Plugged exhaust

[Whitespider]

I believe I may have a restricted exhaust problem.
My '74 loses power (and the engine starts rattling), darn near comes to a stop at times, after running at full or high throttle for about 10 minutes or so... but if I back off to something just a bit over idle for a while the power and acceleration returns. Kind'a acts like it's overheating, which could also be related to plugged/restricted exhaust.

Any of you guys run into an exhaust problem? Was it the muffler or the ports?

Thanks

[crash12888]

I know it will be noisy but remove the exhaust and run it to see if there is any improvement.

Also read this.

http://www.buggiesgonewild.com/gas-y...-hot-pics.html

[Whitespider]

A muffler BBQ?

Well that's a better idea than I had... I was gonna' throw the muffler in the electric oven and set it on "clean" cycle. But don't worry about the wife, I have my own stove/oven out in the shop that I use for non-food things, like casting bullets, heating metal parts and drying welding rod.

I've been soaking the bolts/nuts all day with penetrating oil... hoping it will come apart without breaking hardware tomorrow morning.

[crash12888]

If it's clogged bad and cooked right you will have flames shooting out of the openings so the oven might not be the right idea. there are a few pics of some pretty big flames on here somewhere.
Stoke up the ole fire pit!

[Whitespider]

Nope, the exhaust wasn't plugged, but cooked the muffler anyway just because I had it off. Pulled the pipe and took a gander at the piston... wow is that ever scored bad... but it is 37-years old.

I guess it just flat overheats. I'll just haf'ta refrain from running wide-open throttle for long distance. I can run about a mile at wide-open before the thing bogs, loses power... and it ain't going lean 'cause if I pull the choke it will flat die.

[DOOmsman]

If it is building heat because it is scored up you
should replace the piston before it seizes and takes
out the crank as well.

[Whitespider]

Yeah, well... It did seize! Well not quite, but close. Managed to limp it back into the driveway and pulled the head/cylinder. It's got a .020 over piston in it that was fitted too tight by some back yard wrench turner. I spent a bit of time honing the cylinder, cleaned up good enough and still only measures .017 over... will be ordering a .020 over piston and finishing the honing when it gets here.

Ain't this fun...

**** money pit!

[sc3283]

have you checked cylinder for taper and out of round? You should, to have a dependable piece once put back together

[Whitespider]

Yeah I have...
Taper is less than o.001 and so is out-of-round.
Doubt it will be 100% when done, probably will still have a couple score marks below the exhaust port but the cylinder should be darn near perfect above. Waiting for the piston so I can finish the honing to fit.
I'd have to bore the cylinder to at least o.060 over, maybe more, to make it perfect... maybe would even have to replace the cylinder.
As deep as the scoring is, the "right" way would be to order a pre-fit piston & cylinder kit... but a piston/rings set is $38 and a cylinder kit is over $200... I'll chance the cylinder for now.

Here's a pic of the exhaust side, notice the rings have become part of the piston... I'm not even sure how the darn thing could run like that.




And here's the cylinder exhaust side after rough-honing.

[Craigs carts]

I think I'd spend the $30 at the machine shop and have it bored.