Bronco Forum - Full Size Ford Bronco Forum banner

1 - 20 of 25 Posts

·
Registered
Joined
·
1,299 Posts
Discussion Starter #1
i bought a '86 bronco w/160K about 2 months ago (351W, C6, 208x case, 9" rear) well the vac lines were all hacked up and it didn't idle right but at upper RPM it got smooth so i figured a tune up and vac line repairs would fix everything. well i did the tune up and completely forgot to do a compression check (which i was going to do). so we finaly did one the other day and found out #1 & 2 have no compression so we didn't even bother checking the rest. i bought this as a toy to play off road with so i'm torn on what to do. i don't have enough money to do a complete rebuild or crate motor and still lift it with tires lockers and gears. i figure if i tear into the motor at all with 160K i might as well to a complete rebuild which i don't have time to do. what do you guys think?? unless i can find a decent priced 351W or a decent price to rebuild it for me then i think i have no choice but to sell it! which i don't want to do.

Travis
 

·
Registered
Joined
·
150 Posts
first off, go back and check the rest of them. When it is running, how does it run, this seems slightly weird to me that it will run ok with 2 non-partnered cyl. off. Make sure that your compression tester is working ok, check the rest of them. Figure out why. You may not need a new motor. My advise, for now is to just go look at everything check your compression. run it. If both of these cyl. didnt have compression you will have gas in your oil. Smell your oil. I wouldnt jump to conclusions about a new motor.
 

·
Registered
Joined
·
1,299 Posts
Discussion Starter #4
well it runs like crap at idle but runs better at higher RPM's. i took it to my trusted local mechanic friend and he was going to help me with the vac line mess i have. while it was running he pulled the plug wires off 3 cylinders and it did nothing to the idle. i tuned the edelbrock 1406 carb per instructions also. compression tester was working properly. oh and this is still the first full tank i've ran through it so i don't know if the sender is working properly or not but i filled it up like $60+ and and i've put 75 miles on it and it now reads 1/2 tank! now thats some gas sucking!

Travis
 

·
Registered
Joined
·
1,334 Posts
Did you try a "wet" test to determine if it heads (valves) or rings? If the valves are bad you just need some head work done.
 

·
Registered
Joined
·
150 Posts
haha get used to the gas sucking. as far as the compression goes. While it is running dump sea foam into the carb until it kills. let it sit at least a overnight. Start it up and run. If it has sat for a long time, you might want to try this......

put it in first so that it stays in first. drive it until the rpms are fairly high, maybe around 4000, then just quickly let off on the idle. This will loosen the rings if they have rusted up. whenever we take any of our cars/trucks out of storage for the year, we have to do this at least to two of them. give it a shot.
I dont have to much faith in this solving your problem, but it might make it better until you can afford to do it right.

Also if you decide to do the motor, just buy a long block from a company and switch it over, with a core you could expect around 7-800 dollars. Good luck.

The sea foam is for the rings as well as the other trick. Then if it isnt the rings Look into your valves, is there something sticking in them, or broken springs, pushrods...lot of different possibilities there. Good luck.
 

·
Satyr of the Midwest
Joined
·
17,736 Posts
2fastnaz said:
Did you try a "wet" test to determine if it heads (valves) or rings? If the valves are bad you just need some head work done.
Exactly. You need to figure out WHY there is no compression in those cylinders before anything else. Might be something as dumb as a rocker bolt being loose, a bent pushrod, etc. I'd start with the valvetrain and eliminate that first as a possible mechanical cause. Move on to the cylinder using the "wet" test (aka put ~2 tbsp oil in the cylinder, one at a time) and see what you get for compression readings then. Like bluebabe said, it's really really odd that you're having issues @ idle, but clearing up when engine speed increases.

BTW, how's the oil pressure? My other thought is that mebbe the hydraulic lifters are/have been collapsing, causing further valvetrain problems. This would explain much.
 

