Hey guys long story short my #6 cylinder has 0 psi of compression (others are 1-100, 2-120, 3-135, 4-115, 5-115) head gasket looked ok, the short block was rebuilt at some point (cylinder walls are beautifull and the pistons look newer) the head doesn't look a 1/4 as good though. so head is off, valves look good and so do the springs. thinking of having the following done:
-seals -guides -3 angle valve job -hot tank and clean -deck/shave to square the surface
how much do you guys think would be a reasonable price for the above work at a machine shop?!?!
hoping to take the truck to a show 4 hours away in 3 weeks.
should i replace the piston rings on #6 while the head is out for safe measure?!?! how do i measure the cylinders to see the size of overbore if any?!
this is just a "fix" i do plan on pulling the motor after the show and going through everything!!!!!
this is a 56 235 on a 54 cheby 3100
would greatly apreciate any responses!!!!
Last edited by coolerthanethan; 02/27/20088:50 PM.
I'd make sure I found out why the cylinder has absolutely no compression before I jumped in and spent a bunch of money on a cylinder head. You said that the head was off, start by turning the head upside down, make sure the spark plug is in and then fill the combustion chamber with solvent to see if the valves are leaking. I'd put the #6 piston at top dead center and make sure the edge of the piston isn't missing down to the ring land. Also check the pushrods to make sure that they are straight. Also maybe see if the cam lobes aren't rounded off causing the valves to not open. I've seen in the past that you can make the rest of the engine really worse off by over-doing the cylinder head Don
I'd make sure I found out why the cylinder has absolutely no compression before I jumped in and spent a bunch of money on a cylinder head. You said that the head was off, start by turning the head upside down, make sure the spark plug is in and then fill the combustion chamber with solvent to see if the valves are leaking. I'd put the #6 piston at top dead center and make sure the edge of the piston isn't missing down to the ring land. Also check the pushrods to make sure that they are straight. Also maybe see if the cam lobes aren't rounded off causing the valves to not open. I've seen in the past that you can make the rest of the engine really worse off by over-doing the cylinder head Don
thanks for the tip i'll check the piston and do the solvent trick you mentioned, the pushrods are straight and b4 i pulled the head i ran the motor with no valve cover and the valves were opening. the first sign of trouble before i tore into it was loss of power and it reved way quicker and higher than usual. i changed the oil pan gasket about 2 months ago and inspected the cam, rods and such and everything looked good. i plan on pulling the pan again this weekend.
There are only a few reasons why a cylinder would have 0 PSI with a compression check: 1) the intake valve doesn't open, 2) the piston doesn't move in the compression stoke, 3) a complete blockage of the intake passage in the head; 4) the check valve in your compression gauge didn't open during check of that particular cylinder. Do you mean really mean no measurable compression pressure, or just very low, such as to be taken as "zero"? Crowns occasionally break off pistons at one of the ring grooves, as mentioned, and will result in zero compression pressure, but they make a lot of noise (a huge amount) and cause a 'misfire' you would notice with the engine running. If the push rods and rocker arms are all functioning as you say, or even if not functioning fully, there will be valve action and air entering the cylinder, therefore some level of compression pressure. I can't picture a complete blockage of the intake port for that cylinder. Was that cylinder actually 'dead', as in not producing power? Given all you have said about appearances of everything you have taken apart, I suspect your compression gauge malfunctioned- I may be wrong with that, but if not, you may be going to needless expense to correct something that doesn't exist. There is an inconsistancy with your findings that needs to be resolved.
Before you take the oil pan off, turn the engine to see if all the pistons move as they should. If #6 piston doesn't move as it should, ok, take the oil pan off.
you know my jaw dropped when i saw 0psi yes actually 0 not 5 or 10 or 20 but a fat 0psi lol, soo much that i thought my cheap comp. gauge had busted so i went back to # 5 and ran that one a second time sure enough 115psi go back to #6 for the 2nd time 0psi again.
i noticed the truck running weak from one day to the next, i guess it was running on 5 cyl. and i also noticed like i said it reved up quicker then usuall and to higher rpms. i have yet to rotate the crank by hand but will this weekend. i'll report my findings. like i said i saw both valves moving up and down with no problem which is why i pulled the head. do rods on these motors go so easily? i broke a rod in a 302 ford once and the piston stayed up and the valves where slapping the heck out of it, it was extremelly loud and noticible!!! in this case i hear no unusual noises what so ever from the 235. i did have to turn my idle screw all the way up to keep the engine idling at around 800-900rpms as before the idle screw was 1/4 to 1/2 way for same rpm.
thanks alot for all your responses and please keep them coming!!!!!!
