem to be able to manage with their crap equipment. Most head gasket failures are actually caused by poor machining rather than the gasket itself.
stevieturbo said:
Have you spoke to John at http://www.specialist-components.co.uk/ ??
Is that John Kimmins? Yuxi said:
stevieturbo said:
Have you spoke to John at http://www.specialist-components.co.uk/ ??
Is that John Kimmins? Pumaracing said:
Or even Frankenstein, however.
A) You might want to speak to Mike at Ferriday Engineering. Tell him Dave Baker says hi.
B) I've seen many instances of gaskets overlapping bores slightly in the past and it's caused no problem as long as the engine is running well away from detonation conditions of high compression ratio and/or over advanced ignition timing. There are all sorts of things in combustion chambers anyway that can be termed "hot spots" such as exhaust valve edges and the spark plugs but clearly they don't stop engines running. The nicely rounded edge of a gasket fire ring shouldn't hurt either by that logic and nor does it seem to. You'd want the piston to be at closest 1mm to the gasket though because of rod stretch and thermal expansion of components. If necessary you can chamfer the piston crown edges in a lathe.
I used to build a highly tuned 1700cc variant of the Ford CVH 1600cc engine that had a 2.5mm bigger bore than standard and hence a slightly too small OE head gasket, by about the same 1mm as in your own case as I recall. I had to make a small machining mod to the piston crown edges to clear that safely and I've had engines to that spec running happily for many tens of thousands of miles in both road and track day use. In fact it was one of the most popular, torquey and reliable engine specs I ever built. The gasket overlap never caused a single issue.
If my mate Garry Muir ever posts on here he'll tell you about one car with one of those engines I built for a guy in the Aberdeen area that was such a giant killer at Knockhill track days, and road use, that it had a queue of people waiting to buy it whenever it came up for sale just because of the engine in it. I think it got owned by 4 people in the same circle of friends over the years and some 40,000 miles of "cane the arse off it" thrashing day in day out.
So been there, done that, got the T shirt and I think you'll be fine. Block and head surface finish is always critical though and needs to be finer than most machinists seem to be able to manage with their crap equipment. Most head gasket failures are actually caused by poor machining rather than the gasket itself.
I think your 'success' was that you tuned the engine to run far away from what the components should truly have delivered had they had a properly engineered gasket for the application in the first place.A) You might want to speak to Mike at Ferriday Engineering. Tell him Dave Baker says hi.
B) I've seen many instances of gaskets overlapping bores slightly in the past and it's caused no problem as long as the engine is running well away from detonation conditions of high compression ratio and/or over advanced ignition timing. There are all sorts of things in combustion chambers anyway that can be termed "hot spots" such as exhaust valve edges and the spark plugs but clearly they don't stop engines running. The nicely rounded edge of a gasket fire ring shouldn't hurt either by that logic and nor does it seem to. You'd want the piston to be at closest 1mm to the gasket though because of rod stretch and thermal expansion of components. If necessary you can chamfer the piston crown edges in a lathe.
I used to build a highly tuned 1700cc variant of the Ford CVH 1600cc engine that had a 2.5mm bigger bore than standard and hence a slightly too small OE head gasket, by about the same 1mm as in your own case as I recall. I had to make a small machining mod to the piston crown edges to clear that safely and I've had engines to that spec running happily for many tens of thousands of miles in both road and track day use. In fact it was one of the most popular, torquey and reliable engine specs I ever built. The gasket overlap never caused a single issue.
If my mate Garry Muir ever posts on here he'll tell you about one car with one of those engines I built for a guy in the Aberdeen area that was such a giant killer at Knockhill track days, and road use, that it had a queue of people waiting to buy it whenever it came up for sale just because of the engine in it. I think it got owned by 4 people in the same circle of friends over the years and some 40,000 miles of "cane the arse off it" thrashing day in day out.
So been there, done that, got the T shirt and I think you'll be fine. Block and head surface finish is always critical though and needs to be finer than most machinists seem to be able to manage with their crap equipment. Most head gasket failures are actually caused by poor machining rather than the gasket itself.
Engine output of road cars has risen dramatically in the past 20 years because the control systems are capable of finding the raggedy edge of detonation during the majority of engine operation modes, and the knowledge of component and calibration optimisation has improved.
The OP would be best off spending the money on the 'real' gasket and then not have to worry about detuning the engine so much that he might as well have just put a tuned A series in from one of the many specialists that offer them.
GavinPearson said:
I think your 'success' was that you tuned the engine to run far away from what the components should truly have delivered had they had a properly engineered gasket for the application in the first place.
