'86 W150 pinging/vaporlock symptoms

Hi all,

I've owned this truck for about 8 years, and around six years ago, I tore down the 318 to the long block to refresh it (estimated 140,*** on the motor at the time, half a million on the truck). While doing that job, I cleaned out the intake manifold, rebuilt the 2bbl, checked the heads for leakage, checked the cam lobes, cylinder walls, pulled the oil pan, checked the big end bearings, pulled out the non functioning compressor/condenser, ripped out the smog, welded up the stock exhaust manifolds, did the timing chain, bypassed the brain box in favor of 70's electronic ignition, (carb is 70's vintage Carter BBD), went to a 180 thermostat instead of 195, did plugs, wires, and all the rest.. I've gone from this being my DD to one of six cars in my fleet.. I've probably only put about 20,000 on it since.

So, here's the problem.. At highway cruising speeds, (65 MPH, 727 TF, 3.23 Sure Grip rear) this thing pings constantly.. It probably has for a while, but with an empty cat, and a glas-pack, the noise drowned it out until I heard it next to a jersey barrier. When towing, or under heavy accelerating load, it can shut off momentarily.. no popping, pinging, or drama, it just stops working until I let off of the gas, and feather the throttle back in.. The vacuum system is sealed as far as I can tell... I figured the ethanol was lowering the boiling point of the gas going to my mechanical pump, so I re-routed the line in front of the electric fan, and the radiator, changed the fuel pump (mechanical, Chinese electric versions are doo-doo squirt), and the problem persists. As for the pinging, I assumed a vacuum leak, or the vacuum and/or mechanical advances were too aggressive at around 3-4000 RPM under light to medium load.. Dizzy is set to around 10 BTDC, vacuum advance is disconnected (helped a little).

All that rambling brings me to this: I'm thinking of switching to a 4bbl setup anyway, likely an Edelbrock 650 carb/manifold combo because I've got it laying around.. I plan on leaving the cam stock, because I have six other cars that need work, and a cam isn't in this truck's budget. Assuming I stay stock, what mechanical/vacuum advance do you guys run/recommend? Should I go to the 4bbl, what ideal dizzy/carb/jet combo should I look at assuming a stock cam profile? I ran the 650 on my '68 Satellite for years in the same config with decent power/fuel ratios...

And the damned shutoff problem.. I still swear by vaporlock, it only happens in summer, usually in traffic, or while hauling/towing.. My hope was that the aluminum carb and manifold would help the whole thing run cooler.. I've also since learned about the delta-T effect, and might put the 195 T-stat back in..

Sorry for the length, I figured I'd waste everybody's time up front instead of forty replies asking me for running conditions, settings, etc..

Anyone make it to the end, and have any ideas?

Matt

you may want to try adjusting the timing some might run a bit better at about 14* instead of 10*. this could possibly be causing your truck to run hot. also what electric fans are you using?

a 500cfm carb would be best but a 318 will run with a 650cfm carb just not as efficient as a 500cfm carb.

an aluminum intake and carb will most likely not help the vaporlock issue. is the return line hooked up and the filter clean?

Thanks for the reply..

I've got it around ten initial because I was trying to keep the mechanical advance down. It's around 28-30 at the 3000 rpm range, which shouldn't be terrible.. The electric fan is a pusher through the radiator on a toggle switch.. It's the largest size sold at the parts store. My primary is still the factory stock unit, which does fine most of the time. I got the electric for sitting in NoVa traffic, and towing. What 500 CFM carb do you recommend? Yes, filter is clean, but there is no return.

Holy Hell! Carter BBDs are only 280 CFM? The poor motor's like a sprinter trying to breathe through a straw. Well maybe not a sprinter, I'll go with speedwalker, or a really determined guy with a limp.

you got to sometime play with timing until your truck is happy. each truck can sometimes be happier with different timing.

you might want to check your mechanical fan to make sure it is working properly. there should be no for a pusher fan if the stock fan and cooling system are working properly. what is the electric fans cfm rating? the return line is usually there to help prevent vapor lock. if it was disconnected it can't really do its job.

i think there is only 1 500cfm edelbrock carb with electric choke and vacuum secondaries. a 650 would work if you have it but it would be a bit much carb.

the 280cfm carb is more than fine for a stock engine as long as it is working properly. not sure if i really trust those BBD carbs.

Again, thanks for your time..

So, I've driven the truck again today, to make sure I remembered the symptoms correctly, and I do... However, I noticed that the "vaporlock" issue mostly happens under heavy throttle out of a stoplight, loaded down, going up a hill. What's noteworthy about this, is that it happens right after the 1-2 shift when the RPMs drop, and the motor doesn't have enough grunt to recover. Also, the pinging happens above 3000 RPM, or around 65 on the road. I'm running 32x11.5x15, with stock factory lift. Stock tire was the 31x10x15.. I did some research on the BBD, and found that it makes a peak CFM of 280-285 at 3000 RPM. Methinks, the motor is undercarbed at speeds beyond that. VA highway speed limits are 70, this happens constantly around here. The aerodynamic profile of a vending machine probably doesn't help my case any. As for the pusher fan, I agree that the stock system should be adequate especially in the minds of the engineers in 1967 when the setup was invented. D.C. suburb gridlock in 95+ degree heat with 5,000 lbs of empty truck however, probably never crossed their minds. Throw a load, or a trailer and a C-body on the back, it gets worse.

There never was a return line that I've found, only the vent from the float bowl to the charcoal cannister which would only have fuel in it if the needles stick. I've owned dozens of 318 2bbl cars and trucks, (60's and 70's vintage) and haven't seen a return line. Is it possible you're thinking of the TBI setup? This is my first 4x4 318, and as such, the heaviest vehicle I've owned. My guess is the sixties engineering was having fits with the weight of this thing and the eighties fuel and emissions standards. This is the only 318 I've ever had problems like this with.

I've got a Holley 390 somewhere that I'd intended for my wife's Valiant, but now that I'm building a junkyard EFI setup for it, do you think the 390 CFM is more appropriate for this wheezebox 318? do they make a manifold for it?

Sorry I write novels.

Matt

*Edit* Now looking at Thermoquads.. Small Primaries are attractive, Large secondaries can't overcarb due to natural vacuum limitations

i would play with the timing. i think a 2 barrel should be fine even for 70mph.

it don't matter where you live. as long as your cooling system is working properly and your rad is not clogged or low on fluid your truck should run just find temp wise. i have not had a mechanical fan on my truck for at least 2 year and never really need my electric fan as long as my truck is moving.

i forget exactly when dodge started installing return lines on all there engines but i think it might have been in the mid 70's. they installed them to combat vapor lock. your truck should have had one from the factory. since you have a small block engine they were less prone to vapor lock but there is the odd small block that might have more issues with it but then again the timing being not just right could also cause the engine to run hotter than it is suppose to and cause vapor lock.

if you got the holley 390 you could try running it. i found that the holley 390 i have just never had the same kick as the 670 cfm street avenger i had. ideally i wouldn't mind a 570cfm holley but i don't got the money to buy one so i am just sticking with what i have.

thermoquads can also be good but i have been told they can be a bit temperamental to tune.