Porting the Edelbrock Pro Flow XT 7137

and posting the math here would certainly not hurt either

I measured the forward ports width through the throttle opening, using a dial caliper. The height I measured using a tape though it was difficult to be accurate. A pair of inside lathe calipers, reaching in through the runner would be better.

I'm considering also my tooling for the tb adapter project. I have a friend with a drill press I can use but I prefer to have my own. I also have to make two cuts in thick aluminum. I may have to use a hand saw and just take my time.
 
dealing in facts beats guessing all the time,
and you get FACTS about port size by careful measurement.
just remember the runner wall thickness is subject to damage if you get overly aggressive removing metal,
the old "measure twice cut once" advice holds true
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https://www.harborfreight.com/6-piece-telescoping-gauge-set-5649.html

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https://www.homedepot.com/p/General-Tools-12-in-Inside-Caliper-454-12/202545173?cm_mmc=Shopping|THD|G|0|G-Pro-PLA|&gclid=EAIaIQobChMI6J6Lq8Si2AIVlbrACh1ZWQfYEAQYAiABEgI5TfD_BwE&gclsrc=aw.ds&dclid=CLqo4rHEotgCFVLZwAod5HoAtg

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Amen to that. I plan on using a lathe caliper to monitor wall thickness as I work on the runners. Right now the manifold is at the welders getting the plenum top removed. I hope to have it back tomorrow. I'll post photos. With the plenum top off, I'll be able to better measure the runner entrances.

I wasn't able to get my mind around working the lower runners without being able to clean up the plenum walls and runner entrances. Now, I'll be able to do a thorough job. Photos tomorrow I hope.
 
The set of bore gauges from HF looks like a real bargain. I also found a 3 piece caliper set on eBay at a good price. I have mics and dial calipers.
 
Ordered a caliper set from Amazon this morning. Paid a little more that I could have for them but gave me a chance to use a old gift card I've had for too long. Welder picked up the XT yesterday and I got it back today with the top removed. Wish just a little that I had been more clear about the guidelines. I really should have drawn out the line for the but I thought the guy understood my instructions. It's okay, I'll have him weld over the two areas where I think he got a little too close to the runners. In one spot you see where he nipped the top edge. He's a good old guy and he's super reasonable so I'll cut him some slack here. After I work on the runners I'll have him add material to the areas of concern, then I'll form them where I want them before he welds the top back on.

At any rate, here is the open plenum.
 

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Here is one port entry with minor cleanup, minimal material removal using an 80 grit roll. After smoothing the rough surface, I followed up with 120 grit sandpaper to get really smooth. The photos suck but looking at it under the light, the finish looks good. I won't do more until I have calipers so I can measure and monitor runner size and wall thickness. I won't do anything on the outlet end until I mark it up to match the gasket.

I made a change of plan last night as I considered clearance between the driver's side fuel rail and the throttle cable bracket. With the long Bosch IIIs I was planning on using, it would have been tight, maybe undoable. The Bosch IIIs are 2.5" from seat to seat. As far as the injector bungs intrusion into the runners go, the Bosch IIIs also would have sat deep, not allowing for much trimming of the bungs. After some research, I decided on the Edelbrock PICO style injectors. They are the newer short design. 1.15" from seat to seat. They also have a large base that abuts the bung and limits depth. Basically, just the o-ring inserts into the bung with very extension past that. This will allow alot of trimming of the bungs inside the runners. I'll get the injectors in hand as soon as possible so I can use one for reference and work on trimming the bungs.
 

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BTW, as you can see here, the shape I saw in the runner entries( thinking they were not rectangular) was an optical illusion caused by the viewing angle through the throttle opening and the joining of two angles midway along the runners' vertical dimension. Looking at them straight on, they are pretty much rectangles, with a very slight widening midway along the vertical axis. The split angle in the vertical dimension will still help cut turbulence. As I polish the plenum interior, I'll define this and the other angles designed into the plenum walls and floor. The runner entries as cast measure 1.49" x 1.96". The partially polished runner measures 1.51" x 2.05". That's measured with my dial calipers which aren't a great tool for this. I'll measure again when I have lathe calipers.

