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Discussion Starter · #1 ·
Hey guys - Is there a way to tell if a motor has a Mechanical vs. Hydraulic Cam without tearing the motor apart? I purchased a 1967 Mustang w/351 Windsor in 2021. The engine was built a few owners ago. I contacted him and he cannot remember. I've done a fair amount of work on cars through the years, but I am by no means a professional and don't have a lot of knowledge with motor building. I'm just a car/mustang enthusiasts and typically can figure out how to get whatever I need done by researching online and with help from people like yourselves.

Having said that, the reason I ask about the Cam is I believe I may have a bad seal on one or more of the valve springs. I have blue smoke at startup but then it goes away once the oil is burnt off. I do not get any blue smoke while driving, its just at Startup. So I am thinking the oil is getting into the cylinder walls through a bad valve spring seal. Compression checks were good, so I believe my rings are still good. I will need to adjust the valves once I go to put everything back together. Apparently I need to know if I have a Mech or Hyd cam in order to do that.

The motor has Jim Miller Mid-Lift Roller Rockers.

I contacted him/the company asking about adjusting the valves and he was not very much help. He seemed a little annoyed as I think he deals mostly with Professional builders and I did not have the knowledge to answer his questions. I did a little research online and it seems these were a very good quality roller/rocker setup and the guy who made them was respected. Does anyone have any knowledge on these specific roller rockers on how to property adjust? Or can I just follow any Mid Lift Roller Rocker adjustment tutorial?

Attached is a couple photos of the Roller Rockers. It has Canfield Aluminum Heads.

Any help here is greatly appreciated guys. Thanks!
 

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With hydraulic lifters the pushrod will be preloaded into the spring-loaded lifter and under some tension. You will not be able to easily turn the pushrod with your fingers if it is adjusted properly. With solid lifters there is a small amount of clearance left in the valvetrain that is measured via feeler gauge between the rocker tip and valve stem and set accordingly. The pushrod will turn freely in your fingers on the valves that are fully closed. Regardless of where the engine is in its rotation, some valves will be partially open and some will be fully closed. Grab a few different pushrods to test if you aren't sure which ones are open or closed. You will know immediately as soon as you take the valve covers off and grasp a pushrod between two fingers and try to turn it.
 

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mechanical cams require lash at each cyl TDC.

take cyl #1 and put it at TDC on compression stroke - remove valve cover on pass side - grab rockers for cyl #1...if they are loose (both), measure the lash with feeler gauges - probably around .015" or close to it. That would be for a mech cam.

If there is no lash, you shoudl be able to twist the pushrod in your fingers but have no up and down movement - this is lifter preload of a hydraulic setup...which is typically around .030".

In either case, for setting up your adjustable roller rockers, follow the mid-lift instructions.

Yes they should be 7075-T6 bodies and and made in the USA trunions/assemblies.
 

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take cyl #1 and put it at TDC on compression stroke - remove valve cover on pass side - grab rockers for cyl #1...if they are loose (both), measure the lash with feeler gauges - probably around .015" or close to it. That would be for a mech cam.

If there is no lash, you should be able to twist the pushrod in your fingers but have no up and down movement - this is lifter preload of a hydraulic setup...which is typically around .030".
Be careful to look for the up-and-down movement. Even a properly set up hydraulic will usually allow the pushrod to spin.

Ford spec for the 289HP C3OZ-C cam is .021" cold, .018" hot.
 

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I've generally noticed mechanical tappets are noisier. They have a very distinct sound. Hydraulics are generally whisper quiet with no valve train clatter. Not a conclusive test but it can give you a pretty good idea of the type.
 

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I've generally noticed mechanical tappets are noisier. They have a very distinct sound. Hydraulics are generally whisper quiet with no valve train clatter. Not a conclusive test but it can give you a pretty good idea of the type.
Flat tappet hydraulic are definitely louder than modern OHC and roller....but still does not sound anything like a flat solid lifter.

OP your blue smoke can also be from worn valve guides. It is not a sure fix to swap out seals...though it may help as both could be worn.

It depends on the history of the car, and where the guides started as far as tolerance and machining technique on the last rebuild. But if you go to the trouble to swap valve stem seals by compressing the cylinder with air (there is a special spark plug insert kit for those) you can swap the seals with heads installed. But the only way to check valve guides is to disassemble valve train and measure with a small bore micrometer to see if they are out of spec.
 

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Discussion Starter · #8 ·
Flat tappet hydraulic are definitely louder than modern OHC and roller....but still does not sound anything like a flat solid lifter.

OP your blue smoke can also be from worn valve guides. It is not a sure fix to swap out seals...though it may help as both could be worn.

It depends on the history of the car, and where the guides started as far as tolerance and machining technique on the last rebuild. But if you go to the trouble to swap valve stem seals by compressing the cylinder with air (there is a special spark plug insert kit for those) you can swap the seals with heads installed. But the only way to check valve guides is to disassemble valve train and measure with a small bore micrometer to see if they are out of spec.
Thanks for this. Seems to make sense to try and replace the valve guides as well then. The car has Aluminum Canfield Heads, I have the part # somewhere. I've never ran these kind of heads but looking online it looks like these were more common about 10-20 years ago. Hopefully I can find the correct valve guides and Spring seals.

The car was in the same family since the 90's. Several owners in the family. Best I can tell is it sat for a good while and was not driven much for several years recently. All the gaskets on the top of the motor were shot so it barely ran. Replaced those and did a major tune up. Installed proper carburetor and updated the ignition system and the car has ran excellent. The car didn't blow any smoke at all when I first got it. And really as I drove the car more, everything seemed to improve. These cars definitely like/need to be driven. Then I started seeing blue smoke just before the winter hit and thought the rings were shot, but the compression check showed they were working so I thought from sitting maybe the spring seals had also wore out as well and oil was getting into the cylinder wall from the heads. I'm by no means an expert, that's just the most logical next thing I could think of. It's always tough not being the person who built the motor trying to troubleshoot. It's fun though, and partly why I got back into another muscle car.
 

