Nailhead advise

[BulldogDriver]

Well I thought I was going to fire my Nailhead back up after more then a year of working on the car.
 

Pulled the spark plugs out to prime the motor with oil and noticed that #2 cylinder was wet and black. All the others were fine. This motor had been rebuilt and has less then 500 miles on it.
 

So the first thing was to see if it had compression using my thumb and it did. Then did a leakdown test and with a 90# reference showed 72#. So next did a compression test on it to verify the tester wasn’t the problem and got 125#. Next went to check #4 cylinder and when I removed  the compression tester adapter this is what it looked like. I had checked with a plastic straw to make sure there was enough depth for the adapter and it appeared to be, but wasn’t  that lucky. Stuck a camera down in the cylinder and yes I can see some of the brass. 
 

So I’m going to try sucking the brass out of the cylinder. 
 

My question is if I can’t get all of the brass out am I going to have to put the cylinder head off? 

 

Ray

[telriv]

Bob,

 

The adapter that was used was too long & broke off a piece of brass. Blow in some air, make sure the valves are closed. Some pieces should blow out. Then crank it over WITHOUT the plug in & some more may come out. Brass is soft & shouldn't do any harm. He's lucky IF he has 8-1 compression with 125pds. of cranking compression.

 

Tom T.

[JohnD1956]

Will the brass stick to a magnet?  If so how about manually rotating the engine till the piston is near the top of it's cycle and then try running a magnetic pickup tool through the spark plug hole?

 

[telriv]

Sorry but brass is not magnetic.

[avgwarhawk]

Get the piston to top dead center. Use a long dowel with some sticky putty on the tip. Try to get out what you can.  Replace the plug and fire it up. Brass is soft. Should not cause any major issue as it gets blown out of the exhaust valve. 

[60FlatTop]

15 hours ago, BulldogDriver said:

 I had checked with a plastic straw to make sure there was enough depth for the adapter and it appeared to be

You had the conscious thought that the adapter was too long and took the step to verify. Interesting.

 

I have never done that while checking compression. I can't recall any time I was suspicious. But you were and your suspicion proved right. It is odd that the adapter chipped. Brass is pretty malleable and I would have expected it to be flattened. Colombo, Monk, and I wouldn't have been satisfied. The head is not that hard to remove. I would be more concerned at why it chipped. Or was it already chipped and you just noticed it?

 

On the retrieval of the chip, some "sticky stuff" on a piece of clothesline sized rope pushed in the hole at TDC would probably pull it out.

[arnulfo de l.a.]

I would pull the head if anything for peace of mind. I think that is BRONZE which is a harder alloy than brass and will do damage.

[BulldogDriver]

Thanks to all for the advise. I was able to get the few pieces of brass back out with compressed air and adapted a 3/8” copper tube to a vacuum. Did a compression check in all of the cylinders and they were all around 120-125#. Need to research this, I suspect the cam is not dialed in. 
 

Always something.

 

Ray

[telriv]

IF it was a stock rebuild with the available cast pistons, like I mentioned, your compression will likely be about 8-1.

Reason for the low compression readings.

Even IF the cam is not dialed in correctly, even IF it was, it will NOT be a major diff. in compression readings.

Again, just my thoughts on he subject.

 

Tom T.

[avgwarhawk]

Yes. 8-1 compression. Now, I see the cross hatch from honing.  The engine has 500 miles after rebuild.  The piston rings in the cylinder have not settled/seated in IMO.  It could take 500 more miles or more  to have that happen.  In short, the engine needs drive time.  The compression test in such a fresh rebuild may have been to soon.  Try to get out more broken compression tester and drive it. Let all of the rings seat.

Edited March 19, 2022 by avgwarhawk (see edit history)

[BulldogDriver]

Tom it was a stock rebuild. Cast pistons and not sure about the cam. Engine had been rebuilt about 20 years before but it sat on a dealership’s showroom all that time. I suspect they started the engine to move it around and nothing else. Cylinder walls were glazed so had them deglazed and new moly rings.

 

I thought stock engine was 165-175 psi. Did the rebuild with Best gaskets. I guess the extra thickness of the head gaskets have that great of a decrease in pressure. 
 

Engine ran good before deglazing, drove it cross country 3 years ago, and only noticed a problem when I pulled the intake to do the dual plane mod and block the heat ports to the carb. 
 

So tearing the front end off the engine isn’t going to be of much benefit on this build. I would rather not do something that doesn’t have much benefit. 
 

Your thoughts would be greatly appreciated. 
 

Ray

[telriv]

Ray,

 

EVERYBODY falls into the belief that the engine has 10.25 compression ratio from the factory. In reality the best I've EVER measured on a stock, original, un-rebuilt "Nail" from the factory was 9.75-1 & that's with the piston "in the hole" at .040" which is rare. Normally most sit in the hole approx. .055" for even lower compression. So now where are we?? About 9.5. Add to that the thicker head gaskets at a normal of .035"-.042" compressed thickness opposed to the stock shim gasket of approx. .015" compressed is a loss of approx. .77-1 compression loss. So now were at approx. 8.4-1 or less. 

