2.8L Power? Why is my rebuilt 2.8L so slow...

['84 Bronco II]

Hello,

It has been a while since I have posted on TRS, but I think this is probably the best place to ask about my 2.8L.

My 2.8L was pressurizing the crank case about a year ago and blowing oil out about as fast as I could dump it back in. In addition, it was pretty gutless, and had some pretty good valve noise going on.

I got tired of trying to nurse it along, and decided to rebuild it. This was the first engine I had rebuilt on my own, but I got through it all right. The engine was bored out .030, and the crank was turned .010 under. I put new pistons, rings, lifters, cam, and bearings in it. I essentially did a stock rebuild on it.

I have been driving it for about 3000 miles now. It doesn't leak a drop, and it is a lot quieter now, but it did not seem to pick up any power over when it had a bad cylinder and was blowing oil everywhere. If anything it seems like it has a little less power now. This is very disappointing, but I was wondering if anyone might have an idea of what is going on. I have trouble getting to 65 mph!

 

['84 Bronco II]

Also, I have removed all of the emissions components, and converted it to a duraspark ignition system. I am using a Motorcraft 2150 carburetor with a 1.08 Venturi.

 

[wildbill23c]

May sound pretty dumb, but I know with my 84 Bronco 2, if my carburetor isn't adjusted just right its really sluggish, lacks power, takes forever to get up to speed, etc.

Ok, so how do I tell if my crank-case is pressurizing? I don't think I'm blowing oil anywhere I do have a pretty good oil leak going on around the oil pan, but what do I need to check? PO of my bronco 2 didn't do it any help so I'm trying to find and diagnose things the best I can, but this seems like something I should check on.

 

[kimcrwbr1]

What is the gear ratio for the axles and are you using a gps to measure the speed? Also what size jets are you running try some #43s if your still running the 50s I guarantee smaller jets will give you more upper end ponies.

 

[kimcrwbr1]

May sound pretty dumb, but I know with my 84 Bronco 2, if my carburetor isn't adjusted just right its really sluggish, lacks power, takes forever to get up to speed, etc.

Ok, so how do I tell if my crank-case is pressurizing? I don't think I'm blowing oil anywhere I do have a pretty good oil leak going on around the oil pan, but what do I need to check? PO of my bronco 2 didn't do it any help so I'm trying to find and diagnose things the best I can, but this seems like something I should check on.

Just watch the breather tube coming out the oil filler cap if you get alot of blowby put in a new PCV valve and see if it helps. You cannot clean a PCV just replace it with regular tuneups. Probably the most neglected part of preventive maint. I used to have really bad blowby until I replaced the valve guide seals. When you replace the PCV also put in a new breather filter in the air filter housing so the block breathes properly.

 

[wildbill23c]

Just watch the breather tube coming out the oil filler cap if you get alot of blowby put in a new PCV valve and see if it helps. You cannot clean a PCV just replace it with regular tuneups. Probably the most neglected part of preventive maint. I used to have really bad blowby until I replaced the valve guide seals. When you replace the PCV also put in a new breather filter in the air filter housing so the block breathes properly.

I've replaced the PCV Valve, but haven't replaced the breather filter yet on the oil fill cap. I get some vapors coming out of the oil filler cap vent all the time, but if I remember right my 84 ranger did the same thing. Don't really know if some is normal or what. The PO has some sort of spectre air filter crap on it so it don't have the factory air filter housing, maybe this is why it was receiving too much blow by and clogging the air filter.

 

[kimcrwbr1]

Blowby is cause from rings and valve guide seals. Have you tried a decarb on the motor get a can of seafoam and bring the engine up to temp. At a high idle slowly pour 1/2 the seafoam in the carb and immediately shut the motor off for 1/2 an hour. Then start it up and run it around 3000 rpm until the smoke show stops. Do it outside on a windy day the more it smokes the more carbon it is burning up. The filter media in the breather is supposed to catch the oil and drip back into the engine before it gets to the air filter. You can allways put in a PCV for a larger V-8 will help but the only real cure is a rebuilt engine.

 

[wildbill23c]

Blowby is cause from rings and valve guide seals. Have you tried a decarb on the motor get a can of seafoam and bring the engine up to temp. At a high idle slowly pour 1/2 the seafoam in the carb and immediately shut the motor off for 1/2 an hour. Then start it up and run it around 3000 rpm until the smoke show stops. Do it outside on a windy day the more it smokes the more carbon it is burning up. The filter media in the breather is supposed to catch the oil and drip back into the engine before it gets to the air filter. You can allways put in a PCV for a larger V-8 will help but the only real cure is a rebuilt engine.

