Missing on one cylinder - 351C

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boilermaster

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Hey Dude,

Good enough picture for me to agree with Don C. you had a leak.

Please follow up with C9ZX's advice about the valve springs.

Still take my advice about measuring the cam's lobe lifts.

Give each pushrod a spin while both valves are closed on each cylinder to see if any are bent. 

There are a few different ways to establish correct lifter preload, however the amount of preload can vary, depending what brand and vintage of

lifter is used.

I would still like to see some pictures of your lifters (still installed) with the pushrods intact.

At this point we do not know if there is a problem or not, so there is no point in disturbing their settings until camshaft lobe lift is determined to be good or not.

I am sure how I would go about this, but I don't know your skill level

Please understand why I want you to take this one step at a time

Boilermaster

 
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On measuring the cam lobes, do you have either a dial or digital caliper, or a dial indicator? I would leave the lifter in place, easier to tell when you're at the base or peak of the lobe. Slowly turn the engine by hand while pushing down on the lifter, measure the difference between the lobe peak and base. Watching a dial indicator is the easiest way to get the peak and base readings.

 
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That's definitely a big enough leak to cause enough oil to quickly foul the plug, as well a making it too lean to fire before it starts sucking in oil.

With that much of the gasket missing I would want to make sure it isn't stuck in one of the valves.

I think Chuck (c9zx) also had this kind of failure.
Yes, I did. It was on a Boss 302 but, same problem, sorry azz print-o-leak fel-pro gaskets. Use anything else. Chuck

 
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Thanks again everyone for all the replies and helpful info. I have a set of digital calipers. Can I use that to measure the the cam? If so how? I'm not sure how to get a fixed point to reference and where to even measure from.

And I'm about to order some gaskets and new bolts and we not have one vote for Felpro and one against so we'll see how we end up. These look like Felpros that are on it so I am tempted to go elsewhere.

 
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Couple of people have used the Mr. Gasket part and said it worked fine. SCE and Cometic make quality parts and are available in different thickness, if you need that. Chuck

 
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Does your calipers have a depth measurement rod? If not, you won't be able to use them. If so, slowly turn the crankshaft by hand while pushing down on the lifter, until the lifter is at it's lowest point. Measure from a point on the lifter guide to the top of the lifter, and mark that point. Turn the crankshaft until the lifter is at it's highest point. Measure from the same point on the lifter guide to the top of the lifter. Calculate the difference between the lobe peak and base.

 
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Does your calipers have a depth measurement rod? If not, you won't be able to use them. If so, slowly turn the crankshaft by hand while pushing down on the lifter, until the lifter is at it's lowest point. Measure from a point on the lifter guide to the top of the lifter, and mark that point.  Turn the crankshaft until the lifter is at it's highest point. Measure from the same point on the lifter guide to the top of the lifter. Calculate the difference between the lobe peak and base.
Had a few minutes to try and get a measurement or two. This is just ballpark as I was doing this myself in the dark and really couldn't get a good angle. But a quick check of both intake and exhaust lifters are about .340. Again I need to check this again when I get some help and some better light, but that's what I'm seeing at the moment. Is that good, bad, other?

Thanks!   

https://lh3.googleusercontent.com/GfCF7am_oMbXzPtXEN2EgyzsIcndhG8PhxD4s550j7fziCEZrnxIJpARFEr6GRQw0VHodfkAR0ed6mP-u_DIdaOQlQgEUS1qreN7AV4q_CEauYlv5hAIXX5QTWQ7M39nsRCBMDDZav0=w1204-h903-no[/img]

 

boilermaster

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Dude,

Pretty good picture there.

it clearly shows that the #1 cylinder intake gasket is/was messed up.

shows a clean engine with what looks like aftermarket hardened pushrods.

in the picture you just posted  1 cylinder intake is at or near it's base and #1 exhaust is at or near full lift.

it appears to me that you do have hydraulic lifters.

Looking at your video that you posted earlier, I am GUESSING that you may have either Crane or Comp cams roller rockers.

if anyone thinks differently please respond.

that PROBABLY means that you could have a rocker arm ratio of 1.73 (comp) or 1.7 (crane)

So 0.340'' x 1.73 = 0.588 lift at the valve and 0.340'' x 1.70 = 0.578'' if you measured as Don C posted.

Just as an example (you should of had a distance measurement from the top of the lifter to the block, say 0.060'' then you rotate the engine until you get the highest lift from the cam lobe, 0.340'' so 0.340''- 0.060'' = 0.280'' that would be 0.484'' @1.73 and 0.476 @ 1.70 ratio.)

The 0.588'' and 0.578'' calculations are both pretty high lifts and in the example that I gave would be pretty close to a 351c 4v stock cam.

I am choosing to not comment on what i see in regards to lifter preload just yet, because in that case a picture is worth nothing.

I am hoping that you will measure all 16 cam lobes and give actual lifts and post results before we get into lifter preload because you CAN have perfect lobe lift and still have a collapsed lifter or lifters.

If you have 0.340'' lobe lift and the lifters are NOT collapsed, that will make some good heat in that #1 hole.

Boilermaster

 
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Amazing feedback as before. Again thanks much for helping me get this sorted. I think you are right about the Comp rockers, looking around at photos, this is the closest I've seen to what is in this motor. They might be slightly different, but far closer than anything else I've looked at. 

COMP Cams High Energy Die-Cast Aluminum Rocker Arms

Yes I will go back and measure them all and post before putting this back together. 

On a different note, this intake does have a heat crossover. The old gaskets didn't have an opening for this so one side was still covered, the other was burned through. I'm thinking of blocking the hole with some thin aluminum. Any downside to doing that? We don't really get winter here so I'd just assume have the top of the engine cooler. 

