There may not always be pressure in the exhaust port. When the exhaust vale opens, a pulse of hot high pressure exhaust gas moves through the port into the manifold, followed naturally by a pulse of negative pressure. While all 8 cylinders combined will create positive back pressure in the downstream exhaust system, right at the port there will be constant cycling of positive then negative pressure.
H D truck engine sodium valves.
- Thread starter reddog565
- Start date
There may not always be pressure in the exhaust port. When the exhaust vale opens, a pulse of hot high pressure exhaust gas moves through the port into the manifold, followed naturally by a pulse of negative pressure. While all 8 cylinders combined will create positive back pressure in the downstream exhaust system, right at the port there will be constant cycling of positive then negative pressure.
KULTULZ
Well-known member
While early AM Carousing With My Browser ...
This is from the other forum-
He's the man and has the final say.
Why the seals are not listed in the MPC I have no idea. But this info may be useful to someone one day.
In addition and IMO ...
..., the heads were designed and intended for low RPM usage. They have smaller valves and are not power producers.
This is from the other forum-
SOURCE- http://forums.y-blocksforever.com/Topic146422-2.aspx
He's the man and has the final say.
Why the seals are not listed in the MPC I have no idea. But this info may be useful to someone one day.
In addition and IMO ...
..., the heads were designed and intended for low RPM usage. They have smaller valves and are not power producers.
KULTULZ
Well-known member
- ADDENDUM -
OK, Mr. Eaton says there are seals on the HD Engine sodium filled EXH valves. As usual, I begin wondering (as I do when staring at a lit match), there has to be something else going on here.
So I pull out my SHOP MANUALS (1955 and 1957 - I have no 1956) and begin to cipher.
EDIT -
The 1957 SHOP MANUAL shows the EXH VLV seal in the ILL of the EXH VLV ASSY
So, my contention is that FORD did not use EXH valve seals on the sodium filled valves until the 1957 model run.
This is in no way to contradict Mr. Eaton. It explains why one year doesn't have them and another year has.
The seals sourced from EGGE (excellent supplier BTW) must be for a 1957 HD engine and/or earlier retro-fit.
Last edited:
Final thoughts for a while... I guess I should have checked with the barn before I had these heads rebuilt. I certainly would have done away with the sodium valve and probably would have taken it to a more old car machine shop...that's why the barn is so helpful, could have saved me a lot of aggravation.... Thanks to all you guys for your replies.
KULTULZ
Well-known member
OK ... follow up ...
In the 1954-55 FORD TRUCK SHOP MANUAL, PG 16, Table 1 will give what TRUCK ENGINES received EXH VLV seals.
The 256 w/ sodium filled exhaust valves did not have seals.
There are many differences between PASS CAR, TRUCK L/D and H/D FYB engines, all for a reason.
I would show the chart but my scanner is still on the fritz.
BASIC PN 6571 valve seal chart shown below -
In the 1954-55 FORD TRUCK SHOP MANUAL, PG 16, Table 1 will give what TRUCK ENGINES received EXH VLV seals.
The 256 w/ sodium filled exhaust valves did not have seals.
There are many differences between PASS CAR, TRUCK L/D and H/D FYB engines, all for a reason.
I would show the chart but my scanner is still on the fritz.
BASIC PN 6571 valve seal chart shown below -
Attachments
Last edited:
rotorwrench
Well-known member
Aircraft engines have been running them for a very long time on the exhausts. Oil and air cool these engines so they need good heat transfer to the valve guides. They use high chrome guides now days so that they will last an overhaul period. They do pretty well with the late guides. I've only seen one valve fail in the last 40 years and it was an intake valve. The reason it failed was that that particular engine had a loose fuel injector that was making it run lean with power. I ended up with it after a customer purchased the aircraft on one of those "Good Deal" purchases. It failed within 50-hours after he purchased it. I didn't get a chance to inspect it before he started flying it. So much for Good Deals.
We still inspect the exhaust valve guides every 300-hours on these engines but I think they could go a lot longer now than before they changed to the hardened steel valve guides.
We still inspect the exhaust valve guides every 300-hours on these engines but I think they could go a lot longer now than before they changed to the hardened steel valve guides.