Cams

[Ivan]

What are the numbers cast into the older series of cams?

[trbig]

2H7



Tod

[Ivan]

Cool thanks.

[XSokieSPECIAL]

As long as we're talking cams, would there be any benefit in putting the older high lift longer duration cams in my SG?

Greg

[Steptoe]

if they fit

the intake, it'll give you more oxygen on the intake stroke, ergo more bang on the ignition stroke = more pull/torque.

[trbig]

I used to run the early cams on my later head which is essentially the same as yours. (My YICS ports are blocked off) It made the bike run well on the top end, but was a dog/no torque on the bottom end. Also, for some reason, with this setup, I could get almost no vacuum readings at the carb boot nipples for a carb synch?? Before you start to think of other reasons this might be happening, I didn't change a thing... simply swapped the older cams for the newer 3H5 cams and now I have lots of vacuum reading at the carb boots??

Anyway, I was running both intake and exhaust. I have heard of running the early intake with the late exhaust cam but haven't personally tried it.


Tod

[Ivan]

Seems this subject is terribly elusive.

From what I can tell, the late model cams jacked up the overlap and lobe seperation angle on the exhaust to compensate for emissions. The intake duration was lengthened to compensate and some other strange brew stuff was put in the profile mix.

It seems that I read somewhere the exalted engine guru suggested running the early model exhaust to get the LSA more in tune with conventional thinking.

I can't say for sure because everyone that comments on cams with any authority seems to have a different take on the proper way to do it.

Yet another thread said the 79 specials had a hotter grind than the standards even though there were no part number differences. I think it was the same thread that suggested the E cams were the hottest grind of all of them.

I don't know. I am just shooting in the dark, and thought I would procure a set of early cams to mess around with. Try one then the other. Then mess with advance and such. Just another large iron in a small fire.

If nothing else, maybe my settlement will allow for a wiseco kit and some mega cycle cams.

[Steptoe]

cams

the reason a lot of people put "lump cams" ,the intake is always larger than the exhaust because its the same as the valves. Intake larger than exhaust. Exhaust is being expelled under pressure from another piston firing where as intake is like breathing in,you can blow air out a lot harder than you breath in,,, longer intake opening---more air in.

[XSokieSPECIAL]

Seems this subject is terribly elusive.

From what I can tell, the late model cams jacked up the overlap and lobe seperation angle on the exhaust to compensate for emissions. The intake duration was lengthened to compensate and some other strange brew stuff was put in the profile mix.

It seems that I read somewhere the exalted engine guru suggested running the early model exhaust to get the LSA more in tune with conventional thinking.

I can't say for sure because everyone that comments on cams with any authority seems to have a different take on the proper way to do it.

Yet another thread said the 79 specials had a hotter grind than the standards even though there were no part number differences. I think it was the same thread that suggested the E cams were the hottest grind of all of them.

I don't know. I am just shooting in the dark, and thought I would procure a set of early cams to mess around with. Try one then the other. Then mess with advance and such. Just another large iron in a small fire.

If nothing else, maybe my settlement will allow for a wiseco kit and some mega cycle cams.

Huh?

[trbig]

It seems that I read somewhere the exalted engine guru suggested running the early model exhaust to get the LSA more in tune with conventional thinking.

I've never heard of anyone in the know suggesting using the early model exhaust cam. But as you stated, the '78/79 cams are the same part number and no different whether standard or special. I'm thinking I left my early cams at John and Kat's. Might check with them and work out a deal to ship them if you want them... if I didn't give them to them. I can't remember.. lol.


Tod

[81xsproject]

I run the early intake on my 81. It is a great combo. Just barely not as hot on the top as both late, but the bottom power seems to be retained. It is a great combo I would highly recommend.

[tw1980]

Ivan I can't find your post on turning the cam sprockets around.I'm curious how it worked.Did someone pull the thread?

Terry

[Ivan]

Ivan I can't find your post on turning the cam sprockets around.I'm curious how it worked.Did someone pull the thread?

Terry

Its here.

It definitely moved the max torque point up a ways. I think I need to rejet, since it seems to be lean now. I haven't had much saddle time and my muffler broke last weekend, not to mention its getting cold. The throttle seems more snappy than before as well.

[tw1980]

Thanks Ivan,it's getting cold here as well.It's going to snow tonight.I'm going to try your mod when I check the valves,probably this weekend.I don't know when I'll be able to post results but I'll try to get it done ASAP weather permitting.

Terry

[Ivan]

That's cool Terry.

If you get the chance, and have the tools, see what kind of advance it gives. I am guessing about 5 degrees, from the math, but I could be wrong.

It would be nice to have access to a dyno that doesn't cost $30 a run.