Thanks

 
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Heat crossover, Do you really need it on your car? are you using an Autolite 4300 carb? If not. no you don't need that crossover in my opinion. I blocked mine off as I'm using a Holley 670 carb. This is on a 71 4V by the way, so I'm assuming they're basically the same. I did this because there is no need for heat under the carb, plus it will, burn the base plate even with a steel insert gasket. Heat will vaporize the fuel and can cause hard hot starting, did on mine anyway.

A thin piece of aluminum won't last 5 minutes. There are I believe, gaskets that are supposed to block off the heat riser, but sorry, I have no reference to them.

The option I chose was to insert 1/16" SS plates into the intake, plus use a small piece of .020" thick SS carefully inserted into the gasket. Over this insert, I smeared a small amount of exhaust sealing paste for good luck. That was done 4 years ago now and has worked very well. An infra-red thermometer shows even temps all over the intake, no hot spots around the carb and the car start without issue when hot.

Here's a pic.



Block off plate is recessed into the opening, then "stitched" in place with a center punch in about 6 locations. (Blue arrows)



 
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OK cool, I didn't think it was needed and seemed like it could hurt performance once up to temp. I'm running an Edelbrock Performer 1407. Aluminum melts at around 1,200°F. The exhaust gas is hot, but surely not that hot? I was thinking a small piece behind the gasket on the head side. That said, I do like the idea of dealing with this at the intake like you did.

Thanks

 
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Seems kind of counterintuitive, having a turkey pan gasket to keep hot oil off the intake, but then put in an exhaust crossover through the intake manifold. Maybe some, but not completely. The crossover served two purposes, one is to warm the carburetor base to improve fuel atomization in cold weather and the other is to heat up the choke stove so the automatic choke would open.

If you still have the mechanical automatic choke with the choke stove inserted into the intake manifold, do not block off the crossover.

Older cars used to have a flapper with a thermostatic spring, to open and close the flapper, that would close when cold and partially block the exhaust manifold on one side to force hot exhaust through the intake manifold crossover. These typically rusted shut after a year or two. A favorite trick was to block the intake manifold crossover to give a more staccato exhaust note, especially on deceleration (back-rap). This was before "H" and "X" pipes. I think the thermostatic flappers were phased out about the same time exhaust pipe crossovers started being used.

 
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OK cool, I didn't think it was needed and seemed like it could hurt performance once up to temp. I'm running an Edelbrock Performer 1407. Aluminum melts at around 1,200°F. The exhaust gas is hot, but surely not that hot? I was thinking a small piece behind the gasket on the head side. That said, I do like the idea of dealing with this at the intake like you did.

Thanks
 Dude, I don't really think I'd trust a thin piece of aluminum to stand up to constant heating. Even at 1200 f melt point, under the intense focused heat I don't think I want to risk pulling the intake to do again. Just my thought on it. I wasn't even sure that .020" piece of SS would last long.

On mine, I did remove the stove tube, cut it off and put the cap back on. Another little thing I did was to thread and screw in a couple 5/16 set screw in the holes that are in the corners of the carb base, just another block off just in case the other end let go. Add to that, I also have a metal insert gasket under the 1" fiber spacer I use. My goal was to keep my carb cooler and it works. The car only gets driven in summer, so heat is not needed. By the way, I do have the original 4300 4V and the base plate is so burned, the entire carb is useless without it being replaced, not that I'd ever want to use it!

I posted some time ago on exactly how I modded the intake block off.

Geoff.

 
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Measured the rest of the lifters and got from .323 to .340 on all of them. I chalk up the variance on poor angles and accessibility. Most were on the lower end of that range.

Then spent an hour or so just trying to get the old gasket off. Got about 1.5 cylinders cleared. I need to get a stiffer putty knife and I'm tempted to use a torch briefly. If you have some magic there in all ears [emoji3]

Got the broken bolt out. Looks like the old one was a tad too long and ran out of threads when trying to torque it down.

FWIW I also spun each push rod to look for any obvious bends and didn't see anything.

 
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Intake back on today. Letting everything dry overnight before trying it out again. Will report back and thanks again for all the amazing help on this.

 
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Started up today and the good news is that all 8 are hot and it sounds better. Bad news is it looks like I did a crappy job on the Permatex on the rear manifold seal as it's leaking oil like crazy. So looks like I need to start over with pulling the intake off. Not sure what I missed, spent a lot of time making sure things were clean and well prepped. Oh well.

Said it before, but thanks again for all the help getting this far and helping get thins sorted out.

Thanks

 
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I didn't see the oil coming out, but assumed it's the manifold seal as I didn't touch the sensor and that whole area was full of oil. I'll confirm before ripping things apart.

 
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I didn't see the oil coming out, but assumed it's the manifold seal as I didn't touch the sensor and that whole area was full of oil. I'll confirm before ripping things apart.
Back in 2016 when my motor had to be rebuilt again, I had a major leak there too. The engine builder put the rubber end seals in against my request not to, so I assumed that was the cause of the leak. I pulled the intake and reassembled it using a good 1/4" + bead of "The Right Stuff". Tip here, make sure you extend the bead up about a 1/2" from the corners where the heads meet the block. The corners are where it's likely to leak. Guess what, it leaked again. In my frustration, I called the engine shop and the builder said "Oh, I may have forgotten to tighten up the plug on the oil sensor "T" adaptor" . That was the cause of my leak!!

Just thought I'd mention that little issue I had.

What did you do about the heat cross-over?

Geoff.

 
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