sorry bout yer misfortune von but i gotta tell ya, this is a fascinating read on diagnosis. i may hafta keep checkin in just because of the knowledge and tuning info on display here. hope ya get her sorted out soon.
I may have missed it, but I don't think you have run the valve lash, just looked at the rockers and assumed they were working alright. If it were me that is one of the first things I would try, sounds like tight valves on that cylinder when running. If you have already done that, and can't find anything external, then pull the intake and check port match, and gasket integrity.
if you pull the pcv valve out and plug the hole in the valve cover you can put a vacuum gauge in the other valve cover and if you get a vacuum reading on the gauge your leak is under the manifold hope this helps R
Will be back at it tonight , and its supposed to be a real hot one today up here ,I'm just taking one step at a time . Checked for obstruction , negative. Undid the pcv from the front carb and blocked it off. Next test is tonight
Glad to hear it's NOT a plugged intake runner. I almost fired up a Poncho engine when I noticed something odd on the base of the plenum. There was a few bits of mud. After pulling the intake & doing a closer inspection, I found a Muddauber's nest in the runners to the rear cylinders. That would have been a friggin mess! Now I use a Boroscope on all used engines I buy.
i see no point in questioning the other 7 cyl. they are doing the job , that one has decided to not play along.. the other cyl..are not influencing this dead cyl. so i dont see the point. but the compression is good in the dead hole..so its something else, also if the valve lash was such that one of the valves in that cyl wasnt closing..i wouldnt get 150..(right)..? I do plan on doing a complete comp. check on all 8 , just not right now while im dealing with one problem child and i still havent ruled out the dropping of a valve seat,,i guess its also a possibility.. so im thinking lippy, and Highlander and others that follow the vac. issue is probably the problem, (i hope) I plugged off the pcv feed from the front carb, that sucker could really pull some air , and im going to try again tonight, if that doesnt cure it..on to blocking off the front and rear carbs to see if thats the issue. my plan is take the path of least resistance first, do 1 thing at a time, that way i will know what cured it, and go from there. i see no point in tearing off the upper end until i have exhausted all other possibilities. heat gun at 2 paces tonight after 5 by the time i got all my work done last night it was hot muggy and miserable, and 9:30 and i had already put in 10 hrs at a hot miserable job so i hit the shower and the sack
Because even though the vacuum is percieved as "even" it isn't at idle. It's pulsing 1 cyl to another. If it has any measure of a hipo cam that effect can be magnified or intesified. There's the possibility of the runner not matching also...single vac leak. As was discussed above, if the heads were cut, block decked, or both, there's no way to know if was done with the proper amount of "give a fuck". Coulda been some schmo doin his 8hrs. It is after all just a SBC. You're on the right path. You could "farmer" diagnose it too. Dribble a bit of fuel in the barrel closest to the runner and see what happens. Safest way is with an oil can. As I post this though, it's still a dual plane with a common center carb. No idle screws on the end carbs if I got that right. Then that would be simply poor distribution at idle and something that you may or may not want to fix. The fix would be a bigger jet for that side. Keep me in the loop. I'm winding down this fuckin Packard 12 project but I'm checkin in online now and then...
I hope this is it man..it has its possibilities. as far as the deck , fit and runner to that cyl. i looked at it..it matches well..so thats a good thing..i could see right down to the intake valve stem..clear sailing for any fuel if not interupted.. also noticed.. the runner to #3 runs under the runner for #1..and there is a rise in the floor of the plenum at that point..it could be acting like a "dam" when the plenum isnt properly saturated with fuel mist. or if there is a vac. draw large enough to upset the flow.. i didnt notice if off idle that cyl came to life, but i dont think so..i had it up to around maybe 2500 rpm or so, and still not life in that cyl...but that was before i disconnected the PCV and plugged the port.. today / tonight i will know if the pcv port was the problem or not..if not..on to blocking carbs..wish i had a set of thin plates to block with..i'll figure something out..one step at a time i know you been buisy..same here..but i still need to help you with that
Out of curiousity, have you tried switching the #1 plug to another cylinder? Didn't see it mentioned. Easy cheesy and gives another degree of confidence when moving toward the hard stuff. Sparking in air isn't really the same as sparking under cylinder pressure, and you may not see carbon tracking if it's got a manufacturing defect. Good luck!
Hey shifty yep , first thing i did..and than i went and bought new plugs..and they have lived in other cyl. thruout diagnosing this problem.. its fuel feed..im almost positive. plug looks just like it came out of the box....after its been running..the others are coming up nice and coco brown tan...this ones still white and clean looks just like a new Autolight 85 i think Wires good, cap good..i timed it with that cyl..the inductive pick up would have shown if that cyl wasnt firing..
