valve stem height - need some help

-
Here's the latest update, with many thoughts. Let's start at the beginning. My primary goal with these heads is weight reduction. When I find it, this 383 will go in a 67-69 Dart or an equivalent car. Saving weight up front is important, as I'm more of a street handling guy than a balls-out straight-line guy. I am not trying to build a giant killer, just a fun and spunky street car for my own pleasure. The fact that these heads should be quite a performance improvement over the existing 906 heads is icing on the cake.

I fully respect the wide variety of opinions posted so far, and I get it that intelligent and informed folks can look at the same information and come to completely different conclusions.

That said, the first question is - does the difference in valve stem heights make any difference for the kind of build I'm after? To use round numbers, the exhaust valve stems are about .040" shorter than the intake valves. My first thought when working on this build is to go hydraulic cam, partly to re-use the existing valve train parts. I understand a solid cam is generally a better deal, but again I'm not trying to squeeze out the final tenth of available ET in the quarter mile.

The root cause of this stuff is the EX valves are shorter than the IN valves by about .040. I measured each valve for OAL along with the measurement from the top of the retainer groove to the top of the valve stem. By the time you do the math, it all works out right. Basically, the EX valves are .040 short in comparison with the IN valves. If this is No Bid Deal, I can clean up the heads, put them back together, and call it a day. If it is a big deal, then I will call SpeedMaster and see what they say about using two different valve lengths.

Other than the stem length issue, the heads look quite good. One of them is from 2018, the other is 2015. The newer head is clearly better machined, but it won't take long with a 6" burr to fix all the casting flash issues and have some really nice heads.
 
Have u taken into consideration that u need .600-.630 offset intake rocker arms. U will still need adjustable rockers no matter how u look at it. So everyone that got heads on sale prolly never thought to get some. Kim

82791E93-9C61-4519-9E95-596DF399AD5C.jpeg


19D92822-75D0-46D8-BCFD-F09065D3D19F.jpeg
 
I kinda been wondering about the same thing. What diameter intake valves are in these heads? Oh, and you measured the valve lengths? How long are they?
 
For some reason, I was thinking the OP’s heads were the 210cc version(RPM copy).
Probably because I wouldn’t have considered the 265cc head as a viable option for his application(383 Street car).

Imo, the 265cc “victor” style head is a very poor choice for what the OP is describing as the finished product.
A part number, or a couple pics would clear up what he’s working with.

If the 265’s are what he has, I’d look into sending them back and buying some Stealth heads instead.
 
Last edited:
PRH said:
For some reason, I was thinking the OP’s heads were the 210cc version(RPM copy).
Probably because I wouldn’t have considered the 265cc head as a viable option for his application(383 Street car).

Imo, the 265cc “victor” style head is a very poor choice for what the OP is describing as the finished product.
A part number, or a couple pics would clear up what he’s working with.

If the 265’s are what he has, I’d look into sending them back and buying some Stealth heads instead.
Click to expand...
IMG_20191213_112505.jpg
IMG_20191213_112542.jpg
 
oldkimmer said:
Have u taken into consideration that u need .600-.630 offset intake rocker arms.
Click to expand...

I did not think of this, and thanks. Good point and I bet you are right.

PRH said:
If the 265’s are what he has, I’d look into sending them back and buying some Stealth heads instead.
Click to expand...

These are the 265cc version, so between an inappropriate head and the valve stems being goofed up, I am returning them. I will chalk this episode up to good intentions but not enough research to ensure I order the right parts. I will work on this project moving forward, with more input to best parts to order.

Many thanks to all who helped out on this - I keep learning, even if it's the hard way sometimes.
 
Yup...... that would not have been a very good overall combo.

Send em back.

Though.........If you added a 4.25” stroker kit to your plans...... they’d work just fine.
 
