Quick description of the beast needing help:
1981 Fleetwood Tioga
1979 ChevyVan G30 chassis
1976 BBC 454 with quadra crap carb - unknown miles, has been cammed fairly aggressively, ,low vac at idle i.e. 15in hg at best during idle. not sure if it has overlap or if a valve needs adjustment because the vac gauge fluctuates just ever so slightly at a regular pace, but goes steady once rpm are above 1000rpm or so.
I have a small (too small) electric fuel pump because i could not get the mech fuel pump to work again after removing it to inspect it a couple months ago.
it claims 32gpH free flow, which is fairly accurate, but it is woefully insufficient for any acceleration over 1/8th throttle.
I will have it dyno'd if i have time before november, but i want to get the timing correct once i find my timing light (we just moved after a storm totalled our trailer house) and everything is packed away still. I know that if i punch it for example in our fully loaded RV around 9,500-10,000lbs to cross a busy street it will lift the entire front end about 5"-7" until the fuel pump cant keep up (about 3 seconds)
It has a HEI dizzy from a 400ci SBC that was just gone over and rebuilt by a reputable shop in california just under 4000 miles ago, not sure if the advance curve is ideal for a BBC but it is all i have to work with until i get back to work after my foot heals.
I have heard so many varied opinions for initial and total timing, I think i hear the most that BBC like 36-40 total and 12-16 initial.
I do not have the vac advance connected yet because i literally have no idea where my timing is, but it sounds like its pinging (ticking) under the slightest highway load so it makes me think the timing is too far forward, but i did retard the dizzy a few degrees by ear, but the starter still kicks back some when the engine is at full operating temps.... i always thought that the engine shouldnt kick back unless its over heating i.e. 210F+ but i have a hard time getting it to start when cold (70F ambient) if i retard the timing much more than it is now.
I want it correct so i can get the most MPG out of this RV, i got 6.8-7.5MPG after deducting for several hours of idling and in town driving at probably 4MPG. I would like to be seeing 8MPG towing the suburban but i didnt even get 8 when not towing it, and i was going 55MPH for most of the 160 mile trip and a few sections about 7 miles long i was ringing out at 3000rpm going 70-75ish due to traffic density in a larger city.
My wife swears that i was going 55MPH for atleast 100 miles of the trip according to her GPS in the other truck and she was holding the same speed as me right behind me...
i did the math RPM x Tire Size / 336 / mph =gear ratio (Final) and i was steady at 2400RPM hardly ever higher and never any lower and that comes out close to a 3.73 ratio, but the sticker under the hood claims 4.10's, i will be jacking up the axle later today to rotate the tire and see how many rotations it really has.
I see people with larger Class C's and tow a jeep/car behind them and they can get 9-11 mpg with no overdrive, and big burly V8's, and I had a almost identical motorhome as this one, loaded almost the same but instead of a flat towed suburban it was a 25ft bumper camper and it weighed over 7000 lbs because it was extremely overloaded and i still managed about 12mpg with that but the only difference was that RV had a 400 SBC.
I will also this weekend probably retard the timing once it is hot until the start doesnt kick back anymore. and see what timing that is once i find my light next week.
What i need to know mostly is what kind of idle speed should i be expecting using the idle screw? and what is usually safe for a BBC on 87 pump gas for total and initial advance?
https://www.facebook.com/MudiGGer25/posts/10208588594125107
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