I also can see a solution for my screw up on the plenum cut and its proximity to the runner entries. I was going to have the welder add 1/8" to the plenum height anyway to replace what was taken away in the cut and very slightly increase volume. What I'll do to correct the cut mess up is have him weld a layer of 1/4" bar stock around the top of the base and fill any gap to the inside of the added material. Then, I'll shape the runner tops and recreate the plenum walls into the new material. I'll then remove the necessary material from the plenum lid to arrive at the desired added height. It's additional work but I caused this myself by not clearly marking where the cut should be and by proposing a cut too close to the plenum floor to begin with. At least it's fixable.
 
you look like you've got a good start, and that intake will certainly be better,
than the stock config once you've modified it.
Id take the time and effort to open the runners up a bit larger than the 1.51 x 2.05,
how much is obviously up to you but about 1.6 x 2.10 would be closer too what Id be shooting for if it was my intake while its apart
 
Thanks Grumpy. 1.6 x 2.10 is certainly doable and sounds good to me.
One thing I remembered quickly tonight is how hard these castings can be. Just the minimal clean up on half of one runner took some time. The 80 grit roll I was using has a tough time cutting. I'll order more rolls, some 40 and 60 grit for cutting. The kit I have has quite a bit of 80 and 120. No 40 and very little 60.
I'm really bugged about the cutting of the plenum. I had planned for a better cut than what I ended up with and was originally going to make the cut higher, further away from the runners. I changed the plan at the last minute and now its going to have to be fixed. Ill take the XT back to the welder on Tuesday and get it taken care of right away so i can move on with the work.


Like you said and I already know, measure twice cut once. Also, never make snap decisions just before building or changing something. As I could have guessed, my last minute judgment overlooked important details and left me with more work.
I think I have come up with a pretty good plan for fixing it though. I'll cut the bottom .750" from each side of the plenum top. Since the welder's cut isn't real straight, the pieces I cut from the top will match up. I think I can get straighter cuts too, which will help the final weld go better maybe. I'll have the pieces I cut from the top welded back on to the bottom. Then I'll recreate the floor wall transitions and the runner tops. I'll rest much easier when this screw up is fixed and I can get on with the progress.
 
Looks like you are doing an excellent job of thinking about how to obtain your end goal ! Yes, you said
you made a mistake, but how many have you done? One Means a mistake or two is inevitable.

I do have one question ..... Everything I've read says you don't want a smooth surface in the intake
port. Rough helps keep the fuel particles in suspension, where smooth causes the particle to pool in
the intake port. So the question is why have you decided to go with smooth, just wondering what
information you are using? One advantage of rough is the 40 grit would allow faster cutting.
 
rough and smooth are fairly relative terms, smooth in an intake runner generally refers,
too the mirror like surfaces that were almost thought too be mandatory in the 1950s-early 1960s
but you certainly can,t get a "smooth surface texture "
with anything in a flapper wheel of 80 grit or larger grit

http://www.thepolishingshop.co.uk/acatalog/Flap_Wheels_Long_Reach_.html

http://www.thepolishingshop.co.uk/acatalog/Flap-Wheel-10mm-x-10mm-x-3mm-Shank-Std.html

http://garage.grumpysperformance.com/index.php?threads/where-to-buy-abrasives.3422/#post-9070

http://garage.grumpysperformance.com/index.php?threads/porting-can-help.462/page-3#post-72525

http://garage.grumpysperformance.co...-by-step-guide-with-pictures.5378/#post-71848

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Looks like you are doing an excellent job of thinking about how to obtain your end goal ! Yes, you said
you made a mistake, but how many have you done? One Means a mistake or two is inevitable.

I do have one question ..... Everything I've read says you don't want a smooth surface in the intake
port. Rough helps keep the fuel particles in suspension, where smooth causes the particle to pool in
the intake port. So the question is why have you decided to go with smooth, just wondering what
information you are using? One advantage of rough is the 40 grit would allow faster cutting.

Concern with fuel droplet suspension applies to wet flow intakes, where fuel air mixture flows through the intake runners. The XT, like any port injection manifold, is a dry flow intake. Only flows air. Smooth walls means less restriction and turbulence. A smooth surface also reduces total surface area and heat transfer from the metal to the air.

Yes, this my first time modifying the XT manifold. Though I've built numerous high performance engines throughout my career and many had heads and intake porting done my me.

I am notoriously guilty of making snap decisions that end up costing me. After all my planning and thought, I let one moment of impulse thinking cause this major set back. If this were one of my many fabrication projects, I might scrap it and start over. Since this is a several hundred dollar manifold, I will just have to fix it. It will take some time but with care from here on, the result should be good.
 
