Porting the Edelbrock Pro Flow XT
 

Some of you may remember me threatening to get my hands on one of these new EFI tunnel ram intakes from Edelbrock. While I had some delays getting here, I did finally get my hands on one late in November.

As promised, I have cut the plenum top off and am in the process of working the runners and plenum over. The XT is already a pretty decent intake. If you were going to install it on un-ported heads you would be best to bolt it on as cast. This SBC version (p/n 7137) appears to support around 420-440 hp at about 6K rpm out of the box. For my purposes, installing it on ported Twisted Wedge G2 heads with a ZZX cam, it deserved a little attention to make the best of what is a very good design. EDIT: The 420-44hp range is from a 350cid with good aftermarket heads and matching cam. One installation on a 383 resulted in 460hp and 506ftlbs torque with an as cast p/n 7137.

I have heard concerns of the runners being too thin to allow porting to Felpro 1205(2.09 X 1.28). I myself had the same concern when I first looked the piece over. After opening up the plenum and going to work on a runner, I will state here for the record that these concerns are unfounded. There is plenty of material for at least the 1205 runner size. From my measurements, there is still a good 3/16" of wall at the thinnest point on the ported runner.

The as cast runners measure 1.99 X 1.49 at the entry. You can see in the photo the difference between the 1205 gasket and the runner exits.

The ported runner entry measures 2.10 x 1.60, an increase of about .100" both directions. This I've done to match the increase of the runner exit to the 1205 dimensions, maintaining the original taper between entry and exit. As you can see in the photo, I've stopped just a hair short of the full 1205. I may leave the exit there, aside from some detail work and finishing, as there is a minimal affect on flow from this small difference(about 1/16"). This way, I'm covered for alignment of the intake to the heads.

The large protrusion of the injector bung into the runner is another issue. I was going to install Bosch IIIs, which are 2.5" long and would have sat deep in the bungs, not allowing for much if any trimming. I decided instead to go with Edelbrock injectors that are 1.15" seat to seat and will sit against the top edge of the bung with only the o-ring and a very thin retainer sitting in the bung. This should allow for alot of trimming on the bungs. I'll have the injectors soon and then I'll finish the bungs.

For now, here are some progress photos.

Re: Porting the Edelbrock Pro Flow XT
 

Do you have cam/head info on that 383 you mentioned? ....While I don't presently have a plan to take my extremely ported TPI off my 383.... I feel it's only a matter of time (few years?) before I inevitably switch intakes, and really push my combo. I always like the looks, and somewhat rarity of the PFXT, but that rarity made reviews scarce.

What are your reasons for going this route as opposed to others? Super Ram, HSR, etc. etc. No shortage of good reasons, I'm just curious what yours are.

I look forward to seeing what you do with it.

-and good to hear on the 1205. That's why my RHS head ports are.

Re: Porting the Edelbrock Pro Flow XT
 

I'm sorry. I wrote a detailed reply and even posted links but as is common lately, the site dropped my login before I was finished. No time now to rewrite the post. I'll try again later. I really don't like all the active crud on the site these days.

Re: Porting the Edelbrock Pro Flow XT
 

Here are the links anyway:

https://www.corvetteforum.com/forums...ttle-body.html

http://www.superchevy.com/how-to/vem...flo-xt-intake/

http://www.edelbrock.com/automotive/...hevy-442.shtml

Re: Porting the Edelbrock Pro Flow XT
 

My choice of the XT is I suppose for my own reasons. I don't think we can compare the Superram to any of the better options today. The SR for one thing is long since discontinued and getting harder to find. Its complexity of assembly makes it a chore to work with and it just can't match the potential of either the HSR, the miniram, or the XT.

My reason for not going with the HSR is for one thing, it's not an air gap style intake and may be more succeptible to heat soak in hot weather, low speed cruising. It is also pretty tall for the 3rd gen hood line and makes hood clearance tight. There is no question of the HSR's performance potential. I see many successful builds using it.

The Miniram, while it is a strong performer, is a compact design to clear the hood of the C4 vette. I think that a taller, intake with slightly longer runners and larger plenum has more potential for average torque over just as wide an rpm range.

