engine and drivetrain Weber 38 dgas carburetor.

[rover1]

I need some advice got a '76 02 schrich cam 284, jd pistons, tii distributor. msd 6A ignition, Carter fuel pump. I cant get engine to idle even sometimes it idles high 1200 rpm and sometimes it's low 500 rpm. Main jet 135, Air corrector 185, Emulsion tube f50, Aux venteri 4 idle jets 50. I check it for a air leak while engine running I spray carburetor cleaner at veriuos points on the carburetor but has no affect. Also has a hesitation on excelleration. I think that carburetor has a problem with the progression circuit.

[wagnerf15]

Shoot me an email at wagnerf15@sbcglobal.net and i'll attach an old web archive file i have about tuning the 38 DGAS. I haven't had the chance to work on mine yet, so i can't give it my endorsement, but it seems to make sense. I can't attach anything to your email on the forum, or i'd do it here.

Jim

[TobyB]

umm, check your timing when this happens.

This sounds a lot like a failure of the springs in the mechanical

advance in the base of the dizzy.

If your timing jumps a lot, then it's time to rebuild the distributor.

This is why I think the 'ball in a hole' method of timing the cars is

dorky... it makes troubleshooting things a pita.

The other thing to look at is the power valve diaphragm in the carb...

t

[bigjim5551212]

check your fuel pressure and your vacuum hoses. nothing more than 3 psi for fuel. we have the Malpassi fuel pressure regulator available

[Guest Anonymous]

I need some advice got a '76 02 schrich cam 284, jd pistons, tii distributor. msd 6A ignition, Carter fuel pump. I cant get engine to idle even sometimes it idles high 1200 rpm and sometimes it's low 500 rpm. Main jet 135, Air corrector 185, Emulsion tube f50, Aux venteri 4 idle jets 50. I check it for a air leak while engine running I spray carburetor cleaner at veriuos points on the carburetor but has no affect. Also has a hesitation on excelleration. I think that carburetor has a problem with the progression circuit.

If your carb is not properly adjusted I doubt you will be able to get a steady timing reading - even with a properly adjusted idle.

If the fuel pressure is too high (you mentioned the electric fuel pump), it may force fuel past the needle and seat and all the float adjustments will be meaningless.

The make of the pistons is meaningless to me. If you have high compression and a hotter than stock camshaft, there is a very good chance that your carb is jetted far too lean (especially with main jets of 135) I would expect that 145's might be more appropriate as a starting point and maybe lower number air correction jets. Likewise, the only idle jets I have been able to satisfactorily use have been 60's.

IF your carburettor is jetted too lean, I'll bet you can't get the engine to idle off the idle circuit and you have the throttle plate open too much to compensate. The "idle" speed swings you mention are a strong indicator of this OR a serious vacuum leak. ALso, you want to make sure you are not trying to run the engine with the fast idle system engaged so that the linkage is adjusted as though the choke is on. You did not mention whether the carb has a choke, that the choke is fully on or off when you adjust the carb.

UNless you have a bad/leaking accelerator pump diaphragm and/or severely worn and leaky throttle shafts, I do not think you have a problem with the carb other than poorly selected jets and/or maladjusted floats.

Of course I said this before to another FAQ'er with a similar complaint. He challenged my thinking claiming his engine was professionally tuned and therefore the problem had to be with the carb. I took a trip to look at his car. I discovered that the jetting was different than he described and none of his spark plugs were gapped properly and one of them had no gap at all!

Good luck!