[cls]

Would anyone here know what the max useable lift would be on a set of Pontiac D Port heads with out cutting the spring pads

thanks

[OINK 1]

Stock stuff- .454"
Ferrea 5000 or 6000 series valves F5143's F5144's- .580"
Ferrea-F5063's F5066's - .650"

6000's are for solid roller cams.

Need help?
1-303-776-0877
Pontiac Gregg

[steve25]

you can get .050" more with out cutting the spring seats by going to a different spring/ retainer and matching + .050" valve locks, but you will need to check your retainer to rocker clearance dependant on your push rod lenght.

[rumair]

a guy i know named tom introduced me to a guy named lee a few years ago in virginia. lee had a kick-a** V-headed firebird with some contraption on top of the engine that forced in a bunch of air. i wonder what happened to lee and his car?

[ta man]

I used crower's 68404 springs and had .536 lift no issues with stock valves.

[Tom Vaught]

Send a note to Marty Palbykin, Lee. He posts on the board occasionally and will respond. The #62 cast iron castings that were on his "d-port" twin turbo engine had a big roller camshaft.

Tom Vaught

[screamingchief]

Originally Posted by cls

Would anyone here know what the max useable lift would be on a set of Pontiac D Port heads with out cutting the spring pads

thanks

As a cavaet to the current comments,let me add that this also depends on the specific head castings in question,and what length the OE valves were.

The late model heads ('71 up) use a shorter valve length to start with,so adding longer valves can gain quite a bit of room.

With the earlier HP/big valve heads you start out with a longer valve,so there's less room with the commonly available valve lengths.

Using the stock '67 to '70 length valves in the '71 up heads adds .100" right off the bat,so you can see how that comes into play here.

My '71 #96 heads are like that,5.090" valves replace the 4.090" valves.

That yeilds an IH around 1.700",and there's room for .650" lift and still have adequate clearance before coil bind and/or retainer to seal clearance.

I could easily add .100" to that by going to the RAIV length valves in those #96 castings,so the later "smog" heads can be set up to manage .750" lift with minimal effort and the right valves.

The earlier '67 to '70 big valve/small chamber heads will need custom length valves to handle that sorta lift,they'll manage around .650" lift max with the RAIV length valves,and standard valvetrain hardware.

As mentioned plus height retainers and locks can add some to that,just as long as you dont run into interference issues with the rocker arms being used.

As far as machining the seats,they're plenty thick (avg. .250"),so I would'nt be uber-paranoid to cut them some should they need it,just keep it reasonable (.090" to .100" or so) and they should hold up just fine.

Though without quality porting the point of all that lift is sorta lost in the mix.

HTH

BP.

[71 Ventura II]

WARNING: Before investing in offset retainers check the end of your rocker arms! I found out the hard way that not all roller rockers have a "larger" roller at the tip. In my case we tried installing +.050 retainers to get the installed height needed but found out the body of the Crane Energizer roller rockers hit the retainer before the roller at the tip touched the valve! CRAP! We ended up pulling it apart and machining the spring pads.

Note: Harland Sharps would have worked as they have a large roller wheel at the tip. Not sure about other brands. JD

[D. Miles]

I had 5.20 RA-IV Length valves in my # 13's with standard height titanium retainers and +.050 locks, the installed height was 1.875 so I assume the spring seats were cut, I used Comp Cams 938 springs with a .660 lift roller and 1.65 rockers which brings the lift up to .726, after valve lash would be .698... I loved that motor/combo! I would suspect super stock guys would laugh at these lifts though... D. Miles

[455-4+1]

As Screamingchief said it all depends on what the chamber cut depth is to begin with, a smaller chamber needs longer valves to get the same installed height

We ended up with 1.950" installed with a slight seat touchup on a set of 48's (small chamber)
2.125" dia intake, 5/16" stem, 5.300" long

[steve25]

Do not use a true RA4 tulip type intake valve in a stock, or even more so ported D-port head, as you will drop low mid air flow numbers a bunch. That valve was made to work in RA4 heads that start off having .060" more short turn height than a high comp D port has, no less a 71 and up head.
I have never tested the RA4 valve in a stock 6X head so it may not drop flow numbers, if I have time over the weekend I will find out.
Just as a side note, the RA4 tulip exh valve will add 10 to 15 in low lift exh flow so that makes it a good drop in for added installed height.

[Brian Baker]

Is there really any point in running more than .650" lift in any d-port head, ported or otherwise, considering the flow numbers level off around .550"?

[D. Miles]

Originally Posted by Brian Baker

Is there really any point in running more than .650" lift in any d-port head, ported or otherwise, considering the flow numbers level off around .550"?