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if thats the only mistake you,ve made,
your so far ahead of most of us we can,t see your tail lights !

the first time I replaced a clutch I was about 16,years old,
and I was so damn proud that Id managed to remove and replace the transmission and replace the clutch....
until I found it would not release once it was back together....
so I was forced to go ask this old geezer who must have been something like 50 years old...
that worked at the local Pontiac dealership, and he instantly deduced,
that Id installed the clutch disc facing the wrong direction, from the symptoms.....
Like I said, we mostly learn by making mistakes and if were smart,
and by watching other people make mistakes.
.
.

and you can bet you remember which way a clutch disc faces after that
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if thats the only mistake you,ve made,
your so far ahead of most of us we can,t see your tail lights

Thanks Grumpy, for at least trying to help me feel better.

It's still early in the project. Plenty of time yet for mistakes. I'll feel so much better when I've got this first big one fixed. Better yet when this project is finished successfully.
 
Concern with fuel droplet suspension applies to wet flow intakes, where fuel air mixture flows through the intake runners. The XT, like any port injection manifold, is a dry flow intake. Only flows air. Smooth walls means less restriction and turbulence. A smooth surface also reduces total surface area and heat transfer from the metal to the air.

Ok, yes I see what you are saying, I just did not think about it being fuel injected. :confused:

You might want to try cross buffs, they work well for polishing. They would be the next step, between
cartridge rolls and felt wheel and rouge.

https://www.summitracing.com/parts/...8r_cx-DL__ge-TtTptiBDtcyrs7deiu8aAp7_EALw_wcB

https://www.summitracing.com/search...sives-cross-buffs?autoview=SKU&ibanner=SREPD5

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Thanks Indycars. I have considered cross buffs. The runners of the XT are straight enough though that with the.plenum top off, I can run sandpaper through each one quite easily. The 120 grit produces a very nice finish, following the 80 grit roll.

I've seen rouge used on intake ports before. I don't know if that smooth a surface is really necessary in an intake runner. If I want smoother, beyond 120 grit, I can follow with finer paper. I have some 220 laying around. The most important and beneficial part of porting, as far as I know beyond defining runner shape for a straighter flow path, is removing casting flash that can cause turbulence. A smooth surface, to a point, also reduces mean surface area by the flattening of what was a rough, jagged cast surface. I dont know how much benefit there is in going past a 120 grit finish. I never have.

I've seen the nearly chrome port finish Grumpy referred to earlier. In some cases, without much real improvement of the flow path. This was done on old factory head castings that would never go much past 220cfm anyway but I can't imagine the polish did much good in a poorly defined port.
 
a mirror polish surface, on intake and exhaust ports used in the 1950s-1960s, was done mostly for "marketing"
it did little to increase flow, or reduce flow restriction but it did surely increase the new potential owners pride of ownership,
and the ability of the guys selling the heads to put them next to a stuck production cylinder head,
and have an obvious difference they could point out, and if it was done correctly I.E. the port shape and contour and increased cross sectional area,
the surface finish was at best a very marginal issue
 
Hi Grumpy. I like your post about clutch assembly. I remember very well doing the same thing myself. Wondering the entire time why the pressure plate was going on so hard. No better way to learn I guess. This way we never forget.

I achieved 2.1" x 1.6" today at the entry of the first runner, using a 60 grit roll. I also marked the 1205 opening at the same runner exit and took that out to within 1/16". I'll go back through it with 80 then finish with 120. I'll also restore the radius at the entry, which I cut into quite a bit taking the runner out to these dimensions. I'll post photos tomorrow after this next step.

I need the inside lathe calipers I ordered last week. I need to take measurements to be sure the taper is right. I'll use an unported runner as a pattern and take measurements at several points for reference. I'll try to maintain the same taper as I enlarge each runner.
 
Here are some photos of the progress so far. As you can see, I have more work to do on the runner exit and a little more work on the entry radius. Already the difference between as cast and after porting is pretty obvious. I'm not finished with the injector bung either. Once I have the injectors, I'll cut the bung back to just cover the injector. Hopefully, this will result in a big reduction in size of these darned bungs. Anyway, I'm pleased so far. I remember thinking I would need to add material to get the runners out to a 1205. Turns out there is plenty of material. I'm getting more excited about getting this thing finished, installed, and the EFI tuning finished. Got a long way to go before then but each step is one step closer and so far it's going well.
 

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