advice on valve guide replacement on alu head

[Belgian1979]

I'm going to get my heads redone. Alu heads with bronze guides and hardened seats (Dart pro 1 alu with 1.550" springs)

What is the best procedure to get them done, what not to have done, what to look out for, which guides to use etc?

[mag2555]

To keep from having a corrective valve job done I get guide liners put in and hopefully get them Diamond honed to size, if not then ball honed.

[ProPower engines]

Dart heads use a very thin guide and replacements can be had in undersized ID's to suit a correction but checking the ID and OD for runout is important so as not to change the original guide and stem center line.

After you get new replacement guides from Dart that are .001 undersized of your stems being re-used mic the stems in the area that is going to contact the guide.
And now ream the guide to about .0005" from finished size then hone to finished size. A solid carbide reamer is the best way to go there as it will be dead nuts to size compared to any HSS bronze reamer made currently. Use a Sunnen style or Goodson diamond hone that uses a rigid honing stone assembly. A flex hone will take forever and not really be straight and evenly sized the length of the guide ID.
Now machine all the valves to the same valve seat face to tip height.
Machine the valve seats parallel and all the same height to the deck face. Confirm seat and valve face's for runout .0002" max. on both then carry on with the cleaning and reassembly.

Thats the short version. Some assembly is required

[Belgian1979]

I'm not doing this myself but will bring them to my machine shop but need to know what to choose. I think Dart performed a pretty bad job on the guides as the heads only have about 4k miles on them.

[fabr]

Poor rocker arm geometry will kill guides. Have you confirmed the sweep ?

[Belgian1979]

Poor rocker arm geometry will kill guides. Have you confirmed the sweep ?

yes and I use shaft rockers (the correct ones for the head btw)

[ProPower engines]

I'm not doing this myself but will bring them to my machine shop but need to know what to choose. I think Dart performed a pretty bad job on the guides as the heads only have about 4k miles on them.

It does not really seem to matter what brand when assembling bulk parts the QC is lost because of the options are just assemble what you have on the bench and no select fitting of parts.
There is now an accepted tolerance level on stem clearance and they will go looser then tighter when ever possible.

I am familiar with those heads and .0008-.001 on the intake stem and .0012-.0015 max on the exhaust stem.
As the intake stems do not really grow any but the guides will get bigger when the head warms up increasing the clearance.
The exhaust stems grow much faster then the guide will thus they need a bit more clearance.

If the heads were ported in makes it hard to put liners in the guides are they are only .437" OD and depending on if you have the 8mm or .3415" stem size it can be tough to make them stay put without cracking the original guide.

I use a piloted carbide reamer and under size ID guides that the OD and ID run out is no more then .0002" combined so as to not relocate the original valve job. It int. and exh form cutters can be had direct from Dart as well to duplicate the original valve seat diamentions thus allowing your shop to touch up rather then re-create a new seat height as well as its location.


But hone fitting your valves to the new guides will make them last much longer and the fact that you are using a good shaft rocker set-up should eliminate the thrust load on the stems that cause the guides to wear out pre-maturely.
But you can also get a longer guide to support the stem more which will help with longevity by measuring how much room under the retainer you have for some extra length for more support at the top of the guide. If you are using a tall installed height spring set-up you may have more spare room then you think. Its worth checking.

[BillK]

Dart heads use a very thin guide

Dave,
Curious why you say that ? I have only done a few but the ones I have done have had pretty typical .502" od guides. I actually just went and looked at a couple of guides I have on the shelf and thats what they are.

Personally I have not had problems with guide wear on them and I wonder if the op has some other issue causing the problem ?

[Belgian1979]

I'm not doing this myself but will bring them to my machine shop but need to know what to choose. I think Dart performed a pretty bad job on the guides as the heads only have about 4k miles on them.

It does not really seem to matter what brand when assembling bulk parts the QC is lost because of the options are just assemble what you have on the bench and no select fitting of parts.
There is now an accepted tolerance level on stem clearance and they will go looser then tighter when ever possible.

I am familiar with those heads and .0008-.001 on the intake stem and .0012-.0015 max on the exhaust stem.
As the intake stems do not really grow any but the guides will get bigger when the head warms up increasing the clearance.
The exhaust stems grow much faster then the guide will thus they need a bit more clearance.

If the heads were ported in makes it hard to put liners in the guides are they are only .437" OD and depending on if you have the 8mm or .3415" stem size it can be tough to make them stay put without cracking the original guide.

I use a piloted carbide reamer and under size ID guides that the OD and ID run out is no more then .0002" combined so as to not relocate the original valve job. It int. and exh form cutters can be had direct from Dart as well to duplicate the original valve seat diamentions thus allowing your shop to touch up rather then re-create a new seat height as well as its location.


