GN1R Heads?



If interested, you can see my Tech Page for flow #'s comparings different heads.

I don't have pics...but PT&E/Jim Byrne's car ran 8.60s@166 at Reynolds with these heads and a single 88 turbo. I believe Terry Houston has the R heads as well and he's gone 160+. Gary Harmon's car went 8.99 with the regular GN1s in a car that looks stock enough to drive to work! They are definitely working.
WOW! Depending on the weight of their TR they are making around 1000HP at the motor!:eek: Thats awesome! I thought only stage heads could take you that far.
I think I have seen pics of a set on a thread here before comparing them to stage heads ( I think it was in the for sale section) but its gone along with the awesome pics.I hope someone will step up and post some for us to keep, for everyone to see.:)
Also these GN1R heads are they different than just a set of regular GN1s with a MAX effort port job? or just the same? whats the cost on a set of GN1Rs anyways?I could just call Cottons but Im lazy:D maybe he will respond or some other vendor.hopefully someone will post some pics!! ANYONE??
Someone correct me if I'm wrong, but its my understanding that GN1Rs are a GN1 head with a larger combustion chamber (shrouds the valves less) for the larger bore of a 4.1 block. You can order them unported, or full race ported like most people do. I believe they cost the same as a full race ported set of 8 Bolt GN-1 Alum heads.

Heres some pics of a ported alum stage 2 head...
R headz

Just got a set from ol Jack C. Fully race ported.
Here's the "real meal deal" on them.
1.900" int. 1.600" ex.
46 CC chambers.
356-t6 alum.
M-2 tool steel seats.
1.250" springs @ 1.750" 100# seat pressure.
Manganese bronze guides.
Lifts exceeding the .500" max MAY require machine work and the springs MUST be changed.:eek:

Only problem I see w/ these heads is the lack of Helicoils in the threads. My last set had many holes only partially tapped. haven't looked these over yet.:) ACCESSORY MOUNTING THREADS ARE METRIC!!!
Other item they mention is the hyd lifters should be set w/ .025 to .065" preload.

Back to helicoiling my hole:D
If the GN1R's are different than the GN1's I would like to put some flow #'s on my tech page if somebody has them...

"CODY suspension system, and NO snubber. "


GN 1R flows

Kevin, I had 2 sets of the "regular" GN 1's.
I flowed the first set and got 205CFM @.500 int. and 176 on the exh.
I had a set LIGHTLY ported and got 220 int.@ .500 and 188 exh.

As I recall, didn't the early Champ alum heads have the valves relocated? When I got my first set of 8 bolt Champs, the rocker shafts had to be changed.[T&D's were originally on C. iron production heads] [The snap rings were about .100" too close to the rockers.
The guys at T&D knew exactly what I needed. I had to do some swapping of shims to get the rockers centered up. I had to redo this when I put the 14 bolters on the stage 2 engine also.
I talked to CAl H. @ BG this yr. He had bent a valve and had the heads off. He showed me the heads and offset lifters he was running w/ the "R" heads. [He had one of the first sets]
maybe he can chime in and come w/ some flow #'s.

Cu round,
Back to looking at my heads:D
Are those Isky lifters? If so what rev kit are you running? And do you know the spring rate by chance? Thanks for any info you can give me.
Chuck are those the "regular" GN1 specs you list there? If I recall the "R" heads I have cc'd at about 50cc, also have slightly larger int and exh valves (1.95, 1.65). The flow numbers you list were similar to what my old set of ported GN1's flowed, about 230 int and 190 exh. Don't know what numbers these new ones would put up, but probably not alot more.

CNC Ported Stage 2 vs. CNC Ported GN1

I think I have seen pics of a set on a thread here before comparing them to stage heads ( I think it was in the for sale section) but its gone along with the awesome pics.I hope someone will step up and post some for us to keep, for everyone to see.

Here is the comparison pictures I took between my CNC ported GN1 heads and my brothers CNC ported Stage 2 heads. No comparison!:eek: When he gets his motor back from the machine shop I will post a comparison of the exhaust ports.

The only REAL flow diferance between the GN-1's and the GN-1R's is in the larger valves. They are designed for the big bore motors and have the valves moved apart in order to fit the bigger valves. Remember, when you order heads from Champion, get them set up for your application. Just like telling them what springs you need, you can also specify what valves you want. On my own heads, I chose 2.00 intakes and 1.600 exhaust.

Do they flow as much as Stage2 heads? NO. Are you going to run faster with Stage2's? I would say that depends on your combination. They sure haven't slowed Terry Houston down much. For a street car I'll take the GN-1's.
I found the records and they put in 1.95 and 1.625 in mine. Looks to me like they may have moved the plug a little closer to the chamber center too in the new castings?

Attached is a pic of the chamber side in mine; this is before the locwire grooves were milled in 'em.



  • gn1rbotts.jpg
    34.4 KB · Views: 400
So, What are you guys paying for these custom GN1s?,and whats the waiting time to get a pair customized for your needs?
GN "R"zzz

TurboTR, I was reading the specs off of the sheet that came w/ the heads. I ordered them from ol Jack Cotton as my early heads are cracked in the usual place between the lower row of bolts.
It sounds like Cal has explained pretty well that I have a set of "R" heads,[they're marked as such], but got the "standard size" valves. I didn't know they were available w/ the bigger valves and the larger chamber. [My engine is 4.030]. I guess it's another case of buyer ignorance. Don't know what the difference in cost is. Cal??
For my use, these will work fine and will most likely flow more than the pocket ported heads now on the engine.
As for the flow #'s I posted, they were from memory and at my age "CRS" can rear it's ugly head at the most inopportune times.:eek:

Oh well, back under my heads:D
Re: GN "R"zzz

Originally posted by Chuck Leeper
I didn't know they were available w/ the bigger valves and the larger chamber. [My engine is 4.030]. I guess it's another case of buyer ignorance.

Same here, I was definitely out of the loop on this when I got mine 2.5 years or so ago and I am really disappointed about that. Since that time, I've had them welded up several times, and had to get and port a third head. Makes it tough to "upgrade" to the R's now when the gross national product of a 3rd world nation is already invested in these. Someday...

Has Champion got these cracking problems solved yet?,or are people still having problems with the new supposedly better sets?
also what is the general price range for the GN1Rs?,complete heads only, no valvecovers,rockers,etc,included.
GN 1Rzzz

Art and folks, The "R" heads were not available til just recently, from what I know anyway.
Here's what I was told by those supposedly "in the know".
heads were cracking due to:
1.Overtorquing and crushing the internal columns in the casting.
Tom told me to torque to 75 on long/65 on short.
2.Overheating. Keep EGT'S at 1700 0r less.
3.Detonation [and OUTRAGEOUS BOOST] was causing the long studs to stretch more than the short and thus putting the stress at the line of lower bolt holes, causing the cracks in that area.
I did this and they cracked anyway. And this at NEVER more than 20psi. [and MINIMAL detonation.;) ]
The "R" heads have alot more "meat" in the lower area and I've heard no reports of cracking. CAL???
Supposedly, once the old heads are welded and used as an 8 bolt application, they will live well. Don't know, but am going to find out once these new heads are on and the old 1's are fixed at Champion.
I'm outa here!!:D
Gotta go "pull my head out!!:eek: