Hey all, been a short time, right to the point. ALSO, I am sure there is a tread in here somewhere..However...
Fighting this 70's 460, want to say 73 or better for the heads are a D3VE-A2A, BLOCK DOVE..So I have done all this to it since the first issue.
New Accel coil, cap and rotor. Has pertronix pick up, Bosch wires (shouldn’t have, and autolite 26 plugs, right now at .040. Have a Holley 4150 or 60, 700 CFM Holley manual secondary’s, and I rebuilt it. The 460 also has an edelbrock performer intake. Now the PO told me he thought the guy he bought it from said it had a mild cam.(?).
OK, so before I put all this on, we were out driving, stopped and got some gas, took off, down the road, the ol truck starts shuddering, running like crap, wouldn’t even pull its own butt through an intersection. Got it home, started looking at timing, (10 deg at this time, first tried 8 deg.) and of course all of the above mentioned parts later...
The truck will run idle and accelerate AS LONG as you don’t STOMP on the gas. Once you do that she back fires, not all the time but most the time. Will run down the road ok, but sometimes when you get in it, she will back fire once again. Sounds like most of it from the carb, not out the back. I have adjusted and adjusted, and did I say adjusted, set, called friends; all seem to think the carb is ok.
SO, I go to do the ratchet to the crank turn and distributor test. I can get right between 3 to 4 deg back in forth before the distributor starts to turn. So, 3 deg one way, then the distributor rotor will turn, back the other way 3 deg and the distributor starts to turn. Is that to much paly in the timing chain and would that be a reason it is back firing when you try to STOMP on it.
That amount of slack shouldn't be causing all this trouble, but that amount of slack is probably "the limit" before you start getting issues like a wandering idle and maybe backfire trouble.
You have a big carb with mechanical secondaries. That could contribute to a full throttle bog and backfire. Mechanical secondaries are not good on heavy vehicles.
You talk about getting gas and then the truck didn't run good after that. Bad gas a possibility? Have you run through that gas or are you still running it?
You've made several changes here. Going back to before the suspect gas and other mods--how did it run then? Did you have backfiring? Wandering idle?
You timing chain may be in need of replacement, but I do not think it is the source of your issues. The gas is number one, the mechanical secondaries a strong second. Fuel filter, accel pump, cross firing wires, vacuum leaks all in there as well.
85e150six4mtod and ArdWrknTrk,
Thanks first off for your support!
Wandering idle. Nope. Runs as smooth as can be.
Secondaries, unhooked them and still when you stomp it, back fire. Not all the time, just some of the time.
Newer gas now.
When I purchased the truck, it ran, well.. ok. BUT no back fire, HOWEVER, the linkage was hooked up to only open the primaries and maybe the secondaries a little bit. But again unhooked the secondaries and again, back fire.
Fuel filter good. changed it.
Fuel pump, yea need to check for how much pressure.
I was thinking vacuum leaks to. have a friend stopping by this weekend to check that out. I am not sure of the best way to do that.
When running at idle I am pulling 12 in. vac. and bit lower in gear. Automatic.
I have been told the a vacuum secondary would be best. Funny cus the guy that restored the truck, did it to haul a trailer and show cars.?
I also checked compression, all at our around 140PSI.
Plugs, put in new, ran it pulled them and black like not oil wet, it was like soot. This was before adding the coil, and cap and rotor. Now they are a bit cleaner but not that gray look you are looking for.
I have been fighting this for so long now, I want to just take it to the curb, but dang I really love the truck. But again, when you buy something that that person knew very little about the truck, very hard to know what cam is in it, if any. Why it was set up like it was.
Guys, I will check these things, vacuum leak test for sure. Again, so much thanks!
will let you know!
The vacuum deal, hummm...low vacuum, bad timing, and or timing chain?
I read somewhere, low vacuum is a possible sign of timing chain. I hate to go there but man I want to get this thing runnning right. Dont need to STOOP it at every light, just want it to run like it should IF you need to stoop it.
Rebuilt the carb, but will do the idle screw test. I have another power valve. It had a 6.5 in it so thats what I put back in it. I know it is suppose to be calculated via Hg.
Yes it seems ot pull ok once you get going. If you say, pwer brake it a bit, then hammer on it, it seems ot pull thru ok as well.
Will check for vac leaks.
Also, was some cams set at like 4 deg advance, so mbe why the stright up timing set.?
Will let you guys know. Going to the garage
OK, I went thru the steps to determine vacuum leaks.
Eliminated one at a time and pluged at vacuum tree.
I saw a very small increase in vacuum once brake booster, but only from like 12 to 14.
NOW, I did the garage trail on intake leak. Sprayed some starting fluid around the intake, and low and behold I found a leak. Sparyed some and I could hear the engine bog down and where the leak is, the starting fluid would also like percalate and bubble up. ALso saw an increase in 1 to 2 HG during this time frame. Read about 15.5 Took some penitrating oil and sprayed it as well and did not see the results like the starting fluid.
SO I pulled the intake off last night. Now I have to fiqure out the belly pan and its relation to gaskets. This belly pan has gaskets between the heads and pan and again between the pan and intake. Some eliminate this pan, some dont pending aluminum or cast intake. Mine is a Edelbrock performer.Wondering if you use it, does it need gaskets on both sides.
maybe this should be another thread.?
Will advsie as I move forward. I willl also note the issues and the conclusion, if there is one.
Edelbrock SPECIFICALLY states to never use a valley pan gasket with their aluminum intakes.
It is no wonder you have intake leaks.
Are the pins pulled from the block front and rear?
Someone that installed the Performer and didn't bother to follow the instructions is likely to crack the manifold or never get it to seal.
Also, just throw the rubber 'great wall' gaskets away and run a high bead of '"ultra" black or gray silicone there.
Those rubber gaskets won't stay without their locating dowels.
Yea well a gasket on both sides of the pan.
So we will elminate the pan!
The curved gaskets were installed under the pan,, not on top. And if I understand, yes there are small holes in this area where the curved gaskets go, front and rear as well.
Are the pins pulled from the block front and rear?
Not sure I know what you mean by this. ?
I am going to check for cracks for sure! I have some magna flux spray stuff.
VAcuum at idle is, was, 12 to 14hg. so no advance at idle would just sit at the timing mark. Which now is at 10 deg.
It would idle good, and if you accellerate normally not an issue. When giving it gas, timing would advance, once vacuum line was hooked back up. Top out at about 30 deg, at about 3000RPM.
Will take some pics and attach soon.
I really really appreicate all the help! Will advise.
My truck is plumbed from the factory with manifold vacuum to the distributor through a restriction.
It was running much more advance at idle than that with the vacuum connected.
Your truck has (some kind of) cam, so naturally it may be different.
The stock manifold has holes and the block has dowel pins.
They fit together on the assembly line and can't shift that way.
The Performer is not drilled for these and will never set down with them still in the block.
From what you're saying the PO at least pulled the pins. (holes in both sides)
Even if they didn't bother to listen to what the manufacturer made quite clear in the instructions.