Last edited by coolerthanethan; 02/27/200811:29 PM.
The connecting rods are pretty durable, and if one failed, you would hear noise. And vibration if it broke and was thrashing around. When you did the compression check, did that cylinder should have sounded much different from the others- that is to say, no 'compression' sound. The broken piston is becoming more likely. If the head broke away from the skirt and stayed at the top of the cylinder, as it might under ring tension, you might not hear any noise; unlikely, but possible. The same condition you found with your Ford, but without the valves hitting the piston, and without the piston pieces banging together. This is all speculation so far. But at least, your compression gauge is working...
Cooler it sounds to me like you got a broken ring or a stuck ring . When you done the compression test was the motor cold or did you warm it up first? I have always been told that the engine temp had to be at least 180 before the rings would seat properly.
Something makes no sense on this problem. Short of a piston that didn't go up and down, the "hole" that allowed cylinder pressure to escape to atmosphere would have to be almost as large as the intake or exhaust valve opening...that's big!
A simple blown head gasket or stuck or broken ring would still allow the cylinder to build 'some pressure'.
If either valve was hung completely open, you would have other real obvious symptoms, and if the piston weren't going up and down, well...suffice it to say you would probably know that too.
Zero cylinder pressure on a compression test would have to have additional telltale symptoms....I think!
I would question the test procedure on that cylinder.
your valves may just be set to tight on number 6 or you may have a flat cam or broke spring cheack it out first and just fix whats broken unless you want to just trow money at it good luck
Seriously... For $75 I had the head on my 235 checked, all leaky valves reseated (3), All sticking valves freed up (6) and surface milled .010 to get it flat. But I knew that these things needed fixing.
Cooler it sounds to me like you got a broken ring or a stuck ring . When you done the compression test was the motor cold or did you warm it up first? I have always been told that the engine temp had to be at least 180 before the rings would seat properly.
SLICKT
i ran the engine for about 15 min before i did the comp. test.
No compression in one cylinder, next cylinder has normal compression, zero again on the offending cylinder: gauge seems to be working.
Head is off, all valves appear to be 'normal', no broken or badly burned valves; therefore, valves are not the cause of 0 PSI.
Had visible valve action before removing the head: no inoperative valves, therefore air is getting into the cylinder, and being more or less contained by the valves, so some compression pressure would be measureable.
If the timing gear broke during operation, the engine would have stopped where it was, and there would have been noise during the last few revolutions. Compression could be zero or very low in some cylinders, depending on valve position, if the camshaft didn't turn during the compression check, but 5 cylinders have reasonably normal compression. Conclusion: timing gear is not broken and camshaft is turning.
Engine seemed to lack power the last time the vehicle was driven, no reported noise during the last operation. Is that a fair statement?
So: air in reasonable quantity is getting into all the cylinders; examination indicates no broken valves, the head gasket is in reasonable condition, and there are no holes in pistons. At this point, a broken piston with the crown separated from the skirt, above the wrist pin seems the most likely possibility. Turn the engine, fuel line plugged, and see if all the pistons move as expected; if one doen't go up and down as it should, there lies the trouble.
Yes...do keep in touch, and take pictures too. The split personality piston diagnosis would be about the only way for this to exist, and it certainly would fit the bill for Ripley's Believe it or Not.
ok here are my findings for the weekend. rotated the crank by hand all pistons including #6 move up and down beautifully. cleaned up the piston surfaces and turns out they are 040 over. as i thought when i pulled the pan before the short block has been previously rebuilt, and doesn't see to have many miles on since.
put the head on the bench upside down and level put some gas in the #6 chamber and left it for about 30 min. came back and none had leaked through. so i pulled the 2 valves springs and noticed the intake valve had some noticeable play in the guide and would slide right out, as the exhaust valve moved up and down freely BUT had to be turned side to side to be pulled out and had 0 play.
i then put both valves on the bench and spun them and both spin true and don't seem bent at all, although both have a few nicks on their edges.
i also took a closer look at the head gasket sealing lines on both the block and head to see if there might have been a leak through there. judging from the head and block and condition of the gasket looks like there was a good seal all the way around.
i forgot to check the pushrods for straightness but i can do that tonite.
i also noticed that the #6 valves had the most carbon build up by far of all cylinders
so could a small amount of play on the intake guide/valve cause the 0psi? thats the only thing i can think off. i'm thinking of going ahead with the head rebuild new gaskets and hope for the best. unless anyone has any better suggestions?!?!?