Then add to that the ALL IMPORTANT quench/squish area, which should be a minimum of .025"-.050". This is VERY IMPORTANT for detonation resistance as well as power & fuel mileage. A stock piston in the hole at .040" with the stock shim head gasket is just slightly out of this important area. So not a big deal. At .055" in the hole we are, again, just outside this ideal quench/squish area at .070". Again, not ideal but much closer than the .125" or more. One reason that another same exact engine seems/appears to run & have more power than the next even built on the same day.

Now add to that a stock cast replacement piston sits in the hole at best .065". A loss of another .015" under stock to the more common at .080"-.095" & now you end up with closer to 8.1-1. Don't forget these replacements HAVE TO FIT all the different deck heights the engine could have been machined to at the factory. 

I've seen, & after the owner/machine shop added together ALL the facts/figures some came up with 7.5-1 or less.

Add all these factors/facts together & now you know how I can come up with that figure. 

You don't know how many calls I get asking questions about not having as much power as the original worn out engine had compared to their newly rebuilt engine. 

It ALL has to do with the details. 

That's one of the reasons I spent so much time designing MY forged pistons. Everyone is custom built for your engine & it's specs. that are provided to end up with a more ideal set-up. There hasn't been one set that has mirrored another in all the sets I've sold. 

Again, just my thoughts on the subject.

 

Tom T.

Edited May 5, 2022 by telriv (see edit history)

[BulldogDriver]

Tom

 

Thanks for the detailed explanation. All of the reading I’ve do on the forum has related to the optimistic numbers for compression on a nailhead.

 

I had a chance to think about the low compression numbers and realized that I hadn’t set the throttle wide open. A senior moment, the numbers are now in the 170# range. I feel a lot better about that. 
 

Was able to start the engine up for the first time in almost 2 years. Did a bunch of stuff over that time; SS exhaust, posi rear, fix stupid leaks, finish AC replacement, rebuild console, replace interior.
 

Might even get a chance to drive it by summer!

 

Ray

[XframeFX]

On 3/19/2022 at 9:13 AM, telriv said:

Add to that the thicker head gaskets at a normal of .035"-.042" compressed thickness opposed to the stock shim gasket of approx. .015" compressed is a loss of approx. .77-1 compression loss.

TX again Tom. Your pistons are definitely a major solution to this. Do you design them to compensate for composition head gaskets as well?

 

If doing just a valve job to a low mileage nailhead, will there ever be a source for replacement steel shim head gaskets?

 

I realize manufacturers see little compensation in producing parts for the long obsolete Nailhead. But today, we can buy one of several flavours of a particular part for SBC which is also obsolete.

Currently, Best Gasket is the 'best replacement head gasket" to use?

[telriv]

John B. & others.

 

I know it's been since March when the question was asked.  NO, I don't think Best head gaskets are the best.  They are ALSO  a thick gasket when compressed. They are liked because they have a slightly better tendency to stop oil leaks where the oil is feed into the rocker assemblies as they have a SLIGHTLY better sealing in this area as the Felpro gaskets & others as they are a multi layer gasket & oil has a tendency to leak between the layers of gasket material. It's mostly important where the rear hole dead heads at the block in the rear.  There is an easy solution to this, BLOCK off the oil hole. IF you measure the length of this hole you will find it's about 2" long. One end starts at the oil hole by the rocker stand the other ends at the head bolt. IF you use a #7 drill to enlarge this hole slightly it can now be tapped for a 1/4" Allen head set screw. Be careful as since this hole is at a slight angle a little material needs to be removed from the opposite end where the stand bolts to the head so the drill goes straight into the hole. Only drill down about 1 1/2". Tap & Install & tighten the set screw.  NOW oil can NEVER leak out this hole as it's permanently sealed. The set screw CAN'T come out from the top as the rocker bolt will prevent it from coming out of place. Same with the head bolt. Since you didn't drill all the way through & tightened the set screw it CAN'T dislodge in any way. Even if you did dill all the way through the head bolt itself will prevent it from coming out.

Shim steel gaskets I can get. 401's are easier as of this time. 425's are becoming harder to get since the 425 was only made late '63-'66, but they are available. 

 

Tom T.

 

Edited September 26, 2022 by telriv (see edit history)

[XframeFX]

On 5/5/2022 at 1:56 PM, telriv said:

I know it's been since March when the question was asked.

I discovered Tom's reply just now after a search for solutions to my lumpy JT.

 

No Silver Bullet without tearing things apart. It ran fine all through the 80's so taking small steps. Only major was a valve job in '93 and I did not like how it ran on startup. But then, I couldn't drive it with the rest of the car apart before being moth-balled.

Fast forward to the last 2 years where I've been driving it and trying to tame the beast, it runs fine below 170 degrees, doesn't even require choke/fast idle on cold start. Enjoyable ride to a car meet. The pattern is on the return trip, that idle! Oh, as of recent, a hint of black smoke on cold start for a few minutes.

