[66460GAL]

I subscribed to Scotts Re-Carnation site months ago and have been through it several times but I am still a little confused. I have D3VE heads and when reading about and looking at the pictures on the modification to the "bump" the pictures AS CAST do not look like mine. In the pictures the bump looks like it is maybe half the height of the valve boss, on my heads they are the entire length of the boss from ceiling to the end. When I started to remove the material, the bump "opened up" in the center due to the hole that runs up through it into the horizontal passage. I have removed all of the "bump material down to what I would consider the valve guide boss and until the horizontal bump was smooth with a small hole in the ceiling. I did not remove the horizontal passage as I have read in earlier posts people have drilled straight through the heads and driven a rod through the head. I did not modify the valve stem boss either. What part of the bump was supposed to end up looking like an air foil? And if I do not modify the valve boss am I leaving a lot on the table? This is for a street driven 4000lb Galaxie looking for 400-450 hp. I have gasket matched the intake already, followed the exhaust port instructions and bowl area below the valves but just do not want to hit water. Can someone please tell me what I am missing here and if there are different styles or am I just not seeing the picutres clearly.

Thank you

 

[chilly]

The thermactors I've personally seen are always as large as you describe.

 

[66460GAL]

T-Bump Size

Chilly,

Ok so then what part of the bump do you shape into the "fin". When I started to remove the material the center opens up leaving a right and left vain. I would assume that the right side would make the most sense. By removing all the material so that it looks relatively flat in the back have I caused damage, or have I still improved the flow and just not optimized the potential. Also should I shape the valve boss into a fin now to help or is this not necessary for my application.

Thank you

 

[chilly]

Hmm, the ones I've seen, there's plenty of meat left to do a vain straight off the valve guide, and then the hole is further down the port then where the vain ends. If you have pics they'd be very helpful to figure out what you have there.

Also, yes, I do think cleaning up the guide boss is helpful. I found it pretty simple using a 3/8" bit to get in there and slim it down.

 

[Paul Kane]

If you ground the thermactor bump all the way down and no longer have material from which to form a directional vane, you are still okay since these heads are so damn restrictive on the exhaust as cast. Your flow results can still be plenty improved with the proper contouring, smoothing and blending.

Grind the valve guide boss down flush with the top of the bowl. That and the removal of the Thermactor (plus bowl blend and short turn) will be more than adequate for your 450HP requirement, and should you choose to have your heads reworked on a flow bench in the future, there will still be enough materail remaining for "tweak & tune" of the ports.

Paul

 

[The Mad Porter]

When looking at the exhaust port from the bowl position the thermactor boss is with in about .080" of the top of the guide in as cast heads. If they have been modified or rebuild the valve guide boss could be taller and even with the thermactor boss.

I raise the guideboss until it is even with the thermactor boss when I start my bowl work anyway. When you begin to remove the boss (with the hole drilled) just leave the portion to the left of the drilled hole and then angle it toward the exit in the same plane as the roof.

Hope this helps... :mrgreen:

 

[66460GAL]

Thank you Chilly, Paul, and Scott

Sorry no pictures Chilly but these are plain jane D3VE's. Paul thank you for helping me sleep better I thought I may have ruined my heads by full removal of the bump. Scott your explanation was very clear and I meant to say left side in earlier post. Ok so off to do the short turn, the bowl blend, and modify the valve boss.

Thanks again

 

[ROADTOAD]

Plugging thermactor holes with rod in distribution passage

I read something about this using a rod rather than plugging each individual hole in the exhaust ports. Sounds alot easier than tapping & plugging 8 holes. Does the distribution passage need to be redrilled from each end, or can a rod of a certain diameter be simply driven in ?(assuming the passage is clean) What diameter rod? 1/2"?

Sorry for the half-assed hijack

Kirkwood

 

[ellisont]

a 1/2" rod works fine. I've been running a set of D00E-AB that way for years.