[Rusted535]

Has anyone installed the 612 stroker kit from Hitchcock's?
If so, how is it going?
I'm wondering about longevity. I ride almost everyday, 49-50 mile round trips.

Or is it more of a weekend hot rod type modification??

[ace.cafe]

I've done a few 612 builds on Iron Barrel Bullets. None on CGT, though.

My opinion is that it is more suited to sidecar use, or for mostly two-up riding in hilly locations. In other words, it's a puller.

Not much of a hot rod, since it revs slower and peaks rpm lower, and is generally aimed at lower rpm riding.

The parts are good quality though, and if you have a real bad vibration problem, it might help it out some. However, it will probably have more vibes than a good smooth CGT because of that long stroke of the 612.

Personal preference sort of thing.

Should be reliable, but not necessarily longer lifetime. Maybe a bit longer with the better bearing set.

[RedCGT]

Would the results be any different with the custom head and cams?

[ace.cafe]

Would the results be any different with the custom head and cams?

Not really, unless it also had a bigger throttle body or bigger carburetor. The 34mm stock throttle body would be a limiting factor. It also limits the 535, but not as severely. As a result, you reach approximately the same hp out of either one with a full out build, but different performance characteristics from each. The 535 just revs faster and higher, and makes its hp a bit higher in the rpm curve, while the stroker works at a bit lower rpm. I think the best Hitchcock 612 dyno figure shows about 1 hp higher than we have seen from the best 500/535 jobs over here, but it is almost within a margin of dyno error/variation. 

Anyway, the comments about the behavior from the previous post are still accurate, IMO. It comes down to how you like your power delivery.
The long stroke generally also gives a bit more vibration, due to the faster piston speeds, all else being equal. If you have a bad vibrating 535, you might see some help with that from the nice quality Hitchcock crank. But if you have a smooth 535, you will likely notice more vibration from the 612.

My personal opinion is that you can do better with a 535, and if Hitchcocks makes a standard 90mm  stroke version of that crank, like they do for the iron barrel engine, that would be a good foundation for the build. They make a very good crank, although a bit steep in price.

The experience from several of my iron barrel customers that built the 612 is similar, and at least 3 of them went so far as to take out the 612 crank and go back to the std 90mm crank from Hitchcocks, and were happier. Some of the others kept the 612 and liked it.

None of our all-out CGT 535 builds have had any problems with the stock bottom ends, although our sampling number is admittedly quite small for CGT.
I can't speak for GHG ,but I don't remember any reports of his UCE builds blowing out any stock bottom ends either.

[AzCal Retred]

Ace - using the 103mm crank with a standard 6.5 forged piston should yield a light piston and "less" vibration than the 87mm version, yes?
The longer stroke calculated by my SWAG methodology should yield a CR of about 8:1, which seems pretty streetable/pump gas friendly.
This should make a nice tractor motor good for running between 2000 - 3500 RPM with about 28-30 HP? Sounds like a good touring set-up to me if it works that way.

[ace.cafe]

Ace - using the 103mm crank with a standard 6.5 forged piston should yield a light piston and "less" vibration than the 87mm version, yes?
The longer stroke calculated by my SWAG methodology should yield a CR of about 8:1, which seems pretty streetable/pump gas friendly.
This should make a nice tractor motor good for running between 2000 - 3500 RPM with about 28-30 HP? Sounds like a good touring set-up to me if it works that way.

Are you referring to an iron barrel engine? I am not aware of any low compression piston for the UCE.

The stock piston on a UCE is around 8:1, and a long stroke crank would make it higher. I think that the combustion chamber may take that without detonation, but I haven't actually tried it.
The acceleration of the mass in the long stroke would not yield any lower vibration, and probably still more than any 535. But I sort of do see the point you are making there.

If you want a lower rpm puller, or maybe even tourer, or want to use a sidecar, I think those are the realm of the 612.

[AzCal Retred]

Thanks for the info - sorry to clog up your UCE thread! I was searching on Iron Barrel thread & it jumped to here, I didn't see it was a different thread.  - ACR -

[KD5ITM]

So if your normal cruising RPM on the roads and Highway are no more than 4000 RPM, would the 612 kit be suitable for better acceleration and performance?

[ace.cafe]

So if your normal cruising RPM on the roads and Highway are no more than 4000 RPM, would the 612 kit be suitable for better acceleration and performance?

Probably not for acceleration. The longer stroke engine is slower to rev.
But it would give better pulling performance.

[jez]

It's so good to have a proper time  served engineer here to give advice. I asked Paul Henshaw about this a while ago and he mirrored your comments. "probably wouldn't be any faster".

[Bullet Whisperer]

It's so good to have a proper time  served engineer here to give advice. I asked Paul Henshaw about this a while ago and he mirrored your comments. "probably wouldn't be any faster".

That doesn't sound like something I would have said about a full 612 kit, but ...
 A 612 kit is bound to give more power, just through being a larger engine, but I don't know what comes with the kit altogether. The crappy standard cams and valve timings are what seem to restrict the UCE engines in the main, certainly for revs and the full 612 kit for iron barrel machines comes with cams and all sorts of other stuff to go with it and work in harmony with it, as I would assume such a kit for the UCE / GT machines would.
 However, if a long stroke crank alone were fitted and nothing else were changed, then, I think the results would be rather disappointing and probably troublesome in regards to fueling, pinking and performance.
 I made a couple of 535 GT's capable of around 100 mph, with very quick acceleration, by fitting carbs, performance cams [timed to my specs] and shortening the alloy barrels. This yellow one could rev past 6500 rpm and covered the ground very quickly ...

https://youtu.be/IRr8P0TnbBA

 B.W.

[jez]

I think you were referring to it's on the road performance, ie it wouldn't have been any faster accelerating at normal road speeds

[Bullet Whisperer]

I think you were referring to it's on the road performance, ie it wouldn't have been any faster accelerating at normal road speeds

Here is the one and only 612 engine I have built, perhaps the rolling chassis was not ideal, but with a couple of vital 'tweaks' of my own, the engine ran like this ...

 https://youtu.be/Fm-Nmpz18fI