Technical rebuilt Ford 390 catches on fire when i try to start it

hi guys, i just swapped my 352 out for a rebuilt 390. the 390 has an RV cam and high compression pistons, i think the compression ratio is about 10-1 but it's no higher than 11-1. anyways, when i try to start the engine it starts with some effort then the carb catches on fire, if i retard the timing it wont start. i also backed the idle mixture screws out a bit from the setting for the stock 352. but it still catches on fire, right now its regular 87 octane fuel, do i need to run plus or premium? and is that even why it wont want to start? i think the cam is set right, before i put on the chain cover, the markes matched up, but whos to say the rebuilder diddent mess up with his little paint marks. thanks guys

 

Do you have good fuel pressure? Is the fuel pump new?

 

Check your cam timing and maybe get a good stock cam.

 

the fuel pump only has 3k on it so its pretty much new, but i primed the carb and it still did the same thing. and it wants to run, it will actually run for a few seconds then backfire through the carb and die. i'm gonna play with the ignition timing a little first before i tear into it at all

 

I had a fuel pump go bad on my 428, with a very few miles, but a couple years old. See if your accelerator pump is giving a good shot. Mine had less than 300 miles. I blame it on the new gas we have.

 

ok, the accelerator pump is giving a good shot so thats not it, but is it possible that the timing is so retarded that it's catching on fire, the more i advance it, the better it wants to run

 

Move the distributor around as someone tries to start it. If you did everything right when assembling the engine it should start right up when you find the magic spot. If it won't start then you need to retrace your steps.

 

things that go wrong dont usually piss me off, but this did, haha 100% my fault. i found the problem. there was a little washer thing on the gasket below the carb spacer & that was making it sit funny & giving it a huge vacuum leak that surprises me it even ran for a few seconds. now that is fixed, but the problem now is that i burnt out my starter or solinoid trying to start it before i found that. i think its the starter cause it clicks when i try but wont start. oh well just more $$ haha

 

Re charge your battery !!!

 

Maybe the battery is dead from all the starting attempts. It could need a boost or put the battery charger on it.

87 octane way too low. You need high test. The rule is the octane should look like the compression ratio. 87 octane is good for 8.7:1 compression. 92 octane good for 9.2:1. Naturally this is not a hard and fast rule, just a guide. Your engine may run ok on 92 octane hi test or you might need some octane boost but 87 octane regular is too low.

 

charge the battery and retighten all the electrical connections as the heat from cranking will loosen them and you need 700-800 amps to get that starter to engage .

 

I was gonna say that we had the same issue on my dad's o/t project, turned out to be miss-matched intake manifold/head ports causing a huge vacuum leak. but it looks like you found the problem, good job.

 

i went to town to get a replacement starter and solonoid because it was only $10, and dont worry, haha my battery is charged, haha. i made sure to keep a charge on it the whole time i was trying to start the engine

 

and by the way, the started had 211k on it, the truck was mainly used for long trips,(not alot of starter use) so it was probably about time anyway.

 

yep, bad starter. it runs now & i fixed the vacuum leak, it runns better but still wont idle, i think theres still a vacuum leak somewhere, i hope its not an intake manifold, wish me luck

 

You may want to pull the carb and check where the washer was, I've seen where a carb was tightened down on a return spring and it left a groove in the base of the carb. If it's an aluminum intake it could have indented it as well, or damaged thee gasket if that wasn't replaced.

 

I'd first check to see if the carb base/spacer is still flat and sealing. Spray a little ether on it while running.

 

Sounds like you still have a vac leak, hemirambler is right, ck the previous leak first to determine that its not still leaking. FE intakes are more difficult to check for intake leaks while running because the intake is part of the head and the mating surface is under the valve cover. Running with valve covers off to ck for leaks with starting fluid, ether or whatever, becomes a messy deal. If you put a vacuum gauge on the dipstick tube and its pulling a vacuum, thats an indication of a lower intake leak, which means the intake probably needs to come off and a new gasket carefully installed.

 

ok i got it running good now, it idles great, but the vacuum is only 14-15 psi at 500 rpm, is that ok on this engine?

 

Vacuum looks like retarded timing to me unless the cam is much more radical than most RV cams. Is the gauge reading smooth or does it hunt (mixture issue).

 

have U tried going the other way? I mean, if retarding it makes it worse............

 

it reads smooth at a little over 14, what worries me is that i was trying to break it in with some break in oil, but i had to go, so i told my dad to start it up and hold it at 2000 RPM for 20 min, but he started it and let it IDLE for about 15 min. and then since i thought he did what i told him too, i took it for a spin to see what she had, everything works fine, but im worried that because it wasent run properly for the first 20 min that something is gonna go wrong down the line, should i worry about that?

 

The running at 2000 rpm is to break in the cam, it helps get the lifters spinning so they don't wear in one spot. You could still do the break in routine, if it's damaged already it won't hurt and it may be fine. If it did damage you'll know soon enough when the cam lobes go flat. I'd try breaking it in properly and then run it, you have nothing to lose at this point, and it may be ok. Jim

 

Ok, thats good news because thats sort-of what i did, after i took it for a spin the first time, i found out that my dad idled it, then i took it for a spin and kept it right between 1800 and 2500 for about 25 minutes. Does that sound ok?

 

That's probably the best you can do, short of tearing it down and replacing the cam and lifters again. Time will tell if it damaged them.

 

ok that sounds good, thanks, how exactly does the low RPM damage the cam? Just not the proper heat to burn the zinky oil into the metal and wear down the high points?

 

RV cam?

 

ill get the specs on the cam tomorrow, its time to go to bed now, haha, then ill see what some of you guys think of it

 

Whatever damage was done idling is done. Breaking the cam in after all the idling time is not going to fix it. Hopefully it wont go flat, but keep an eye on the oil and change it often for awhile so you can see if there are sparkly particles of metal in it. If you lose the cam and a lobe goes flat it will cost you the engine, as the metallic particles will be pumped through the bearings and they will be taken out too.
Make sure you are adjusting the idle air mix, and timing for maximum engine vacuum. If you adjust the mixture screws until you have max vacuum signal you should have a good running engine. Once you get to that point make sure both screws are equal by shutting the engine off and checking how many turns each screw has form bottoming out. Also be sure to not turn the screws in tight! Just lightly to the stops as you count turns, then match the two at an average of each count.

 

ok, so iv put over 100 miles on it since yesterday, mostly just driving it pretty easy, and everything is still working good, no bad sounds or anything. i tuned it up with an initial timing advance of 12* and i tuned the idle mixture to the best vacuum and it's pulling about 17.5 on the vacuum gauge. and it runns better the more i drive it