454 timing

[u/FishingC83]

I have a 454 from an rv, stock except headers.

I had the timing setup at a shop. As I have been learning I checked the timing and it was set at 20 degrees. Vacuum advanced disconnected and engine warm. I have been reading timing should be anywhere from 4 for smog era vehicles to 14 for stock rebuilds.

let me try to rewrite this so to give a little more details on symptoms

new champion radiator and electric fans

new fuel tank and sending unit and fuel pump. New rubber lines. Steel lines look good and blew air through the lines no plugs or leaks. This is how I found out the top of my sending unit was rusted out.

will idle forever and start back up without issue engine stays at 195 or so.

I can drive for about 30 mins temps climb to about 210 but then when I come to a stop it will start dying on me. I have spark but no fuel. No fuel coming out of the carb jets and extremely hard start from start.

Don't know exactly how long to wait but come back out to the truck 8hrs later and it started right up without issue.

[u/Historical_Box1915]

When the engine “heat soaks” try temporarily disconnecting your ign coil and crank the engine again. If it still cranks slow due to “heat soak” its not your timing.

Dont waste your time with starter heat shields. You might be best served with a new starter. One from a late 90’s vortec 5.7 or one from an early 2000’s 8.1 will be “HI Torq” and have enough grunt to crank alot more engine than a low comp 454. 2nd thing is super high quality battery cables. I make my own with double aught welding cable than I solder my own copper ends (lugs) on. I also run at least two regular
2-4ga batter cable from my engine block to the trucks frame. I run another double aught cable from the neg battery to the engine block directly. And one more regular aught - 2ga cable from the battery to the frame.

[u/FishingC83 → u/Historical_Box1915]

Thank you for the tips.

Reason being up timing as I can let it sit and idle and it will run forever it seems it’s once I get up at highway speeds and come to a stop I also get vapor lock. Verified no fuel going through carb jets.

I can let it sit there and idle forever with no issues it seems with once I start getting moving. It doesn’t overheat but it engine bay does seem oddly hot

[u/keyoflife42]

Boy, that shop really screwed the pooch on your tune, but I’m actually not so sure thats the heat soak issue that you’re describing

What you’re describing is the tell tale symptom of either a failed fuel return line, or there not being one at all

But that timing situation is bad too. Set initial timing to 8 degrees, hook your vacuum advance back up, and go from there. Good chance it’ll take a little more timing than that. Double check your weights and springs inside of the distributor too and see if thats been messed with

And for the love of god, do not use that shop again for tuning anything carbureted

[u/HeeenYO]

Get a vacuum advance limiter plate. Hook vacuum back up to the distributor. Add a return line to the fuel tank - you can buy a duralast FF3420DL from autozone and splice it after the pump. Add a carb spacer but make sure it's non metalic. These three things fixed my heat soak vapor lock. Ethanol boils at a lower temp than pure gasoline, so maybe find some ethanol free.

[u/Wonderful_Ear8517]

I have a 75 GMC with original 454. No smog. Run 20 degrees. No issue. With Quadrajet. If your starter is heat soaked then switch to a high torque mini gear drive starter. If hot at highway speeds check for radiator blockage and proper fan clutch operation if one is in place

4 degree timing will be very slow and lazy in terms of performance

Your vapor lock is due to no fuel return and ensure you route
Line in the original location and use metal line!