power loss due to loss of compression

[66Sprint6]

Some of you prolly have been hearing about my drop in compression in the #1 cylinder. The car still runs well and strong at that, but I was wondering what I might be losing power wise due to the loss in compression. The compression check shows 180-185psi for 2-6 cylinders, but #1 is only at 90. What do yall think? Im interested because it already runs strong and it has half the compression in one cylinder, wonder what it will be like when I fix it.
Matt

 

[Anonymous]

Wow thats a huge differential; doesn't it run rough? That cylnder has got to be eating up a lot hp being not balanced compression wise with the other cylnders. I have a truck with the same problem only that the one cylnder is only off by 35 psi and its very noticeable at idle when driving I can here the difference and it's a V8

 

[66Sprint6]

It doesnt run too rough, but then again, I wouldnt know smooth if it bit me in the...anyways, lol. That car has idled rough since I can remember, and its the smoothest its ever been. It does have a bit of a "bump" or shake to it, and it IS almost like its in rythm at idle, so I wonder if thats it, the #1 cylinder. Man, I cant wait to get that fixed and see how much smoother it gets too!!!!!!! It used to make my dad car sick it was so bad.
Matt

 

[mugsy]

What is the lies per gallon like? I had the top ring in one cylinder basically gone and the motor got 13 mpg. It seems that most people here get close to 20 with a good motor. The mpg will also tell you if there are problems.

tanx,
Mugsy

 

[66Sprint6]

Oh boy, not sure what the mpg is to tell the truth, but it doesnt seem too aweful good. That may be because of my extremely heavy right foot tho, lol. I dont know. Im really hoping and praying its somethin simple I can fix, but if not, it still runs, Ill just have to get it fixed when I get a good break.
Matt

 

[SixFoFalcon]

When the original 170 started to die on me (138K abusive miles), I could feel the car getting sluggish off the launch but it felt fine at 2K rpm and up. I drove it around on 5 cylinders, and then 4 cylinders for a few months until I was unable to spin the bald tires in the rain. Finally pulled the head and found a nice hole in the top of piston #6, and #2 had a piece missing near the edge of the piston, and the adjacent cylinder wall was pretty badly scored. My dad, who was the real expert on engines at the time (me being 17 and all) couldn't really explain it except to say it was from abuse. I guess that's what happens when you drive around at WOT in first gear all the time. My dad wouldn't let me upgrade to a bigger engine until the first one blew, so I won that battle the only way I knew how.

Anyway, here's a quick test to see where you're leaking. Pull the plug on the weak cylinder. Use a small funnel to pour about 2 tbsp of 30 weight oil into the cylinder. Crank the engine (no start) for a few cycles to distribute the oil evenly. Recheck compression. If you gain considerable compression back, you are looking at leaky rings. If you gain nothing, the problem is probably a bad valve seat.

As far as how much HP you are losing, I'd say you are probably losing a few ponies right off the line, where you'll notice it most on the butt-dyno.

 

[66Sprint6]

SixFo,
We did the compression check with oil and the results were the same. Thats the only reason I havent concidered the rings as the culprit. Its funny you say everything was good after 2k rpm, mine runs like crap around 1500rpm but once she hits bout 17-1800 she is ready to FLY! Doin any speed at 1500 is just plain annoying it shakes so bad. Hope I can get her fixed tho, would like to get her runnin smooth all over! Thanks for the help, this is all encouraging!
Matt

 

[addo]

You've got a head issue for sure (the car, I mean ). Picking up "quality" at higher RPM is often a sign of running rich at lower speeds. This can be due to a burned valve or damaged seat. The low RPM manifold vacuum drops, and your carby power valve opens.

Ah well, easier to fix than the block.

 

[66Sprint6]

Addo,
So what your sayin is either way, the head is gonna have to be pulled. Im going to put the new seals in and see what that does, but I tell ya, Im bout fed up with this head. If I had the money, I would have a 78+ head on there, shoulda done that from the beginning
Matt

 

[mugsy]

Another thing to check on #1 cylinder... how are the rocker arms adjusted? Could it be that the arms are adjusted too tight and one of the valves are not closing all the way? A bad or leaky valve could be caused by lots of things, but try the simple fix first Then tear into the engine. My engine's compression was in the 140 range and I thought it was bag rings... well it was that AND the PO installed a newer, thicker head gasket without milling the head. But with your comression around 180 for the rest of the cylinders, it sounds good.

tanx,
Mugsy

 

[Anonymous]

what is the proper adjustment for a rocker arm?
c

 

[mugsy]

My '65 Shop manual gives a gap or "lash" specification after the push rod has been pushed down into the lifter all the way. Personally I have not found a good method of pushing the lifter down; I just tighten until the push rod is spinning s-lo-w-l-y. I don't know if this is correct or not. The manual shows a specific tool that is used that grabs the shaft and then pushed down in the arm near the push rod. The other way to do it, if the valve is being held open, is to just loosen the adjusting nut in small steps and see what happens.

tanx,
Mugsy

 

[addo]

I've never had luck with the bleed down method.

