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Old 08-11-2016, 08:45 AM   #21
Big hammer
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Default Re: Engine power

I just installed a rebuilt engine, doesn't have the power I think it should have.
Thinking out loud, is this a case if it isn't broke mess with it until it is?
Sometimes fresh engines don't seam to preform like we think they should !
Iam for drive it, get some miles on it before we condemn it. Just maybe when things become happy in their new home, it will be better! Optimistic Big Hammer :-)
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Old 08-11-2016, 08:49 AM   #22
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Default Re: Engine power

How does cam profiling help you with your current issue? If the cam were reground then all the lobes should be the same?
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Old 08-11-2016, 09:06 AM   #23
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Default Re: Engine power

Mitch//pa: Have not done leak down test. Idle is a little rough, Spark OK, I connected the blower end of a Shop-vac to the tail tile then to the carb. I used soapy water to check for leaks at manifold.

gweilbaker: Distributor seats and no wobble.

Big hammer: I do not like the difference between 1-2 and 3-4. Something is wrong.


tbirdtbird: I agree a reground cam should be correct. But a rebuilt engine should also be correct. Since it is not correct I did not assume that anything was correct so I am trying to check everything. I am going to check the resistance using the hand crank with the plugs out. I will report my findings. Thanks

Bob
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Old 08-11-2016, 09:26 AM   #24
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Default Re: Engine power

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Originally Posted by Bob Johnson View Post
I just installed a rebuilt short block. It did not have the power I thought it should have. One of the tests I did was to short out each spark plug one at a time while the engine was at idle. Shorting out plugs 1 or 2 would slow the engine down a little. Shorting out 3 or 4 would cause the engine to stop.

The short block is a complete rebuild. 0.040 under pistons, new babbitt, new valves, adjustable lifter, reground cam, Snyder 5.5 head. The carburetor and distributor are from the old engine, which ran good.

I have checked the following;
Compression -- 85-90
Timing -- Spot on
Valve timing -- Cyl 1 and 4 have almost identical valve timing profiles.
Manifold leaks -- Check intake and exhaust NO Leaks
Spark plugs -- New plugs, swaped them 3<>2, 1<>4 no difference
Distributor -- I set timing to 180 off and swapped spark plug wires 1<>4, 2<>3 no difference

I am out of ideas. Do you have any?

Bob
It may just need to be run in, My rebuild engine did not come alive till 400 miles and really turned on around 1500 s most likely it is just tight.
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Old 08-11-2016, 09:30 AM   #25
Bob Johnson
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Default Re: Engine power

Removed spark plugs. Using a torque wrench I found that the maximum torque to get the engine to turn over was 35 ft-lb. But the maximum to keep the engine turning was 25 ft-lb. Using the hand crank a sharp 1/4 turn pull will rotate the engine just over one full revolution. Is that too tight? Is there a better way to check for a tight engine?

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Old 08-11-2016, 09:40 AM   #26
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Bob, PM sent
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Old 08-11-2016, 09:40 AM   #27
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Default Re: Engine power

I spent 4K-5k and I did some of the things your doing( nervous)
I shorted out my plugs and yep 3-4 no difference. Keep the head nuts torqued, change the oil often, coolant in radiator, I had to adjust the points often until the points rub block wore in. With about 750 mi on it, it's now running smoother each time! If it does not over heat, no smoke out the tailpipe, bad noises,etc, I would get some miles on it before you condemn it, at one point I was ready to take my motor back and get my $$ back.
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Old 08-11-2016, 09:40 AM   #28
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Default Re: Engine power

True that a new engine will be tighter and needs to be broken in before it reaches full potential, but still the front 2 should be putting out equal power.

I would take the fan belt off so the air flow doesn't mess with this test, then use an unlit propane torch and move it around the intake and carb mount to check for vacuum leaks. If there is a leak, then the propane should make the engine smooth out and speed up. You should be able to do this test in one minute or so, and that short time should be fine with the belt off.

Also check the amount of spark at the tip of the screwdriver when you lay the blade against the top of the plug then move the tip toward the base of the plug. Each of my plugs gives about a quarter inch spark, and you can feel the same RPM drop.

With the bad distributor the other day #3 only gave about a 1/16" spark as I did the short to ground test.
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Old 08-11-2016, 11:11 AM   #29
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Dave PM sent
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Old 08-11-2016, 11:44 AM   #30
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Default Re: Engine power

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There are two rebuilders near Easter Island?
Vince,

See his latest location:

Maybe he is in deep water!!

I think that he might be in "THE WITNESS PROTECTION PROGRAM" ...

