need help engine troubleshooting-----Long read

[bigbadchev84]

ok well i have posted here time to time about my project car i have been tinkering on in my freetime, it is a '71 ford maverick (my first car) that i got back when i was 15, it has since been stripped of its 170 6cylinder and the shock towers have been shaved and modified to fit a 351w in the 350-400hp range....so says the machine shop. well i have been having nothing but fits breathing life into this thing and blew a head gasket on initial break-in, i got ahead of myself and didnt bleed the block, it was my fault i should have noticed it only took 2gallons of water. got the gasket replaced and fired it up again, it ran rough at first, i revved it a couple times and it made a tink and smoothed out perfect.

ive got over $3000.00 into this motor and the tink sound i heard was making me nevous, i pulled the valve covers to find that i had bent the #2 cylinder intake pushrod. i replaced fired up again, ran rough, revved and same noise, frustrated i pulled the cover off again to find a broken rocker arm on the same valve, i figured it was something to do with my EBAY heads i got for it. i pulled it and took it to the machine shop, they said the valve was slightly bent and binding, new valve, valve guide and off i went, re-installed and still could not get it right, on ford the rockers are torqued not adjusted like a chevy, in frustration i had set the torque wrench too high and stripped 2 studs.

I went and bought a new head from the parts store, installed and ran worse than before, changed plugs,wires,cap,rotor and coil and swapped carbs and a new dizzy, still nothing it would run, but not smooth and would backfire on revving. checked compression and all was good at 180psi per cylinder, but noticed 2 of the cylinders were full of gas well i stuck the plugs back in and fired it up to the same thing, i figured i better check the firing order AGAIN, well i couldnt find my Haynes manual, and found an old chiltons instead, well it appears that 3 of the wires were out of place, i fired it up and it ran WAYYY smoother, i revved it a couple times and it backfired and popped, i have always timed by ear and all the sudden BOOM the loudest backfire i have ever heard, i am assuming from the 2 plugs mentioned before being soaked with gas finally sparking, well after that it was back to not running smooth again, what are the chances of it just needing another set of plugs? where should i start here? im tired of just throwing time, money, and parts at this thing!!!

Sorry for the long read, but i figured to get an accurate answer the whole story needed to be out there

PS-the Haynes manual is going in the garbage, i have since found it and it has mis-typed the firing order in the book

 

[ARAMP1]

After all the time and effort, a new set of plugs shouldn't be that much to spend. Also, I'd throw a timing light at it. Other than that, I've got nothing for you. Good luck with it man. Should be a screamer when you're done.

 

[bigbadchev84]

After all the time and effort, a new set of plugs shouldn't be that much to spend. Also, I'd throw a timing light at it. Other than that, I've got nothing for you. Good luck with it man. Should be a screamer when you're done.

yeah thats true, im just getting frustrated with the thing and hoping someone with a little more insight can help me out, i dont have a timing tab on the car otherwise i would try that. yeah the thing should do pretty good for itself, the car wieghs in at 2900lbs, so it will be fun, just keep reminding myself its gonna be worth it in the end, thanks guys

 

[78Suburban]

hang in there, you'll get it figured out eventually. I don't suppose your timing chain is actually a tooth off, throwing your whole cam timing off? Just a thought.

maybe you should find TDC compression stroke and get you a timing tab to put on there. Are you sure the advance weights on your dizzy are good? Is the parts store head you bought basically the same head as the one on the other side of the motor?

Are the plugs really black from the unburned fuel from the bad firing order? If so, I've found that starting fluid and a wire brush will clean em up pretty good, because when I was having all those valve issues the unburned fuel was fouling my plugs. I got really good at cleaning plugs!

Just hang in there, it took me months of troubleshooting my motor to make it run correctly. I still get a hick-up every now and then, I'm thinking it was another rocker stud I had that was questionable.

Hang in there Justin, you'll figure it out

 

[78Buford]

hang in there, you'll get it figured out eventually. I don't suppose your timing chain is actually a tooth off, throwing your whole cam timing off? Just a thought.

I wouldn't doubt it...sounds like a timing issue to me. The backfiring is likely the result of the cylinders firing at the wrong time.