Hey Cooler. PLEASE remove the photos above and provide links to them only. We have a strick policy of not allowing photos on the Page as the space for them costs far too much to allow for them. Thank You.
Hey Cooler. PLEASE remove the photos above and provide links to them only. We have a strick policy of not allowing photos on the Page as the space for them costs far too much to allow for them. Thank You.
Cooler, Were you able to do a leak down test before pulling the head? This would tell you where the air is going-(crankcase, exhaust, head, cooling system etc.
Very nice videos and pictures. No, the looseness in a valve guide wouldn't cause 0 PSI compression. The tightness you described with the exhaust valve is not unusual, but might indicate carbon build-up on the stem- from valve guide wear or the stem O ring seal leaking.
As a bit of insight, make sure all the valve springs are installed right side up- the ones in your picture are correct, with the close coils at the bottom. A spring being upside down won't cause 0 compression, but it likely will lead to valve breakage, a hole in a piston, a lot of noise and shaking before you stop the engine, then 0 compression in that cylinder. But from all evidence, you aren't there yet- fortunately.
I agree with atomarc- there is still something missing here. Back to a malfunction with your compression gauge? While that likelyhood seems to have been eliminated by your previous checks, your disassembly and accompanying pictures haven't shown any explanation for the loss of compression. What did the engine sound like when you did the original compression check? With all the spark plugs out, and the gauge attached to a cylinder with zero PSI, you would only hear the normal starter "whirring" of no compression, not the usual "grunt" (for lack of a better word) of compression. Do you remember what you heard for that test?
This is a hard one so Ill ask the obvious. I am sure you have done this but did you check compresion with just your finger? I did hear of an engine with a crack and wedge of metal missing were the spark pulg threaded in, very low compression but not 0. like I said a hard one.
I have a few questions on rebuilding a 235. Most of the kits I have found a listed for a 57 and engine. The serial #s on my 54 tell me that it is a 55 engine and head. Will these 57 and up work on my earlier motor? What are the differences? I know that later engines used different lifters, are they interchangable? The best and most complete and economical kit I have found is from Northern Auto Parts. Has anyone used it? I believe it has a Federal Mogul cam, is it any good?
You might want to make sure that the bad cylinder had the correct length pushrods or could it have been possible that the valves were set to tight and holding the valves open? Just a couple ideas.
well guys thanks for all the responses and help. i ended up dropping off the head at the machine shop earlier this week, should have it back hopefully sometime next week. i'll throw it all back together adjust the valves and see where i am. i'll keep you guys posted!!!
well got word back from the machine shop. good news is head will be done tmrw. bad news is the bill.......... $399.00
after magnafluxing the valves they found cracks in most of the intake valves and some exhaust valves. the valves on # 6 being the worse, he said were not too far from breaking clean off on the stem. the valve springs all checked in at half or less the rate the specs call for. and to top it off pretty much all the guides need replaced. so i'm getting all new valves, springs, guides, seals, valve job, decking .008 and a complete head gasket kit for the above mentioned price. i guess its a fair price for the parts and labor, i'm just glad one of those valves didn't break before and destroy my clean rebuilt shortblock. will be throwing everything back together this weekend and i'll post the results along with some pics.
so far you've spent 399.00 plus your time and you still don't know why you had zero compression in that cylinder. I'd do more homework before you put things together to make sure you have things in order/know whats going on.
so far you've spent 399.00 plus your time and you still don't know why you had zero compression in that cylinder. I'd do more homework before you put things together to make sure you have things in order/know whats going on.
well considering everything i've checked and that the valves on number six were probably stuck open from A: tired 60 year old springs and B: possibly overtightened rockers. my money is on the head. if you or anyone else has anything else for me to troubleshoot b4 throwing it all back together be my guest and point me in the right direction. but imo there is really not much else?!?!
i was planning on having the head rebuilt at some point in time in the future when i pulled and freshened the motor anyways. so it's not like i wouldn't have spent the $399 sooner or later. I AM however very glad i'm not gonna need to rebuild the shortblock because of a dropped valve!