The way I see it, say you have heads (most of the ones I've had anyway) that don't have great or super low and mid lift flow numbers but they have great high lift numbers, my 13's weren't bad at mid lift but were crappy at low lift but really came alive above .600, peak flow if memory serves me was 264.8 @ .600 263 @ .650 and stayed above 260 cfm all the way to .750 but was under 240 @ .550. So having a cam with .700+ lift and heads that don't gain flow above .600 but doesn't lose flow either and the fact that there are no cam lobes that would go to .600 lift and stay there for a long period of duration, the trick is to go past your peak flow lift IF your heads DO NOT lose flow at higher lifts, it's sort of like holding the valve open in your peak flow lift range. I used an aggressive lobe with 1.65 rockers to get to my peak flow target fast, the car really responded when I went to the larger cam and responded again when I went to the 1.65 rockers, I wish I had a set of 1.7's to try back then... D. Miles

[60man]

Originally Posted by Brian Baker

Is there really any point in running more than .650" lift in any d-port head, ported or otherwise, considering the flow numbers level off around .550"?

Really ?? Any D-ports..Sort of...My KRE's Bubba..

[Brian Baker]

I was referring to factory heads, Troy.

'Miles, I hear what you're saying and it seems we are on the same page somewhat. Your heads were within just a few cfm from .600", .650", and up. My point was with this being the case, and the valve being at peak lift for such a short amount of time, why go with a higher lift cam? If peak flow happens between .600" and .650" and starts to drop at higher lifts, why go with a .700" lift cam? Wouldn't this hurt velocity by allowing the port flow to "slow down" or would the inertia created by the velocity over-ride the ports flow slowing down, thus still filling the cylinder efficiently? And then there's the aspect of unneccessary valvetrain stress from the higher lifts.

[HWYSTR455]

I'm with Brian on this one, have seen no point in going over say .550 in MOST cases, on a D-port. If you look at factory head flow charts, the drop is actually at .469 or so, but you gain some when you clean up the ports and bowl. Duration should be used to 'hold the valve open', not lift, or that's my line of thought. Even on the heads 60man has the numbers posted, you'll see there's minimal gain from .600-.700. Port velocity is the key in D-ports, was always my impression...


.

[cls]

Hey Fellas thanks for all the comments on my question.....I am using #62 heads and going with roughly a 650 lift cam....so I appreciate the help....

Rumair....yes the bird was running good but apparently leaked water on #6 all winter long and rusted the bore .....we also lost the rod bearing from hydrostatic pressure when we were dyno tuning right before Pinks came to Charlotte ....so no pinks for me...I am so fed up with the V's that I am going to a set of Dports and just blow the **** out of them and see if I can run in the 8's in the 1/4 anyway....it is going to be fun to try....

Also let Brian keep his title of worlds fastest centrifugel blow thru Pontiac for the next year or so before I take that back from him....;-)

Hope you are doing well.

Lee Schwilm

Also if anyone is interested in a complete ram air 5 topend for an alchohol steup with blower cam, headers for a stock frame rail 70 bird, complete heads ready to bolt on and a sheet metal custom injected intake with rails please contact me at 704-458-9128....the heads leak water on the exhaust ports so this set up would only work well with alchohol.

[455-4+1]

Originally Posted by Brian Baker

Is there really any point in running more than .650" lift in any d-port head, ported or otherwise, considering the flow numbers level off around .550"?

Depends on the head, my iron D-ports were still going good @ .775

Not bad considering they were over 280 @ 0.500" @ 28" on a 4.21" bore

[Brian Baker]

Originally Posted by 455-4+1

Depends on the head, my iron D-ports were still going good @ .775

Not bad considering they were over 280 @ 0.500" @ 28" on a 4.21" bore

Define "going good". Was the flow at .775" roughly the same as at .650"? Or was it still climbing? This is an area I'd like to hear on from some engine builders/tuners, particularly those with experience in porting and flowing heads. In my mind, it would seem like a waste of mechanical energy going with a .750" lift cam (for example) when the airflow in the port levels off at .600" or .650". And what of a case where the flow at .750" is lower than at .650" but is still within 3-5 cfm? Would you still shoot for lift a little higher than where peak flow occurs? Does the velocity in the port overcome the slightly lower flow numbers and still fill the cylinder efficiently, due to the short amount of time the valve is in this area and thus not allowing time for the velocity to lag with the flow? Things that make me go "hmmmmmmmmm".

[John Bailey (GTOKID)]

My 6x heads did not stop flowing at .550 lift...and I had a old superstock roller and it out ran my RA4 solid lifter motor.(both 455's)