 

FlatTop's tip on intake manifold distribution led me back to carburetion. 4 tan sparkplugs on the left side of the AFB and 4 sooty black plugs on the right primary throat. I swapped left/right metering rods. Now all 8 plugs are black.

I have $$$ in a rebuilt AFB otherwise, a 750 CFM 1411 E-Clone would be the next step. Maybe the carburetor is not the problem?

 

One step forward/2 steps backwards on this, any advise?

 

Also, on the head gasket. I used FELPRO. So what is the symptom when there's a leak in the oil passage? Lack of oil at the upper end? The oil leaks between the gasket layers to where? Combustion chamber? Cause of black plugs?

 

Hoping Ray's issues are solved. Haven't heard any follow-up.

 

Thanks!

 

 

 

 

 

 

Edited September 26, 2022 by XframeFX (see edit history)

[carbking]

If you changed metering rods from side to side and changed the richness of the carb, then:

 

(1) one of the metering rods is wrong/badly worn

(2) one of the step-up pistons is badly worn

(3) one of the step-up springs has lost its tension

 

If you have a micrometer, should be easy enough to determine which of the above.

 

The step-up pistons are a much softer aluminum alloy than the body casting, THUS THEY ARE SACRIFICIAL! They are designed to be changed at every carburetor rebuild. The better carb kits have them. The outer diameter should measure 0.405/0.406 inch.

 

Jon

[XframeFX]

8 hours ago, carbking said:

The step-up pistons are a much softer aluminum alloy than the body casting

Thanks Jon. I was unaware of soft pistons. They were quite tarnished when I had them out, springs were of equal height.

 

Adjusting the idle needle valve on the driver's side was successful (the side with once tan sparkplugs). However, the other side, no response.

 

So now, it's back to the AFB as the cause. Running rich as if the carb came from an entirely different engine. Certainly not meant for my 401.

 

My rebuilder used a NAPA Kit that obviously had no meter rod pistons. His claim to fame is having an ultrasonic cleaner. He then painted the carb silver.

 

There are Edelbrock 1411 carbs in stock locally, 750 CFM so, larger. Has anyone had success with this carb on a 401 out of the box?

 

 

 

 

 

 

Edited September 27, 2022 by XframeFX (see edit history)

[carbking]

John B. - before totally throwing rocks at your AFB, what is the identification number stamped on the edge of the flange? Should be 3503s.

 

If it is, remove the carb, turn it upside down, and examine the lower idle discharge port in each of the primary throttle bores. The casting is thin in this area, and I have seen a few that some ham-fisted "mechanic" split due to over-tightening of an idle mixture control screw.

 

If the number is not stamped, have the carburetor, a pencil eraser, a magnifying glass, a strong light, and a pair of young eyes, and call me.

 

If the number is the 3503s, and the castings are not damaged; rebuild it. One of the simplest of all carburetors to rebuild.

 

Jon.

Edited September 27, 2022 by carbking (see edit history)

[XframeFX]

3 hours ago, carbking said:

examine the lower idle discharge port in each of the primary throttle bores.

3503 it is. I have two and the unit on my Riv was the best as the other had an extra mounting hole drilled in the Flange probably by a "ham-fisted mechanic"🆖

 

Can barely see in the image (top image after the rebuild) but both ports were good when I had the AFB off. I was able to adjust both needle valves this PM. Had to turn the idle down low to see response from each needle.

 

Update today: I inspected the metering rod pistons and they were both scuffed on one side. Swapped with those from my 2nd 3503 which had identical rods but 1.5" springs instead of 1.28" springs in my carb. I used the longer springs along with the better pistons. You'd think longer springs would not help my rich condition but I'll see. All 4 pistons measured about .43" OD. Hopefully the seats are good.

 

I spent $400 on the rebuild and he had it done the next day. Seems he gave it a dip in his ultrasonic cleaner, threw in a NAPA Kit and a quick coat of aluminum spray. My expectation was a ready to run carb at that price.

He did not re-use my original clip on the accelerator pump. Can only mount the rod on the outer hole with an incorrect clip when the spec says middle hole (lower image)

 

More miles and then I'll check on those plugs again. Also, idle quality when up to temperature, my issue. No thumping below 170 degrees.

Once resolved, another oil change is in order. Everything smells of raw fuel, burned fuel and oil.

 

Sincere thanks on this.

 

 

 

 

Edited September 28, 2022 by XframeFX (see edit history)

[carbking]

John - the length of the springs is not the issue, it is the compressed tension.

 

Just making the assumption that both sets of your springs use the same diameter wire and same number of turns/unit, then the longer springs will be richer, as they would hold the piston higher. With the piston higher, a smaller diameter of the rod would be in the jet orifice.

 

After I wrote the above, I pulled the bill-of-material; and measured the spring.

 

Spring is 61-259, free length 1.31 inch.

 

Pull a used "spring clip" from your spare carb for the pump rod, although the outer hole results in the LEAST amount of pump shot.

 

EDIT: the rods should be stamped 16-219

 

Jon.

Edited September 28, 2022 by carbking (see edit history)