Monster 2786 Type 4 build

It's been almost a year since I have updated this thread. I still have my 77 Puma GTE and still have the monster type 4 engine mounted to a Ranch pro comp suby geared transaxle. To update, I installed the engine with the new LE200 HAM super heads last fall and the engine runs like a scalded dog, alas I still have a small amount of compression leak around the surface where the cylinder top seals to the head. The engine runs amazing, the leak cannot be heard or felt even though in my mind there is power being lost. The reason I even know about the leak is the gas and oil mix that gets spit out on the floor during cold starts. I even believe the tiny leak seals when the engine comes up to operating temps., but I can't prove that. Regardless, I am not going to settle for this issue on an engine that has the amount of time and money invested as this engine has, it is around $15k at this point. I spent the winter setting the project aside and gathering more information about the issue. The block mounting surfaces and heads are all flat and square, therefore we have ruled this out as the problem. The engine is set up at this point for a little over 10:0 to 1compression which makes holding the seal even harder. What I have been told and come to believe is the issue of having much larger pistons and cylinders than designed for. The engine has 104mm pistons and cylinders that are being held in place to create an airtight seal with 4 studs. This is much greater distance between each stud than the engine was designed for, and we are trying to hold in more compression than originally designed. Some people that have fought the same issue on these big type 4 engines ad 2 additional studs to each cylinder having to modify the block and heads to do so. Big job big dollars, but it works. Another way this is solved is by having a small groove cut into the top of each cylinder and a pc. of piano wire laid into the groove and attached to the cylinder in some many of which I know not at this point. When finished the hardened wire protrudes above the mating surface of the cylinder top by .015". A .040" copper head gasket is used in conjunction to allow the wire to bite into the copper when the heads are torqued into place creating to perfect dam seal in the process. George at European Motorworks is one of the many people that I spoke with that suggested this approach, in fact he is the one I sent my cylinders, to have the piano wire modification done. He did the work within 2 weeks and charged me a very fair price. I have done business with George in the past and find him to be a great resource for all things air cooled, especially big type 4 engines. I received the cylinders back this afternoon and will be reassembling the engine this week. I will do a leak down test once the heads are torqued in place and report back once the beast is running. Thanks for sticking with me and reading this long post. I love this forum and the people on it. Carlise or bust,, Sorry, I am bringing the Magnum not the Puma. Is there anyone that wants to bring the Puma for me?

One of the pics show what spits out during cold starts now and should be eliminated once the engine is back together. Stay tuned motorheads, more to come soon!

Jimmy, beautiful engine. I can see why you want to get it right. I suspect the piano wire mod should work with the soft copper gaskets. I saw some evidence of head lift on a high hp 930 engine I built once, but not enough to drip. Thanks for the update and good luck!

A true beast! Good for you.

If I wasn't bringing the Coupe I'd take you up on the offer to drive the Puma.  Man I love that car!  See you in a few weeks.

I thought or sure you were going to split the case, drill the heads, and 6-stud it, but I'm super-curious how this works out for you.

If Carlisle wasn't in May, I'd be all over your offer to drive it out.

I'd never heard the piano wire trick, but then again I haven't worked on any type4 Big Boy motors!

Looking forward to seeing you Jimmy.

If the piano wire doesn't work, I am going to send the sort block out to California to have the 6 stud modification done, Stan. The guy that would do it suggested trying this first because of the small amount the compression that is leaking. I am on this pony to the end and I am set on getting it right. Hind sight I would have gone a little smaller on the P&C size. I wasn't aware of the possibility of this issue. Live and learn. Thanks for all the constructive comments.

Follow up to the piano wire O ring modification to seal the cylinder to head better. I annealed the .040" thick copper head gasket rings so the hard piano wire can sink into them. I torqued the heads down and did a 100psi leak down test and am happy to report that there is zero leakage at the heads. In fact there was only 2-3% leakage shown at all and that was the little bit that gets by the rings. This is the lowest leak down I have personally seen on an air cooled engine build. I got the rest of the engine together and back in the car this past weekend. The engine runs amazing. I decided to drop the compression ratio back from 10.5 to1 down to 9.5 to1 and I think it actually runs better. I was getting detonation at the higher compression and had to back the timing off to eliminate it. I now have the timing at 32 degree at 3500 rpms which has the distributor's advance at full. It is a real screamer. I think I feel safer opening the engine up at the lower compression also. I think it was a good decision and will make the engine more attractive to a future owner. I am going to drive the little rocket for a few days to get it tuned in and then adjust the valves again. I am going to offer the Puma for sale shortly, so if anyone is interested PM me or call and we can discuss. Jim Vickers 812-972-4516. Thanks for taking this journey with me. This one has been a challenge, and think, it all started with a $1500.00 to good to pass up Type 4 engine. That $1500.00 sure has cost me! Vroom , vroom!

@Jimmy V. - Absolutely brilliant! Congrats on solving the problem, I know you're relieved after all this time getting it right.

THat car looks awesome! you could always sell that engine alone

Well, you slayed it, Jimmy!  It was a lot of work and head scratching (and probably a beer or two) but you did it.

Congratulations!

In hindsight I would not have gone so large with the engine because of the issues that going so large of diameter with the Pistons and cylinders brings because of having only 4 head studs to hold down the large diameter. Many builders add a 5th stud to give additional clamping force. Live and learn. All good now.

Further follow up on the Monster type 4 engine in my Puma. I have been driving the Puma all week and have approx. 400 miles on it. It is running perfectly and is scary fast and fun. The Pro Suby rancho transaxle has near perfect gearing and is good match to the HP and TQ. this engine puts out. This engine has a lot of torque. I am going to try to get the car on a chassis dyno to see what this engine has in it. I have one small oil leak coming from a valve cover gasket which I plan on replacing tomorrow. It feels so good to get this engine running the way it should. I am also very happy that I dropped the compression ratio, it was the right decision. This car will be on the market soon, if anyone is interested PM me.

@Jimmy V.- I'm sure it's a monster!  How high does it rev with power?

It is pulling strong at 6500rpm and that is all I have taken it to because of the rev limiting rotor in the distributor. If you remember I had a throttle cable stick open and over rev the un-rev limited engine to who knows how high and snap the cam off at the cam gear. So I now have a rev. limit rotor button. The cam is a Web cam 86B/86C grind which is fairly aggressive. In the light Puma and the big displacement it still works great. I have plenty of torque from 1500 and on.

@Jimmy V. posted:

It is pulling strong at 6500rpm and that is all I have taken it to because of the rev limiting rotor in the distributor. If you remember I had a throttle cable stick open and over rev the un-rev limited engine to who knows how high and snap the cam off at the cam gear. So I now have a rev. limit rotor button. The cam is a Web cam 86B/86C grind which is fairly aggressive. In the light Puma and the big displacement it still works great. I have plenty of torque from 1500 and on.

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