gas IH 345 intake popping

[6.9poweredscout]

ok here's my basis on this being good in an idi diesel forum, IH gassers are built to diesel specs AND redline at the same RPM as an IDI, plus this scout is the orange scouts older brother. oh and i traded an IDI f-250 for it!

this is a '74 scout II 345 with about 30K miles on the ticker. i replaced a bent pushrod and a lifter when i got it, then i noticed this intake pop, i replaced EVERY ignition component and swapped a distributor. also swapped a known good carb. still does it. it idles smooth accelerates well, but anything more than 1/4 throttle it pops out of the intake and it sounds like popcorn. if i ease into it it'll take longer before it pops loud enough to hear. usually happens 1800-2000RPM's and the pitch and quickness varies with the press of the skinny pedal. i'm at a loss i have no idea what it is. has anyone seen this before????

i have a youtube video, this is accelerating to wide open throttle. don't mind the blip at the end i recorded it with my droid and got a text!
http://www.youtube.com/watch?v=7kuwDf_mGKo

thanks
-Jon

 

[dave186]

do the 345s have any sort of EGR passages in the intake or head?

 

[Optikalillushun]

is the intake gasket squeezing out the back? friends j truck had this happen, poppin n stuff while on the pedal...the back of the intake gasket was pushing out just a tad when it romped it...weird i know.

 

[jwalterus]

whatever it is, it sounds serious, I've never heard anything THAT bad coming out of an intake on a gasser that kept going for more than a couple more seconds

maybe you are slapping a valve with a piston??

or maybe someone put some jiffy-pop in as a fuel additive

 

[6.9poweredscout]

it's an early non emissions intake. i think it is a vave issue but i have no idea.

-Jon

 

[94f450sd]

sounds like its floating a valve.what pushrod was bent,intake or exhaust?

 

[Freight_Train]

My bet is the valve is bent or chipped.Something caused the bent pushrod.Do a compression test on it and I bet you will find one hole low.Good thing is you can save it on the cheap now if it is just a bad valve.

 

[6.9poweredscout]

Bent on the intake side. When I did a leakdown test on that cyl I compressed the spring and you could hear air coming out of the carb, when id pull up on the valve it'd thunk then seal up.

-jon

 

[94f450sd]

Bent on the intake side. When I did a leakdown test on that cyl I compressed the spring and you could hear air coming out of the carb, when id pull up on the valve it'd thunk then seal up.

-jon

so you have to pull the valve up for it to seal?bent valve

 

[seawalkersee]

Broken spring, burned valve, dropped seat, 'nother bent push rod. Compression check and look at the plugs. Let us know what they look like but I bet it is an intake valve problem.

SWS

 

[BigRigTech]

Sounds like a bad intake valve letting compression back into the intake....Any noises in the exhaust note?

 

[THECACKLER]

You can put air to the cylinder through the plug hole, and see where it leaks out. Tail pipe would be exhaust valve, intake manifold would be intake valve, crankcase would be piston.... Anyways, I'd go with a stuck intake valve. Try douching it with oil from above, even PB Blaster and pushing or tapping lightly on it so you can work the lube in. Then go back with 2-stroke oil. If it frees up put the rest of the 2-stroke oil in the tank and run it.

 

[6.9poweredscout]

I was compressing the spring with a valve spring tool so the valve was loose, it'd slide down and be open, when id pick it up itd seal. I checked the springs the best I could they all look good. Exhaust sounds ok, hard to tell under WOT. The plugs were nice and tan, I replaced them, I will check again to see if ones a little different.

-Jon

 

[VanBoy]

Ah, the 345 V8.... I've got two industrial version with a PTO set up on them. Loudest things I've heard when going at 2000RPMS. Granted, I tamed them a bit when I mufflers on them. Made them run better too...funny, maybe back pressure does help....

 

[Agnem]

Sorry man. Even the basement has a basement.