Last time I bought, about 35 years ago, it was $21.00 for 5 Gal. Crazy how prices have skyrocketed!

 

It is possible to tune your timing curve in your engine for a specific gas quality. Using just your ears and a stopwatch. If you are only a few octane points away from optimum.

W.O.T.
Over 3000 rpm, best done with a stopwatch. Make sure you begin 6-8* too low on total timing. Sneak up on optimum. Vacuum unplugged. Lower E.T. means more HP. Increase timing (2*/test) til E.T. levels off. Back off 2* for safety. 2nd gear or 3rd gear pull. 28-32* likely, vs 36* likely for ideal gas quality. Serious damage happens quickly at W.O.T. , & before you can hear It, so a stopwatch is your friend under W.O.T. If you hear any rattle / heavy knock here back off instantly. But with a stopwatch you should not.

Part throttle.
Light to medium throttle transitions. Listen carefully for any audible quick ping/rattle. Retard vacuum advance to remove it. 10* vacuum advance likely. OEM may be as high as 24* A quick (low rpm) mechanical curve is not your friend here either slow it down to ~3500. This is the most likely area you will need to tune. Side pipes obviously make this audible method very difficult.

These are just the basics. Have done this many times, on different cars. There is plenty of research and guidance on this method online and in written documentation if you look deep enough. I would suggest D. Vizard for one. Much easier in the long run that dealing with race gas or boosters every tank. The vacuum advance portion can almost always be improved on any car. Especially now since today's gas is completely different from 70s gas, that these cars were designed for. Even if the Octane is the same, the gas is not.

 

IFanyone were to go this route with ethanol you must be aware that you need to seriously increase the amount of fuel you move through the engine meaning much larger jets in a carb.
E85 has 82,000BTU's vs pure gasoline at 114,000 BTU's
29% fewer BTU's mean you need alot more of it or your mixture is going to be extremely lean and you risk hurting the engine. I have taken apart a few Holley's built for alcohol and iirc the jets were 15-20 numbers higher.

 

None of the L46's, L-79's or the LT-1's had 11:1 actual.....more like 10.5:1.....

AvGas is designed to run at altitude.....do not run it straight.....lower boiling point is a bad thing too.....

My opinion....stay away....it will do jack and **** for you....spend time optimizing the vacuum advance curve as opposed to the mechanical....

9 degrees is not enough.

Jebby

 

Thanks to all... as said early in the thread... the prior owner was an aviation mechanic at sky harbor airport... he had constant access to AVgas, he mixed it 30% with 91 octane for many years more so for fuel stability as the car sat for some long periods of time over the years (he owned it since 85)... he's done this for years and the car starts, idles, runs and pulls perfect even after sitting non daily driven since 2019 though he did take it out now and then, not a puff of smoke, old plugs I removed all looked excellent... fuel was about 6 months old when I purchased the car and I just put new gas in last week (10 months for old fuel now)

I was of the impression I would need to continue to raise the octane untill I called him and he told me it was only for fuel stability because of sitting and he used to run 93 octane just fine.

I can't get 93 octane so found 110 near me and I did a 10% mix with 91 to create 93... all is good, had the car out for a while this past weekend and runs out perfect... again no issues at all, fluctuates around 190 temp and fires right back up even after long drives so I feel im good now, frankly not sure it wouldn't be fine at 91 octane but I feel good about bringing that up a bit.

to the best of my knowledge which is clearly limited... I changed plugs, wires, rotar, cap, condenser, coil and points (I set to .019 initially) after that I set initial 9 degree timing to set dwell at 30 degrees... I then set total timing at 36 degrees at 2700 rpms, this landed my initial timing about 12/13 degrees, dwell still at 30 degrees, I turned the air/mixture screws at 3.5 out and left it there by the idle smoothness... I am still only at 13 for vacuum (highest at 3.5 turns out) and not sure if thats the added cam which the car has (dont have the specs) but again the cars runs out great with no issues, smoke, run on, starting problems, idle issues, rich fuel small etc.

OK having said all that I am now working under the hood clean up and detail, I am installing an electric headlight conversion kit (please refrain from the hassle) and I am going to install an edelbrock 2101 intake so I will be doing the whole timing/dwell thing again and will refer back to this thread to dial things in more if needed.
this is a weekend cruiser and nothing more for me, I plan on keeping this one and will make sure I pursue correct ignition above all after the new intake install.

 

You’ve been around long enough to know this but I’ll say it anyway.
After you install the new intake, check, double check and triple check the air cleaner to hood clearance, before you drop the hood the first time.
Also don’t forget to measure the distance between the top of the carburetor vent tubes to the bottom of the air cleaner lid.
There has been numerous discussions about the importance of this between Lars, Jebby and Leigh.
Have fun and keep us updated!

If you haven’t purchased your electric headlight conversion kit yet, forum member Richard Hayes, Richard454, sells the best quality kit on the market and his customer service can’t be beat.

 

thank you OCB, I was reading on this stuff this morning, I plan to use the 2101 edelbrock intake which I understand is minimal higher than stock, keeping stock carb and air cleaner as well... I believe I should be fine with hood clearance but gonna check when I get home from travel this evening with foil what I have now and again after intake install before shutting hood.
I am thinking of electric choke conversion... I know the eddy intake has provision for divorced coil, it is currently not setting to full choke all the way right now, I am reading about adjusting but thinking about just converting with electric kit, living in Arizona I wouldn't mind doing away with the cross over on the intake and I no longer have the heat riser... I will likely post new thread when im getting to that point.

As for the electric headlight kit I purchased the $200 kit from ebay from discussion with a few members here that used the same kit with success and all positive reviews on the kit.

Thank you again for the clearance heads up, I always appreciate you guys on here.

 

Understand you'll run a spreadbore Quadrajet carb.
Very similar height & configuration is (discontinued) Weiand P/N 8004 Action Plus
IIRC, some comparisons have shown the 8004 has a slight performance advantage over the 2101.

*Regardless which intake choice; Do run the correct thick gasket-insulator beneath Qjet. This especially so if you do Not block exhaust Crossover beneath plenum.

 

Block the crossover....just do it....1204 Fel Pro gasket....
Use 1/4" thick composite Q-Jet spacer gasket...the open one....
The Weiand 8004 is a good piece but Holley's casting has gone down the ******* in recent years....the other really good piece is the Chevrolet ZZ4 intake...which Edelbrock casts...

Jebby

 

Living in Arizona, I would definitely block the crossover.
I haven’t run a choke on any of my builds for at least five decades.
My daily drivers have chokes but not anything else.
I know it can get cold during the winter in some parts of Arizona but a choke isn’t all that necessary.

 

I ran the OEM mechanical coil choke on my LT-1 w/ OEM Holley for 30 years with the intake heat crossover blocked off.
It would start just fine, even if I wanted to go out in 30* weather.
The choke just kept it up on fast idle for a minute or so. No big deal.
With the cam I had in there, it liked that anyway.

Trying to remember how many times to pump the gas, based on "X" temperature, is just part of the charm of these old classics!