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Flat tappet hydraulic are definitely louder than modern OHC and roller....but still does not sound anything like a flat solid lifter.

OP your blue smoke can also be from worn valve guides. It is not a sure fix to swap out seals...though it may help as both could be worn.
Pretty much true.

OP's blue smoke at startup probably is seals and may possibly be both seals & guides. My '68 does that but with all of about 5000 miles total use on the heads,
more likely stem seals......
 

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Before you condemn your valve seals and, especially, guides, you may want to check for other sources of a smoky exhaust on start-up...

a. Pull the PCV valve from its hose and look for oil wetness on the inside of the hose. There shouldn't be any. If so, that could be an indication of a faulty PCV valve, excessive crankcase pressure (blow-by) or poor baffling in the valve cover below the PCV grommet.

b. If you have an automatic transmission, pull the rubber hose going to the modulator hard line and check for fluid inside. There should be none. If so, replace the modulator.

c. If you have power brakes, pull the hose at the booster check valve and check for brake fluid inside. If so, rebuild/replace the brake master cylinder and booster.

Other sources of engine smoke can include...

1. Gasket mismatch/failure or angle mismatch between the intake manifold and cylinder heads causing oil to enter the intake port(s).

2. Poorly sealing rings allowing oil to enter the combustion chamber.

3. Loose engine bearings.
 

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Pulling a valve cover and examining the seals is a pretty quick job, then you'll know. And if that's the problem, the repair is surprisingly easy, can be done with the engine assembled, in the car. A few hours' work.
The little seals should be soft and pliable, and should stay in place on the valve stem. If they slide down, or are hard, they are trashed and need to go.
 

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Canfield heads....... might be PC or hybrid seals.
 

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Discussion Starter · #13 ·
Canfield heads....... might be PC or hybrid seals.
Thanks. Whats the best way to find out what seals I will need? I don't see much online for Canfield Heads. I was thinking about calling these guys --> -=CPR -Canfield Cylinder Heads available in 54cc, 58cc, and 65cc configurations. The perfect addition to your weekend warrior!=- since it looks like they sell Canfield Heads to see if by giving them the Part & Serial #'s they could let me know. My heads Part# is 20-450-58-0 and Serial 0598-2177
 

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Discussion Starter · #14 ·
Before you condemn your valve seals and, especially, guides, you may want to check for other sources of a smoky exhaust on start-up...

a. Pull the PCV valve from its hose and look for oil wetness on the inside of the hose. There shouldn't be any. If so, that could be an indication of a faulty PCV valve, excessive crankcase pressure (blow-by) or poor baffling in the valve cover below the PCV grommet.

b. If you have an automatic transmission, pull the rubber hose going to the modulator hard line and check for fluid inside. There should be none. If so, replace the modulator.

c. If you have power brakes, pull the hose at the booster check valve and check for brake fluid inside. If so, rebuild/replace the brake master cylinder and booster.

Other sources of engine smoke can include...

1. Gasket mismatch/failure or angle mismatch between the intake manifold and cylinder heads causing oil to enter the intake port(s).

2. Poorly sealing rings allowing oil to enter the combustion chamber.

3. Loose engine bearings.

Thanks everyone for the help, much appreciated. I have not tackled this yet but have noticed that it seems to be getting progressively worse. There seems to be oil burning while driving sometimes now. It's not always, but I will notice after going down hills on compression strokes, using the motor to slow down, when I come to a stop I will notice it will blow some smoke. Does this sound like the culprit is in fact the rings?


A. PCV is new

B. I have the TKX Tremec 5 speed manual

C. Manual Brakes

1. This could be something to check. I did pull the intake as it has failed intake gaskets and installed the Fel-Pro 1250 from Summit Racing. I want to say when I installed they weren't a perfect match but I would have to re-check.

2. Based on it getting worse as I drive the car more, I am thinking the rings may be in fact the problem.
 

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I would pull the intake again and check those gaskets again. I have never had an issue with the printoseal Felpro gaskets but I know plenty of people that have, although that's mostly on FE engines. What were the compression readings? If you think the rings are going then I'd do a leakdown test.
 

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Have you performed a compression test/leak down? Not having any reliable history and it seemingly getting worse is pointing in the direction of ring wear.
Apologies if this has been asked and answered.
 

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1965 Mustang GT. 11.898 @ 113.646, all motor, three pedals
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I've generally noticed mechanical tappets are noisier. They have a very distinct sound. Hydraulics are generally whisper quiet with no valve train clatter. Not a conclusive test but it can give you a pretty good idea of the type.
I kinda like the clatter 😉
 

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Discussion Starter · #19 ·
Have you performed a compression test/leak down? Not having any reliable history and it seemingly getting worse is pointing in the direction of ring wear.
Apologies if this has been asked and answered.
I bought the car last year. I did an initial compression check, and it seemed to checkout but that was my first time doing a compression check. I’ve since watched a few videos on how to perform that. So I’ll do a wet and dry test and record the numbers. I also just bought a leak down test kit and plan to do that as well.
 

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1965 Mustang GT. 11.898 @ 113.646, all motor, three pedals
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I bought the car last year. I did an initial compression check, and it seemed to checkout but that was my first time doing a compression check. I’ve since watched a few videos on how to perform that. So I’ll do a wet and dry test and record the numbers. I also just bought a leak down test kit and plan to do that as well.
Leak down can be a useful diagnostic tool. For most accurate results, the motor should be at or near running temp. I shut it off and give it 10 minutes for the headers to cool off a bit.
 
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