Alex Avila

Hey again. I try to park my car in the garage and with some acceleration the car dies. It runs good on leveled ground. Although when I accelerate kind of high it feels like it wants to turn off when the idle comes down. Engine rebuilt 500 miles ago carburetor was rebuilt, new hei distributor. All filters are new. Could I possibly be loosing fuel pressure? Fuel pump is also new. Although it is a cheap mechanical one from autozone.

Vintage Chief

It runs good on level ground at 55 mph?
When you accelerate from 55 mph or any mph, does it hesitate?
Do the secondaries open up and you feel the kick-down when you hit WOT?

Vintage Chief

I read in another thread you don't have a tachometer and you have an HEI distributor?
You should have a tachometer - you don't need an in-dash tachometer, you need some type of tachometer though. You also need a timing light to establish your timing and a vacuum gauge to determine your A/F mixture.
You might simply be experiencing improper A/F mixture and/or inadequate timing. You need to get these numbers dialed in.
What type choke you have? Electric or mechanical?

Alex Avila

No hesitation at high speeds. Runs good besides at take off sometimes. I agree with the A/F mixture I have it dialed in to where it runs perfect at idle. But I am running into problems.. I'm new to the old school so I'm not sure how to do all that. Timing is at 12 anything more and anything less it starts to backfire

Alex Avila

It has a 2bbl Rochester mechanical choke. Not sure about secondaries

coppercutlass

Check the float level. If the floar is off it will hesitate on hills as tye fuel sloshes past the vent and it will do the same of heavy acceleration as the fuel sloshed back

Alex Avila

You know what. I remember my buddy that rebuilt it said he adjusted it to fit a Pontiac. That it should be the same thing and I kind of went off that. What would be the spec for the float on the olds?

Vintage Chief

That's fine. You do understand the original distributor had mechanical points which opened & closed relative to the distributor rotation (based upon the lobes contained w/in the distributor) - the lobes open & close the points. The points are set to a gap - like you set your spark plugs to a gap. The initial gap of the distributor points is enough to start the engine - then you would have opened a small plate (window) to adjust the dwell - which in effect is establishing the correct point gap at a specific RPM. It's this initial RPM and the point gap which established a good working basis for the distributor to send it's electrical pulse to the engine (high voltage) coil which then feeds your spark plugs in the correct firing order. Therefore, your initial RPM and dwell would be critical to establishing your tune-up. With your HEI distributor you don't use the mechanical points - instead the HEI IGN module senses the distributor lobes and sends this information to the high voltage coil. It still remains essential you establish the correct RPM during the tune-up phase, and you establish the correct dwell in order to establish an optimal timing. It is my understanding the HEI generally prefers much more advance than the normal advance using standard distributor points. Others will chime in, but I believe you should be looking more towards establishing an advance which is closer to a timing of ~16*. You don't want to lower the timing on an HEI, you'd prefer to add more advance. I use the distributor points as I use the OEM standard distributor and the optimum advance on my engine is 12* BTDC. Yours should be higher.

The final critical part regarding the tune-up is establishing the correct A/F mixture for the vehicles engine - which is orchestrated via the carburetor. In order to set the optimum vacuum on your vehicle (which should be in the range of 15" Hg to 17.5" Hg) you use a vacuum gauge. Use a T-connector in your vacuum line off the manifold vacuum, hook up a vacuum gauge at the T-connector, and turn your A/F mixture screws to the highest vacuum you can obtain on the engine. That will provide you w/ the optimal vacuum on your engine, and the best A/F mixture for your carburetor which ultimately feeds the engine it's fuel during the entire throttle/carburetor profile curve of the engine. It's this "curve" you're trying to establish which operates properly at idle and at WOT. This is a general write-up. There are many YouTube videos explaining the process of tune-up for an engine - in particular the 350 cid engine.

If you have more questions, don't hesitate to ask and review some videos. You do need to get the basic parameters of a good engine tune-up completely dialed in to achieve optimum performance which might be where you're struggling. Good Luck!

Alex Avila

Sheesh!!! That's some awsome information. I will retry the timng at 16 btdc. I dont have a tach or gauges to do the rest but ima have to get some real soon and look up some videos..my hei also has vaccum advance adjustment I messed with that a little bit but I felt no difference nor did I hear any pinging while I was fooling with it.

Alex Avila

Well I'll be damned!!!.... my timing is at 16 btdc and I sat the A/F all the way back down and started to half turn them out and nk more hesitation.... don't mean to sound ignorant doing it without the proper tools but i wanted to adjust it so i can make it to the store haahha. Looks like harbor freight has some cheap ones. What yall think?


[Edited]

And holy hell do I have burn outs now !!!

A/F mix screws were way too far out in the beginning. What tachometer do you gentlemen recommend?

Vintage Chief

You actually set the A/F mixture as most would do w/o a vacuum gauge. If you have a good ear for what you're attempting - you can achieve a very good A/F mixture listening to the pitch of the engine.
Regarding a tachometer I can't make any recommendations - I own a 40 year old Sears timing light & an old Sun Tachometer. I do have newer tachometer hanging about which I purchased from Harbor Freight some years ago because my Sun Tachometer went South on me for a spell until I got it back up to working condition. I purchased a digital readout inexpensive tachometer from HF. Glad you're coming around.

coppercutlass

If bumping uo your timing helped. Try to change the timing curve with a curve kit. You can throw lightweight springs to bring your mechanical advance much sooner which is always good for performance. Within reason

Alex Avila

Thanks I believe once i use the gauge it will be on point. I'm new to the old school and I love this group. I found a decent tachometer for 20 bucks at Walmart waiting for it to get here in the mail. Thanks alot

Alex Avila

Will this help even if my mechanical advance is able to be adjusted? It has a screw inside the mechanical advance port that is supposed to be adjusted using an Allen wrench. I tried fooling with it but I have the least idea on how to.

coppercutlass

I'm pretty sure the screw you speak of is for your contacts. The mechanical advance you have to remove the cap to change the weights and springs.

olds 307 and 403

A dial back timing light is best to figure out what curve is in the distributor. You want 36 to 40 total depending on your compression ratio and cam. I find the Olds V8 like a lot of part throttle timing but the two factors above along with fuel octane limit how much your motor will tolerate. The factory HEI setting is usually 20 degrees for base timing.

Alex Avila

Its built to stock specs. I have a timing light with the dial back..

olds 307 and 403

Check the advance curve. That will tell you how much initial timing to add. A total of 38 to 40 without vacuum advance is acceptable on a low compression Olds V8.