compression and copper head gaskets
08-12-2003, 05:48 PM
#1
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compression and copper head gaskets
My new stroker motor has too much compression and is pinging on pump gas (91 octane). So I am considering using a thick copper head gasket to drop the compression.
Has anyone had experience with these ?
Anyone used Gasket Works ? see link below
http://www.headgasket.com/gaskets.html
Should it be O-ringed or not ?
Does a thick gasket pushing the heads out further affect timing with overhead cam engines ?
A thickness of 0.125" should give me 10.2:1 which should be fairly safe, halfway between stock S4/GT (10.0) and GTS (10.4) ratios.
A thickness of 0.093" would give me 11:1
How much compression can we get away with on pump gas without replacing the ECU ?
Has anyone had experience with these ?
Anyone used Gasket Works ? see link below
http://www.headgasket.com/gaskets.html
Should it be O-ringed or not ?
Does a thick gasket pushing the heads out further affect timing with overhead cam engines ?
A thickness of 0.125" should give me 10.2:1 which should be fairly safe, halfway between stock S4/GT (10.0) and GTS (10.4) ratios.
A thickness of 0.093" would give me 11:1
How much compression can we get away with on pump gas without replacing the ECU ?
08-12-2003, 06:57 PM
#3
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I agree, based only on my vast well of knowledge gained from reading car magazines and long technical internet posts but never actually doing this myself yet, that pinging results more from not enough tuning than from too much compression.
Definitely check that your new bigger fuel pump is sized and powered to deliver, your new bigger fuel filter isn't choking the flow, your new bigger injectors are sized properly, and that whatever computer you're running is either tuned (aftermarket computer) or tricked (stock computer) to not run lean and die a horrible death. Oh, and they say timing is important too.
Keep us posted!
Definitely check that your new bigger fuel pump is sized and powered to deliver, your new bigger fuel filter isn't choking the flow, your new bigger injectors are sized properly, and that whatever computer you're running is either tuned (aftermarket computer) or tricked (stock computer) to not run lean and die a horrible death. Oh, and they say timing is important too.
Keep us posted!
08-12-2003, 08:10 PM
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Nobody that has answered seems to believe I really have too much compression. So here is the number. The compression is 12.1. That's from stroker crank, 5.85" rods, 968 pistons, 1.4mm head gasket, and milled heads. It would take one hell of an ECU to make that work on pump gas. I have been considering an aftermarket ECU (particulary the DTA P8PRO), but they are not smog legal and would have to be hidden from visual smog inspection.
"If you lower the compression, you will loose power"
True. But so will knock sensors retarding the timing.
I am willing to trade some power for reliability. Pinging can destroy a motor.
"an eight of a friggin' inch???? isn't that a hellovalot?"
Yes it is. But that's what it takes to drop 12.1 to 10.2
"pinging results more from not enough tuning than from too much compression. "
Tuneability is limited without an aftermarket ECU.
I have an air/fuel meter mounted in the dash. The mixture looks good. It runs very well on race gas. But I need it to work on pump gas. I have a Bosch 0 580 254 044 racing fuel pump (capable of supporting up to 700hp), rising rate adjustable fuel pressure regulator, and 30 lb injectors(Bosch Ford Motorsport). It should not be lean or fuel starved. The meter does not indicate that.
"Hey Chris - a stroker? When didja build that, ya crazy bastid?"
From October to August.
"If you lower the compression, you will loose power"
True. But so will knock sensors retarding the timing.
I am willing to trade some power for reliability. Pinging can destroy a motor.
"an eight of a friggin' inch???? isn't that a hellovalot?"
Yes it is. But that's what it takes to drop 12.1 to 10.2
"pinging results more from not enough tuning than from too much compression. "
Tuneability is limited without an aftermarket ECU.
I have an air/fuel meter mounted in the dash. The mixture looks good. It runs very well on race gas. But I need it to work on pump gas. I have a Bosch 0 580 254 044 racing fuel pump (capable of supporting up to 700hp), rising rate adjustable fuel pressure regulator, and 30 lb injectors(Bosch Ford Motorsport). It should not be lean or fuel starved. The meter does not indicate that.
"Hey Chris - a stroker? When didja build that, ya crazy bastid?"
From October to August.
08-12-2003, 08:15 PM
#6
Chris - While I am absolutely exstatic that you got that motor together, and I am very interested in meeting with you sometime to see it and your workmanship, I am concerned, as the others are, about the pinging's source.
If you compression is anything over 11.5, then, oh yeah, your going to ping. Do you have a way of making the actual number pop out of some caluclations from the parts that you used?
Danno, of the 951 boards (and www.gururacing.net) has some headgaskets that I may be getting for my rebuilt. I am unsure if they can be had in different thicknesses, but they do have rings.
An ECU can be had for your car with all the bits and pieces for around 3200, as this is the process I am currently taking, and that is my percieved budget. www.dtafast.co.uk, and louis Ott and Devek are known distributors in the West coast. I am doing it differently, but its some info you may have not had.
