Cool, thanks for your help.

lookin for the best pipe,plug combination for my tuned GRP .21. It is so low on power compared to my sport(silver head)GRP. I must be using the wrong clutch,pipe & plug combination. It does not seem to like a sportwerks 053, dynamite 053 or a jp3.

what plug,clutch&car?

the grp pipe is the same as the dynamite 053 so thats odd right there. i had great success with my grp with the grp pipe. it is a little low on torque compared to a v spec and orion motors, even the nova motors. but thats what gives the great fuel mileage. i ran the stock clutch setup on my 8ight and it worked great. with it in my mugen i ran 1.0 springs with the lightweight shoes and 13t bell and it was really good. and i was running mine with a number 5 grp plug and 8mm restrictor. you could use a #4 plug, a little hotter, but make sure you have the 8mm restrictor.

Is it broken in yet? Carb opening all the way? I know mine didn't run well until I had at least a gallon through it. Or is it used? Does it have good enough compression?

My setup which runs quite well is a Dynamite 053, OS P3 plugs, 6 mm restrictor with 4 plastic shoes and 4 black springs.

Its currently in HB D8. I have used several diff clutch setups on it so far. the latest being a firioni 4 shoe set up. tried a losi setup 2 carbon's & 2 alum green & gold springs-that just killed it.so far it seems to like the hot bodies clutch & firioni best. has stock restrictor & shims. I thought about trying a GRP pipe but from the last few comments that might be a waste. has a grp #4 plug. I just hate to think this thing doesn't make any more power than what I'm getting out of it now.It has over a gallon of fuel through it now & just barley has any mech pinch but great compression. It just has no power on the bottom & its not very fast.

I have ran the GRP 21 for a couple of yrs. and have had good luck with it. It definately does't have the best bottom but mid and top is great. I run A FIORONI clutch, dyn 053 with a p3 plug. I tried the GRP #4 and #5 plugs much longer then I should have. Try the p3 plug made a big difference for me.

I also lost most mechanical pinch at 1 - 1 1/2 gallons on both the .21 grps but I now have aprox 5 -5 1/2 gallons with great compression.

grp 2053/odonells 97t/m2c 4shoe clutch with reg/hard shoes and 1.0 springs on my truck ...soft light shoes and 1.0 for buggy

I ran grp's all last year and at the beginning of this year mostly the turned version and 2 were modded. They always ran best with a p4 plug and a dynamite 053 pipe with a long header in the truggy for added bottom end. There was no beter pipe than a 053 for these engines. The grp 2053 is ok it is just a little restrictive.

Does anyone still run the GRP "untuned" .21? I was just wondering what plug would be the best to run. I have a couple MC-59s and a few O.S 8s. The OS seems to be shorter so I wasn't sure if I should throw it in or not. Thanks.

59s are too hot and os plugs are for os motors only beacuse they are shorter.
O'Donnell 77 or 99 should work just fine.

Perfect man. That was going to be my next option. Thank you.

I run od 97's and 99's and they work great i actually have to buy a lipo battery for my starter box because my untuned had so much pinch it killed my gel cell. But odonell 77's are too short because i run them in my touring car

Finally ran a bunch of fuel through my GRP yesturday, Its a tuned GRP that I bought used from a local racer. He said there was close to six gallons on it, and he couldnt get it to tune well but I got a NIB rod with it. I took it apart checked out the carb and it would not flow at all untill the LSN left the spray bar so I stuck on a diffrent manufactures carb.
Took out a thin headshim (I had a thick and thin one installed) using an odonnell 99t plug dynamite 053 pipe, os 2050 header, 6mm restrictor stock AE clutch, 16tooth bell in my rc8 Im really likeing the results. Smooth power, just enough snap and killer milage. The only downside i can see is my plug might be a little cool as it will flame if its slightly rich.