1986 Bronco with 351w, C-6, Towing package, Edelbrock carb, everything else is stock.

Yesterday I went through patches of mud and water and everything seemed fine although have way down the 4 mile stretch it seemed low on power. The rest of the day seemed normal and really didn't notice anything wrong until the ride home on the highway. I had no power, the pedal was just about floored and there was a strange hissing sound from the exhaust. I couldn't get the thing past 55 MPH!

I got home, checked the exhaust and nothing seemed bent or messed up. Checked the air filter, that didn't make any difference. There is a banging coming from the cat. converter that seems to change with the throttle. The muffler is a single glasspack style. Does anyone have any thoughts of what it could be?

I'm thinking it's in the exhaust somewhere since the engine runs smooth and the exhaust is making the strange sound. It used to be a deep tone but now it sounds like a ford taurus!!

Thanks,

Mike

 

You probably shattered the substrate in the cat, and it's blocked. You can diagnose it with a vacuum gauge.

 

I have a vacumn gauge but I'm not really sure how that should help. With a blacked exhaust, wouldn't that show very little vacumn? What numbers should I be looking for? Should I hook it to the full vacumn port? Timed Vacumn port? Thanks for the input. I'm really hoping it's just something in the exhaust and not a major problem. I really think it sounds too smooth to be a single piston issue.

Mike

 

Did you go to that link? The bottom L gauge on the second page is what you should look for.

 

i agree with you steve83 on the cats innersbeing destroyed and blocking the exhaust. that was an EXCELLENT site on the vacumn gage interpretation. i will definetly add it to my favorites. thank you much.

 

Sorry, I completely ignored the link. I thought it was one of those auto-links like "exhaust". Didn't even notice that it was underlined! Wow, that site is great! I'll give that a try to see what else is wrong as soon as I can.

Anyhow, I took the exhaust down last night and looked in the cat and there was a bunch of broken pieces laying around all over the place. Most about 2x2 inches or so, but I could clearly see through it and into the y-pipe. Turned around and BINGO! A large piece circular on one side was jammed in the glasspack. I bet there wasn't 1 sq inch of area around the piece. It fit perfectly in 1/2 the pipe. I dug it out and and spent the next 10 min. trying to walk the rest of the pieces out of the cat. I eventually just broke them up with the handle of a jack and started the bronco. It shot stuff every but cleaned it out in the process.

Re-attached everything and it runs like a champ now. I need to go get the exhaust fixed where I had to cut it loose of the glasspack though. I'll probably get a new high-flow cat put in too, might as well be legal sometimes.

Say, you wouldn't have any good links to edelbrock carb tunning would you? I think the carb is out of adjustment. I promise I'll try all links on all replies.

Thanks again,

Mike

 

I'm not into carbs any more. I think the only carb link I have is http://www.bob2000.com/carb.htm .