I think that while many of us wish we can do CRAZY things with the stock ECU, getting a different one will solve so many headaches (and make new temporary ones) by giving us unlimited tuning.
I am unsure if your pinging could be from timing or fuel. Have you contacted John Anderson at all?
If you compression is anything over 11.5, then, oh yeah, your going to ping. Do you have a way of making the actual number pop out of some caluclations from the parts that you used?
Danno, of the 951 boards (and www.gururacing.net) has some headgaskets that I may be getting for my rebuilt. I am unsure if they can be had in different thicknesses, but they do have rings.
An ECU can be had for your car with all the bits and pieces for around 3200, as this is the process I am currently taking, and that is my percieved budget. www.dtafast.co.uk, and louis Ott and Devek are known distributors in the West coast. I am doing it differently, but its some info you may have not had.
I think that while many of us wish we can do CRAZY things with the stock ECU, getting a different one will solve so many headaches (and make new temporary ones) by giving us unlimited tuning.
I am unsure if your pinging could be from timing or fuel. Have you contacted John Anderson at all?
08-12-2003, 08:40 PM
#7
Nordschleife Master
Use an EGT, not an O2 sensor.
O2 sensors are VERY inaccuret outside of stoceometric.
I've just ran into a similer problem. Some PO had adjusted the mixture way rich, and then advanced the timeing. This give you a bit more power, but kills your fuel milage, and throws the HC emissions through the roof. About 2-4 mpg too... It also introduces a drivibility problem. Yuck. For the longest time I thought I was jsut a bit rich of stocometric. Later I found out that I was WAY rich, and there was no way to know it by the O2 sensors readings.
Anyways, long story short, once you hit about .8 volts on the O2 sonsor, you know your rich of stocoemetric, but not how rich. You could be a little, you could be a lot, you just don't know.
Get an EGT, and then measure your temps. This away you'll know if your actualy lean or not. Plus, you can use the information for later tuneing for power.
That said, I'm willing to bet that you've got too much compression. When stock 928s had 10.4:1, on 91 octane, 12:1 is probably too much.
Lowering your comression, but keeping proper ignition timeing will result in less lost power, better fuel economey, and probably lower engine temps, right? Assumeing I understand the things correct.
As an asside, do you think an EGR valve might help limit the pinging? I know after 79, pretty much none of the 928s where so equiped. I'm also told they help reduce knocking. This away you can keep maybe some of your high compression, so when you can switch to race gas, you can keep most of the power, but at the same time, when you switch to pump gas, active the EGR valve to keep it form knocking?
The EGR valve would have to be set up so it only opened when mannafold pressure was near WOT. Maybe you could use one of GM's electric ones, do the plumbing yourself, and tap into the WOT enrichment circut for the LH-jetronic? This away, when you went to the top part of the throtal, the EGR would open, flow some exaust gas in, and while it would make it a bit less on power, it would limit the knocking, right? Then add a switch in the cockpit labled 91 octane, race octane. Maybe?
Anyways, good luck.
O2 sensors are VERY inaccuret outside of stoceometric.
I've just ran into a similer problem. Some PO had adjusted the mixture way rich, and then advanced the timeing. This give you a bit more power, but kills your fuel milage, and throws the HC emissions through the roof. About 2-4 mpg too... It also introduces a drivibility problem. Yuck. For the longest time I thought I was jsut a bit rich of stocometric. Later I found out that I was WAY rich, and there was no way to know it by the O2 sensors readings.
Anyways, long story short, once you hit about .8 volts on the O2 sonsor, you know your rich of stocoemetric, but not how rich. You could be a little, you could be a lot, you just don't know.
Get an EGT, and then measure your temps. This away you'll know if your actualy lean or not. Plus, you can use the information for later tuneing for power.
That said, I'm willing to bet that you've got too much compression. When stock 928s had 10.4:1, on 91 octane, 12:1 is probably too much.
Lowering your comression, but keeping proper ignition timeing will result in less lost power, better fuel economey, and probably lower engine temps, right? Assumeing I understand the things correct.
As an asside, do you think an EGR valve might help limit the pinging? I know after 79, pretty much none of the 928s where so equiped. I'm also told they help reduce knocking. This away you can keep maybe some of your high compression, so when you can switch to race gas, you can keep most of the power, but at the same time, when you switch to pump gas, active the EGR valve to keep it form knocking?
The EGR valve would have to be set up so it only opened when mannafold pressure was near WOT. Maybe you could use one of GM's electric ones, do the plumbing yourself, and tap into the WOT enrichment circut for the LH-jetronic? This away, when you went to the top part of the throtal, the EGR would open, flow some exaust gas in, and while it would make it a bit less on power, it would limit the knocking, right? Then add a switch in the cockpit labled 91 octane, race octane. Maybe?
Anyways, good luck.
