rdm20fan
Member
- Messages
- 212
- Location
- Near Chicago, IL
Hey Guys,
I've been pushing my 1st gen 1UZ more this past year.
I had a couple problems and I wanted to share.
Maybe a few of you have had the same issues. Here is what I have learned.
13-14 PSI about 450 RWHP issue
I blew out a stock head gasket (Composite) a few years ago right at about 13 psi.
With my rebuild I used the GS400 head gasket (MLS) at 14 psi I would start blowing coolant out of the radiator overflow. This was probably about 450HP to the rear tires. At this point the Toyota head bolts are stretching allowing the compression to get past the gasket, and into the coolant passages. This builds pressure in the cooling system, and pushed the coolant out. On a composite gasket this pushes the gasket out of the way, and you have a head gasket failure. With the MLS gasket it allows the pressure past, but usually re-seats itself when the high cylinder pressure stop.
I kept wasting time chasing over heating issues, when I should have been putting in new head studs.
20 PSI About 600 RWHP issue
Same thing as before, but I was running ARP head studs. It's hard to sometimes think of a bolt acting like a spring, but under the high cylinder pressure the combustion is enough for the bolts/studs to actually stretch until the pressure is gone then they pull back. This is usually the case until it is to much for the bolt/stud to take and it stretches past the point where it will not spring back.
The reason I listed my boost PSI, and what I think the car was making HP level is because I'm pretty sure it doesn't matter how you are making the HP. (Turbo/Supercharger/Nitrous/High Compression, cams) The combustion pressure to make that level of HP is what is lifting the head, not that actual 21 lbs of boost.
23-24 PSI close to 700 RWHP issue
Since the head gasket was re-seating itself after each pass down the drag strip. Chris and I decides to try and up the boost level, and just blow coolant into the over flow.
After each pass we would just drain it, and refill the cooling system in order to try and run a 10 sec pass
(We didn't get there this year)
The motor started breaking up in 4th, 5th gear when the boost levels would get that high.
We were blowing out the spark. The velocity of that amount of air rushing into the cylinder was to much for the coil to continue to drive spark across the sparkplug gap.
We re-gapped the plugs to a smaller gap, and it got better, but didn't go away. At 25 PSI the motor was breaking up bad and wouldn't make any power.
Don't know whats next for my 1UZ. I was thinking of O-ringing the Heads/Block.
Also thought of having the Block/Heads drilled, and tapped for larger studs.
Next would be to also get new MSD coils.
To o-ring, and drill new head studs will probably lead to long periods of down time for the car, and I don't know if that's the route I want to go right now.
The SC is pretty fast as it is. Maybe turning the boost back to 15-17 psi, and enjoying her for a little bit might be a good place to be for a little while.
What do you guys think?
Hope this helps someone going through the same.
Thank, Bob
I've been pushing my 1st gen 1UZ more this past year.
I had a couple problems and I wanted to share.
Maybe a few of you have had the same issues. Here is what I have learned.
13-14 PSI about 450 RWHP issue
I blew out a stock head gasket (Composite) a few years ago right at about 13 psi.
With my rebuild I used the GS400 head gasket (MLS) at 14 psi I would start blowing coolant out of the radiator overflow. This was probably about 450HP to the rear tires. At this point the Toyota head bolts are stretching allowing the compression to get past the gasket, and into the coolant passages. This builds pressure in the cooling system, and pushed the coolant out. On a composite gasket this pushes the gasket out of the way, and you have a head gasket failure. With the MLS gasket it allows the pressure past, but usually re-seats itself when the high cylinder pressure stop.
I kept wasting time chasing over heating issues, when I should have been putting in new head studs.
20 PSI About 600 RWHP issue
Same thing as before, but I was running ARP head studs. It's hard to sometimes think of a bolt acting like a spring, but under the high cylinder pressure the combustion is enough for the bolts/studs to actually stretch until the pressure is gone then they pull back. This is usually the case until it is to much for the bolt/stud to take and it stretches past the point where it will not spring back.
The reason I listed my boost PSI, and what I think the car was making HP level is because I'm pretty sure it doesn't matter how you are making the HP. (Turbo/Supercharger/Nitrous/High Compression, cams) The combustion pressure to make that level of HP is what is lifting the head, not that actual 21 lbs of boost.
23-24 PSI close to 700 RWHP issue
Since the head gasket was re-seating itself after each pass down the drag strip. Chris and I decides to try and up the boost level, and just blow coolant into the over flow.
After each pass we would just drain it, and refill the cooling system in order to try and run a 10 sec pass
(We didn't get there this year)
The motor started breaking up in 4th, 5th gear when the boost levels would get that high.
We were blowing out the spark. The velocity of that amount of air rushing into the cylinder was to much for the coil to continue to drive spark across the sparkplug gap.
We re-gapped the plugs to a smaller gap, and it got better, but didn't go away. At 25 PSI the motor was breaking up bad and wouldn't make any power.
Don't know whats next for my 1UZ. I was thinking of O-ringing the Heads/Block.
Also thought of having the Block/Heads drilled, and tapped for larger studs.
Next would be to also get new MSD coils.
To o-ring, and drill new head studs will probably lead to long periods of down time for the car, and I don't know if that's the route I want to go right now.
The SC is pretty fast as it is. Maybe turning the boost back to 15-17 psi, and enjoying her for a little bit might be a good place to be for a little while.
What do you guys think?
Hope this helps someone going through the same.
Thank, Bob