That's what I'm affraid of, I've been dumping money and parts at this thing since November and ran across this thread about the blowby and now its like great another expense I'm not sure I will be doing, this thing is getting closer and closer to the scrap yard the more issues I find. I'll try some carb system cleaner here in the next week or so. I wonder if something failed due to the head gasket failure? I had the head gaskets replaced in it not too long after I bought it because I could see coolant in the oil, maybe it damaged the cylinder walls and washed them down, which I guess if that's the case its a rebuild that I won't be doing, I just don't feel this truck is worth putting that kind of money into given the shape the body is in currently. However I'd like to try and at least get what I paid for it from getting rid of it.

 

[kimcrwbr1]

As long as the compression is good and reasonable oil pressure run it till it pukes. Put in a PCV for a 351 and see if it helps the blowby.

 

[MastuhWaffles]

Are you running break in oil?

 

[wildbill23c]

Are you running break in oil?

No, due to my major oil leak due to a screwed up oil pan I am running whatever oil is cheapest right now until I get time to remove the oil pan and replace it. At who knows how many miles it's done past any break in period LOL. Trying to figure out a temporary filter or something or maybe a plug to put in the oil filler hose that's just there due to the previous owner removing the factory air cleaner which I'm thinking the blow by problem was the reason.

 

[enginepaul]

84 Bronco - That lack of power may be in the tuning. Check the spark timing and also the carburetor. Maybe even a vacuum leak.

I don't think it is internal in the engine - unless (and I doubt it) the cam isn't installed correctly.

 

[kunar]

cam timing would have been my first guess. have you checked compression?

 

['84 Bronco II]

Thanks for the replies everyone. I almost forgot about this thread.

MastuhWaffles, I am not running break in oil. I was a bit concerned that maybe that is what I did wrong, but there has not been any metallic particles in the oil, which I have changed several times since the rebuild. Do you really need to put break in oil in a 2.8L? I have not noticed any loss of power since I initially fired it up.

The cam timing should be correct. The timing gears are keyed to the crank and cam shaft, and they have timing marks. I was careful to make sure the cam was installed on the correct tooth, so there is not really anywhere I could have gone wrong there.

I am pretty sure I don't have a vacuum leak because I am pulling around 17-18 inches of mercury at idle if I recall correctly, and I am at 4000 feet, so you can't really expect much more. I have my idle set to 900 rpm. My ignition timing is spot on. I set my timing and idle mixture with a vacuum gauge.

The carburetor was rebuilt by Pony Carburetors before Jon passed away and has never given me any trouble. It seems to work really well because my truck does not hesitate or stumble and it always fires right up, even in -5 degree weather. That said, I have never fooled with the jets on it, and I don't know which jet size I am running. Do you really think some different jets will make much of a difference? Anyways, as far as functionality, the carburetor is in perfect working order.

The only part of the ignition system that could be suspect would be the coil. I am still running the canister coil I pulled out of a junked Pinto several years ago from when I originally swapped in the Duraspark system. I don't think the coil would really affect the power, would it?

Also, I just got my 5.13s swapped in, and although it is quicker off the line, I am still facing the same top end power problems. It is still hard to maintain 65-70 mph on the highway.

The engine runs really nice and smoothly, but I think I will check out the compression as Kunar suggested. Thanks for the replies, I will try and remember to check back this time!

 

[bobbywalter]

cam timing would have been my first guess. have you checked compression?

me too...that or valves/cam was wiped....should have seen a shit ton of metal though.

Thanks for the replies everyone. I almost forgot about this thread.

MastuhWaffles, I am not running break in oil. I was a bit concerned that maybe that is what I did wrong, but there has not been any metallic particles in the oil, which I have changed several times since the rebuild. Do you really need to put break in oil in a 2.8L? I have not noticed any loss of power since I initially fired it up.

The cam timing should be correct. The timing gears are keyed to the crank and cam shaft, and they have timing marks. I was careful to make sure the cam was installed on the correct tooth, so there is not really anywhere I could have gone wrong there.

I am pretty sure I don't have a vacuum leak because I am pulling around 17-18 inches of mercury at idle if I recall correctly, and I am at 4000 feet, so you can't really expect much more. I have my idle set to 900 rpm. My ignition timing is spot on. I set my timing and idle mixture with a vacuum gauge.

The carburetor was rebuilt by Pony Carburetors before Jon passed away and has never given me any trouble. It seems to work really well because my truck does not hesitate or stumble and it always fires right up, even in -5 degree weather. That said, I have never fooled with the jets on it, and I don't know which jet size I am running. Do you really think some different jets will make much of a difference? Anyways, as far as functionality, the carburetor is in perfect working order.

The only part of the ignition system that could be suspect would be the coil. I am still running the canister coil I pulled out of a junked Pinto several years ago from when I originally swapped in the Duraspark system. I don't think the coil would really affect the power, would it?