Inductive pickup is not a test of plug fire, but will tell you if the ign system is throwing voltage. Subtle difference but can mislead the heck out of a troubleshooter. Definitely not the case here, hope you get er figured out soon. Good luck!
yes right you are..but it ruled out the cap, the coil, the wire and rotor..i stuck the plug against a ground and it fires.. They should be good..i moved a few of the new plugs around..no difference..#1 still dead.. im just hopeful that the location of the PCV into the back of the base on carb #1 (front carb) is the culprit..life couldnt be that easy for me..im a bit pesimistic..but i should know tonight. Im going to make that cyl fire even if i have to push fuel to it to prove its fuel related or not
I think I'd go ahead and take a compression check on the other seven just for the hell of it and write it down. At least down the road you can compare and guage engine condition later from it. Ok, now I may get some chuckles here but I think if the comp checks out ok, I would put the car together, and go run the crap out of it. As long as it's got good oil press ect... You guys are gonna think I'm nuts but I also would flood it once. You know not till it's running out the pipes, but just to where it starts hard once. I wonder since Fink described this runner arrangement if it's just got a dry runner. Since it's on the end. A dry runner will not get WET until it gets wet once. Capish? That sounded stupid didn't it? In other words, get them dueces kicked in cause it may be bad runner design and a cyl that's just a tad weak. Lippy
So if the theory about vacuum pulses is right then where you put a vacuum gauge is gonna make the reading of it diffrent? I don't see that. But that may or may not have anything to do with VRF's problem. I am gonna check my sbf with a temp gun to see what they read. Is there an audible diffrence if you pull the plug wire off while the engine is running??
Right on..I do intend to do a full comp check..eventually..im trying to keep my thoughts centered on this one thing for the moment.. my thinking is, the other 7 are living up to their job..I'll get to them later. and you may have something there in getting the runner to wet up.. with the pcv blocked off (the feed not the pcv its self) im going to run it up tonight..i plan on cracking all 3 WFO quickly after she warms up
A cylinder needs 3 things to work properly Compression Fuel Spark One of these is "off". My guess it's the carb not giving enough mixture to reach that far cylinder. Hey, it's just a guess. Also, I wonder if you have a hydraulic cam that's just a hair tight on lash. Try lashing those 2 valves like a solid stick at .005 just for the helluvit. If it fixes it, either the lash was tight and pumped a valve off it's seat when oil pressure comes up, or you have a weak valve spring
I'm about ready to drive over there, but it's almost lunch time. Wanna see if it's firing on #1? Pull that left side header off and start it. Make sure you don't have any gas sitting close by. Take the rpm up and take a look. If it will cook a corndog, it's ok. LOL. Lippy
You'd be surprised how a slightly weak valve spring will affect the idle. But, it'll work perfectly just above idle and beyond. Another quick way to check.....while it's idling with the valve cover off, take a good size flat screwdriver and twist slightly between two coils to increase spring pressure slightly and see if the motor smooths out. Again, I didn't read all posts, so I don't know if your prob is limited to idle only
Good point! The valve springs could be weak or wrong. But I would think with 150psi that at idle the valve spring would be better and not worse than at 2k or above. Keep this thought about the springs though. The PCV is definitely a strong possiblility. I will be awaiting your results tonight. Last thing, and it may be really crazy, is the intake manifold cracked between two runners, and that the fuel from #1 runner is being sucked into the other cylinder? You say that the #1 runner runs above #3. could it be cracked (or be defective, bad pour) above #3? Just because you get 150psi doesn't mean this could not be the issue. Hope it is only the PCV! I was also going to mention some weird scavenging of the headers that might cool the exhaust down more so than on other cylinders!
My SBF are all reading within 20 degrees of each other. I did notice that you have to get the laser dot centered an the tube to get an accurate reading. But you probably knew that. Are you only going by the temp guns reading that the cylinder is dead? I know you said the plug reading was diffrent. But since you haven't driven the car I don't see how a plug reading at no load is accurate. If it's dead, in a motor that small you should definately hear it even being a new motor to you.
I noticed you have Autolite plugs in it. Maybe it's Ford/Chevy related. Get a set of AC 45's and throw in it. Poor small block chevy, being treated like a Ford. Lippy
I would almost be inclined to take the intake manifold off, and put a single 4bbl manifold on it, to see if that fixes the problem. If nothing changes then it is in the block... if it does then it the intake or carbs.
"New" doesn't always make it "right". I see junk new shit too often. It's too easy to check by zero lashing temporarily to discount the possibility, rather than assume it's OK because it's new. But, it may be more likely one valve's a bit too tightly adjusted and when it bleeds down, it gives a good "cranking" compression reading. I'm just trying to cover the basics that often get ignored while one looks for a more complex problem
I think you missread my question. Im asking if you did a RUNNING compression test. Not if you checked ALL the other cylinders, which in the rules of K.I.S.S., would be first on the list. A compression test on a cranking engine is not a good diagnostic on a troubled diagnostic tree. Remove the plug, insert your compression tester, START the engine. CLEAR the comrpession you built while cranking and then take readings...you might be surprised at the EXTREME differences in cranking and RUNNING compression. Then, check compression while cranking and RUNNING on atleast one other cylinder. It will take you all of 5 minutes and sure beats pulling heads, intakes, carbs, measuring valve lash, inserting air through said cylinder. I say this after YEARS of finding other people missed diagnostics by running a RUNNING compression test. Or don't, and maybe im wrong.
Ever watch a 'professional' mechanic in a shop assemble heads? NEW springs every time, every shop? Some shops don't even check them. One in particular, a shop in Campbell, CA. Everybody all around thought this guy was THE engine builder. Not mentioning names, but Neal had a comeback on a simple SBC shortblock replacement that he did the heads on...Third time it was back, he had the covers off, and was bewildered. I pushed some valve rockers down with the heel of my hand, found it on the first one...others were soft, but one was like 8 pounds seat tension... He still denied it could be the problem...
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