Jump to content
kencombs

valve guide sizing

Recommended Posts

Shopping for 230 valve guides.  I've always thought the intakes and exhaust are the same.  But, now I find that Sealed Power has two part numbers:  VG419 and VG420.  One for intake, other for exhaust.  Same length and OD but different IDs.  And this is what's weird to me:  The exhaust is .3445 ID, the intake is .3425.  I would expect the exhaust to be larger???

 

I think, when trying to make sense of the two pn's that they may have decided to make them to 'finished' size and not require reaming.  But, the smaller exh seems wrong to me.

 

Any experience with this???

Share this post


Link to post
Share on other sites

Well, I answered part of my own question.  I got the sizing info from a web site that sells these, Carter's.  I went to the manufacturers catalog and confirmed that there are two valve guide part numbers.  And they vary in ID, but the exhaust is .002 larger as I expected.

 

So my remaining question is:  has anyone use these sealed power parts and did they install OK without reaming??

 

I've found a vendor that has the six packs of guides MUCH cheaper than most.

Share this post


Link to post
Share on other sites

exhaust valves themselves are always smaller as it takes less to move hot gasses.....intakes are larger because it takes more to move cooler gasses.....and in guide size the very fact that the exhaust valve will operate at a greater temp than that of the intake as the intake is cooled by the incoming air/fuel mixture..these higher heats will result in a greater expansion rate of the valve at operational temperature.

Share this post


Link to post
Share on other sites
9 minutes ago, Plymouthy Adams said:

exhaust valves themselves are always smaller as it takes less to move hot gasses.....intakes are larger because it takes more to move cooler gasses.....and in guide size the very fact that the exhaust valve will operate at a greater temp than that of the intake as the intake is cooled by the incoming air/fuel mixture..these higher heats will result in a greater expansion rate of the valve at operational temperature.

Agree, that's why I expected the stem clearance to be higher cold, with the larger guide ID on the exhaust.  But, these Sealed Power brand guides are the first I've seen that have different PN's for intake and exhaust.  Presumably that negates the need for reaming after install.

 

I'm looking for someone who may have used them and can confirm that. 

Share this post


Link to post
Share on other sites

The factory intake/exhaust valve guides for the flathead sixes are the same.... #1124959

Late 30's up through 1956 including 218,230, 236, 251 and the 265.

This out of several factory MoPar parts books.

I have never needed to size factory guides.

After market sometimes is questionable.

Counterbore up on the exhaust.

Share this post


Link to post
Share on other sites

intake stem to guide clearance...     .001-.003  

exhaust valve stem to guide clearance....        .002-.005

 

while the valve guides may be the same, the fact that application will determine the stem to guide clearance and is a reamed factor on install...

Edited by Plymouthy Adams

Share this post


Link to post
Share on other sites

I'm aware of the single part number for factory guides, but the Sealed Power brand provides two. And Sealed Power is an excellent brand IME.  The factory speced clearance for the exhaust is .002 greater than the intake, which is provided by the sizing of SP.  Since the factory guides (and valve stems) are the same size, but speced for greater installed clearance reaming is recommended.  But, I'd rather not buy another reamer!  We've all seen recent posts here of people having sticky valves due to insufficient clearance, or at least suspected to be due to that.  I haven't seen confirmation after a teardown..

Share this post


Link to post
Share on other sites

most folks will not post that they have erred on a task at hand...….many will not post that they overlooked a very simple task...it is often the little things that pop up as folks seemingly think, ah, that would be too obvious....well, that is furthest from the truth......

Share this post


Link to post
Share on other sites

Suggest you go to the Technical tab at the top of this webpage. Click on it then click on Tech Tips in the drop down window. Read every thing especially the paragraph on installing valve guides. Intake and exhaust valve guides are not installed the same way.

Share this post


Link to post
Share on other sites

Install your new SP guides..... measure with a ball gauge and mike the stems... ream to fit if you have to. You might have to but a reamer...that's the way it goes.

That's the only way it will get done to your satisfaction. 

Share this post


Link to post
Share on other sites
36 minutes ago, Don Coatney said:

Suggest you go to the Technical tab at the top of this webpage. Click on it then click on Tech Tips in the drop down window. Read every thing especially the paragraph on installing valve guides. Intake and exhaust valve guides are not installed the same wayvalv.

Yes, this isn't my first rodeo, that's why I was suprised to find this brand that had two different pn's.  Size difference that is.  Counterbore up/down is to trap oil on the exhaust to aid lube, not trap to prevent sucking into the combustion chamber on the intake.  Another example of really good engineering mother Mopar, along with water distribution tube and hardened valve seats.

 

I'm always amazed at the longevity of our flatties compared to brand F and C. 