Most lifters will gradually spring up after sitting a while with no load - unless they're seriously sticky. I use the method where you set #1 on TDC compression first, and then rotate the motor for other adjustments. Remember it's a four stroke, firing order 153624. One third of a turn past #1TDC is #5TDC and so forth.

With the lifter adjustment backed off to the point your pushrod can be jiggled marginally in the socket, let it sit a few seconds to fully spring up, and check this again. Now gradually tighten the adjuster until you can no longer jiggle the pushrod up and down in its sockets. A shade more tightening and you should be able to notice a tiny drag when twiddling the rod between your fingers. From that point, one full turn of the adjuster and that's it. Do intake and exhaust on #1, then turn to #5 as described above, and continue through the motor.

Cheers, Adam.

 

[Anonymous]

ahh....my mechanic will love this info....

basically...that is over my head.

I am still working on "how a carb works" in my head...tooo....much...information.......

 

[mugsy]

Addo,

Thanks for the info. I didn't like my method, but I really didn't know WHAT to do to make it right. I just move the pushrod up and down until the play was gone, then twisted the pushrod until I felt drag. I bet my pushrods are still "loose". I'll give them the full turn after the lash is out.

Chaz,
This is all simple stuff; just remove the valve cover, look at the rocker arms and it should all come together. As for the carb thing, I bought books on Holleys and Quadrajets and read them. It also helps to have a carb that is apart because the drawings can be a challenge to follow. But carbs are real easy.

tanx,
Mugsy

 

[Anonymous]

i just sold my two 1100's to Butch here....I dont need them and it pays for my valve cover...

but I tried to see how one of the 1100 works. I took some of it apart.

then I took some of my spare holley apart...and thats how I figure out my linkage was sticking on my choke...

I am a visual hands on person. If you draw it or I can touch it, I can figure it out...verbal...no good

so I am sure if I open up the cover (which I will when I change to chrome) I can see a little more and understand it..

so far I have changes carbs, fuel pump, changed alternator and starter, added export and monte bar, and fixed the shifter linkage...all brand new to me

next I have to tackel removing the springs to chop them 1 inch...

MY BIGGEST FEAR IS I WONT GET IT BACK TOGETEHR RIGHT AND HAVE TO BE TOWED

[/i]

 

[Anonymous]

Here are more detailed instruction to what Adam has described above:
(this is also on Mike's FSPP site)
Valve adjustment - Hydraulic lifters only:
Disconnect the coil wire first for safety, making sure the motor won't accidentally start. Remove all the plugs, so that the engine is easier to rotate during the procedure. Make sure to mark your plug wires before disconnecting, so you don't mix up the firing order when reinstalling them.

Rotate the engine until the number one (#1) cylinder is on TDC just after the compression stroke (you can feel the compressed air by putting your finger over the spark plug hole). Now you can adjust the following valves:
#1 intake - #1 exhaust - #2 intake - #3 exhaust - #4 intake - #5 exhaust

rotate the engine until the number six (#6) cylinder is on TDC just after its compression stroke (one full revolution of the crank shaft). Now adjust the remainder of the valves:
#2 exhaust - #3 intake - #4 exhaust - #5 intake - #6 intake - #6 exhaust

Adjust the valves by backing off the adjuster so that the pushrod can be easily rotated between your thumb and forefinger. Then slowly tighten the adjuster until you can no longer rotate the pushrod. Tighten the adjuster an additional ¼ turn, for the proper preload on the hydraulic lifter.

Note: The valve adjustments should be done on an engine that has been warmed up. Make sure to let it cool off sufficiently so that you don't burn your fingers while rotating the pushrods. It is also a good idea to place a drop cloth or oil pan under the car/engine to prevent oil drips on the floor.

 

[mugsy]

Ragtopdudeman,

Thanks for the info. Sounds like I was a little too "gentle" when I did my adjustment . I figured it was better to be too loose than too tight 8) . Too tight can cause burnt valves and or expensive things .

tanx!!!

 

[addo]

The only real reason I go in thirds over two crank revolutions is that some longer duration cams might still be actuating the lifter if you just go the "one-two" stage adjustment. Plus it's a logical sequence that can be applied to any motor, as long as the firing order is known.