As cast, the XT has height issues of its own. The throttle body that Edelbrock sells to fit it is a fat 90mm single round throttle. Wedged between the T-stat and hood, it makes for a tight fit. Fortunately, the plenum top itself is about the same as the TPI at 8.2". By adapting the XT to accept a dual TB, like the 58mm I already have, the entire unit can be trimmed down to 8.2" making hood clearance no problem. With care taken to design the plenum entry correctly, I think I can even produce as good or better plenum function with the dual TB, than with the 90mm single. I'll include my work on the TB adapter in this thread.

Re: Porting the Edelbrock Pro Flow XT
 

I agree with everything you said, lol. SR, HSR, MR....completely agree. My performance choice would've been the HSR, but I really don't like the TB coming straight off the plenum. While it would fit my Iroc hood, I think it sometimes looks odd with CAI ducting, etc. etc. I'm a lover not a fighter. Gotta look good, lol.

Also interested in what you're saying about the PFXT TB. Didn't realize clearance was an issue with that round TB. Looked at that link but didn't really study it.

Honestly I've been working fairly steadily on this car since I pulled the L98 2 years ago. I'm honestly ready to take it off "project" status, and put 'er back on "car" status. Still.....idle hands need car parts, and a new intake is inevitable. This has been on my radar for awhile, but haven't done a whole lot of research.

Thanks for the feedback.

Re: Porting the Edelbrock Pro Flow XT
 

That guy's running 200cc heads with the LPE 219 cam, and he's hitting 6800 rpm. I'm using a similar Voodoo cam, but with RHS 180 heads. Really be curious to see what the XT does on my engine. My main complaint (which I knew would be) isn't power, but that it falls flat 5k. TPI. Cubes. Gotta love it. If I could pick up 1000 RPMs, it'd be worth it for time between shifts alone, let alone power.

Re: Porting the Edelbrock Pro Flow XT
 

If you're referring to the Corvette 383, peak hp with the XT was at 5,250 and peak torque at 4,300. The article stated that he was shifting at 6,300, but that was way at the very end of the power curve. If you look at the dyno chart, the motor was out of breath by then. I would attribute the low rpm tq and hp peaks, in large part, to the small runner exits on the XT and the restriction past the injector bungs. When you look closely, especially with this unit on the bench, the injector bungs are a major choke point.

Edelbrock tech has talked like this intake can support 550hp as cast, simply by going with larger injectors. I would really like to see them prove that. I will tell you right now, there is no way it will ever support that kind of power. Not without porting. The 383 in this article did pretty well, considering. With the ported XT and a more suitable cam, the 383 with ported Dart 200cc heads would get very close to 550hp.

Take a look at my latest photo, pretty much finished with the initial runner, which I'll use as a pattern for the rest. I've opened up around the injector bung and shrunk it down as much as I feel comfortable doing. I used the wealth of material on each side of the bung to bring the runner out at the top corners. The top of the runner is where the effective flow will occur. I want to be sure to provide an open path through this area.

This runner should shift peak torque upward about 500rpm from as cast. With my 240/240 @.050 .560/.560 cam and ported G2 heads, this should result in a 5,000rpm torque peak. This intake, as ported should easily support 550hp and 6,800rpm from a 383. And, I haven't really enlarged the runners that much. So it should still provide good torque from 2,000rpm.

There is still alot of material in the runner walls. You may even be able to take this thing out to a 1206 without need for welding on the runners. The only issue is accessing the runner entries, which requires cutting the plenum top off.

I've been looking over some sheet metal intakes. When this XT is finished, it will be every bit as strong as most any of the sheet metal intakes I've seen for the SBC. In fact, it has a better plenum and runner entry design than most of those so it should even do better. And, for a fraction of the cost.

Re: Porting the Edelbrock Pro Flow XT
 

Nice job so far

Re: Porting the Edelbrock Pro Flow XT
 

Nice work....that looks really good!:thumbsup:

I saw that 6300 as 6800, my bad. late night eyes going out on me, lol

Re: Porting the Edelbrock Pro Flow XT
 

Don't feel bad, I do that a lot. It helps that I've read that article a dozen times. The same with every other write up I could fond on the XT before I bought it. Thanks for the positive remark on my port work. I'm close to finished with the second runner. I'll post photos tomorrow.

