Valve stem seals - which ones?

[72 Challenger]

Hi everyone,

Took a break from cars to teach myself how to weld but I'm back in the drivers seat looking to fix a bad oil burn on startup that goes away after a few seconds of running.

I suspect my valve stem seals are done. Typical heavy blue smoke on startup, goes away quickly.


My question is which ones do I buy to replace. Some background info:

Engine is a 1970 date coded 340, stroked to 416 ci, with challenger T/A heads.

It runs a crower cam 31243 with a dual spring set up Crower part number 68405.

There is a note in the build documents of the engine that says "retainer/ seal clearance only good for 450/460 lift" but the advertised lift specs on the cam are .480 intake and .503 exhaust.

No where in the build info is there a part number for the valve stem seals.

Am I overthinking this? Is a valve stem seal the same no matter what? Are they the same for intake and exhaust?

I have tons of information on the build, so please ask questions.

I'd like to order parts soon so I can work on this over my Christmas holiday.

Cheers!

[RJChallenger]

Intake and exhaust are different style/shape seal. they basically are the the same as in they control the amount of oil that gets past them. This is very true on stock engines with a single valve spring. It gets a lot more complicated on performance engines with double springs and /or dampers. That note sez that there isn't enough clearance between the valve seal and springs. I would look very closely to see if the springs have damaged the seals causing the smoke on startup?

[Brads70]

If it's not all bone stock ( and it sounds like it is not) then you need to see what the engine builder used for valve seals. Usually they get machined for  Viton type seals.

[72 Challenger]

If it's not all bone stock ( and it sounds like it is not) then you need to see what the engine builder used for valve seals. Usually they get machined for  Viton type seals.

Definitely the only thing left stock is the oil pan lol.

Is there a way to see this with the naked eye?

[72 Challenger]

Intake and exhaust are different style/shape seal. they basically are the the same as in they control the amount of oil that gets past them. This is very true on stock engines with a single valve spring. It gets a lot more complicated on performance engines with double springs and /or dampers. That note sez that there isn't enough clearance between the valve seal and springs. I would look very closely to see if the springs have damaged the seals causing the smoke on startup?

I will look into this. The engine build is twenty years old, but only 2000 miles on it. Built by a reputable shop too.

[Brads70]

If it's not all bone stock ( and it sounds like it is not) then you need to see what the engine builder used for valve seals. Usually they get machined for  Viton type seals.

Definitely the only thing left stock is the oil pan lol.

Is there a way to see this with the naked eye?

I'd bet yours will look something like these, but you need to know the stem diameter of the valve etc... The top of valve guide at the head casting is machined to suit them
https://www.jegs.com/i/COMP-Cams/249/516-16/10002/-1


Stock type valve seals look more like these....
https://www.jegs.com/i/COMP-Cams/249/502-16/10002/-1

[jimynick]

Valve seals that are rated for .020 less than the stated lift of the cam would make me wonder why they were used in the first place. Are the retainers stock height? What's the installed height and how does the actual height relate to the manufacturer's spec? Coil bind or proper spec? Are all the valve guide bosses the exact same height or could you have a couple of tall ones that squish the seals? How does a straight edge fit across the valve stems? Cracked seals? Lots of possibilities, eh? Good luck 

[MoparLeo]

Since it took until post# 4 to get more important info, When did the mileage get put on ? 20 years ago or jusr recently ?
 Even shops with great reputations make errors sometimes  or get some bad parts sometimes.
You will most likely  need to remove the heads to properly install the seals unless they are umbrella seals and you have the tools and air pressure to do them on the engine.
If they are the Viton seals the valve lift should have been checked before the guides were cut to accept the seals. If the lift is too high for the seals they will be damged when the engine runs.
 Never assume anything you haven't done/checked for your self.
What do the spark plugs look like ? Leak down test ?

[72 Challenger]

Since it took until post# 4 to get more imporatnt info, When did the mileage get put on ? 20 years ago or jusr recently ?
 Even shops with great reputations make errors sometimes  or get some bad parts sometimes.
You will most likely  need to remove the heads to properly install the seals unless they are umbrella seals and you have the tools and air pressure to do them on the engine.
If they are the Viton seals the valve lift should have been checked before the guides were cut to accept the seals. If the lift is too high for the seals they will be damged when the engine runs.
 Never assume anything you haven't done/checked for your self.
What do the spark plugs look like ? Leak down test ?

I will try and get all of the info:

Most of the mileage has been up on since I owned the car I got it in 2019. from 2001-2019 it had sub 1200 miles put on it. sat for long periods of time while the owners spent his winters in Florida, some years with zero mileage.

In order to do this job I have compressed air and I have a comp cams shaft mounted spring compressor suitable for mopar small blocks. Was looking to do this job with heads in car.

Spark plugs show a range from normal running conditions on some and oil on others but the worst one is drivers side rear of engine, black and oily.

Compression on all Cyl's is fine all around 180 and within 12 psi.  I do not believe this is a bad oil ring or a valve that is not closing. The smoke on startup is pretty bad especially if the car has say for more then a day.

I can see on the engine invoice under item Check spring - Install a few valves and check installed spring height & record, test new and old springs for compatibility with camshaft.

Here is the information contained in the file:

Guide clearance int: 0.0020
Guide clearance ext: 0.0026
Valve seat height N/A
Installed height: 1.680
Spring pressure Closed: 115
Spring pressure open (o.500 lift) 280 pounds
Coil bind: 1.130


from the advertised camshaft specifications: Intake has a lift of .480 and exhaust is .503

Does any of this information help? I will try and call the shop but i suspect that they will not have information on a build from 2001.

[MoparLeo]

If the guides are tight there should not be heavy oil on any plugs.
 Clean and switch the #1 plug with the # 7 plug and start the car and drive it around until the smoke clears up.
Let cool down and recheck those 2 plugs.
If #7 is now cleaner you may just have a bad plug.
How long since the plugs were changed and what brand and part#, and what is the gap ?
Stock ignition ?

[72 Challenger]

If the guides are tight there should not be heavy oil on any plugs.
 Clean and switch the #1 plug with the # 7 plug and start the car and drive it around until the smoke clears up.
Let cool down and recheck those 2 plugs.
If #7 is now cleaner you may just have a bad plug.
How long since the plugs were changed and what brand and part#, and what is the gap ?
Stock ignition ?

Car is away for the winter so taking it out is not going to be an option for about 4 more months!

Plugs were changed for the beginning of the 2023 driving year. Champion Rn14YC, gap is the stock setting. Ignition is a Mopar electronic box with a mopar performance coil. Car is a 1970 that was changed from points to electric ignition. New plug wires and a reproduction distributor cap.

[MoparLeo]

Another thing is, you say there is heavy (blue)smoke on start up. Even with bad seals, if the guides are tight and the everything is supposedly new, there should not be that much oil on top of the cylinder heads to get into the guides when you shut it off.
 Have you actually verified all of the listed work was actually done, or only seen the out side of the engine?
Had the valve cover off ? The oil should drain back down pretty quickly after it runs off of the top of the valves/springs. Not fill up the area around the valves.
An nder valve cover inspection is really the first thing to do. Yake pictures and post them for us.
 Pictures are a great help when trying to figure out/guess what a problem can be.