Describe what a high duration cam should feel like?

[Anonymous]

So now that things are together and running I am back to my original argument that I may have too much cam for my own good...

or I have other trouble and I am just blaming the cam...

but here is the thing, I have little experience with High duration performance cams.
I am running a 260/270 cam with 1.65 ratio rockers so this is a little heavy. but it has 110 degree lobe centers so it is not as bad as a 108 cam.

Here is the thing, I understand the lobey idle, but should it vibrate?
in other words my whole car shakes from the rough idle, chugga, chugga, chugga... shake, shake, shake.... it is worse cold and better hot, but still very shakey?

since I am still breaking things in I have not really opened her up yet, the most I have run on her is 3000 rpms... so I am not sure what the range from 3000-5500 feels like yet. but the range from 1000-3000 is nice, but short.... shifting all the time, I am hopeful, that I will have more room up top if I need it.

Just wondered if you guys could help me with some tips on the way things should feel.

I still idle at 1000 rpms, and it is very lumpy, I pushed that up a tad to about 1100 and it smoothes out, but makes first gear a bit tight... go under that at all and it dies or will not stay running.

I am also having trouble with the choke no my 2300... when closed the car will not start, open it slightly and it helps but the RPM range is too low because the choke tang on the throttle only really kicks in when it is completely closed? I am going to play with adjusting this some in the morning.

But it took me twenty minutes this morning to get it started and keep it running at the 1000 rpm range. I had to bump that up to get some stability?

 

[Falcon62]

Jimbo - I don't really consider a 260/270 duration to be "high" but maybe that's just me. 8) I have the 260 Comp cam in my 200 and it's not very lopey at all until I get the idle down under 800rpm or so, and even then it's not real noticeable. Your high ratio rockers won't have any effect on your duration, only lift.

Your cold start problems are uncharacterstic and sound like you have some work to do with your choke settings. Other than that, I don't have much else to offer at the moment.

 

[FastRonald]

8)
Did you run the engine at moderate r.p.m. as recommended at start up?

Do you have adjustable rockers?

Do you have the correct length push rods?

Did you set the timing to macth the new specs?

 

[CobraSix]

My Comp Cams 260H is pretty smooth. It shakes the car alot when the engine is cold, but after about 2 minutes, it is smooth and you don't even notice it. I think it's tuning on my part since my choke isn't working.

Slade

 

[Anonymous]

8)
Did you run the engine at moderate r.p.m. as recommended at start up?

Do you have adjustable rockers?

Do you have the correct length push rods?

Did you set the timing to macth the new specs?

YES... 30 minutes at 2000 rpms...
YES...
We used chevy rods that are a little shorter than stock, but we also milled and decked the block. they adjust down fine and seem to be no problems.
The timing is advanced, since I cannot get the rpm range down under 1000 rpms it is hard to get it on, it reads off the inidcator at that idle speed, something around 16 degrees. (There is no ping, and no room to retard it any it dies if you move it any real distance back, it only moves in the advance direction and that speeds things up more....)

This is a really heavy vibration and stumble and my vacume at idle is 16.5hg.


?

 

[CobraSix]

When I had the problem of getting my RPMS below 1000, it was because I never timed it right. Make sure you are setting the timing with teh vacuum off (if you are still using it).

IF not that, maybe a vacuum leak is causing the problem. Check you idle fuel mixture. Maybe it is too closed off and you are having to rely more on the transition circuit to fuel the car.

My tuning problem when I put the new engine it was because of not disconnecting vacuum advance and then having the timing too advanced and the carb too choked off.

Slade

 

[addo]

Vacuum is good for a lumpy cam. Sounds way overfuelled, too. Can you check the A/F ratio at your garage?

 

[Anonymous]

I can set the AF mixture with a vacume gauge... my only real method.

I will play with that later... right now I have to drain the coolant and fix a leak on the water pump... then I want to install the Mustang Steve clutch setup I got yesterday....

once that is done I will fire it up and continue working on the engine.

 

[Anonymous]

I agree with addo. Sounds like too much fuel
I dont know what duration you got at 50 deg but if its recommended range is 3000 up sounds as if its a fairly serious cam.
My 250 has a very mild cam and sounds very lumpy on occasions due I believe to too much fuel at idle.

 

[CobraSix]

Yes, 16.5 inHG is good vacuum for a higher duration cam. My 260 is around 16-18 inHG.

I think Addo has a good idea...something with the fuel.

Slade