Ok, i thought i'd bring back an old thread rather than start a new one... I see there are varied opinions on the GRP vs V-Spec topic... My question is, is there anyone who can give me a comparison between a GRP 21MRT and an OS Speed? I've been running a speed for about a year now, (I have 2 actually) but i was interested to try the tuned GRP.... Any thoughts?

Cheers....TIA!

The GRP is no harder to tune than any other engine. Run a small idle gap, a lean bottom end and a fat top. DON'T TUNE TO TEMP either because they like to run cool. And tuning to temp is not the way to go for any engine.

I think it's all in the drivers in your local area. The fastest guys in florida are sponsored by someone else other than GRP, so obviously they run whatever it is they are sponsored by. Or, you may have die hard Nova or OS guys and then they crowd sways that way. Truth is we have a great choice of .21 engines on the market today.

In my area since I run GRP a lot of racers have now switched to GRP. They have someone to help them at all the races tune, etc. They love them. The OS is a great engine but without a doubt the rod and crank pin last much longer on the GRP's. It is my experience that the GRP gets some of the best fuel mileage out there today. It's really a good mill, with deceiving power. It's smooth and lays down the power very well. It may not sound as fast as a OS or NOvarossi, but if tuned correctly on any straight you go down with another mill will show you different.

I'll tell you guys something that I feel makes it more than worth it to run a grp over any engine out there. Once it's time to start thinking about a new p/s on your engine you can send it back to horizon hobbies in ontario, ca(attention adam drake), along with two fresh bearings, and Adam/Horizon will install your bearings and give your sleeve a fresh pinch all for no charge. This gets you a fresh engine that's ready to go for another few gallons. A few of my local guys have done this and for about $50-60(cost of bearings and shipping) you have a fresh engine. MAke sure to include your contact info with it.

Well, after about 2 gallons on mine the bottom of my con rod fell off rendering the whole engine useless

I bought GRP because of longevity claims. Broke it in heat cycle method by the bible. Always ran with good smoke stream. To have that happen, along with the fact that I could never find bottom end in my TRUGGY. I went with something else.

NOW, there are plenty of happy GRP owners, it IS a good engine, but I will never run one again unless its a screaming deal, and for truggy I'd go with a .28.

I have run a GRP .21 tuned version in an 8T for the last race season with very little problems. I did notice a little lack of torque in the heavy truggy but I upped the spring rate in the clutch and went to a long header to max out the torque and was pleased with it. I have recently purchased a powerhouse race modded GRP .21 non tuned and this motor smokes the tuned version in performance and mileage. I average 11.5 min per tank which is +1 min longer than the tuned version and I don’t see any issue with not enough torque. I did switch to an 8T 2.0 and even used the stock spring setup of gold and green which is much weaker than the all silver spring setup I was running before. I will have to see if it lasts like the tuned version. I had 6-6.7 gal on the tuned version and it was still running strong. I replaced a front bearing at 5 gal and that’s it. I have sold the tuned version so no more comparison but I am sending a new GRP .21 tuned version to powerhouse for their turbo mod. I am sure I will be happy with it. I have run an OS V-spec and it did not make it past the 5 gal mark. The compression was gone and the front bearing was gone too. Tune was not difficult just don’t touch the middle needle ever. If you do you will wish you never did, there is no going back after you touch the middle needle. GRP gets my vote I will prob buy a 4th.