 

[bigbadchev84]

i have installed numerous timing chains and did this one no different, when i first fired it originally it idled perfect, just overheated and blew a head gasket and messed up that one valve i am guessing, then yesterday it idled great until the backfire, witch had to have been from the cylinder loading up from the wrong firing order (thanks haynes manual), ill try to get a new set of plugs in it tonight or tomorrow, hopefully thats it

 

[78Suburban]

what carb do you have? i don't guess the backfire cooked anything in it....I think edelbrocks are fairly immune to backfires, but if a holley ever spits up, its bad news, blows out a power valve or something.

 

[3 on the tree]

You probably already know this, but Ford used different firing orders tween 302 and 351. If you by chance used a 302 cam, then you need to use the 302 firing order. I don't understand why you had to shave the shock towers. Years ago, I put a 70 351W Mustang motor in a 63 Fairlane, along with the Mustang headers. All I had to do was dimple one tube on the drivers side. Right now, I am searching for the right body for my 429 T Bird engine. Any ideas????

 

[JEBSR]

"i pulled the valve covers to find that i had bent the #2 cylinder intake pushrod. i replaced fired up again, ran rough, revved and same noise, frustrated i pulled the cover off again to find a broken rocker arm on the same valve"


My biggest concern is the fact that the valve was bent. What bent it? Did you check the top of the piston when the head was off? What type of pistons are you running, Has the deck height been altered, heads milled, what are the lift specs on the cam, etc. What I'm getting at is do you have enough clearance for the cam your running or is it pushing the valve into the piston

 

[Chevy305]

your problems are in either timing, or valve train.

I'd start with a new set of plugs and properly time the engine.



78Suburban: You are thinking of older Holley carbs. The new ones all have power valve blow out protection so it won't blow out if the engine that its on backfires.

 

[bigbadchev84]

You probably already know this, but Ford used different firing orders tween 302 and 351. If you by chance used a 302 cam, then you need to use the 302 firing order. I don't understand why you had to shave the shock towers. Years ago, I put a 70 351W Mustang motor in a 63 Fairlane, along with the Mustang headers. All I had to do was dimple one tube on the drivers side. Right now, I am searching for the right body for my 429 T Bird engine. Any ideas????

the shock towers on a maverick tend to be extremely tight with the 351w im not familiar with fairlanes but the maverick had a stock 302 option, the 351 is 3" wider than a 302 because of the longer stroke, that makes plug changes, header bolt access a pain in the butt without notching the towers. i have already confirmed that it is a 351w firing order also.


"i pulled the valve covers to find that i had bent the #2 cylinder intake pushrod. i replaced fired up again, ran rough, revved and same noise, frustrated i pulled the cover off again to find a broken rocker arm on the same valve"


My biggest concern is the fact that the valve was bent. What bent it? Did you check the top of the piston when the head was off? What type of pistons are you running, Has the deck height been altered, heads milled, what are the lift specs on the cam, etc. What I'm getting at is do you have enough clearance for the cam your running or is it pushing the valve into the piston

i believe a got a crap set of heads from ebay and the valve must have been slightly bent from the get-go, i checked the pistons with the head off and everything was in order, they are a little over a 10.5:1 compression flattop piston that have been clearanced for up to 2.02/1.6 valves, i am eventually gonna stick some alum heads on when money allows, it has a decent cam in it, i dont have the specs with me know but it required me to have a 1800 stall convertor.

the thing that gets me is once i fixed the firing order it ran smooth idleing, just wasnt timed right for higher rpms, then after the backfire i couldnt even get it to idle smooth again.

it looks like it will be a couple more days before i can get out there to work on it so i will keep you posted

 

[3 on the tree]

If you are running a Holley, the backfire probably blew the power valve, letting extra fuel trickle in while idling. Probably not enough to make the exhaust black, but enough to make the idle sloppy. I have had this happen on numerous older Holleys.

 

[bigbadchev84]

still no dice there....i am running a 600cfm edelbrock

 

[bigbadchev84]

You probably already know this, but Ford used different firing orders tween 302 and 351. If you by chance used a 302 cam, then you need to use the 302 firing order. I don't understand why you had to shave the shock towers. Years ago, I put a 70 351W Mustang motor in a 63 Fairlane, along with the Mustang headers. All I had to do was dimple one tube on the drivers side. Right now, I am searching for the right body for my 429 T Bird engine. Any ideas????

here are some pics of how tight it is after notching the towers

 

[mouse]

Sounds like a timing issue to me too. If you can get a timing tab on it, you can properly set the timing and at least eliminate it as the problem if it doesn't fix it!