Head clearance for OPS 67 with drum valve

[Grub]

I'm coming over to the US with Ozzy team for the nationals but before I leave I'm trying trying to figure out what is the best head clearance for the new OPS 67 in my 1/8th scale.

I've run it with 29 thou and it ran very hot with a p255, so I have taken all of the shims out and it is now 22 thou (which I think is closer to where it should be).

Does anyone have any thoughts on what it should be?

The older OPS 67s I have, have both got 24 thou head clearance and run fine.

Grub

Hi ho, hi ho, off the to the states we go!

 

[TimD]

22 thou' ?

What bowl volume in CC's and what nitro % are you running Justin?

I don't run anywhere near that much clearance with my 67's. 12 to 16 thou' max on 50%.

Tim.

 

[Grub]

25% nitro and standard button, don't know what the volume is

 

[Roy Munoz]

I use to run some OPS 67 and they use to like 14 tho ..I had a Rossi drum rotor in it...It was in my old scale of the 82 Altas Van Lines....

 

[TimD]

I think OPS used to sell engines with a head for 4:1 fuel that had less volume than the nitro version. It could be that you have the 4:1 head if it kills plugs at a low clearance.

Aim for 14-16thou clearance if you get it skimmed. Adjust the bowl volume if it starts killing plugs.

 

[dannyual767]

Guys, I know I'm going to sound ignorant here but here goes anyway. How do I measure my clearance on my OPS engines? I've got two of them: OPS .65 that I bought brand new when I was in high school in 1979 and a .67 that was given to me about a year ago by a gas boat racer.

I've never had much luck in all these years with that .65. In fact, I broke the conrod on it last spring. One of the local racers had pity on me and gave me his old .67 because he had no need for it. I cleaned it up and it seems to run alright but I really don't know much about these OPS engines. They seem very tempermental to me :unsure: . BTW, I bought a new rod for the .65 off ebay last December. It was hard to find and everyone, including Aeromarine, told me that it's not the same as the .67 conrod. I've got it all back together now .

BTW, I do have a decent dial caliper that measures down to .001". Also, I"ve never run more than 20% nitro fuel if that matters. Thanks!

 

[dannyual767]

Anyone??

 

[ClayGlover]

There is a search feature on the forum that works great.

I did it for ya, read this past thread-

http://www.intlwaters.com/index.php?showtopic=4244&st=0

 

[dannyual767]

Thanks for doing the search for me Clay. It was good, educational reading.

 

[ClayGlover]

By the way guys, I found some plastigage that should work for the small displacement engines (range .001"-.009") -

http://store.summitracing.com/partdetail.a...t=DCC%2D4286819

There is a larger size, but I can't find it anywhere-

"Plastigage SPY-1 (yellow) .009 – .020 (.23MM – .50MM) range"