Last edited by coolerthanethan; 03/12/20087:33 PM.
ok guys well here is the scoop. everything is back together......
previous compression test:
1-100, 2-120, 3-135, 4-115, 5-115, 6-0
compression test with rebuilt head, no other changes
1-150, 2-155, 3-155, 4-145, 5-145, 6-160
yeap the worse cylinder is now the best!!! picked up at least 15-20 horsepower. truck is quieter, revs easier, picks up was faster.
had a minor issue with the rocker oiling system which maybe you guys can help with?!?! the oil isn't making it up the tube and instead coming out around the oiling tube. any fixes for this issue?!?! i made a video to show it (i hadn't adjusted the valves yet on it, why the rockers are noisy)
also had another minor issue with overheating. i had noticed the head gasket water passages were about 1/4-1/2 the size of the passages on the block/head. so i said to myself i'd trim them. however i forgot to and just bolted on the head. well the truck used to never overheat, used to run in the middle of the gauge and now its almost all the way up top. this with a 160 stat and an aluminum radiator. i'm pulling out the stat as a temp fix but will eventually need to replace the head gasket and trim the passages. anyways just thought you guys should know for future reference.
Pulling out the stat is not a good fix, and never run the engine long without adjusting the valves. In fact, a poor valve adjustment may be why the engine is overheating.
Paint & Body Shop moderator A lone amateur built the Ark. A large group of professionals built the Titanic.
Ok, cooler, glad to hear you finally have compression, and the price with gaskets is pretty reasonable. Its reasonable to assume at this point that the valves for that cylinder were at least sticky and not closing properly. Now, at the risk of being the bearer of bad news, the spring on no. 4 intake valve is upside down- your pictures show that, and it needs to be corrected. The close coils go at the bottom. The others look all right, as much as I could tell. You may be able to change the spring without taking the head off; you have to be careful, and keep the cylinder pressurized with air, so the valve doesn't fall into the cylinder. Then you have to take the head off...
For added emphasis, don't let anyone talk you out of changing that spring, even if you have to buy another head gasket set. You will regret it in the future if you don't take care of that now.
As for the rocker arm oil, it often takes a few minutes for oil to be delivered up there, but after 2-3 minutes there should be plenty of oil. A likely cause of that trouble is that the line is plugged. It passes through the block and attaches to the oil galley on the left side of the engine. Try disconnecting it from the galley and rocker arms, and blowing compressed air through it. That may work. If not, leave it disconnected at both ends and fill the tube with carburetor cleaner- strong stuff that has xylene, acetone and tolulene as components. Berrymans Chemtool is a good one. But be careful with it- that stuff is also paint remover.
Doesn't the supply tube for the center oiler on this year engine come off the rear cam journal...I think it does. The earlier (much) engines had the supply tube from oil distributor, through the water jacket and into the center oiler.
As Tiny would say...I might be full of crap on this.
I just looked at the pictures and it sure does look like one spring on #4 has the tight coils up. It might be my bad drugs but it also looks like there is a huge amount of valve stem sticking up above the retainers!
Do those valves have the two grooves and the keepers were put in the bottom groove..the one the oil control ring goes in.
I'm not sure, but I looked at a picture in a service manual and the amount of stem protruding doesn't seem to be anywhere what Coolers pictures (nice) show.
Stuart, I think you are correct about the oil line- in the pictures it appears to connect to the back of the block, rather than near the center as it does with the older engines. That raises the question of whether the oil line is plugged or the camshaft bearing is installed incorrectly. A quick check on the bearing would be to disconnect the oil line at the block connection and run the engine to see what comes out of the port. Hopefully, a good squirt of oil. If not???
As I remember, the intake valve tips are quite a bit longer above the spring than are the exhaust tips- but that is a pretty foggy memory right now.
And while you're at it, check to be sure the springs are down in the recessed area of the head where they belong and no hung up on the edge. I found that on two of mine when I got it back from the rebuilder.
Are you still having trouble getting oil to your rockers? One cause can be by not replacing the one head bolt with the oil passage built in. The factory bolt is drilled with a 1/8th hole which allows oil to rocker shaft. I beleive '55 to '62 235 heads had this bolt. It has to be located in that oil passage hole. Good luck, Greatdane
