Anyone grinding cams for Desoto Hemis?

[Truckedup]

Vintage motorcycle racing engines? Be nice not to have to choose from grinds that are 60 years
old...

megacycle makes that triumph twin cam, the 510-x2, which is relatively new. 296@020, with 0.375 lift. the rest of their stuff is repro or their own old stuff, like you say

i just looked at the MAP website, and they have what appears to be a new one with 326@ 020 and 0.450 lift. god forbid. their hot stuff seems mostly out of stock, maybe permanently these days.

Kevin , if we could get some guys to commit I really believe we should see what Mike Jones can come up with... Do you have airflow specs for the modified head?. Rob Hall never gave me any...

[Truckedup]

opps

[dorset]

no, i didn't get any at the time. i know he keeps the records, obviously, because he mentioned flow figures at the time that pleased him. maybe i can get him to answer the telephone.

the 510-X2 cam from jim duer was a surprise to me, because he recommended 103/105, and it did so much better at 106/109 in the triumph. i'm wondering where i might find anything else in that motor before i go to a different grind.

[Truckedup]

The Sifton 390 cams I use are from the 60's and are a rework of the 50's Jomo 15. The 390 has a bit less duration but faster lift and was intended as a flat track cam.
The fact that both our bikes are very close in speed with similar areodynamics but different cams an engine tuning might be saying something .....
Sifton used to test his grinds on dyno engines...Does Megacycle test their stuff?
When degreeing the cams I use .050 lift for duration because it's a better example of the cam profile, plus it's what car guys use for pushrod engines.

[dorset]

i don't know whether megacycle dynos anything or not as part of R&D, but i doubt it. they're mostly selling pretty well-trodden paths.

i think our similar speeds mean that we're probably near the end of horsepower on these old beaters and are looking mostly for accumulating small gains in aerodynamics if we want to go faster. the fastest NA naked triumph 650 on gasoline is alp sungertekin's 139.226, and i'm guessing we would need some 6 or 7 more horsepower more to go from 135 or so up to that. i think a big part of his accomplishment is his very intelligent custom frame and riding position. that fastest he's ever gone with a production frame is 127.092.

i've always used 0.020 for comparing cams because it's the traditional british motorcycle unit. next time i have a the motor on a stand i'll map it out at 0.050 and see what it looks like.

[Truckedup]

Tim Joyce claimed to be making 75 plus hp @8000 RPM at the rear wheel on his 750 Triumph when he dominated his circuit racing class...That would be about 66 hp from a 650...Mine origanally made 55 hp on the dyno, then some changes, picked up more speed, so maybe 58 hp..So more power is possible.I believe Joyce told me Hall did his engine head, same guy that did ours. But Joyce avoided giving me details. John Healy said the big power 750's had drastic changes to the intake ports. Lots of welding and moved up quite a bit along with moving valve springs...Joyce used 38 and then 40mm carbs....
So...My engine with the nitrided stock crank can't handle 8 grand....but yours can.....Gotta find out if Hall really did do the head on Joyce's bike...His main sponser is D&D cycles...I think that MAP cycles also played a role...

[dorset]

hard to see what tim joyce was doing to th ehead unless you made a pest of yourself in the pits. but 75 at the rear wheel is pretty rarified territory.



stock there's only a slight downdraft to the intake ports, and none at all on the exhaust. wasn't there someone who welded tubes in there once to make em point down? the modifications to the valve train doing that are beyond my abilities for sure.

8000 is doable on a billet crank, at least a few times, but i keep thinking of the main bearings precessing like the north pole doing it.

[Truckedup]

A Google seaach brought up a 2007 Brit Bike thread on Tim Joyce, AKA, Phantom 309.He just ran a newly built 750 Triumph engine in his racer on the dyno. 73 Rwhp @ 8000 rpm. He mentioned it had a beat up Leo Goeff head and MAP parts inside. Several photos of the bike show the carbs mounted in the normal position , so no extreme port modifications at that point in time...Tim was a bit concerned with running the engine repeatedly to 8000 for a 20 minute race. Probably better to search on Brit Bike and spare these car guys from more stories of 1930's design air cooled turds...

[dorset]

lol

off-topic is my spirit animal

[Kingbee]

hard to see what tim joyce was doing to th ehead unless you made a pest of yourself in the pits. but 75 at the rear wheel is pretty rarified territory.



stock there's only a slight downdraft to the intake ports, and none at all on the exhaust. wasn't there someone who welded tubes in there once to make em point down? the modifications to the valve train doing that are beyond my abilities for sure.

8000 is doable on a billet crank, at least a few times, but i keep thinking of the main bearings precessing like the north pole doing it.

Nice 2 wheeled Desoto

[Large_911]

Isky and Hot Hemi Heads both have camshafts for the early hemi. BTW - I have a 331 out of a ‘53 Desoto.

[Large_911]

We can grind almost anything.
I'm making a set of custom tool steel cams for a 1912 Packard, right now.
Compared to that, your Desoto is modern.

I heard some real good things about you guys on a truck pulling forum. I just might be contacting you over the next couple weeks