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Surging at 3/4ths Throttle


amdavidson

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As part of a greater engine bay/de-smogging effort, I just finished install of the a rebuilt Weber 38/38, a Cannon intake manifold, a Tii exhaust manifold, and a 002 distributor. I then adjusted my timing and tuned the idle mixture using the redline instructions (http://www.redlineweber.com/html/Tech/38_dgas_tunning.htm)

Took her for a short drive and the throttle response off idle is great, cursing at light throttle is great, but if you goose the throttle it surges up and takes a while before returning to idle.

Here's my jetting:

Idle Jet 50

Mains 135

Air Corrector 180

Emulsion tubes F-50

Anyone have any ideas? I'm a little stuck.

Lucy: 1975 Sahara

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I dont seem to have a ball on my flywheel anymore... I put the car and pushed it all the way through several compression cycles looking for it (I have a long flat driveway).

So I used the cam gear to find TDC, and noticed the flywheel had a crease at TDC, (presumably where the ball once was?)

I then used an engine analyzer to rev to 2500RPM and set the timing with a light and that crease.

I should probably also mention that I installed a new cap, rotor, condenser and points which I gapped to .016 inches.

Lucy: 1975 Sahara

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Don't you want to set the baseline timing to the ball at 1400?? That's what I do with my car, and it runs rock solid.. 008 distributor with points.

When I first got the car, I couldn't see the ball well at all. So I tightly taped a small wad of steel wool on the end of a flat head screw driver and, with the motor idling, gently put the driver in the timing hole until it brushed the edge of the fly wheel and buffed the ball nice and shiny. Gutsy move I know, but once i was in there, it really wasn't bad. I was able to apply some force to get a good scrub.

2002 newbie, and dead serious about it.
(O=o00o=O)
Smart Audio Products for your 2002

 

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I dont seem to have a ball on my flywheel anymore... I put the car and pushed it all the way through several compression cycles looking for it (I have a long flat driveway).

So I used the cam gear to find TDC, and noticed the flywheel had a crease at TDC, (presumably where the ball once was?)

I then used an engine analyzer to rev to 2500RPM and set the timing with a light and that crease.

I should probably also mention that I installed a new cap, rotor, condenser and points which I gapped to .016 inches.

So the car is now 25deg late on the timing. The groove (and it is the only one on the wheel) is TDC.

A radiator shop is a good place to take a leak.

 

I have no idea what I'm doing but I know I'm really good at it.

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The car is 25 degrees late because I set it at 2500? or because I should not be setting it at the groove?

I'm a little confused.

The groove that I was seeing seemed to be repeated several times around the circumference of the flywheel.

The car seems to idle well, and run well at part throttle, would that be the case if my timing was off my 25 degrees?

Lucy: 1975 Sahara

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He is speaking of the notch on the pulley.. its to help get to TDC. And maybe with a mechanical dizzy, you're supposed to use 2500 as if it were a Tii, but I haven't.. that's a grey area for me.

I'm of the "if it ain't broke.." cloth myself, but if there is any doubt in your mind, I recommend getting the motor set to TDC using the cam marking technique(<-- thats a link), once this is done twist the distributor so that the notch on the rim (under the cap) is centered on the tip of the rotor button (that will be cylinder #1), then set the revs to 1400 and time to the ball.

Take it out for a spin and if it still has the issue, or is better but has a flat spot before 5.5k, then twist the dizzy a touch in either direction and retest until it does what you want it to. If the original problem persists, let us know.

2002 newbie, and dead serious about it.
(O=o00o=O)
Smart Audio Products for your 2002

 

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So to get the distributor installed, I pulled the valve cover, found TDC with the mark on the cam sproket, and also checked that both rockers were floating, and installed the distributor with the rotor aligned to the notch. (The exact same as the cam gear method you linked to)

I also also looked down the sight hole in the bell housing and tried to find the BB this way and that's how I sighted this groove in the flywheel.

Is JimK saying that this groove is not where the BB was and that I need to look for something 25 degrees retarded from there?

Lucy: 1975 Sahara

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Just out of curiousity, what side of the car should you be standing on when you look for the BB? Is there any advantage to making your own marks if you have the head off and use a dial indicator to locate TDC? I am about to disassemble a motor and will face the same issue.

Are you running something other than a stock cam to justify the 38/38 carb? Too much carb for the cam and motor can easily cause this problem.

Ahlem

'76 2002

'90 M3

'90 535i 5 speed

'89 325is '91 318is

'87 325is

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I also also looked down the sight hole in the bell housing and tried to find the BB this way and that's how I sighted this groove in the flywheel.

Is JimK saying that this groove is not where the BB was and that I need to look for something 25 degrees retarded from there?

The BB is not where the groove is. It is clockwise from the groove on the flywheel about 2 3/8 inches from the groove. When I said the engine is retarded, then it needs to be advanced. Turn the engine counter clockwise to find the BB or with a timing light, turn the distr housing counter clockwise very slowly while at the specified rpm to sight the bb.

A radiator shop is a good place to take a leak.

 

I have no idea what I'm doing but I know I'm really good at it.

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