Ported A429's Valve Job

Howdy Folks, I am putting together a cast crank 501 for my Bracket race Fox Body 86. I picked up a set of A429's that have been heavily ported. The valves that were in the heads were a little beat up. It looked like they had been floated. The keeper grooves were damaged and there was some fretting on the keepers/retainers. I am replacing all the valves and the retaniers.
The valves that were in the heads have a multi angle backcut 15'/30'/45' seat on both the intake and exhaust. I know that the backcut is a good thing on the intake, but does anyone have any input with backcutting the exhaust valves?
Back in the 80's I did high-end head work in a shop that specialised in SBF. Back then I didnt find a significant benefit to backcutting exhaust vales on the flowbench. I am a low buck racer working out of my garage now, so I don't have access to a flow bench anymore, but I do have access to a valve facer.
The heads are early A429's 2.245/1.76 and I am aware of the clipping isues. I'll be running a conservetive SR cam 248/260@.050, .675 lift, to keep the car slower than 10.0' ET's Any input would be appreciated
Thanks, Daniel

There's a lot to be said of your A429's. Wait for Charlie's response!

Dave.

I'll be waiting to.

ustahava67 wrote:Howdy Folks, I am putting together a cast crank 501 for my Bracket race Fox Body 86. I picked up a set of A429's that have been heavily ported. The valves that were in the heads were a little beat up. It looked like they had been floated. The keeper grooves were damaged and there was some fretting on the keepers/retainers. I am replacing all the valves and the retaniers.
The valves that were in the heads have a multi angle backcut 15'/30'/45' seat on both the intake and exhaust. I know that the backcut is a good thing on the intake, but does anyone have any input with backcutting the exhaust valves?
Back in the 80's I did high-end head work in a shop that specialised in SBF. Back then I didnt find a significant benefit to backcutting exhaust vales on the flowbench. I am a low buck racer working out of my garage now, so I don't have access to a flow bench anymore, but I do have access to a valve facer.
The heads are early A429's 2.245/1.76 and I am aware of the clipping isues. I'll be running a conservetive SR cam 248/260@.050, .675 lift, to keep the car slower than 10.0' ET's Any input would be appreciated
Thanks, Daniel

Back-cutting the exhaust valves will depend greatly upon the angle which the backside of the valve is already at.
Is it a tulip or a nailhead or something in-between; it all makes a difference.
What valve lift are you seeking an improvement as different angles will help somewhere but hurt in others.

As with a lot of things in an engine - "one size does not fit all".

ustahava67 wrote:Howdy Folks, I am putting together a cast crank 501 for my Bracket race Fox Body 86. I picked up a set of A429's that have been heavily ported. The valves that were in the heads were a little beat up. It looked like they had been floated. The keeper grooves were damaged and there was some fretting on the keepers/retainers. I am replacing all the valves and the retaniers.
The valves that were in the heads have a multi angle backcut 15'/30'/45' seat on both the intake and exhaust. I know that the backcut is a good thing on the intake, but does anyone have any input with backcutting the exhaust valves?
Back in the 80's I did high-end head work in a shop that specialised in SBF. Back then I didnt find a significant benefit to backcutting exhaust vales on the flowbench. I am a low buck racer working out of my garage now, so I don't have access to a flow bench anymore, but I do have access to a valve facer.
The heads are early A429's 2.245/1.76 and I am aware of the clipping isues. I'll be running a conservetive SR cam 248/260@.050, .675 lift, to keep the car slower than 10.0' ET's Any input would be appreciated
Thanks, Daniel

Daniel,

David does a good job of embarassing me,,,,it's gotten to the point I can't take him out in public anymore.

As to your questions,,,you are correct, there is no need for a backcut on the exhaust. The intakes like a backcut that is 15* shallower than the seat angle. So a 30* backcut with a 45* seat is ideal. What is more important than the angle of the backcut is the width of the backcut. A width of about .075-.085" seems to be a sweet spot.

Remedies for the clipping issues are to;

1. Reduce the size of the intake valve, which is what Ford did.
2. Reduce the size of the exhaust valve.
3. Sink the valves.
4. Cut a 45* chamfer from the margin to the face of both valves.
5. Open up your valve lash in order to effectively shorten your duration a little bit.
6. Make sure your springs are strong enough to not let the valves float.
7. I'm sure there are a few other tricks that I have forgotten.

Hope this helps,
Charlie

Charlie, The original valves show some witness marks of very slight clipping. The guy I got the heads from was running a 275 @.050, .780 lift cam, I'm thinking Ill be OK with the shorter cam but I haven't mocked it all up yet.
Randy, I am replacing the valves with a set of 'lingenfelter' BBC 2.25 intakes I found on ebay and a set of ferrea TFS exhaust 1.760. The A429 exh. valves were a tulips, the ferrea's are a nail head. My main concern is not hurting the low lift flow since I'll be camming the engine down.
Thanks to ya'll for the tips on how to deal with this and make it work well!
I am happy to be getting back to a 385 engine. I started racing again about 5 years ago and have been whipping on a SBF 347. My first 385 was a 429 that I put in my 67 fastback in 1983 back in the day!
Daniel

ustahava67 wrote:
Randy, I am replacing the valves with a set of 'lingenfelter' BBC 2.25 intakes I found on ebay and a set of ferrea TFS exhaust 1.760. The A429 exh. valves were a tulips, the ferrea's are a nail head. My main concern is not hurting the low lift flow since I'll be camming the engine down.
Thanks to ya'll for the tips on how to deal with this and make it work well!
I am happy to be getting back to a 385 engine. I started racing again about 5 years ago and have been whipping on a SBF 347. My first 385 was a 429 that I put in my 67 fastback in 1983 back in the day!
Daniel

To help the low lift flow, back-cut the exhaust valve to 20 degrees until the valve seating area is just barely wider than the seats on the head; (hand lap a valve to see how wide the actual seating area should be). That back-cut will probably be 1/4" wide.
That will help flow from .050" valve lift to about .250" valve lift and hurt some flow from .250" valve lift to about .350" valve lift.

Personally, I wouldn't go for low lift flow unless the maximum valve lift is around .500" or less or the camshaft has to wide of a separation. A 35 degree back-cut of a nail head exhaust valve, up to the inner seat size will help slightly in the middle valve lifts and pretty much be the same everywhere else.

Hi Randy thanks for the tips. I am not looking to enhance low lift flow so much as just not take away from what's already there,so I know which direction I'll be going . Thanks Daniel