 

I recall looking for a good F flathead to rebuild at my Dad's salvage back in the early/mid '50s.  We had a big stack of them so I started pulling heads.  23 blocks later  I found one that wasn't cracked!!  And it had to be sleeved on one cylinder to correct a wrist pin score.

I' m sure it has happened, but I've never encountered a heat cracked mopar flathead. 

Share this post


Link to post
Share on other sites
20 minutes ago, Dodgeb4ya said:

Install your new SP guides..... measure with a ball gauge and mike the stems... ream to fit if you have to. You might have to but a reamer...that's the way it goes.

That's the only way it will get done to your satisfaction. 

personal satisfaction BUT in truth the only way to do the build mechanically to verify you are within specs....blue printing is nothing special, blueprinting is done with every build if you follow the book as it is the very adherence to the specification as put forth by the engineers.  

Share this post


Link to post
Share on other sites

The factory MoPar intake valves are relieved (or undercut) at the bottom while the exhaust valves are relieved at the top.

The exhaust guides have the counter bore up to shield the valve stem from hot exhaust gases. The exhaust valve relief edge helps to scrape carbon out of the guide.

The intake guide of course goes down to shield against excessive oil reaching the valve stem.

The intake valve relief edge helps to scrape oil back down the stem.

Some after market replacement valves do not have this machined relieft on the intake and exhaust valves.

Exhaust valves with out this relief at the top of the valve stem can stick open . Engines recently rebuilt can stick valves because of sitting for long periods of time and the tight stem clearance being new. If thats the projected future of the engine maybe wider valve stem clearance etc.

A lot of factors in the valve train to consider on these old flatheads depending on how they will be used.

 

Share this post


Link to post
Share on other sites

I bought my valves and guides from Terrill Machine in De Leon TX 254-893-2610

Its worth a call. They are very knowledgeable 

Share this post


Link to post
Share on other sites

It seems that you could use a dial indicator to measure the clearance, per the specs in the rebuild manual and use those measurements to determine if you need to ream the guides or not.

Share this post


Link to post
Share on other sites
3 hours ago, Matt Wilson said:

It seems that you could use a dial indicator to measure the clearance, per the specs in the rebuild manual and use those measurements to determine if you need to ream the guides or not.

 

I'm hoping that by buying the guides I mentioned, reaming can be avoided. They are the right size, according to the catalog, so if they don't shrink when pressed in, I should be good to go.   Otherwise, I'd need to use a ball gauge and reamer.  Dial indicators don't work well since the place you have to measure is so far above the guide itself the clearance is magnified.  But I can do that just to get a 'ballpark' figure.  that should confirm the need/no need.

 

On a side note, the stems in this old block show no wear at all.  But, they seem to have been replaced at the last rebuild, as they are nice and thick.  Block is .040 over and crank is a nice .010/.010.  New exhaust valves, grind seats and valves, rings, and bearings should fix me up.

 

Haven't used my seat grinder or valve grinder is years.  Had to replace belts on the valve refacer due to age and or mouse damage.

 

But, had 3 new seat stones of the right size and angle in the box.  Cheap valve job!  Just have to by guides.

Edited by kencombs

Share this post


Link to post
Share on other sites

One way....

Check valve and guide  wear/ clearance with dial indicator @ approx 3/8" valve lift....or with ball gauge and mike.

Like  shown in the shop manual.

Share this post


Link to post
Share on other sites

Hello,I had occasion to install a set of these sealed power guides last July. I drove the original to the block out with a bit in the air chisel, cleaned the bores out  with a  wire brush and let the block warm up in the 100 degree temperature in front of the shop. I chilled the new guides in the freezer for about 10 minutes,then gave the bores a shot of WD40 and drove them in with a two pound hammer and a piloted driver. My machinist friend loaned me two hand reamers and the handle to turn them with,only a very light cut was required. I would buy these guides again,the fit was good and easy to finish ream. James

Share this post


Link to post
Share on other sites
9 hours ago, James Repair said:

Hello,I had occasion to install a set of these sealed power guides last July. I drove the original to the block out with a bit in the air chisel, cleaned the bores out  with a  wire brush and let the block warm up in the 100 degree temperature in front of the shop. I chilled the new guides in the freezer for about 10 minutes,then gave the bores a shot of WD40 and drove them in with a two pound hammer and a piloted driver. My machinist friend loaned me two hand reamers and the handle to turn them with,only a very light cut was required. I would buy these guides again,the fit was good and easy to finish ream. James

thanks for the info, just what I needed.

Share this post


Link to post
Share on other sites

As Bob states above, there are special tools for checking small bores that is common with valve guides and well, any small bore....these often can be delivered to your door and are complete in set of 4 sizes to measure from 1/8-1/2 inch for under 20.00 delivered.   Removes the guess work from the equation...

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.

Terms of Use