Engine not running right

[protour_chevelle]

Engine is a 350 chev, a high RPM intake(not sure on who makes it), fairly lumpy cam, and other peices to match. Oh also has HEI.

Problem is, when the timing is set between 36-38 degrees it runs like total crap. Stops at 4k rpm and falls over. Before this motor easily went to 6500. Now when we set the timing to 42-46(Yikes). It pulls hard to 5600 then stops pulling. Now theres 2 possibilities for this problem. I'm more interested in the one though.



1. The timing marker on the engine is off(thus showing wrong timing)

2. Something is going wrong engine was causing us to need low to mid 40's of timing. (more interested in this case)

Any help would be great!

-Matt

[Zefhix]

Did you just install a distributor (or anything) or did you just start the car one day and have problems?

[protour_chevelle]

The distributor was pulled by the previous owner.

I think we have the problem solved though. We never pulled the vacume advance when setting the timing. I think Adam got the timing set to 18degrees initial and 36 total.

-Matt

[Zefhix]

The distributor was pulled by the previous owner.

I think we have the problem solved though. We never pulled the vacume advance when setting the timing. I think Adam got the timing set to 18degrees initial and 36 total.

-Matt

Pretty good cam if it likes 6500RPM and 36*! Glad it's fixed...

[protour_chevelle]

Pretty good cam if it likes 6500RPM and 36*! Glad it's fixed...

Hehehe, We had it running at 45 or so degrees with no pinging or knocking. I'll have to phone Adam and get an update.

-Matt

[Fuelie Fan]

Hehehe, We had it running at 45 or so degrees with no pinging or knocking. I'll have to phone Adam and get an update.

-Matt

If I'm understanding what you're saying, that's no suprise. Anyone with vacuum advance is getting 40+ degs advance at part throttle, that's it's whole purpose. You were still running much less at WOT, because you would have no vacuum in that scenario. I don't think you were in any danger.

[Zefhix]

What RPM did you set total at?

[protour_chevelle]

4k at first, then 3k.

Anyone with vacuum advance is getting 40+ degs advance at part throttle, that's it's whole purpose. You were still running much less at WOT at 4k rpm it was showing 45 degrees. Vacume advance has no affect at 4k rpm if I remember right? Vacume adavance is only for slow/part throttle driving.

-Matt

[streetk14]

Matt, vacuum advance is only active during high manifold vacuum conditions. This means light throttle cruising, and idle depending on what vacuum port you are using (manifold or ported). The vacuum advance should advance your timing at 4K rpms at a cruise, but not WOT. So, when you checked the timing with the vac advance hooked up, 46 degrees was probably only 20-25 peak at WOT. That will definitly make the engine run like crap, but won't harm anything.
Is the HEI in the car stock? Stock HEI's have stiff advance springs & a very slow advance curve. If it has not been re-curved then the peak timing isn't reached until at least 5000 rpm, so be careful. 36 degrees at 3000 rpms could be 45 or more at high rpm. It you install light advance springs, then the total should be in by 3000 rpm.
-Andy

[Zefhix]

Matt, vacuum advance is only active during high manifold vacuum conditions. This means light throttle cruising, and idle depending on what vacuum port you are using (manifold or ported). The vacuum advance should advance your timing at 4K rpms at a cruise, but not WOT. So, when you checked the timing with the vac advance hooked up, 46 degrees was probably only 20-25 peak at WOT. That will definitly make the engine run like crap, but won't harm anything.
Is the HEI in the car stock? Stock HEI's have stiff advance springs & a very slow advance curve. If it has not been re-curved then the peak timing isn't reached until at least 5000 rpm, so be careful. 36 degrees at 3000 rpms could be 45 or more at high rpm. It you install light advance springs, then the total should be in by 3000 rpm.
-Andy

exactly...