Re: Porting the Edelbrock Pro Flow XT
 

I just had a shop complete my 383 with Pro-flo XT. He hasn't put it on the dyno yet. No porting has been done to heads or intake. It's going back into my 87 vette coupe with ZF6. I still have to pay him for the labor before he'll dyno it and give it to me. It's got a comp cam 08-468-8, Edelbrock heads, forged crank, Hbeam 6" rods with Mahle pistons. I'd like to hear more about your Pro-flo XT and perf numbers

Re: Porting the Edelbrock Pro Flow XT
 

Sort of a pro flo xt and doesnt need porting....

https://goo.gl/photos/FH57ounsz6ujVZ6s6

Re: Porting the Edelbrock Pro Flow XT
 

I'd like to hear more about YOURS, when you've got numbers, and have the keys back!

Re: Porting the Edelbrock Pro Flow XT
 

I WANT THAT!!!!!!!!!!!!!!!!!!!!!:thumbsup:

Re: Porting the Edelbrock Pro Flow XT
 

I probably won't have this engine dyno tested, but I will get it to the track for et and trap speed tests. In a few years, I'll be doing a 383 or 406. That motor will probably be dyno tested, depending on my budget at the time.

Re: Porting the Edelbrock Pro Flow XT
 

That's a nice looking intake. If I had seen that before choosing the XT, I may have gone that route. I think the XT has better runner entries though. The XT's are radiused and have a split angle that will reduce or eliminate turbulence. The CB unit could have its runner entries radiused and the runner bolt bosses trimmed down. The bosses could be shaved and studs installed. Any performance numbers using the CB intake?

I really like that it is completely modular and can be taken apart for port work and re-assembled. Can even swap in different runners. It's also a drop floor design which helps cylinder filling at high revs. This XT will be a drop floor when I'm finished with it. My favorite part of the CB intake is the removable plenum top. Think of how that would allow alignment of the intake and cyl head ports during assembly. Gets me thinking again about doing the same thing with this XT.

Re: Porting the Edelbrock Pro Flow XT
 

Just tried to find CB Performance with a Google search. Only CB Performance I find sells VW parts. Would like to know more about that intake.

Re: Porting the Edelbrock Pro Flow XT
 

I think my cb unit is the only one there is. I have their billet tb also. The base is what they offer for webers. It's all seperate pieces so could be easily modded. I'm keeping it like it is. Waa sour enough that the shipper broke the t stat housing

Re: Porting the Edelbrock Pro Flow XT
 

https://www.jalopyjournal.com/forum/...r-sbc.1071105/

Same base

https://rover.ebay.com/rover/0/0/0?m...2F391662573986

I contacted tgem and also pierce manifokds... no one knew what it was or if there were mors. Mine is brand new

Re: Porting the Edelbrock Pro Flow XT
 

Hell time you find one of those or piece one together you could already have a proflo ported lol or buy the cut down hsr

Re: Porting the Edelbrock Pro Flow XT
 

Hello Orr. I'm glad you got into this discussion. I'm sure you remember me talking about the XT two years ago when I was first looking at it. It's exciting to finally be working on it. Finishing it will be a process but I plan to be installing it early summer.

Re: Porting the Edelbrock Pro Flow XT
 

I seen this as an issue when i first looked at the proflo at summit racing. Its a great intake and i wouldnt hesitate to run it but unless you raise the injector bungs or do what you are doing, you'll never get the port area up to make serious power. Great power can be made on a 1205 size but serious stuff needs 1206 and up

For most guys tho 1205 is all you'll need. You could squeeze a high 10 sec pass out of a 1205 on a light car lol

Re: Porting the Edelbrock Pro Flow XT
 

The fluid flow dynamic tests that a kid at MIT did years ago (early 2000s) showed all the airflow sticking to the floor of the runner, not the top where the injector bung hangs down.

