Blown head gasket on my 383? Now more of a diagnosis thread

[terrible one]

Well I noticed that I had some coolant dripping from the end of the radiator overflow a couple of times after a spirited drive, which seemed odd because the aftermarket mechanical gauge never went over 200 and I've got an 16psi cap so it shouldnt boil over until about 260 degrees. Yesterday I did a cold start with the rad cap off and noticed bubbles, really they were very small, more of a foam/ froth that increased with engine speed.

Like I said the car never ran hot and, at least from what could be seen by peeking in through the rad cap opening, no noticeable amount of coolant lost. I guess I'm lucky and it's a very small leak (right now) but either way it has to be addressed.

I've got the engine down to the long block, driver's header out of the way so that head is ready to be removed, the passenger header is hung on the front two studs and can't come off due to the inner fender/ shock tower. Will raise the engine a bit tonight and get that header out of the way, then get the heads off of there and see what we find.  

[cudaken]

While more than likely it is a head gasket, did you check for exhaust gas in the coolant? Very uncommon for a BB Mopar to blow a head gasket. 

Cuda Ken

[terrible one]

Admittedly no I did not, how can you check? I'm bad about jumping the gun, maybe I should hold off on pulling the heads?

EDIT: I searched and found something called a block tester that will test for combustion gasses. Of course the engine has to be running  But that is okay it is good peace of mind to see that the cam lobes and lifters are all good and I did have oil leaks at a couple of the intake runners. I will get it back together and do the combustion gas test

[Cooter]

Lemme guess no puke tank??(overflow jug)
Cars will do this.

[terrible one]

Lemme guess no puke tank??(overflow jug)
Cars will do this.

Affirmative.

Whew! I'm glad I made a post, that kept me from wasting my time. Now I'm just waiting on a valley pan and I'll be able to button her back up.

One other thing I might want to check while the intake is off is the lifter preload 

[rt green]

we use the block tester at work all the time. handy tool. I would have the rad cap tested also. for that matter, a new one is a cheap piece of mind. 

[terrible one]

we use the block tester at work all the time. handy tool. I would have the rad cap tested also. for that matter, a new one is a cheap piece of mind. 

Thanks for the heads up! My local Autozone has the block tester on their loaner program so I will be able to rent it for free. Valley pan will likely not get here until Tuesday but once it's here I can put it back together, then go rent the block checker and settle this for good. Hopefully it won't detect combustion gasses, my fingers are crossed!

[firefighter3931]

A compression test will also show a blown head gasket. Usually you will find two cylinders that read low right next to each other. The gasket usually fails between two cylinders where it is the narrowest. 


Ron

[rt green]

so, how did we come out?  all is well?

[terrible one]

A compression test will also show a blown head gasket. Usually you will find two cylinders that read low right next to each other. The gasket usually fails between two cylinders where it is the narrowest.  


Ron

Thanks Ron, I will put a compression test next on my list  

so, how did we come out?  all is well?

The valley pan came in today. I didn't have a chance to get to it earlier but if all goes well I will get it back together within the next couple of hours, or before the night is over anyways. I'm just about to go out to the garage. Then tomorrow I can flush/ fill the coolant for peace of mind (it's been in there for 4 years anyway) and make sure to purge any air bubbles. If I have enough time I'll go rent the block tester too, fingers are crossed, stay tuned  

[terrible one]

Got the car back together last night and was able to take it for a spin today.

I'm now pretty certain I don't have a head gasket problem. 

When I removed the intake and valley pan I noticed that there was some oil puddled in the bathtub and I could see that #6 runner seemed to have been sucking a bit of oil.

When I put it back together with the new valley pan I took the time to thoroughly clean all of the mating surfaces, check the fit of the intake with the pan and the paper gaskets to see if I needed them or not (didn't end up using any) and put some ultra black RTV at the corners.

This time around the vacuum gauge is pretty much steady and the reading is a little over 18". The needle flutters by about .5 to 1" on the gauge.

This started with an intermittent misfire, and when I borrowed a vacuum gauge the needle was bouncing kind of randomly between 15-18" of vacuum. It would sometimes smooth out a bit or get worse, depending on throttle but there wasn't a pattern to it. In hindsight, now that I have spent some time reading up on diagnosing with a vacuum gauge I can say that my symptoms seem much less like a blown headgasket between cylinders and closest to worn valve guides, which I think would be the same symptoms as the intake leak that I found. I think the the oil getting in the runner/ cylinder was complicating things and maybe causing the misfire  What do you guys think?

I will try and take a video of the vacuum gauge and post it here. But at this point I think I'm being a little bit paranoid about the needle fluttering, hopefully I've got a healthy engine. 

[terrible one]

I still haven't gone into town to rent the block tester, but today I had time to make a video with the vacuum gauge. If it matters, idle (trans in park) is 900RPM. I still see some weird fluttering going on and it's hard to see in the video but the needle has a slight buzzing/ vibration at all times.

https://www.youtube.com/watch?v=mPYqGtzW9VQ


I did some searching and found where someone on another forum mentioned that taking the vacuum reading from a particular cylinder/ port could cause the gauge to vibrate, which does make sense to me. The picture below is the tree that I hook the vacuum gauge to, and it is kind of "isolated" to the #7 cylinder. I wonder how the gauge would act if I hooked it to the base of the carb? I'll need to get a hose adapter or something because that's a 3/8 barb.

[firefighter3931]

Jackson,

The vacuum looks fine....nothing to be concerned about, inmo 

Best place to draw vacuum readings is at the base of the carb. 



Ron

[c00nhunterjoe]

http://www.therangerstation.com/Magazine/Summer2003/VacuumLeaks.htm

This has some decent gif's for vacuum gauges and what the needles will do in scenarios. Just remeber that cam changes will effect the total vacuum so pay more attention to the needle then the number.