Also, I just got my 5.13s swapped in, and although it is quicker off the line, I am still facing the same top end power problems. It is still hard to maintain 65-70 mph on the highway.

The engine runs really nice and smoothly, but I think I will check out the compression as Kunar suggested. Thanks for the replies, I will try and remember to check back this time!

you rolled it 720 and rechecked? did you roll it backwards too and check?


check compression for sure. if the cam was visibly off it should pop and not start well so its odd. but less then full opening on the valves is less power.

 

['84 Bronco II]

I am not sure what you think I should have been checking for by turning the engine. I had to rotate the crank to set the valve lash and I never noticed anything abnormal. I still don't understand how I could have gotten the cam timing off? The crank and cam are each keyed to their respective gears and have timing marks that line up. There really is not a way you can install them improperly without misaligning the timing marks.

After reading about carburetor tuning for the last couple of hours, I think I will take another look at the carburetor and see if I can improve on anything.

Also, I talked to my father and he brought up distributor advance and timing curves. I don't really know much about that, so I will be doing some reading. If anyone wants to chime in on distributors, feel free.

 

[wildbill23c]

I can say this about the carburetors, just a half turn to a turn can make a huge difference. Since you did all this rebuild work, just because the carburetor worked just fine before the rebuild doesn't mean its going to run find after the rebuild. You changed the workings inside the engine, cleaned up some stuff, changes parts, etc. You have to adjust the carburetor to make up for those changes.

I just got a carburetor from a fellow member on here last week, it was cleaned and rebuilt by someone he knew and worked awesome on his rig, however I put it on mine and I had to adjust it for air/fuel mixture and idle speed. It's all in the proper adjustments of everything to get these things to run right.

If you have the computer in your rig still functioning you need to unplug the plug on the back of the carburetor before attempting to adjust it, also do your adjustments after the vehicle is up to operating temperature or you'll never get it adjusted right. I can adjust my carb all sorts of ways, and it will either effect low end power or upper end power. Its all about getting that happy medium between both LOL.

 

[bobbywalter]

I am not sure what you think I should have been checking for by turning the engine. I had to rotate the crank to set the valve lash and I never noticed anything abnormal. I still don't understand how I could have gotten the cam timing off? The crank and cam are each keyed to their respective gears and have timing marks that line up. There really is not a way you can install them improperly without misaligning the timing marks.

After reading about carburetor tuning for the last couple of hours, I think I will take another look at the carburetor and see if I can improve on anything.

Also, I talked to my father and he brought up distributor advance and timing curves. I don't really know much about that, so I will be doing some reading. If anyone wants to chime in on distributors, feel free.

hmm. well.

sometimes one can wrong side the slack on the chain and it gets a bit off. i have seen it before, but you would normally see this when setting lash as its visibly off. which is what i implied when i said visible off in the other post.


but if it was running great with the carb setup for a shit ton of blowby and uneven pulsing....

i would be suspicious of that. but curving the dizzy is another matter.

are you sure the vac advance is operating correctly??

 

[kimcrwbr1]

Get some #41 jets and put them in I guarantee you an improvment in mileage and performance. The 2.8 works best at 10 DBTDC period with my engine. I have tried every combination possible right now I am running #41 jets and still have pedal pulling a pass. Being above 4000' elevation you want smaller jets anyway. It only takes about 15 minutes to change the jets there cheap its worth a try. When pony carbs rebuild their carbs they change the power valve jet size so depending on what vacuum pressure the power valve opens will make a difference also. If you can get it on a dynamometer with a sniffer you can find the right combo for your setup maybe put some heavier springs in the dizzy for a less aggressive advance. It is kinna hard to see your tailpipe at high speeds maybe have someone follow you on the freeway and at high speeds punch it if black smoke comes out the tailpipe your running rich put in smaller jets. I started with #50 real low power pulling a long hill, #46 still puffing black smoke #43s ran alot better but still about 16 mpg running #41s up around 18mpg and alot easier on the skinny pedal. I just hauled two loads of garden dirt with the frame down on the axle with no problem I couldnt be happier. I say go by the tailpipe if it blows black smoke run smaller jets. Does you oil smell normal, if you smell fuel it is definately running rich?

 

['84 Bronco II]

Okay Bobby, now I see where the confusion is, 2.8Ls don't have timing chains, they have timing gears.

The distributor I have now is a rebuilt unit from Autozone and I don't believe it to be a very high quality rebuild. After reading up on timing curves and such, I am pretty suspicious of the distributor. I have the base timing as far advanced as it can go at idle, but I have never had the engine ping under load. If anything, it seems the timing curve may be a bit retarded.

Also, I can't say with any certainty whether or not my vacuum advance is working correctly or not. I am going to try and do a little tweaking on it this weekend if time permits.