buick 350 jet suggestions

My engine is getting tired but still runs decent enough for now. I don't have complete build specs but it does have bigger cam, poston intake, full length headers, dual exhaust with h pipe, and 750 dp demon carb. I used an eBay HEI distributor set at ten degrees btdc. I have played with timing and jets and still have pinging at part throttle at highway cruise. I have adjusted the idle circuit to the highest vacuum I can get which if I remember correctly was about 14. I also have vacuum advance routed to full manifold vacuum.

I'm thinking the primary jets are still too small. I think I have 68 in there now and before I order more I wanted to get opinions to see if I'm on the right path. Planning on doing power tour this year and want to get the cruising sorted out.

Any suggestions will be appreciated.

Thanks.

 

What’s your total timing, all in at what RPM?

 

does the carb have tunable air bleeds? try 72 main jets...they are stock in a 750. there could be other stuff going on. float level could be too low. secondaries could be opened too far making it lean...but these things would cause other issues too like stumbles and hesitations.

 

Before tuning the air and fuel ratio, the distributor must be blueprinted.
You must know the range of timing in your distributor, especially if you have noticed detonation.
Block off the vacuum.
Stick a timing tape on the damper.
Install the weakest springs on the weights.
Use a good timing light with rpm on the dial, but NOT a dial back type.
Know exactly how much advance the distributor has in it.
Determine where the timing can start and end plus initial idle timing for about 34 total.
The distributor may require modification before you can tune anything.

 

I have a 1972 350 distributor # 1112109. It has short advance slots and is among the best factory distributors for performance. A 1972 # 1112110 is similar but for 455 engines.
These are easily interchangable by swaping the gear on the bottom. Use 13 teeth for the 455 and 14 for a 350. This can simplify the timing-tuning problems.

 

Thanks for the help. I currently only have a basic timing light so it sounds as though I need to purchase a better light along with a jet set and distributor tuning kit. I was also thinking I read the cam card that came with the engine said it was already advanced but I will have to dig that out again and see what it says for sure.

 

you may have an adjustable vacuum advance. Maybe adjust it to where you're only adding 10 degrees of advance and see if that helps. Or dial it down even less. This is quick and easy.

 

Oreilly and autozone can get holley jets next day. Maybe try some 72s or 74s . Summit sells a big kit for around $60-$70 but is probably not necessary. but like the other guys are saying...probably a timing issue more than anything.

 

The 30-degree mark at 1.76" on the damper makes timing advance simple to check. No dial-back needed.
A budget timing light is fine. Some expensive dial-back timing lights are less accurate in spite of their price.
I like the Innova with rpm dial best.

 

I like the 1.76 inch tape method and I will try that once it warms up. The car is in storage til spring. I do think it is a timing problem. I'm not sure if the vacuum advance is adjustable but if it is that may help dial it in. The pinging tends to lessen if I give more throttle (I'm guessing less vacuum) without the secondarys opening.