So the other day I went to get a tractor and hooked up my trailor to my 77 f250 and headed off, about 20 miles down the road I noticed after I got off the interstate the truck was running rough just missing horribly. I then proceeded to do a quick check and everything looked good I did a quick burp of the throttle and it cleared up. I decided to not get the tractor and safely make it back home and not hurt the truck. I got her back home but now it was missing all the time. I noticed I needed new wires so I did a cap rotor wires and plugs. all the plugs were burning the same. Timing is still were I left it at 10* BTDC firing order is spot on. carb adjustments make no difference. It has a holley intake and a carter 600CFM mech. secondary carb.

I am just wanting to bounce some ideas off you guys??

If I lost a valve spring you think that would be a possibility?? I noticed while it was running good it would not want to pull past 2500 rpm where as before it wouyld pull hard to 3 grand??

any Ideas would be greatly appreciated I am going to test the compression tonight. and probaly pull the valve covers off and see what I am working with

 

So Last night I puled all the plugs (they have 15 min on them which is not too good to read them) But they appear to be a bit on the lean side. still I am not going to make jet changes until I get more time on the plugs and can read them better.

I performed a compression check and the spread I had on the engine was the left bank 5-8 was all at 140 psi and the right bank was 1-130psi 2-140psi 3-140 psi 4-135psi

so they are all farely close to each other, so I hooked up a vaccum gauge and started the truck, still idled like crap and would pop out the carb if I gave it any throttle. and the vaccum gauge was reading 12 steady, So I double checked the timing and it was spot on at 10* at an idle with the vacuum line plugged, So I bumped the timing up to 15* BTDC and now the vaccum gauge reads 15 steady and it takes throttle much better than before, I have not been able to road test it but it sounds much better and it actually had plenty of power to pull my trailer back up the hill and get it parked where it belongs instead of blocking my exit driveway.

I am still going to pull the valve covers tonight and inspect the valve train.

any other opinions?????

 

sounds like the cam is a little larger than stock, the source of your problems could possibly be: pickup in your distributor could be going out, however popping the VC's to check the top out would not be a bad idea either since what you described also sounds like a bent pushrod/loose rocker. overall i think, with current changes, you'll need to test drive and report back if you pop 'em. compression sounds very good(assumed cold when tested)

 

Yes the engine was cold ( I dont like burning myself)

I believe the cam to be stock, I didnt see any aftermarket stampings on the cam when I installed a edelbrock timing chain set.

I will report back once I check the valvetrain, and test drive.

Also another tid bit is the day it ran like poo, I used alot more fuel than normal but that didnt show up on the plugs?

 

that could be pointing to something....had a similar set up that chugged turning to the left...found out that a float was out of wack, and had some dirt in the needle/seat assembly.

 

Well about three months ago I had to start the truck to move it (had to mow the field it was parked on) Well I had a sunk float that day, it was a quick fix pull the floats out of my spare carter put new needle and seats in it and bam it was alive again.

So Last night I grabbed another set of metering rods and step up springs, this was the set that was used on my 393 stroked windsor before it went to a barry grant carb. I didnt have my micrometer with me. I leave those tools at work. the springs were much softer than what I had in there and the rods were a hair larger in diameter. Thus leaning the carb up a bit. put it all together adjusted my mixture screws to the best lean idle and to the truck for a romp around the property. It is running great again. pull hard to 3,000 rpm. I was only able to drive around the property as my son was with me and his car seat doesnt work well in the truck so I just belted him in and we drove around and checked on the neighbors cattle. had to put it in 4 hi to get to their upper pasture and normally I use four low for that hill but now I just put my foot down in it and she puilled hard up the hill.

I still want to check out the valvetrain but decided to wait till I get the valve covers from a buddy of mine some nice OEM covers that are triple chrome plated.

 

mics do make those float adjustments confident and symmetrical...should the valvetrain check out, id suggest using the stiffer(original) spring w/ larger rod. (get yo mind out the gutter).

 

What I really need to do is find my edelbrock calibration kit rods springs and jets all numbered color coded etc etc so I know exactly what I have done. Right now I am happy with the way the truck is running but I will really know this weekend when I go get my tractor.

This motor was rebuilt before I got the truck and I am really thinking about building my spare 400 so I know what I have and I can trust the truck more for next year when it gets to pull the boat to the lake and have a camper in its bed!