Been re-assembling my 75 Vert L48 4-speed.
I picked it up half through a partial restoration when the mechanic passed away.

Car is stock. Original carb. All new wiring harnesses.

I now have the engine bay re-wired, new starter, new HEI stabbed on TDC, new alum rad, dual electric fans, and got the engine running.

However…I can only get it to start with the gas pedal at the floor. Also, when it starts it will stay running at about 700rpm max as long as I keep my foot to the floor. As soon as I let off, the engine stumbles and dies.

I suspect there is some issue with the choke, but not sure. There are some decent videos showing some basics to check and all appears okay. High RPM is locking, vacuum cylinder near the choke is working, choke plate appears to be working correctly, I hear the accelerator pump pushing fuel…

Any suggestions?

I have a two-minute video of it starting and running that I can email someone.

Thank you for any suggestions.

 

Get in touch with Lars on this forum!

 

Timing first.

Email (don't PM) @lars for his timing papers.

You can post videos to YouTube, it's easy to create an account.

 

You are suspecting a timing issue?

I have read his papers. Good stuff. I will re-read them.

As far as YT, while I hate to open accounts with those places, I guess I will have to face reality one day and do it!

 

Until you confirm otherwise, it's likely a timing issue. What is your timing set to now? And do you have a vac advance, and is it hooked up to manifold vacuum?

Hopefully you got your papers directly from Lars. He updates them, and copies found on the internet are often wrong.

If not a video, can you post some photos from all sides with the air cleaner assembly removed?

 

I agree with Bikespace, this definitely seems like an ignition timing issue first.

 

Always keep in mind and remember: Timing affects carb. Carb does not affect timing. No matter what you do to the carb it won't fix a bad timing problem. Always set up and get the timing right before you ever touch the carb. 90% of all carb problems are timing problems....

Lars

 

I re-read Lars’ paper. It had been a while, and I have low intelligence to start. Excellent read.

I will get my timing light on it and start on getting that timing set before I touch anything else.

Also, I left my vacuum connected to my advance. Wrong. I will pull it off.

The label says 10 degrees BTDC. Car is completely stock. Should I set it at 10, per the label?

Since I cannot get it to idle, should I keep advancing the idle a little twist at a time until I get it running good enough to set the timing?

Not sure where to get going on an engine that will not stay running unless WOT is applied.

Thank you all for your patience and assistance. I am certainly no expert with these old SBC’s!

 

[QUOTE=Bikespace

If not a video, can you post some photos from all sides with the air cleaner assembly removed? [/QUOTE]

Please note this is a work-in-progress where I have no guide other than here. If you see something I should change, please let me know.

I needed the port for the Thermo-Vacuum switch for the electric fan setup, so I moved that TVS to a threaded water neck.

I plugged the Vacuum Advance into a port on the drivers side front of the carb - I think it is manifold vacuum.

 

I am not the carb guy BUT
I don't see the rear upper choke tube connected.

 

That little metal tube runs from the front of the choke to a plate in the intake. The tube from the intake to the rear of the carb is missing. Thus, I am sucking in-filtered air into the choke/carb. I am trying to source the back half of the tube. However, the choke tube is connected to the manifold.

 

You guys are geniuses!
Kinda crude, not exact, but I pulled a wire tight from the center of the distributor cap to the center of cylinder 1. I then estimated 10 degrees BTDC on setting the distributor just to get it to start and stay running.
(My original setting was at about TDC or maybe 1 BTDC.)

I pulled and plugged the Vacuum Advance.

I hooked my timing light and tried to start a cold engine.

Bam! It immediately roared to life and sounds very good with the Corvette Central true dual exhaust and Magnaflows (no cats).

It is idling about 850, per my light.

Even cold, it is running pretty smooth. I watched the choke slowly open as the engine warmed up.

I need to tweak it a little when I let it run until fully at temp. When I put my timing light on it at idle to see where my timing is at, my mark appears to jumping around in the vicinity of 8-10.

Should the timing mark be consistent at one mark or should it jump around when cold at idle?

I did not let it run to fully warm up, because I need to confirm my water pump is working and deal with a small oil seepage on a valve cover.

But we have huge progress going here.

After three years, she is alive!!

Pic when I got her home a month ago. In a thousand pieces and sitting for three years…

 

No - set it to 36 total (with vacuum advance hose disconnected) as outlined in my papers, which will likely get your initial in the low teen range. My papers give you all the specs you need to hit.
I don't show that I have ever sent you my papers - did you get the papers from me, or have you downloaded fake papers off the internet..? If you have the fake papers without a Copyright in the header, request the correct papers directly from me via e-mail.
Good job relocating the vacuum advance hose. You had it on the ported EGR port on the carb. Your carb has manifold vacuum on the forward driver's side nipple, so that's a correct location for vacuum advance.

Lars

 

Lars,
Thank you for your reply.
A few months ago, I found a link via the Corvette Forum for “How to Set Your Timing for Peak Performance.”

However, may I have your current email, so I can request the correct papers to really get this right?

Thank you.

Respectfully,

Darryl

 

Lars,

Below is the link to one of your papers via a web search. I don’t know if this is a fake one.

https://www.corvetteforum.com/forums...set-timing.pdf

My email is DWABoat@yahoo.com

Please send me the information I need.

Thank you.

 

Not a fake one, but it's an outdated 3 year old version. Don't use any of my papers you find posted on the Internet - I don't post any papers.
Lars
V8FastCars@msn.com

??? There is no relationship whatsoever between the distributor installation, rotor orientation, and the center of cylinder #1. None. You want the rotor pointing to the #1 spark plug wire tower in the distributor cap when the harmonic balancer timing lines are lined up around 12 degrees BTDC. The #1 cylinder location is completely irrelevant and has nothing to do with distributor positioning.

HEI distributor correctly installed "square" in the block with plug wire towers in correct locations. Cap removed shows rotor correctly pointing to the #1 plug wire tower location in the cap. It may be pointing in the general direction of the #1 cylinder, which only happens on HEI - not on the points distributors, but the physical location of the #1 cylinder in the block is completely irrelevant and coincidental. On HEI, the rotor should point to the forward, driver's side plug wire tower in the cap. On points distributors, the rotor should point to the forward passenger side tower in the cap:



Lars

 

Good to know. Steep learning curve here.
🧐

 

Also, be aware that your carb is not the correct carb for your car. Your carb is a commercially rebuilt 1978-79-ish 1/2-ton truck carb. Not likely that it will run as it should on your '75 Vette...
Lars

 

Thank you for letting me know.
Glad I didn’t pay top-dollar for a numbers-matching all original!!
As long as it gets me to and from the local cars-n-coffee and Sunday rides with the wife, I will run it and enjoy the car for what it is.

In your opinion, should I begin planning for a Holley or an EFI swap? Will this carb eventually ****-the-bed?

 

Carbs don't "****-the-bed".......they either get murdered by idiots who think they know more than Rochester did or they get gummed up from sitting too long......these carbs have a terrible reputation due to dumb *** 70's and 80's "mechanics" who did not have the ability to go through one properly......just like anything, there will always be a faction of pretentious ******** who live in a fairly tale world and blame everyone but themselves.......but going through a Q-Jet is not as difficult as people make it out to be......
The truck Q-Jet is fine......most trucks had 350's in them and you have a 350......the jetting may be a little off......but get the timing and curve right and drive it......find a correct unit later......
Whatever you do....DO NOT use an adapter to bolt a Square Bore carb like a Holley or Edelbrock to the Q-Jet manifold.....terrible idea. And you may know this already but never buy a commercial "re-man" Q-Jet from anybody......

Jebby