Testing intakes on flowbenches didn't account for the bend the air has to take through the valve area, which changes the path of the flow in the runner. The kid showed that on typical 23* intakes the whole top part of the runner wasn't used anyway.

-- Joe

Re: Porting the Edelbrock Pro Flow XT
 

Too funny, that used to happen to me as well lol. Just an FYI, the next time that happens, just log in immediately after on that very page that it takes you to, your post will immediately be posted as it is saved (pending) until you sign back in. However, if you navigate away from the page it takes you to for another log in it will lose whatever you wrote...

- Rob

Re: Porting the Edelbrock Pro Flow XT
 

Thanks Rob. I usually do that when I get bumped after taking too long on a reply. Honestly, I may not have even logged in yet when I started writing. When I don't visit the site for a while, my auto login doesn't work. I was whining about the site's functions when it may have been my out fault.

This morning, I see that the auto login is working.

Re: Porting the Edelbrock Pro Flow XT
 

Hi Joe. Fluid dynamics dictates that how air flows through a runner will depend on the overall runner design. This of course includes the cyl head intake port that is part of the effective runner. In my case, the cyl head port is that of a TFS G2 head with a 16 degree intake valve and stock style intake port location. This means the air has to traverse a greater curve than on a typical 23 degree head. I provided for this when I ported the heads, smoothing the curve as much as practical and providing the best air flow path possible. Of course on any cyl head intake port, the optimal airflow would be at the top of the port, as straight a shot as possible to the valve. This is why the best race heads have raised runners. It's also why the LS heads, especially the LS3, work as well as they do.

We know that air flows like water, and is susceptible to centrifugal force like any matter. This would tell us that air will tend to follow the outside of a curve. In the case of the XT like most any top feeding intake runner on a V motor, the runners' curve will push air toward the floor. However, as the runner tapers toward the exit, the airstream will be forced into line by the velocity created by the airs own kenetic energy. This will force the air to fill the entire runner exit.

The exception to this would be any jagged or sharp edges that will cause the airstream to eddy and turn back on itself. This will result in effectively, a loss of runner dimension. As if that part of the runner was filled or blocked off. While I give credit to the XT's designers for producing a good runner, it appears that in executing the design, they weren't careful as they could have been in finishing out the injector bung or the runner around it. A close up visual inspection of this area of the runner shows the kind of jagged, sharp obtrusion that will cause air to eddy and turn back on itself, effectively closing off the top of the runner.

Opening up around the bung, smoothing and shrinking this obtrusion, should greatly reduce this effect and really improve flow mass as well as velocity through the runner exit. This in turn will help encourage airflow to the upper portion of the intake port.

Of course, this all theory based on my understanding of fluid dynamics. I don't have a flow bench or fluid dynamics modeling software to prove any of this. I think that this will work out well. If I'm wrong at least no one will suffer for it but me.:)

Re: Porting the Edelbrock Pro Flow XT
 

Doesnt account for area of port size and many engine builders will disagree as results in the field matter more. Port area and how it relates to intake runner length tuning matters.

Head ports on a 23 deg you have to control velocity over the short side radius. Shaping the floor helps and the resulting velocity gradiant from top to bottom is more uniform

On a bad port theres a good chance the bottom is too fast and you'll see more air using that floor rather than roof

If that simulation was true then race 23 deg engines wouldnt need larger ports

Re: Porting the Edelbrock Pro Flow XT
 

Here are some photos comparing the completed pair of runners to the as cast. Pretty dramatic difference. I'll still work some more on the radius' at the runner entries. I think they're still a little sharp. They do look pretty good though.

Re: Porting the Edelbrock Pro Flow XT
 

Sorry I've been swamped so I didn't respond to this.

This is an impressive answer, and your education and background really shows here. It's great to have this type of dialog on here.

I have absolutely nothing to add, you completely explained the reasoning behind what you are doing and how it will impact flow. I wish we had more folks like you on here!

