Trouble With Hills

After installing the header and HEI on my jeep, I noticed that I have issues with long hill climbs (of a mile or so). I hear the ignition start pinging and then it starts to backfire through the carb. Is my timing too advanced? I have the vacuum advance tied in above the throttle plate. Should it be below the throttle plate?

 

Ignition timing is 5° BTC. Sounds like it is too far advanced.

 

Yes. Your timing is too far advanced. Yes. The vacuum advance connects above the throttle plate. Ignition timing should be based on the Octane Rating of your fuel. Five degrees is for 67-72 Octane.

 

I have to time it by ear because my engine originally had the timing marks on the flywheel. I have since replaced the flywheel with a later one so I could use a toyota starter. I guess I could figure out where 5° BTDC is on the crank pulley.

 

Print one like this.
Locate TDC through the #1 plug hole.
Done.

https://1.bp.blogspot.com/_JU6RC7jJ...M/T2lI3aBa0bg/w1200-h630-p-k-no-nu/DEGREE.jpg

 

I wonder if the mechanical advance spring are too weak and I need stiffer ones?

 

With a timing mark and a timing light and tach, you could check what rpm they come in at.

 

we don't have hills here...

 

Lots of corn. Miles and miles and miles of corn.

 

states and states of corn. miles are childs play.

 

I checked my timing and I was at 5° BTDC and then I pulled the vacuum advance off. The mechanical weights went to about 20° advance. When I put the vacuum advance on, it went really far. I plugged that off and went for a drive and no more ignition troubles. I may run with that disconnected.

 

Okay, I am still having issues with too much advance, ignition knocking and popping back through the carb when climbing hills. I bought an HEI spring/bushing kit to change the advance and it came with this handy chart showing all the combinations. My question now is, what does a stock 4cyl distributor advance curve look like? I’m thinking it is something like E or F.

 

Yep , I think you should rebuild your distributor to spec. Then you've got a good base to work from . Get a proper TDC , Zero degree mark on your Harmonic balancer, too

 

It’s a new HEI that I modified to fit a 4cyl. There is no rebuilding to spec. I need to know what the original advance curve looks like so I can match it to one of these HEI curves in the kit.

 

Sorry....Totally misunderstood. I should not have replied , with me not having a clue to what the original curve was.
Hope someone finds it for you.

 

An F-head peaks out between 2000 and 3000 rpm. That would be "F" I'd guess.

But I'm having trouble even imagining an F-head detonating with such a low compression ration.

 

I'm thinking it is too advanced, and with the long stroke, its causing the issues.

 

I think you should try driving DOWN the hills and it will run better.

Seriously though, I looked the FSM don't say what the total timing was but it usually maxes out against a physical stop after a certain RPM. You might try taking your old distributor and seeing how many degrees you can turn the centrifugal advance by hand. Add that to the factory 5 degress BTDC static timing for an indication of the original total timing amount.

 

Or..... Just do it old school , Trial & error ......By ear. That is , if nobody can reply with the OEM Curve chart from the TSM?

 

The obvious solution is a DYNO run.



Don't forget your slip.