This weekend I disassembled my engine for inspection. It was running great, but decided to take a look at it b/c I made a lot of passes this year with it. The last time at the track with race gas, it went 9.83 @ 139. Didn't do too much after that b/c of lack of time. Anyways, the bearings, rods, pistons, thrust, etc all checked out perfect. Really did not need to be taken apart, but oh well gives me something to do this winter:wink: The GN1's suffered minor hairline cracks in 4 of the 6 combustion chambers (between the spark plug and the intake valve). My guess is that these cracks have been there pretty much all season. Appears not to have affected the valve seats. Anyone else ever experience this? Did you fix it, or just bolt them back on and hope for the best?
GN1's cracking between spark plug and intake valve.
- Thread starter KevinB
- Start date
I overheated the car bad earlier in the year. 250+ degrees
Made 80+ runs after that with no problems. My temps usually start out at 160 then rise to about 180-190 at the end of the track. I do not have a fancy radiator and usually just run distilled water with some type of gimmick additive.
Do you repair the cracks or just replace the seats?
Thanks
The heads get welded up and new seats installed.
The reason I asked about water temps..
With a fresh set of heads, I'm usually at 170 on the return road. When my temps start getting hi after a run (over 190 or so), I'll usually find a cracked head.
My guess is around 700hp the cylinder pressure is to much and the heads eventually crack.
The reason I asked about water temps..
With a fresh set of heads, I'm usually at 170 on the return road. When my temps start getting hi after a run (over 190 or so), I'll usually find a cracked head.
My guess is around 700hp the cylinder pressure is to much and the heads eventually crack.
UR50SLO
The Reaper
- Joined
- Jun 12, 2001
I got a set of GN1's used.. they guy I got them from (Dave Poppie) said they never go anywhere... I got some other cracks repaired at champion and they did not repair the one's where they start at the spark plug.
You can send them back down to Champion... they'll fix them.
Up to you... Mine are fine!
~Scott
You can send them back down to Champion... they'll fix them.
Up to you... Mine are fine!
~Scott
So, you run the heads this way? Do they go into the seats?
The heads get welded up and new seats installed.
The reason I asked about water temps..
With a fresh set of heads, I'm usually at 170 on the return road. When my temps start getting hi after a run (over 190 or so), I'll usually find a cracked head.
My guess is around 700hp the cylinder pressure is to much and the heads eventually crack.
Even when the heads were brand new, my car always gets close to 200 at the end of the traps. I never saw a drastic increase from the beginning of the year to the end.
EightSecV6
MDBL
- Joined
- Jul 18, 2001
They all crak there, pressure test them to be sure but we have never had one leak in that spot. I personally wouldnt worry about it.
Will do. Thanks!!
I have a set that i bought from ATR in 2001 and not showing any cracks between the sparkplug holes and intake valves.
I have them right here, just had the guides replaced so i can look at those areas
real good.
But i do run them on the street only with 16 - 20 lbs boost and never have over heated them.
I'm glad i read this thread, it gives me a heads up on what to watch out for with these heads. :smile:
I have them right here, just had the guides replaced so i can look at those areas
real good.
But i do run them on the street only with 16 - 20 lbs boost and never have over heated them.
I'm glad i read this thread, it gives me a heads up on what to watch out for with these heads. :smile:
- Joined
- May 28, 2001
Take a look at the valves while they are apart...
boostingbuick
Going to be buried in this.
- Joined
- Aug 25, 2002
Is this common in the early heads or all the heads? I have a early set.
Not all Alum heads have cracking problems......
Spooled231
Member
- Joined
- Jun 21, 2001
Ive seen multiple things happen with different versions of GN1 heads:
1. valve guides dropping
2. cracked around studs
3. combustion chamber cracks
4. ARP nut and washer pushing through the head at 50ft lbs torque!
I have a set of TA performance SE heads on my car and will be pulling off to check things out on the motor and will let you know if we see any problems.
Thanks
John Martin
1986 Buick T-type
9.71 @ 140
6.21 @ 112
My heads were brand new this Spring.
278cikiller
Active Member
- Joined
- Dec 21, 2007
alum. heads
Hey guys i was wondering i just got a set of GN-1 heads for my stage motor what kind of turbo will i need to make 700 hp our around there thanks for the info .
Hey guys i was wondering i just got a set of GN-1 heads for my stage motor what kind of turbo will i need to make 700 hp our around there thanks for the info .
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