·
Registered
Joined
·
1,299 Posts
Discussion Starter #9
well i just talked to the guy that did the test and he said if i had head work done then it would cure a lot of it. i'm pretty sure he ran a wet test on it cause he only commented on the heads. the guy i bought it from said the heads had been redone a few years ago too. What is the diff of a "wet" and "dry" test? also how much do you think it would run if i took the heads off myself and took them some where to have the redone? cause i really don't want to spend a bunch of $$ on the heads since the bottom end has 160K on it it will need a rebuild too in the future.
 

·
Registered
Joined
·
150 Posts
well think, of it this way, if you get the heads done right this time around, You can just buy a short block later without having to pay for new heads. Just a thought. I am not sure about the price, but if it is more than 150-200 I would take a pass.
 

·
Registered
Joined
·
1,334 Posts
A dry test you just hook up tha gauge and crank the engien, a wet test you squirt a table spoon or so of motor oil in the cylinder and then do the test again. If you get more than ......Oh 10 PSI diffference then you have bad rings, if there is little or no difference you have valve issues. If it's bad rings it will usually make a substantial jump between wet and dry.

I can get a set of heads done for $300.00 or cheaper depending on what you want done to them. With 160,000 on the bottom end a new set of heads could suck the rings out of her so take it easy if thats the route you end up taking.
 

·
Registered
Joined
·
1,299 Posts
Discussion Starter #13
wow has anyone ever delt with these guys^^^ sounds really cheap! also i forgot to mention it runs good and smooth when it gets to around 800-900 RPM anything below that (like in gear and stopped) it's really bad. I think i can get around to checking all cylinders this weekend so i should do a dry test first then a wet and if there is still no compression when i do the wet then the heads are bad right? thanks for the help everyone

Travis
 

·
Satyr of the Midwest
Joined
·
17,736 Posts
Nm...
 

·
Registered
Joined
·
150 Posts
good thinking, I didnt even think about it being per head. All I could think about in my mind was.......cheap cheap cheap, then a valve dropping after the 100 mile warranty...lol
 

·
Registered
Joined
·
1,299 Posts
Discussion Starter #17
I guess i'll just check around localy for someone to rebuild my heads. how do i check the oil pressure? is there a specific gauge i need to use or can any pressure gauge work? where is the factory sending unit located?

Travis
 

·
Registered
Joined
·
82 Posts
what do you mean you have no comp.? do you mean absolutely nothing = 0, i would check the rest to be sure you dont have a crappy comp. tester. i have had more than one read 0 because they were sh**. i dont see how the truck would even get to higher rpms easy enough with two completely dead cylinders, let alone they were the first ones you checked.
 

·
Registered
Joined
·
490 Posts
BIGT2317 said:
well it runs like crap at idle but runs better at higher RPM's. i took it to my trusted local mechanic friend and he was going to help me with the vac line mess i have. while it was running he pulled the plug wires off 3 cylinders and it did nothing to the idle. i tuned the edelbrock 1406 carb per instructions also. compression tester was working properly. oh and this is still the first full tank i've ran through it so i don't know if the sender is working properly or not but i filled it up like $60+ and and i've put 75 miles on it and it now reads 1/2 tank! now thats some gas sucking!

Travis
lmao. thats what my brothers truck is doing know. burnign gas at that rate. i suspect the carb in his case since it idles and drives fine. but i redid my engine at 162k. and yes i had the 351w. i had no compression in cyl 3 and 4 i believe in the back. it turned out i had a bent rod under the intake. i bought a rebuilt engine (ATK) from autozone at the time. ran me $1k. but i then got a 20% discount since i worked there. made it $800 then i got my taxes back. in the end i payed $200 for my rebuilt engine. lmao. im upto 6k miles know. barely broken in. that was last year. i would definetly check all the cylenders. maybe you have a blown head gasket.
 

·
Registered
Joined
·
1,299 Posts
Discussion Starter #20
ok i did the test on all of them and this is what i found. cyl 1-12 dry/12 wet, cyl 2-20 dry/26 wet, cyl 3- 132 dry, cyl 4- 40 dry, cyl 5- 124 dry, cyl 6- 107 dry, cyl 7-106 dry, cyl 8- 118 dry. So what do ya think? i'm guessing the since the wet test didn't make that much of a difference then the heads need rebuilding?

Travis
 
1 - 20 of 25 Posts
Top