Exhaust leak sound, but no leak??

What are you guys thoughts on this one. I have what sounds like an exhaust leak from the rear of the driver side head. It is not leaking anywhere around the exhaust. Any thoughts?

I am leaning toward a burnt valve, but not sure. I dont want to spend much money on this engine because the plan is to replace it in a year or so. I just want to fix it so I can drive it until then.

 

Oh and incidently, how do you get the search to work. I typed in 304 and it said no results. But when I just scroll through threads I see several 304 listings just in the classifieds.

 

Google is your friend.

Google -> "site:earlycj5.com for sale 304"

 

If you have a burnt valve, it will show up in a compression check. Did you look for a loose spark plug? Use a stethoscope to localize the sound.

 

When I disconnect the rear spark plug wire the noise goes away. I havent done a compression test yet, as my compression tester seems to have taken a crap. It sits at 0 all the time.

I may go buy a new one.

 

So when its getting spark, it makes a ticking sound but what you take spark away from the cylinder the noise goes away. Only difference then is there is no combustion in that cylinder which means less force on your valves so I would pop off the valve cover and take a look see. Hope you figure it out.

 

It could still be an exhaust leak. With no ignition, there is no combustion, and no hot exhaust gases. The pressure in the exhaust will be much lower if the cylinder does not fire.

 

We had a stethoscope on it and cannot find any exhaust leak. I ran it with the valve cover off a week or so ago and everything is moving up and down like is should, and no obvious abnormalities. I was hoping to find a broken rocker or something like that, but didnt. I found a 360 from a mid 70s motorhome for $400 that was rebuilt 25k ago, I may just pick up. Unless I can find a decent set of cheap heads I can throw in there temporarily.

I am suspecting a burnt valve.

 

Oh and thanks for the ideas. Keep em coming.

 

Dodge motorhome? Not the same as an AMC 360.

I would not jump to any conclusions... Not until I was able to identify the source of the noise.

 

Oh really? I was under the impression they were pretty much the same and I could use my intake, headers, distributor etc? I spoke to a local speed shop and they told me it would all work.

I just dont want to spend a ton of money on rebuilding heads on a 304 when I am going to upgrade in 6 months.

 

Nope. The Dodge engines are completely different from the AMC engines. Entirely different history and construction. The speed shop doesn't know what they are talking about. They are as different as a Ford 302 and a Chevy 302.

A surprisingly common mistake, often from people who think they know something about cars and engines - always good for a laugh and lots of derisive comments on the Wagoneer forum.

The AMC 360 has been around since 1970, and was derived from the AMC 343, introduced in 1966. Chrysler did not buy Jeep until 1987. Chrysler has its own line of V8 engines, including its 360.

 

Dodge and AMC engines are not interchangeable and share no engine parts. It can be a common mistake, when i contacted Summit about pistons for my AMC 360 they recommended MOPAR replacements, when I questioned the recommendation they said OOPS and changed to the correct replacement pistons.

 

Well, I admit, I am not familiar at all with Chrysler, Dodge or AMC. I have always had Chevy and I can rebuild an LS1 or a 350 in the dark, but this AMC is foreign to me. OK so it might be worth doing some work on the 304 heads.

OK so I will be looking for a differant shop to do any work for me. I have read that the 304 heads work well on a 360. IS that correct? or more misinformation? If that is the case, I dont mind doing up a set of 304 heads, if I can still use them on my 360.

 

304 on a 360 will work but have smaller valves. Would be restrict the breathing. I'm guessing smaller combustion chamber also. Have you determined what you actually have ?
On AMC blocks it is cast on the block on the side between the first and second freeze-casting plug, sometimes not easy to see, the motor mount may be in the way.

 

Yes, 360 heads will not fit on a 304, but vice-versa is ok. A 360 is just a 304 with a bigger bore and different heads. The bigger bore allows enough clearance for larger valves, thus the different heads.

If you want a 360, look around for one. A Wagoneer is the usual donor. Cheaper HP than hopping up the 304.

Nothing exotic about any of these engines ... Chevy, Dodge or AMC. They are conventional pushrod V8s that only differ in design details. If you can work on a Chevy, you can work on an AMC. Any one of the AMC-era factory manuals online will give you all the info you need to work on an AMC V8.

 

I read in some of the AMC hotrod sites that putting 304 heads on a 360 will actually increase HP. I am not entirely sure why. But then I have read other places that the 304 heads suck.

I figured the principles of the engine were pretty much the same. Nothing extraordinary. I have built many engines, but this is my first AMC. I almost scrapped the whole thing and threw a GM 350 in there, but if I can keep it AMC I think I will. My wife likes the old Wagoneers, so if I bought one as a donor, I fear I will end up just restoring it, and my CJ will end up on the back burner. LOL.

 

I saw a post claming 304 heads on a 360 produces more low end torque but it was a seat of the pants assessment. I have never seen anything to confirm that. Really doesn't make sense to me to mix and match parts, the 360's are pretty common around here and Wagoners are pretty cheep. I have seen 1 or 2 free but those were partially stripped missing parts and needing towed. 304's are not as common but I recall seeing a listing in Santa Fe's CL a few months back with 3 304's for sale so they are available.

 

that would be a dodge LA 360