But hone fitting your valves to the new guides will make them last much longer and the fact that you are using a good shaft rocker set-up should eliminate the thrust load on the stems that cause the guides to wear out pre-maturely.
But you can also get a longer guide to support the stem more which will help with longevity by measuring how much room under the retainer you have for some extra length for more support at the top of the guide. If you are using a tall installed height spring set-up you may have more spare room then you think. Its worth checking.

Thanks. Heads are the 215 versions with 1.550 springs. I believe those have valves +.100". I did do some pocket porting to them. Mostly cleaning up the bowls and unschrouding of the chamber. The valves were .341 if memory serves me correctly.

So if I read it correctly it is difficult to take the guides out and it is also hard on these head to put inserts in them?

I would prefer to have the guides replaced completely but it seems not doable or maybe the seats need to be replaced as well? Not sure but I assume that under any circumstances the seats need to be recut.

[Belgian1979]

Dart heads use a very thin guide

Dave,
Curious why you say that ? I have only done a few but the ones I have done have had pretty typical .502" od guides. I actually just went and looked at a couple of guides I have on the shelf and thats what they are.

Personally I have not had problems with guide wear on them and I wonder if the op has some other issue causing the problem ?

In terms of the pattern on the valves: at the time I checked it per intructions and had to order a custom length pushrod. All as per instructions. I remember that at the time I put photos up here of the profile of the valve and I was told it was good to go. With the T&D shaft rockers I do not assume that they have a lot of side forces acting on them. However, when I checked them to replace the valve seals last time: some were good and some had play in all directions (didn't note it, but mostly exhausts had play), not just in the direction of the rocker. I think this was just a bad selection or a too wide guide. Obviously everything was cold when I checked that, but some had a noticable wiggle to the valve when off the seat. Valves are tight according to what my leak down test showed.

[Belgian1979]

I remember that I measured the guides with a 3 point mic. I retrieve the original 2012 measurements.

2 intake: 0.342" (8,71 mm)
2 Exhaust: 0.343" (8,71mm)
4 Intake 0.343" (8,715mm)
4 Exhaust 0.343" (8,715mm)
6 Intake 0.343" (8,72 mm)
6 Exhaust 0.343' (8,715 mm)
8 Intake 0.343" (8,72 mm)
8 Exhaust 0.343" (8,71mm)
7 Exhaust 0.343" (8,714mm)
7 Intake 0.343" (8,72mm)
5 Intake 0.343 (8,714mm)
5 Exhaust 0.343" (8,712mm)
3 Intake 0.343" (8,713mm)
3 Exhaust 0.343 (8,714mm)
1 Exhaust 0.343 (8,714mm)
1 Intake 0.343 (8,718mm)

Seeing the consistency I think this is the way they were machined.
So I would say that both on the intake and the exhaust, assuming the valves were 0.3415 the valve guide clearance would be .0015"
Seems like this was already a bit on the high side.

[ProPower engines]

Dart heads use a very thin guide

Dave,
Curious why you say that ? I have only done a few but the ones I have done have had pretty typical .502" od guides. I actually just went and looked at a couple of guides I have on the shelf and thats what they are.

Personally I have not had problems with guide wear on them and I wonder if the op has some other issue causing the problem ?

The heads I have seen up here have had the .438 od guides which makes them very thin to broach a liner into and have any reasonable press fit to keep it from moving. Now they may have changed the guide sizing but the last set of iron heads used the same short .438 od guides.
But the aluminum can be using a .502 od guide compared from earlier heads I have had here.

The iron heads use a very short OAL guide and compared to the alum. heads that are CNC ported it takes the rigidity and support out of the head around the chamber end of the guide.
Liners in bronze guides is totally doable but I would be curious as to the OAL of the factory guide to see if there can be more support added.

I have some Dart guides here and they are just 1.953 OAL .530 top od. for seal and .438 od is 1.064" then the last .250" is .433od that goes in the head.
Looks like a change has been made along the way but these guides were ordered direct from Dart the summer in august before covid hit.
But I ordered .340 ID so I could finish to suit the job I was doing at the time.

[ProPower engines]

I remember that I measured the guides with a 3 point mic. I retrieve the original 2012 measurements.

2 intake: 0.342" (8,71 mm)
2 Exhaust: 0.343" (8,71mm)
4 Intake 0.343" (8,715mm)
4 Exhaust 0.343" (8,715mm)
6 Intake 0.343" (8,72 mm)
6 Exhaust 0.343' (8,715 mm)
8 Intake 0.343" (8,72 mm)
8 Exhaust 0.343" (8,71mm)
7 Exhaust 0.343" (8,714mm)
7 Intake 0.343" (8,72mm)
5 Intake 0.343 (8,714mm)
5 Exhaust 0.343" (8,712mm)
3 Intake 0.343" (8,713mm)
3 Exhaust 0.343 (8,714mm)
1 Exhaust 0.343 (8,714mm)
1 Intake 0.343 (8,718mm)

Seeing the consistency I think this is the way they were machined.
So I would say that both on the intake and the exhaust, assuming the valves were 0.3415 the valve guide clearance would be .0015"
Seems like this was already a bit on the high side.

