Compression check results, 440

[hemi68charger]

Hey gang.
I've got a miss in my 440 and I'm trying to troubleshoot. I have replaced the plugs, distributor and cap as well I swapped out a set of plug wires from my '69 500 I know work fine and as well swapped out a Edelbrock AFB I have for the OEM 4618SA AVS that was on it. Nothing seems to take away the obvious miss at idle. When you give it throttle, it's response is great and the engine runs smooth (or, shall I say I don't notice any missing). I just did a compression check on all the cylinders..

I got
test1/test2
1: 135/135
2: 135/135
3: 135/135
4: 140/140
5: 145/145
6: 130/130
7: 140/140
8: 140/145

All are within tolerances and min/max's according to the Factory Service manual...

These numbers look ok? My next "guess" will be there's a valve not opening up all the way or something to the extent it is maybe a cam issue?

[Chryco Psycho]

not a compression issue , more likely a vacuum leak starving one cylinder , I assume you have the power brake to the # 7 or 8 runner , try disconnecting it , any other possible leaks ?
I assume you did not drop any plugs when you swapped in the new ones ?

[John_Kunkel]

Hook up a vacuum gauge and report the readings and needle movement.

[hemi68charger]

Thanks guys for the suggestions..
Wouldn't me holding my hand over the air horn at idle show signs of a vacuum leak? i,e idle raises and smooths out if there is indeed a vacuum leak.

I'm going to try the coil and then plug off the power brake booster. Would WD-40 work similar to carb cleaner as far as spraying at the intake/head interface while running to see if there are any leaks or is it better to use carb cleaner? I know if I have a leak, then the rpm will increase and idle smooth out when I spray in the area of the leak, no?

T

[hemi68charger]

not a compression issue , more likely a vacuum leak starving one cylinder , I assume you have the power brake to the # 7 or 8 runner , try disconnecting it , any other possible leaks ?
I assume you did not drop any plugs when you swapped in the new ones ?

dropped any plugs when I swapped them out with new ones? No sure I follow that.. All old plugs out, new plugs in.........

[maxwellwedge]

Dropped on the floor and closed up the gap maybe....

[hemi68charger]

Dropped on the floor and closed up the gap maybe....

Ahhh... nope... nice detective work though.............. BUT, I think I may have found it in the realm of vacuum leaks. I took off the rear power brake booster hose and headlamp vacuum hose...

BTW: Well... I think I found the culprit... The headlamp vacuum hose. I removed both, started her up and hmmmmmm, it sounds/feels better. Then, I put on the power brake vacuum hose, still good. Then, I reinstalled the headlamp vacuum hose and it started back with the lump/lump/lump at idle...  Nowwwwwww, I'll go test drive the car and see what happens. If it's good-to-go, then it's aero-guy/'68-'69 Charger time to determine what is a main source of vacuum leaks in this system.....

Cheers,
Troy

[Budnicks]

Maybe just a lifter bleeding off a little more than others at idle, or maybe a worn camshaft, or maybe worn rockers or shafts that dosen't put the same pre-load on all the lifters, maybe inadequate fuel supply at idle, worn pump rod or eccentric on cam, fuel filter, do you have any other identifying noises or other symptoms ?  Just spit-balling here, it maybe non of them...

[Chryco Psycho]

dropping the plug can close the gap or crack the insulator

[hemi68charger]

Being that I found, at the manifold fitting, the culprit was the headlamp vacuum source, I isolated that system... Sure enough, the vacuum line going into the vacuum canister under the battery was off... Voila, instant vacuum leak.............

Thanks again for everyone's input......

T

[Chryco Psycho]

Cool , I ma glad you located the problem 

[hemi68charger]

Cool , I ma glad you located the problem 

In hindsight, when the car backfired upon starting while I was about to head home from a carshow, the hose must have gotten a nice pulse of air and hence popped off.. It was at that time I noticed the idle problem, but didn't attribute it to a problem with a vacuum leak or hose.... 

All's good on the Houston-front..

[Budnicks]

Cool , I ma glad you located the problem 

In hindsight, when the car backfired upon starting while I was about to head home from a carshow, the hose must have gotten a nice pulse of air and hence popped off.. It was at that time I noticed the idle problem, but didn't attribute it to a problem with a vacuum leak or hose.... 

All's good on the Houston-front..

Good to hear all better now...