Well thanks for that but these engines were running a damn sight more bhp than most people managed to get out of the CVH in similar tune. Big valve ported heads, 285ish fast road/mild rally cam duration, twin DCOEs and about 140 bhp with tractability down to below 2000 rpm. The engines weren't "detuned" in any respect and the gasket overlap was a non issue. 82 bhp/litre is a very respectable amount of power from any 2v engine in road tune and far more than most standard 4v engines manage.Pumaracing said:
GavinPearson said:
I think your 'success' was that you tuned the engine to run far away from what the components should truly have delivered had they had a properly engineered gasket for the application in the first place.
Well thanks for that but these engines were running a damn sight more bhp than most people managed to get out of the CVH in similar tune. Big valve ported heads, 285ish fast road/mild rally cam duration, twin DCOEs and about 140 bhp with tractability down to below 2000 rpm. The engines weren't "detuned" in any respect and the gasket overlap was a non issue. 82 bhp/litre is a very respectable amount of power from any 2v engine in road tune and far more than most standard 4v engines manage.You've taken what is actually a very well designed engine, avoided the det regions which in will lower the PCP and had success.
Our friend with a highly modified block will not know if he has a det issue until he runs the car, but his clamp load could be a real problem. Hence a gasket designed for the job would be a bonus. One where somebody has used a good amount of fuji paper in it's development would be a start.
Clamp load has got nothing to do with the gasket itself and can be addressed by changing the head studs if necessary. As for gaskets "designed for the job" I see no reason to believe these little custom gasket companies have any idea about how to engineer a gasket for a specific application like the OE manufacturers and big gasket companies like Goetze and Payen can do. All the custom gaskets amount to are a basic laser cut copper or composite material in the thickness and shape the buyer specifies. There's no other designing for the job, the clamp load or the engine specifics going on here. In fact IMO the reliability of these custom gaskets is far inferior to OE designed ones and they're often recommended to be replaced at regular intervals which is hardly cost effective at £150 a pop.
The other thing that I can be quite sure of is if the gasket is the one that matches the head rather than the block then the head will overlap it completely and shield it from combustion gasses so the edge of the fire ring will not become a hot spot anyway. It might be a different matter if the gasket protruded completely past both head and bore but even then a nice rounded edge is unlikely to cause a problem.
Finally, most of that last 1mm of the rounded edge of a fire ring doesn't contribute to sealing anyway. Only the parallel elements of the gasket do this and having the very edge sticking out past the bore makes little difference.
Anyway if the OP gives it a try he can let us know he it worked out but I'm sure it'll be fine. My concerns on these highly tuned A series engines are more to do with the block rigidity than any gasket issues. The A series bores flex about like a reed in a high wind at the best of times which is why they were always crap at ring sealing and oil control even in normally modified 8v spec. With 150 plus bhp pumping through them it's hardly a recipe for a long and happy life. Still we tune what we own rather than what we maybe ought to buy which is probably why I spent so much time on A series engine development in earlier times but I wouldn't touch one with a bargepole these days.
Having said that the 110 bhp 1380 A series Metro I built as a road hack back in the early 90s was bloody good fun for a couple of years in such a light car and scared the bejesus out of things that ought to have run rings round it based on the 1.3 badge on the tailgate. It was also completely untemperamental and gave well over 40 mpg in gentle use courtesy of the single HIF SU which frankly I think modern fuel injections systems still find hard to beat, especially if you take the cost and complexity into account.
The other thing that I can be quite sure of is if the gasket is the one that matches the head rather than the block then the head will overlap it completely and shield it from combustion gasses so the edge of the fire ring will not become a hot spot anyway. It might be a different matter if the gasket protruded completely past both head and bore but even then a nice rounded edge is unlikely to cause a problem.
Finally, most of that last 1mm of the rounded edge of a fire ring doesn't contribute to sealing anyway. Only the parallel elements of the gasket do this and having the very edge sticking out past the bore makes little difference.
Anyway if the OP gives it a try he can let us know he it worked out but I'm sure it'll be fine. My concerns on these highly tuned A series engines are more to do with the block rigidity than any gasket issues. The A series bores flex about like a reed in a high wind at the best of times which is why they were always crap at ring sealing and oil control even in normally modified 8v spec. With 150 plus bhp pumping through them it's hardly a recipe for a long and happy life. Still we tune what we own rather than what we maybe ought to buy which is probably why I spent so much time on A series engine development in earlier times but I wouldn't touch one with a bargepole these days.
Having said that the 110 bhp 1380 A series Metro I built as a road hack back in the early 90s was bloody good fun for a couple of years in such a light car and scared the bejesus out of things that ought to have run rings round it based on the 1.3 badge on the tailgate. It was also completely untemperamental and gave well over 40 mpg in gentle use courtesy of the single HIF SU which frankly I think modern fuel injections systems still find hard to beat, especially if you take the cost and complexity into account.
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