GN1-R's, Ported & Unported stock heads.


9 Sec Wanna-Be
May 25, 2001
Since you don't see this kind of stuff posted too much I figured I'd show what a full race ported GN1-R head (out the box) looks like when compared to stock iron heads. This gives people an idea of how much larger aftermarket heads are. I ported the stock iron head you see myself and has been a best of 6.53 at 107 in the 8th mile. Also to note, my "R" heads are not the tall port offered by Champion. There's at least 3/16" or more to make the port taller. I'm sure all the really fast guys have MUCH larger re-worked heads than these.




Now This Is What Im Talkin About------ Some Real Info I Can Use!!!! A+a+a++a
Great info!!! Is the full race port on the GN1's the same port job as the stock heads but just the GN1 head?

Great info!
Great info!!! Is the full race port on the GN1's the same port job as the stock heads but just the GN1 head?

Great info!

Champion ported the "R" heads. I ported the stock heads years ago you see in those pictures. I done them...probably back in 1998.
Great post man, Thanks!

I am going to make it a sticky!
Added more...

Just a reminder...I ported the stock heads myself. I just took a grinder and basically "hogged" them out. They are not ported by a professional.


Below is a stock 1.5" exhaust valve stuck in the intake port bowl area. This is to show how much larger the bowls are when comparing.




Champion GN1 Intake (not production unit) - Stock Ported Intake - Unported Stock Intake

you did a good port job on the stock heads.they actually look better than the ported heads i have.good job.

all things being equal what was the perf. difference between both heads. Was the gain significant ?
Those GN1Rs' are huge :eek: !! What do u use for intake manifold gasket then ?? :confused: Great post man !! :biggrin:
all things being equal what was the perf. difference between both heads. Was the gain significant ?

I don't have back to back data so I will give my best answer. It wasn't worth it for what I've seen but I've also been chasing down AFR problems which I've just now corrected. You can make you own conclusion by reading below.

Iron headed combo up until 2005:

The average time the car ran with the stock block, stock crank, stock ported heads, stock ported intake and 2 1/2 stock intercoolers (tied together), ATR 214-210 roller & 70 P trim turbo was somewhere in the 6.70's at 102-105. This was with 30psi of boost with the car weighing 3450lb. Below is the best timeslips with that combo...

1.453 6.536 107.392
1.479 6.617 106.253
1.548 6.624 106.324
1.536 6.673 104.942
1.583 6.680 107.078
1.548 6.735 105.376
1.554 6.776 103.455
1.617 6.777 105.512
1.530 6.783 101.936
1.534 6.797 101.898
1.515 6.806 102.611
1.532 6.813 101.369
1.562 6.847 101.786
1.671 6.853 106.071
1.574 6.867 99.747
1.685 6.875 106.121
1.652 6.877 104.321

Aluminum headed combo 2006:

Unfortunately, I haven't run the car too much with the GN1-R's because of AFR problems I was chasing down. I changed 3 things since those times above....the heads, the intake and the intercooler...all three are still on the car. I was still using the same 70 P trim turbo and ATR roller cam. The best run was a 6.69 at 104 with 25psi of boost with unstable AFR's. The car also weighed more... about 3580lb. So, I guess I can say that running 5psi less boost and the car weighing 130lbs more these changes helped.

Since the above aluminum headed times, I've a added a FAST XFI... which fixed my AFR problems and added a stroker crank and a 220-224 cam.

Thanks for the input. I don't know what luck everyone else has had but I think it's really hard to beat a good set of iron ported heads on a 109 block application That's why I asked the question of if there were any big difference's that you experienced. Aluminum heads run cooler & heat makes H.P. Years ago when I raced BB chevys I ran into this. The engines actually ran better @ 200 degrees with the aluminum heads available at that time.This may sound contrary to all thats believed with turbo's, but it's worth some consideration. Thanks lou
best post of the year

Thanks for the time put into the pics and information :cool: