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1970 Opel Gt - Purchased July 1972 - Chartreuse - restored - 3000 miles as of 02-16, 2021 -
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Discussion Starter · #1 ·
Trying to figure out what the blip is on the hand held tach and you can hear it as well. Keep in mind aside from the little fluctuation on the hand held tach the car is running perfectly with no other symptoms or reactions.
Intake manifold recently sanded flat, Carburetor placed on a piece of glass and appears to have a flat base, carb dismantled cleaned and reassembled after 11 years and 1800 miles, just in case, new intake studs installed, new fat gasket with Hi Tach gasket dressing installed, new brake booster so no problem with the check valve as the new booster has the check valve built in as part of the unit and I sprayed a half can of carb cleaner all around the carb and the intake manifold with no signs of a reduction/change in power - car is running great but that little blip bugs me, you know..... I have also installed a new valve cover gasket - all components are in place, that is, the snorkel cover, the two rubber hoses from the engine to the carb one being the lower connection of that small hose to below the carb. I guess I know that it has to be a vacuum leak but just hoping it might be something else as I really thought after all of the work listed above that the car would in fact purr like a kitten - like I said earlier the GT is running really well with no noticeable issues at any speed with the exception of that little blip at idle, which unfortunately existed prior to the all of the work mentioned above. Thanks, Carl

 

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Just an idea, put a voltmeter across the battery and see if there is a voltage blip there at the same time. Easier to do with an analog meter if you have one.
 

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What are your vacuum readings on the (carb) ported connection at idle? It should always be zero. From the conversation we had in the past I think that you have the primary throttle plate adjusted properly. There is a small screw on the secondary throttle plate if adjusted too far open either the primary or secondary could be sipping gas from the bottom progression holes any unregulated gas could also cause the irregularity. The engine sounds really nice Carl.

One last thought if everything I just mentioned checks out. If the distributor has lost a spring or there are any problems with either of the springs for the mechanical advance it could also cause a drift at idle, usually less sporadic. Do the idle rpms creep up too high or vary worse at stop lights?
 

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In your test the choke is still 90% closed, what does it do when engine is warm and choke is fully open?
 

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1970 Opel Gt - Purchased July 1972 - Chartreuse - restored - 3000 miles as of 02-16, 2021 -
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706 Posts
Discussion Starter · #6 ·
What are your vacuum readings on the (carb) ported connection at idle? It should always be zero. From the conversation we had in the past I think that you have the primary throttle plate adjusted properly. There is a small screw on the secondary throttle plate if adjusted too far open either the primary or secondary could be sipping gas from the bottom progression holes any unregulated gas could also cause the irregularity. The engine sounds really nice Carl.

One last thought if everything I just mentioned checks out. If the distributor has lost a spring or there are any problems with either of the springs for the mechanical advance it could also cause a drift at idle, usually less sporadic. Do the idle rpms creep up too high or vary worse at stop lights?
So I am embarrassed to say but I still have, on my to do list, to get off my butt and order a vacuum gauge so that I can check that and KNOW where I stand - on my list to do this week. The distributor is a recent purchase from OGTS at a very reasonable price I might add - and while the springs in my old one were just laying in the bottom of the distributor the new one has heavy springs by comparison. I have not connected the vacuum advance/retard lines for a couple of reasons- was told that on a 2.0 that the vacuum tubes from the distributor to the carb are not necessary - so I have capped them on both ends. I do however still have them...
My Current engine - camshaft of .430" lift with a SOLID
grind camshaft, installed with 1.72/1.50 Chevy valves,
and 2.0 (.030" OS) pistons.

So I know you mentioned a combo cam, not being an engine guy, I have to confess that I don't know what that means or how that relates to the need for the vacuum lines. So a little more information would be appreciated.

The blips are hardly noticeable on the tach on the car but very noticeable with the hand held device - so sitting at a stop light idling at say on average 10 RPMs sounds pretty good but it is noticeable.
I had also just reinstalled the carb and the bolts were not very tight so I am hoping that has something to do with it ....will see tomorrow when I fire it up.

Thanks as always for your advice and knowledge....Carl
 
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