Larry Cavanaugh cavanaugh racing heads

Hey guys, Have some questions concering cavanaugh racing heads. Larry was a good friend of mine we grew up together and i have just aquired an engine he built, probable the last one he built for himself. I know nothing about it and have no information unfortunatly, All of his records were on his laptop and his brother could not access it. All i know is it is a 1980 or pre 1980 kz 1000 built has APE cyl. and heads so most likely 1075 or larger, how can i get any info on this? I have engine serial # and scoped some internal numbers piston # 49640, 4287M00200 on the pistons. The crank has a date of july 2011 im assuming it was welded and that was when it was done. I know he used this forum a lot and i would like to put this motor to use in another kz. Any help would be appreceated. Thanks. Dave

Huban1 wrote:

Hey guys, Have some questions concering cavanaugh racing heads. Larry was a good friend of mine we grew up together and i have just aquired an engine he built, probable the last one he built for himself. I know nothing about it and have no information unfortunatly, All of his records were on his laptop and his brother could not access it. All i know is it is a 1980 or pre 1980 kz 1000 built has APE cyl. and heads so most likely 1075 or larger, how can i get any info on this? I have engine serial # and scoped some internal numbers piston # 49640, 4287M00200 on the pistons. The crank has a date of july 2011 im assuming it was welded and that was when it was done. I know he used this forum a lot and i would like to put this motor to use in another kz. Any help would be appreceated. Thanks. Dave
 

Is it possible you wrote down that piston number wrong? Wiseco is the only manufacturer that lazer etches the PN on top.

The closest number to that is  4287M08200 which corresponds to a 82mm 10.25:1 street piston which gives 1393cc and requires a big block (APE cylinder)

Sounds like it, but post some pictures if you can. As for the engine cases the serial number would confirm if it is the stronger MK2 cases preferred by drag racers. A picture would also confirm this.

The head is probably a GPZ1100 head with oversize (38.6mm/33mm) valves done by Larry. You would require a welded crank to run this engine so it is safe to assume it has a pro built crank and all the APE parts in it as well (cylinder studs, nuts, crank studs, crank plate) I would suspect it has APE #K435 cams in it which are the largest recommended for the street unless he went with a K410 cam but I think Larry would opt for more lift in a engine that big. If he went with the bigger cams then he is running shims under buckets.

If you want to run that engine on the street you would need a oil cooler and some RS40 Mikuni flat slides to get the most out of it. With those carbs that is a +140HP engine.

Have you tried emailing "Wiseco" - they came back to me in a couple of days with part numbers for rings and clips to suit some used pistons I picked up from a member here based on photo's (really helpful given I wasn't spending fortunes with them)

Your correct in the piston number i took picture of my scope screen and looking at it again that looks more like it. I was also wrong about the engine year it has no kick start shaft so its probable post 1980 then if i remember correct.I wish i had his records but they were all on his lap top that his daughter had im going to reach out to her to see if she still has it and maybe get into it, some geek probable can there is a world of information on it.My thing when we were young was drags i had a h1 500 built and ported by myself but Larry was the king with the kz's there were 4 of us that had LTD 1000 in the early 80's that's when he started developing his skills. Thanks for the info maybe APE has some info.

That was my next step but i believe i had the numbers wrong another guy replied and he was right on.

Huban1 wrote:

Hey guys, Have some questions concering cavanaugh racing heads. Larry was a good friend of mine we grew up together and i have just aquired an engine he built, probable the last one he built for himself. I know nothing about it and have no information unfortunatly, All of his records were on his laptop and his brother could not access it. All i know is it is a 1980 or pre 1980 kz 1000 built has APE cyl. and heads so most likely 1075 or larger, how can i get any info on this? I have engine serial # and scoped some internal numbers piston # 49640, 4287M00200 on the pistons. The crank has a date of july 2011 im assuming it was welded and that was when it was done. I know he used this forum a lot and i would like to put this motor to use in another kz. Any help would be appreceated. Thanks. Dave

So the engine has an APE (big block) cylinder, and an APE head?  Photos PLEASE.  

          some photos

couple photos     

right side motor no kick start but not sure what goes there   

That looks like a KZ/Z1 head that has APE cam end caps, Larry has probably ported/worked on it, possibly '73-78 vintage.

The intake runners have epoxy/weld? so he could grossly (a good thing) enlarge the ports to flow much more air required for a big CC engine. It is not a GPZ1100 head so the valves are probably 37/31mm unless it has been fitted with larger valve seats in which case the valves could be 42/33mm. The head has been converted to M8 exhaust studs but 4 are missing. I see large GPZ1100 rubber manifolds, probably port matched to the intakes.

The epoxy on the outside of the intake runners is usually done only on drag bike heads, so this could be a bigger valved ex drag head he got a hold of. You would have to take the head off to check what size valves it has but I don't recommend that just to find out, as head gaskets are $$$ these days.

If it was me I would take the cam cover off to check the cam lift and buckets, just to make sure all is OK. No doubt Larry would have already dialed the cams in perfectly for the street.

Its missing the kick start shaft and return spring. You will need to add a block off plate which you can make or buy from APE (Ebay) If it is a street piston there should be no issue with using a electric starter motor to start it. Its just a big CC street motor as I don't see a lockup clutch cover so that points to it being more for street use.

Its also missing the starter motor/cover, the transmission cover/front sprocket, and the clutch release cover. I also don't see a wire coming from under the points cover so it may be missing a ignition plate and or a advancer.

I can see there are wires coming from the generator cover so hopefully all that is intact.

The cases look to be the same vintage as the head, KZ/Z1 73-78, but its hard to tell from those pics.

Is there oil in the pan?

Good information i planned on taking off the cam covers to see what cams are in it. Thank you for the input years ago we talked about a street strip bike i'm thinking this is what he was working on.

Huban1 wrote:

Good information i planned on taking off the cam covers to see what cams are in it. Thank you for the input years ago we talked about a street strip bike i'm thinking this is what he was working on.



 

Spray some WD40 in the spark plug holes and let it sit for a day before turning the crank over.

As for the kick start hole here is the cover :



You can make this out of 3/16-1/4" 6061 bar stock, you don't have to countersink the holes or profile it to the gasket

I use to email with Larry a bit mostly about porting, miss those interactions - RIP