Exhaust leak through carb????

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Dartish

Dartish

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Started my truck this morning, fired up and ran fine as usual. Pulled out of driveway and sounded like a header leaking under light throttle. Had header off other day to change starter and reused the "good" gaskets and they didn't leak. Got to work and started checking and sounds like the tick is coming through the carb. Pulled valve covers and started it. Everything looks fine, but crack throttle a bit and it ticks. Has a new Qft carb, Indy reman heads and Summit 444"hyd cam? Gonna do a compression check. Anything besides a burnt exh valve that could be the culprit. Noticed it seems awful rich at idle now too!!! Any chance I should be looking at ignition system or am I one of the unlucky ones that got a set of Indys crappy valve jobs? They have hardened seats, have around 5000 miles and ran fine til this morning. Any ideas would be helpful since I'm at work and don't have a lot of time to tear into it right now. Thanks
 
Wiped exhaust camshaft lobe, bent exhaust pushrod or failed exhaust rocker arm. You have something keeping an exhaust valve closed.
 
Exhaust rockers all moved at first glance. Gonna pull shafts after compression test and see if I got a valve that mysteriosly sunk overnight. Ran great yesterday. Compession test will show something right?
 
Running comp lifters and push rods after a Summit lifter started ticking on number 2 intake after couple thousand miles but haven't been hearing much good about comp lately
 
Just ran compression test. All holes about 115 to 120 psi. 3 and 5 have about 5!!!! Low, compression 360, resurfaced heads and a flat deck on block according to machine shop that tanked it and cam bearinged it. Funny thing, it don't run hot, radiator hose don't get hard, oil is clean as can be and under hard throttle, seems to run fine. Just my luck
 
Dartish said:
Started my truck this morning, fired up and ran fine as usual. Pulled out of driveway and sounded like a header leaking under light throttle. Had header off other day to change starter and reused the "good" gaskets and they didn't leak. Got to work and started checking and sounds like the tick is coming through the carb. Pulled valve covers and started it. Everything looks fine, but crack throttle a bit and it ticks. Has a new Qft carb, Indy reman heads and Summit 444"hyd cam? Gonna do a compression check. Anything besides a burnt exh valve that could be the culprit. Noticed it seems awful rich at idle now too!!! Any chance I should be looking at ignition system or am I one of the unlucky ones that got a set of Indys crappy valve jobs? They have hardened seats, have around 5000 miles and ran fine til this morning. Any ideas would be helpful since I'm at work and don't have a lot of time to tear into it right now. Thanks
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Check out your plugs and wires. A dead cylinder will sound like an exhaust leak and when its running you will build crank case pressure. Thro a vaccum guage on it.
 
Dartish said:
Just ran compression test. All holes about 115 to 120 psi. 3 and 5 have about 5!!!! Low, compression 360, resurfaced heads and a flat deck on block according to machine shop that tanked it and cam bearinged it. Funny thing, it don't run hot, radiator hose don't get hard, oil is clean as can be and under hard throttle, seems to run fine. Just my luck
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I just went thru the same problem. Turns out I had some stuck lifters. Wasn't letting #5 exhaust close all the way
 
3-5 fire rings are .075 away from each other. Nice place for a blowout. Get to #1 TDC ( or where both valves are closed in 3 and 5) and pull 3-5 plugs. Blow through either and you should hear leakdown in other.
 
No compression on 3 & 5? Head gasket is blown out between cylinders
 
Heavy springs are good for the non floating thing that happens at high rpm's. But, you have to be sure your oiling system is up to the task. Good oil pressure just says you have pressure. Doesn't say #3 cam barring is partially covering an oil port.
 
Been busy doing my normal work since I'm on the clock. The springs are 509" lift singles that came on the heads from Indy. Haven't had time to do a leak test and probably won't. Appreciate everyone's input and ideas but after 44years every engine I've seen with no compression in neigboring cylinders always meant the same thing. Blew the gasket. And it always seems to be 3 and 5 or 4and 6. I've just never had, or noticed it ticking through the carb. Imagine it's the exhaust from one valve Coming up through the open intake valve on opposite cylinder
 
Anyone have an idea how thick the fel pro severe duty head gaskets are? Auto zone site just says they're the best in the world but doesn't give any specs. $30 each but if I don't have to replace them again it's worth it. Didn't think I'd have any problems with the blue fel pros either though
 
Not sure wich ones your looking at but felpro 1008 are .040 give or take, next thicker felpros are .054 iirc.
 
Dartish said:
Exhaust rockers all moved at first glance. Gonna pull shafts after compression test and see if I got a valve that mysteriosly sunk overnight. Ran great yesterday. Compession test will show something right?
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No. Not if an exhaust valve is not opening. It will pass a compression test.
 
It didn't pass a compression test 3 and 5 are dead. Rockers are all going up and down fine
 
Dartish said:
It didn't pass a compression test 3 and 5 are dead. Rockers are all going up and down fine
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I know. I saw your post. You had asked me a question. I was simply answering it.
 
Appreciate it. When I got time I did a lil more checking. 3 and 5 are Basically dead. All the rockers and valves are opening and closing. I'm guessing the gasket blew between the cylinders
 
Dartish said:
Appreciate it. When I got time I did a lil more checking. 3 and 5 are Basically dead. All the rockers and valves are opening and closing. I'm guessing the gasket blew between the cylinders
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Could well be.
 
Odd that it runs at 180 and the radiator hose don't get rock hard but since oils clean and it's not burning coolant, it must just be blowing compression from one cylinder to the other
 
I can throw a new gasket in, but I'm wondering why it won't just blow the new one. Machine shop said the block deck and heads we're fine and would hold the gasket just fine. Especially the fel pros and the low compression pistons
 
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