I see that he moved from Easter Island off the coast of Chile to The Marianas Trench in very deep water near Guam!!
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Old 08-11-2016, 11:48 AM   #31
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Default Re: Engine power

my cover is blown!
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Old 08-11-2016, 12:23 PM   #32
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Default Re: Engine power

Richen the mixture with carb cleaner and see if that smooths out the idle... A little dab will do ya very slowly metering it with a straw not full blast (trickle)...I like to use the wiper vac port.

Since you checked the valve lash and it's ok I am suprised you have not done a leak down to compare each hole

Last edited by Mitch//pa; 08-11-2016 at 12:49 PM.
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Old 08-11-2016, 10:12 PM   #33
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Tom,

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Old 08-11-2016, 10:50 PM   #34
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Default Re: Engine power

What's with all the PM's??? This is a forum.if you want to go off in the corner and whisper, then close out the thread.
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Old 08-11-2016, 11:03 PM   #35
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Default Re: Engine power

PM sent to the guy who knows how to use propane to find vacuum leaks and rich en mixtures...
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Old 08-11-2016, 11:41 PM   #36
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Default Re: Engine power

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What's with all the PM's??? This is a forum.if you want to go off in the corner and whisper, then close out the thread.
I agree. It's best to have everything here so we can all offer advice and all learn by the solution. I'm out of ideas and would like to hear other's ideas.

Can't wait for the solution, and wish I was closer so I could see the engine in person.

The only other check I can think of is to put the engine on a scope to see the spark pattern. My scope won't work until I slip some clear plastic tubing over the bronze spark plug strap. The inductive pickup won't work when it's in direct contact with the spark strap.
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Old 08-11-2016, 11:54 PM   #37
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Default Re: Engine power

This is a very interesting problem and i'm dying to hear what solves it.
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Old 08-12-2016, 12:09 AM   #38
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Default Re: Engine power

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Originally Posted by Tom Wesenberg View Post
I agree. It's best to have everything here so we can all offer advice and all learn by the solution. I'm out of ideas and would like to hear other's ideas.

Can't wait for the solution, and wish I was closer so I could see the engine in person.

The only other check I can think of is to put the engine on a scope to see the spark pattern. My scope won't work until I slip some clear plastic tubing over the bronze spark plug strap. The inductive pickup won't work when it's in direct contact with the spark strap.

I agree that putting it on a scope might help. I am struggling with a couple of the OP's statements.

1. shorting 3 or 4 kills the engine. It can't unless there is an ignition failure in some way... and since 1 & 2 are firing an engine can still run on 2.

2. need leakdown results as Mitch stated

3. separate the mechanical nature of troubleshooting of compression and leakdown vs ignition. Suck and blow/ vs ignition, distributor cam, and ignition components.

It was stated he feels it has low power.... not all engines perform the same.. and I think we can all agree on that!

I say perform all mechanical tests including leakdown on engine, then verifiy ignition and distributor primary and secondary for 100% . points,timing,plugs all set accurately, voltages checked, coil, condenser, dist body, etc verified.

Methodical troubleshooting is key and in order here.
Mike V.... I agree!
Please keep us posted on status.
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Old 08-12-2016, 01:09 AM   #39
Bob Johnson
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Default Re: Engine power

Leak down test.

I have my homemade leak down testing equipment (see picture below). The Restrictor is a plug with a 0.04" hole. I set the input pressure to 122 lbs. Then I measured the pressure in each cylinder. The results were;

1) 104
2) 106
3) 105
4) 106

The air was escaping into the bottom of the engine. This is consistent with other engine I have tested.



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Old 08-12-2016, 01:28 AM   #40
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Default Thinking out loud

Well not really out loud just thinking to the forum.

The main issue here is that shorting out plugs 1-2 do not slow down the idle very much. But shorting out 3-4 will stop the engine at idle. To me this suggests that 1-2 are not pulling their weight. I did short out both 3 and 4 but could only do it with the engine running well above idle. My first thought was why 1-2? How are 1-2 related. They share parts of the head gasket. They both run on the same intake port. They are both on the same part of the distributor horn. The compression test and leak down test would eliminate the head gasket as a problem. I swapped out the distributor horn and rotor. I also cross connected the distributor 1 <> 4 and 2 <> 3. So that should eliminate the distributor. I forced air into the carburetor intake and used soapy water to check for manifold leaks. (I will try starter fluid sprayed on the manifold to block area tomorrow). I took out the plugs and hand cranked the engine. It did not seem to be too tight. I have checked the camshaft profiles and they are all very similar.

I am running out of places to look. Why are 1-2 not as strong as 3-4?

Bob
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