boost for head gaskets
Addict
Rennlist Member
Rennlist Member
Joined: Mar 2004
Posts: 917
Likes: 10
From: Long Island and Lake George, NY
Z has it right.
I ran the stock clutch with 8 psi and 255 rear tires. The clutch was fine, just had wheel spin. When I went to sticky 295's, the stock clutch couldn't hold hard shifts into third, forth, or fifth. There are several options out there now, I had a Kevlar clutch with a heavier pressure plate made by Motorsports SLC in Utah, has held up ok so far.
13 psi has been fine, still running the original 1989 head gaskets in mine, been SC'd since late 2004 or so. With the shark tuner being able to tune for fuel and ignition pretty sure mine has less knock counts than a stock car...detonation kills head gaskets, not the boost psi itself. Many times the force in the cylinder with detonation, has to go somewhere.
As for the cars running hot, make sure the radiator is new or in 100% working order and you will be fine.
And other than normal fluid changes, I haven't needed to touch my car in a year and a half. Pretty reliable for a 23 year old modified car!
Jim
I ran the stock clutch with 8 psi and 255 rear tires. The clutch was fine, just had wheel spin. When I went to sticky 295's, the stock clutch couldn't hold hard shifts into third, forth, or fifth. There are several options out there now, I had a Kevlar clutch with a heavier pressure plate made by Motorsports SLC in Utah, has held up ok so far.
13 psi has been fine, still running the original 1989 head gaskets in mine, been SC'd since late 2004 or so. With the shark tuner being able to tune for fuel and ignition pretty sure mine has less knock counts than a stock car...detonation kills head gaskets, not the boost psi itself. Many times the force in the cylinder with detonation, has to go somewhere.
As for the cars running hot, make sure the radiator is new or in 100% working order and you will be fine.
And other than normal fluid changes, I haven't needed to touch my car in a year and a half. Pretty reliable for a 23 year old modified car!
Jim
Three Wheelin'
Joined: Apr 2011
Posts: 1,778
Likes: 1
From: Singhampton, Ontario/London, Ontario
And back we go to the "pull the heads or not" debate... Is there a clear answer out there? Pulling the heads also means disassembly and reassembly of part of the valvetrain.
Race Car
Joined: Dec 2003
Posts: 4,477
Likes: 5
From: Atlanta, GA
My GT still has original head gaskets, has been supercharged since it had ~170k miles on it. It now has 243k miles, and over 40k was put on it by me. The car is my daily driver for over 4 years now. It is set up to run 8 - 8.5psi. With proper coolant changes and no detonation, you have nothing to worry about.
Dan
'91 928GT S/C
475hp/460lb.ft
Dan
'91 928GT S/C
475hp/460lb.ft
Captain Obvious
Super User
Super User
Joined: Aug 2003
Posts: 22,846
Likes: 348
From: Cambridge, Ontario, Canada
I'm as cheap as they come on this board and I would replace the other gasket. My car only came with bent valves on one head but I've replaced both gaskets. This was years before I decided to boost is.
Thread Starter
Drifting
Joined: Jan 2010
Posts: 3,334
Likes: 8
From: Nebraska
If you are fine with a daily driver I should be fine for a weekend fun car if it is not abused. I like the idea of using the Murph system in the 6 to 9 range.
My GT still has original head gaskets, has been supercharged since it had ~170k miles on it. It now has 243k miles, and over 40k was put on it by me. The car is my daily driver for over 4 years now. It is set up to run 8 - 8.5psi. With proper coolant changes and no detonation, you have nothing to worry about
Dan
'91 928GT S/C 475hp/460lb.ft
Dan
'91 928GT S/C
475hp/460lb.ft
Three Wheelin'
Joined: Apr 2011
Posts: 1,778
Likes: 1
From: Singhampton, Ontario/London, Ontario
That's why i admire your supercharging system... you saw the approx. 6K price for a 928MS or Murf kit and said, **** that, i can do that myself for a fraction of the price. I plan to do the same thing to my 87 when i start making more money.
Rennlist Member
Joined: Jul 2006
Posts: 5,424
Likes: 630
From: Bloomfield, MI
Rember like said all those rubber bits are 20 years old and rock hard.
The worst part is the cleaning, and it all needs to go back together the same same way it came apart and very CLEAN
Get at least 32 Zip lock bags (or 16) and bag and mark each Valve assembly so they all go back right where they came from.
Just got done doing my 86.5.
Just do it, then you know what you got,
Dave K
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Three Wheelin'
Joined: Apr 2011
Posts: 1,778
Likes: 1
From: Singhampton, Ontario/London, Ontario
Pull the Heads off and replace the HG's, check the Valve guides for excessive play, if good just Lap the valves and replace the Valve seals.
Rember like said all those rubber bits are 20 years old and rock hard.
The worst part is the cleaning, and it all needs to go back together the same same way it came apart and very CLEAN
Get at least 32 Zip lock bags (or 16) and bag and mark each Valve assembly so they all go back right where they came from.
Just got done doing my 86.5.
Just do it, then you know what you got,
Dave K
Rember like said all those rubber bits are 20 years old and rock hard.
The worst part is the cleaning, and it all needs to go back together the same same way it came apart and very CLEAN
Get at least 32 Zip lock bags (or 16) and bag and mark each Valve assembly so they all go back right where they came from.
Just got done doing my 86.5.
Just do it, then you know what you got,
Dave K
I think if i pull the heads though i'm going to go the cardboard route, then tape the valvetrain components to the cardboard in the exact same orientation they came out as, and mark the direction of drive on the cardboard.
Rennlist Member
Joined: Jul 2006
Posts: 5,424
Likes: 630
From: Bloomfield, MI
I found the zip lock bags work best for the valves, label each bag by cyl and valve # i.e.:
Cyl #1: I-1
Cyl #1: I-2 (counting valves from front to back)
Cly #1: E-1
Cyl #1: E-2
That’s four bags per cly, containing the valves, springs, spacers, keepers (i also zip tie the spring assembly together so it goes back in the same order top to bottom)
All valves (in bags) for one head fit nicely into a medium size pizza box.
And you get to eat pizza
Cyl #1: I-1
Cyl #1: I-2 (counting valves from front to back)
Cly #1: E-1
Cyl #1: E-2
That’s four bags per cly, containing the valves, springs, spacers, keepers (i also zip tie the spring assembly together so it goes back in the same order top to bottom)
All valves (in bags) for one head fit nicely into a medium size pizza box.
And you get to eat pizza
Captain Obvious
Super User
Super User
Joined: Aug 2003
Posts: 22,846
Likes: 348
From: Cambridge, Ontario, Canada
I found the zip lock bags work best for the valves, label each bag by cyl and valve # i.e.:
Cyl #1: I-1
Cyl #1: I-2 (counting valves from front to back)
Cly #1: E-1
Cyl #1: E-2
That’s four bags per cly, containing the valves, springs, spacers, keepers (i also zip tie the spring assembly together so it goes back in the same order top to bottom)
All valves (in bags) for one head fit nicely into a medium size pizza box.
And you get to eat pizza
Cyl #1: I-1
Cyl #1: I-2 (counting valves from front to back)
Cly #1: E-1
Cyl #1: E-2
That’s four bags per cly, containing the valves, springs, spacers, keepers (i also zip tie the spring assembly together so it goes back in the same order top to bottom)
All valves (in bags) for one head fit nicely into a medium size pizza box.
And you get to eat pizza