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08-12-2003, 09:03 PM
#8
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Uhmmmm, different pistons. Who put that motor together for you?? They should have been able to run some numbers and figure out compression before it was put together. 12:1 is out there for pump gas as everyone has stated.
Have you tried running any racing fuel to see if that stops the pinging. If your car isnt a daily driver then maybe 4 bucks a gallon VP could be your answer. Atleast give it a shot to see how it runs. Should be a screamer.
Have you tried running any racing fuel to see if that stops the pinging. If your car isnt a daily driver then maybe 4 bucks a gallon VP could be your answer. Atleast give it a shot to see how it runs. Should be a screamer.
08-12-2003, 09:11 PM
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"I am very interested in meeting with you sometime to see it and your workmanship"
It isn't my workmanship. I don't have the skill to rebuild an engine. I just planned the project (not well enough apparently) and paid the bill.
"Do you have a way of making the actual number pop out of some caluclations from the parts that you used? "
No it was all cc'd. But there was an error in the calculation. They originally said it was 11.1 but it is 12.1
There is a local DTA dealer in San Diego, Ducastel IIc
http://www.carabox.com/~dps/WhoRwe.htm
but they probably know nothing of 928's.
So Devek or Louis Ott are probably better bets.
"I am unsure if your pinging could be from timing or fuel. Have you contacted John Anderson at all?"
Not yet but I think I will.
I still have a Split Second Arc2 that I got from Huntley I could put back in to play with the mixture.
It isn't my workmanship. I don't have the skill to rebuild an engine. I just planned the project (not well enough apparently) and paid the bill.
"Do you have a way of making the actual number pop out of some caluclations from the parts that you used? "
No it was all cc'd. But there was an error in the calculation. They originally said it was 11.1 but it is 12.1
There is a local DTA dealer in San Diego, Ducastel IIc
http://www.carabox.com/~dps/WhoRwe.htm
but they probably know nothing of 928's.
So Devek or Louis Ott are probably better bets.
"I am unsure if your pinging could be from timing or fuel. Have you contacted John Anderson at all?"
Not yet but I think I will.
I still have a Split Second Arc2 that I got from Huntley I could put back in to play with the mixture.
08-12-2003, 09:36 PM
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"Who put that motor together for you?? They should have been able to run some numbers and figure out compression before it was put together. 12:1 is out there for pump gas as everyone has stated."
They f'd up. I am trying to get them to fix it under warranty.
"Have you tried running any racing fuel to see if that stops the pinging"
Yes it runs great on race gas. But for me that is not an acceptable option. It's too hard to get, costs too much, and means I can not take long distance trips.
They f'd up. I am trying to get them to fix it under warranty.
"Have you tried running any racing fuel to see if that stops the pinging"
Yes it runs great on race gas. But for me that is not an acceptable option. It's too hard to get, costs too much, and means I can not take long distance trips.
08-12-2003, 11:06 PM
#12
Maybe for the time being, so you can drive in the great San Diego weather, you could just stuff it with lots-o-toulene.
Ducastel is a supplier, but I needed other stuff as well.
Ducastel is a supplier, but I needed other stuff as well.
08-13-2003, 12:17 AM
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Chris:
I can privide 55 Gal drums to your door of 100, 110 and 117 Oct fuels at $4+ a gallon. Beyond that I think that with some remapping of the ECU we can pull some timing back to keep you safe on the street.
I can privide 55 Gal drums to your door of 100, 110 and 117 Oct fuels at $4+ a gallon. Beyond that I think that with some remapping of the ECU we can pull some timing back to keep you safe on the street.
08-13-2003, 12:40 AM
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"what cams are you running? "
marc@DEVEK
The cams were done by Huntley Racing two years ago. They are welded cams. They were not optimized for a stroker motor (it was a 5.0L back then) so I may want to change these some time. Also I am concerned over welded cams after hearing of your experiences with welded cam failure. We had to repair a few cam lobes.
marc@DEVEK
The cams were done by Huntley Racing two years ago. They are welded cams. They were not optimized for a stroker motor (it was a 5.0L back then) so I may want to change these some time. Also I am concerned over welded cams after hearing of your experiences with welded cam failure. We had to repair a few cam lobes.
08-13-2003, 01:03 AM
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Hi Derrek,
That sounds like a good deal on the fuel and I appreciate the offer. Thanks. I'll let you know if I need it. I was considering bringing the car to you for dyno tuning once the motor was broken in. But I have not wanted to put any miles on it until the pinging was resolved.
I still think the most direct fix to the problem is to lower the compression. And the easiest way I know is a custom head gasket. And it should be cost effective compared to ECU remapping or an aftermarket ECU.
That sounds like a good deal on the fuel and I appreciate the offer. Thanks. I'll let you know if I need it. I was considering bringing the car to you for dyno tuning once the motor was broken in. But I have not wanted to put any miles on it until the pinging was resolved.
I still think the most direct fix to the problem is to lower the compression. And the easiest way I know is a custom head gasket. And it should be cost effective compared to ECU remapping or an aftermarket ECU.