I have a set of 265 speedmasters. The valve tips are all over the place. If you want to talk to a person at speedmaster that at least knows a little something about these heads talk to Stan. Ext 104. The heads look to be fairly good. I’m sure I’ll have to grind valve tips to get them a uniform height. If I decide to. But what I’ll probably end up doing is straightening up the valve job, and making sure all the intakes are all the same and exhaust are all the same. Thing shin for spring height/pressure. The intake and exhaust valves really doesn’t bother me. As long as geometry is right and valve job is good. I bought new locks, retainers and springs. I may do a hack job of seeing how hard the valves are once I get them apart, and then decide if I’ll buy new valves. If I buy new valves I will not waste a second on trimming these. The other thing to look at is their rockers. The rockers look ok but the oil holes in the shafts are offset wrong. A few of the oil holes are on the spacers. Stock shafts line up perfectly. I also polished the “ball” end of the adjusters, as they were pretty rough and had tons of machine marks left on them. Seemed pretty hard. Had to bear down on them to cut with a file. I have yet to assemble the engine or disassemble the heads.
 
If one were to have the valve seats in these heads cut on a guide and seat machine in a manor that helped with the flow....... the intake seats would end up being sunk a bit.
Then, if you’re paying attention to tip heights as part of the process, you could get the ex tips pretty close to the intake tips when you cut the exhaust seats....... since you’ll likely end up sinking those some as well.

It “could” be done with stones........ but that would a be a pretty looooong process.
 
I don’t think I would want to sink the valves as that will change the cc of that cylinder. Unless of course it equalizes it with the others. Kim
 
oldkimmer said:
I don’t think I would want to sink the valves as that will change the cc of that cylinder. Unless of course it equalizes it with the others. Kim
Click to expand...
he said his exhaust stems were short so sinking the intake valves would just make it even worse...
 
PRH said:
Oh well....... I tried.
Click to expand...
There's a big picture here and it's the Op wanting 50lb off the front of his car.. (mind you that he doesn't own yet LOL)
Now he's unconfident in these heads and finding out he can't just use his stock stamp rockers.. and might as well get a solid cam since he has adjustable rockers and down the rabbit hole he's going.. all the while claiming not to want a drag car or anything like that.. so compounding that with a custom valve job to even all that out is just probably where the overwhelming part begins and again remember this car does not even exist at least in his possession...
 
There are times when I have found it necessary to cut the seats lower and have been rewarded with flow increases. Dropping the valves down some isn't always a detriment. You have to be smarter than your cylinder heads.
 
PRH said:
If one were to have the valve seats in these heads cut on a guide and seat machine in a manor that helped with the flow....... the intake seats would end up being sunk a bit.
Then, if you’re paying attention to tip heights as part of the process, you could get the ex tips pretty close to the intake tips when you cut the exhaust seats....... since you’ll likely end up sinking those some as well.

It “could” be done with stones........ but that would a be a pretty looooong process.
Click to expand...
Before I do a valve job here on new heads......
Measure the valve seat face to tip lengths
Make sure seats are concentric
Measure tip lengths
Measure margins
Measure valve stem diameters
Make valve corrections as needed
Hone guides to proper clearance
Set cylinder head square in vertical mill
Measure valve spring seat depths
Measure valve depths
Make vertical mill corrections as needed
Using one each intake and exhaust valve, one retainer, one set of locks, measure existing installed heights.
Rough in all appropriate int or exh seat angles and depths the same, but still a few thousands proud
Make port and combustion chamber corrections
Finish seats

It gets all your installed heights and tip heights pretty close. During assembly there is still some spring, valve, shim, retainer and lock shuffling to even up the spring pressures.

The procedure varies some from the new to used cylinder heads.
 
Last edited:
oldkimmer said:
Ok IQ52, I have always been told that it’s never good to lower the seat. I stand corrected. Kim
Click to expand...
PRH tried to tell you, "....the valve seats.......cut......in a manor that helped with the flow..........the intake seats would be sunk a bit."
 
RustyRatRod said:
You either have valves that are different lengths or a junk valve job as mentioned. Or both. Those are pretty big numbers for valve stem height differences.
Click to expand...
See it all the time. Exhaust lower than intake valves. If the exhausts are all even with each other, or close.. run it.
Some people I think the seats are going to sink that's old thinking right there...n so they dont cut deep on the exh seats...Others actually like the exhaust sitting prouder in the chamber to cut back Scavenging raw fuel from the intake port and right out the exhaust... it really doesn't matter and it's not life or death whether it's that way or not... in the overall scheme of things though..ideally ...you trim the stem tips off to make them even so the geometry is the same across
 
You must log in or register to reply here.
-

Back
Top