With the stem sizes they use on complete heads I do not ever see a perfect .3415 stem. They vary a few tenth's either way and as per your measurement on #2 int. being .342. My guess is your measuring instrument did not read 10th's??


But yes IMO they come out of the box a bit on the loose side but they are mass produced but I would be curious what the stem size is on the #2 intake measures.

I am just very critical of having too much or more then you need for guide clearance on street stuff since they idle a lot at times in traffic but when you find the back of the valve heavily coated with black gooey stuff thats dripping off thats oil coming through the guide.

[Belgian1979]

I remember that I measured the guides with a 3 point mic. I retrieve the original 2012 measurements.

2 intake: 0.342" (8,71 mm)
2 Exhaust: 0.343" (8,71mm)
4 Intake 0.343" (8,715mm)
4 Exhaust 0.343" (8,715mm)
6 Intake 0.343" (8,72 mm)
6 Exhaust 0.343' (8,715 mm)
8 Intake 0.343" (8,72 mm)
8 Exhaust 0.343" (8,71mm)
7 Exhaust 0.343" (8,714mm)
7 Intake 0.343" (8,72mm)
5 Intake 0.343 (8,714mm)
5 Exhaust 0.343" (8,712mm)
3 Intake 0.343" (8,713mm)
3 Exhaust 0.343 (8,714mm)
1 Exhaust 0.343 (8,714mm)
1 Intake 0.343 (8,718mm)

Seeing the consistency I think this is the way they were machined.
So I would say that both on the intake and the exhaust, assuming the valves were 0.3415 the valve guide clearance would be .0015"
Seems like this was already a bit on the high side.

With the stem sizes they use on complete heads I do not ever see a perfect .3415 stem. They vary a few tenth's either way and as per your measurement on #2 int. being .342. My guess is your measuring instrument did not read 10th's??


But yes IMO they come out of the box a bit on the loose side but they are mass produced but I would be curious what the stem size is on the #2 intake measures.

I am just very critical of having too much or more then you need for guide clearance on street stuff since they idle a lot at times in traffic but when you find the back of the valve heavily coated with black gooey stuff thats dripping off thats oil coming through the guide.

By looking through the throttle bodies (cross ram itb) I can look at the valve with a camera and see no goo caked on the valve.
Most plugs are quite black at the electrode and porcelaine and barely nothing on the ring. The black is also not really wet I must admit. So maybe it is just running too rich.
I also have had difficulty getting a consistent reading on oil level with the accusump in the system. Maybe that has me thinking that it's consuming oil. Have now plugged off the accusump, so need to see if it stays constant after that.

[Belgian1979]

I remember that I measured the guides with a 3 point mic. I retrieve the original 2012 measurements.

2 intake: 0.342" (8,71 mm)
2 Exhaust: 0.343" (8,71mm)
4 Intake 0.343" (8,715mm)
4 Exhaust 0.343" (8,715mm)
6 Intake 0.343" (8,72 mm)
6 Exhaust 0.343' (8,715 mm)
8 Intake 0.343" (8,72 mm)
8 Exhaust 0.343" (8,71mm)
7 Exhaust 0.343" (8,714mm)
7 Intake 0.343" (8,72mm)
5 Intake 0.343 (8,714mm)
5 Exhaust 0.343" (8,712mm)
3 Intake 0.343" (8,713mm)
3 Exhaust 0.343 (8,714mm)
1 Exhaust 0.343 (8,714mm)
1 Intake 0.343 (8,718mm)

Seeing the consistency I think this is the way they were machined.
So I would say that both on the intake and the exhaust, assuming the valves were 0.3415 the valve guide clearance would be .0015"
Seems like this was already a bit on the high side.

With the stem sizes they use on complete heads I do not ever see a perfect .3415 stem. They vary a few tenth's either way and as per your measurement on #2 int. being .342. My guess is your measuring instrument did not read 10th's??


But yes IMO they come out of the box a bit on the loose side but they are mass produced but I would be curious what the stem size is on the #2 intake measures.

I am just very critical of having too much or more then you need for guide clearance on street stuff since they idle a lot at times in traffic but when you find the back of the valve heavily coated with black gooey stuff thats dripping off thats oil coming through the guide.

I've not recorded stem diameter. The device reads in .001 mm. It's not in inches hence the reason why I also gave the mm. The inch size is rounded off. So 8,720mm = 0.3433"

Just need to know if exchanging the guide completely (pressing out and pressing in a new one) is feasable and if so, what also needs to be done apart from having the seats redone.
What are good quality guides in this case for the head.

PS: I would like to keep the top diameter of the guide the same as they were as I use inner spring locators.