Not all new, this engine came from a fellow hamber, was in another vehicle and was driven...although, i bet it was running on one dead cyl. for sure. I dont have the entire history of the build..but believe it was rebuilt to put in the truck it was in. I'll have to go back and ask if he remembers what was done..just to retrace and have knowledge very possibly this engine was running like this for them too, and they didnt know it.. if it wasnt for my EGT probes, i wouldnt know
i know it is a long shot ,but once i had a loose valve seat in a head after the seats were exchanged for hardened seats,, cold cranking compression was good but when running warmed up., the seat would loosen and drop compression on that cylinder,, drove me crazy until i found it, it only moved ever so slight ,just enough to drop off that cylinder
good thought, Ill check that too...how did you come to find that was your problem? i also did a "hot" compression check...engine at operating temp 180/190..still nice and respectable reading of 150#
im thinking...or leaning toward fuel related..or the Vacuum leak or maybe that pcv valve set up off the front carb base???...how did they run vac on these back in the day and not have this issue? both vac systems PCV is off the base (below Butterflies ) on front carb. vac for the distributor is off the center carb i think im picking at straws on this idea...but you never know eh? I'll block them off to see, never hurts to try
I'm guessing vacuum leak too,cap the pcv first and go from there. Had a sbc once with dual bolt pattern for carb (most do),and previous owner had drilled and helicoiled the pattern I wasn't using and drilled thru to the intake runner. My carb gasket only half covered the unused hole and that cyl was dead from the vacuum leak.
### Bingo !! Back in high school the auto teacher drilled this into everyones head !! But here's the trick, all of these need to happen at the correct time. So eliminate the things you know that are working 1 at a time and double check each function. Now I have had an engine fight me like this before. Have you backed the valve adjustment off on this cylinder to see if the preload is too tight ? Just a thought. And have you put a vaccum gauge on it ?? Good Luck >>>>.
is the intake a new one or a used one???use some carb.cleaner and spray the are around the intake while the engine is running if you have an increase in engine speed you have a crack or gasket leak.
Back in the 70's I put a new Edelbrock 4 bbl manifold on a customers 383, luckily it was a running car so I knew it was hitting on 8 when it came in,I fired it up it ran on 7. after spraying water, etc checking for vacuum leaks pulled the manifold back off found the port packed with casting sand up in the middle that never shook out. you know I check every manifold now, but have never run accross it again. you could pull the carb and run a welding wire down the port like I said I have never seen it since but you never know
Compression is also a function of the cam. The bigger the cam the lower the compession will read , overlap, So do all cyl read 150 or just that one??
Well, if you've got compression, your intake runner test shows it to be clear, you have no vacuum leaks, and you confirm a good plug and plug wire, I'd rotate the distributor 45 degrees one way or the other and move all the plug wires one tower over (depending whether you rotate clockwise or counterclockwise) If it's a distributor problem (ie cap with carbon track redirecting the spark to a different cylinder, bad or missing magnet in the Pertronix rotor, or some other weird issue) then the problem will move to either cylinder #2 or #8, again depending on which way you rotate the distributor. I'm subscribing to this one, it'll be interesting to see what you find. I didn't see anywhere previously in this post that confirmed you had spark to that cylinder, just that you'd looked at the plug, and also that you tried a different wire and the problem remained.
i timed the engine off #1 so the inductive pick up on my timing light said there is spark..and the plug also sparks when out and grounded..no carbon track...new cap..missing magnet on the pertronix rotor? dont think thats it either..it wouldnt spark if that was the case
just this one for now..but its the only one giving me trouble, i see no reason to question the 7 others that are doing their job.., and their numbers wouldnt create a problem for #1 cyl. anyways...but i will do a complete comp. check on all 8 tonight.
A long shot: Totally collapsed intake lifter? Cam pushes up, but valve does not open? Missing intake cam lobe?
this is where im at with this thing..most all points to something not allowing fuel mixture down the intake runner to #1 cyl..at least thats how it looks at this point.. a rag?..un punched intake gasket an intake gasket that breeched the valley, and its sucking crank case air and not pulling thru the intake runner for that cyl. or? something as an obstruction..
doesnt look that way when cranking it over with the valve cover off..right after it was running i pulled the cover and bumped her over...both lifters / rockers were in operation..not sure if the lift ratio is right yet or complete, but i will be measuring that tonight with my dial indicator.
I have a 283 that does the same thing. In the shop under no load the #1 Cylinder runs colder than the others. #2 is not AS hot but better than #1. I have tried all the things listed and more. It runs fine once you drive it and both come up to temp under load. It was worse with 3 two's than with the 4 barrel on it now. Has 12,000 miles on it and no problems other than at idle. Will idle all day no load up or missing or popping. Just the cold reading with my temp gun.
as cold as nothing going on in that bore? all other cyl..read 400+ on egt.. that cyl..is at 180/190..like the operating temp of the engine...no combustion going on.
I had one like mastadon mentioned earlier with a vaccum leak on one runner. Fixed the leak ran perfect. Just created a lean condition on one cylinder causing the plug to be dry. Engine cylinder is like any other air pump, draws from least path of resistance. If it draws in uncharged air then the plug will always look new and be dry. Could be intake gasket leaking on the underside if you can't find one on runner on top. Or something around the front carb like the PCV port, base gasket or something.
yep this is a possibility i need to look into also..im going to be going thru the process of elimination on this one...one step at a time
I would be looking at a vacuum leak on just that intake runner also. Here's something to ponder. I have told this before. Years ago I had a 283 with 327/300 heads and an edelbrock three duece manifold with three rottenchesters. Same deal only was #7. Solid 7 at idle. Wide open was fine, on all 8. The intake was for a 265 or 283. I squirted a little gas around the intake and wham, 8 cyls. I got a drop light and looked and the edge of the corner of the port was showing!! Did I fell like a dumbass. Ports were way bigger on the heads than the intake. Outside corner of the intake was actually smaller than the port in the head. It was in a 64 impala and I put it on in the car so didn't notice it. I think you are on to something with the under manifold leak theory. Lippy
What manifold and what carbs are you using? Check this thread: http://www.jalopyjournal.com/forum/showthread.php?t=447600&highlight=demon+six+shooter+problem
I haven't read every word but did anyone mention to put your hand over the secondary carbs to see if they are sucking vacuum at idle, aka blade fitment? I've had several of these 3 2's and had the same problem as you describe and that is a big issue! Good Luck!
I think people really undervalue or underestimate the usefulness of a vacuum gauge, hook one up to it and it will tell you the story of whats going on. http://www.earlycuda.org/tech/vacuum2.htm
yeah, working on that..one problem at a time...hahahha just didnt have the time to put one more thing into the mix
at this point , i dont think thats the issue..but im not ruleing it out..another thing i will be checking that was on my multiple "could be list"
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