-- Joe

Re: Porting the Edelbrock Pro Flow XT
 

Yeah, thanks bro. I just hope I'm somewhere close to half right. What I know of fluid dynamics comes mostly from working with heads and intakes for a while now. I was looking online for information on intake manifold design and found a website with some pretty good tech info. It doesn't offer any equations. The writer accurately implies that the ideal design depends on a whole bunch of variables.

http://www.swartzracingmanifolds.com/tech/index.htm

It does address runner entry radius, which is just what I was looking for. It seems to me like the radius' of my two ported runners isn't as large as the as cast. I opened up the entrances .100" both ways and cut some of the radius out. I'm working on restoring it with some careful die grinder work and sandpaper. I think I'm closer to 1/4" radius than 1/2". The writer of the tech info on this site recommends 1/2" radius on most EFI intakes. I'll work to I get these out there.

I found that a friend of mine, a mechanical engineer, has put together a machine shop in his garage. I'm going to talk to him about helping with my TB adapter and re-assembling the plenum. Where the plenum was cut open, the floor to wall transition was ruined. The top radius' of two runners was cut into as well. I was going to fix this with epoxy, but I'd rather have the plenum walls welded back in and have the transition cut back in on a mill, no epoxy. Then, I can recreate the two runner radius' with my carbide and sandpaper. Finally, when the runners and plenum floor and walls are all done, I'll have the top welded back on.

Re: Porting the Edelbrock Pro Flow XT
 

Damn, I just saw an intake similar to yours, but it had a removable top.
But for the life of me, I can't remember where. IIRC, I think it was black in color.

Re: Porting the Edelbrock Pro Flow XT
 

There is a marine intake that is close in design. Really looks more like the CB unit that Twin Turbo has. I can't remember the name of the maker though. The more I think about it, I'll probably just get it welded back together. I can use my bore scope to look down the runners for alignment during assembly.

Re: Porting the Edelbrock Pro Flow XT
 

Do you mean the thing with the cast in throttle body?

Re: Porting the Edelbrock Pro Flow XT
 

I don't remember it having a cast in TB. I'm so close to remembering the name. There is at least one member of TGO that runs one. It's black and has a removable plenum top.

Re: Porting the Edelbrock Pro Flow XT
 

Is it the black scorpion mercury marine intake? It's based in an edelbrock victor ram

This is the older one with integral tb. Its an edelbrock piece and I think it was available in natural color. I lusted for one but missed it. May have been lingenfelter who had it

Re: Porting the Edelbrock Pro Flow XT
 

This is the victor ram based one


https://m.ebay.com/itm/Mercruiser-35...35?_mwBanner=1

They were available with a straight top also. Had rear mounted tb but the top can be flioped

Re: Porting the Edelbrock Pro Flow XT
 

Heres a guy running the older style

https://www.thirdgen.org/forums/tpi/...pi-marine.html

Re: Porting the Edelbrock Pro Flow XT
 

Finally finished with the bank 2 runners. Still more clean up to do on the entry radius and the plenum floor transitions. You can see in the photo the transition from the plenum rear wall to runner #8. I'm getting a different carbide to help in that area.

Visited a friend of mine Saturday. He's a mechanical engineer who's built a pretty nice machine shop in his garage. He's going to help me with the plenum clean up and assembly. He'll flat mill the horizontal cuts so that I can get those angles right. That is an important part of controlling airflow in this plenum.

It's obvious, looking at the last photo, that the welder cut too deep in the corners. I had hoped for more precision. Instead, the cuts were a little rough. Kinda wish I had made the cuts myself, but at least it's fixable. I'll take it back to the welder and have him build up the areas where he got too deep. Once I have the the runners finished and I'm sure there is plenty of border between the runners and the plenum wall, I'll get it out to the machinist for milling.

He's also going to do the boring on the TB adapter for me. I'm concerned with getting the bolt holes and throttle bores centered right. His vertical mill will make this a lot easier.

Re: Porting the Edelbrock Pro Flow XT
 

Got my rails and injectors yesterday. Mocked up one rail and injector to look at depth in the injector bungs, if there was still room for more trimming. You can see these PICO injectors sit back in the bung about 1/4", so there is still tons of room for trimming. For now though, I think I'll leave them as they are. I may still do more work around the bungs. I am going to get a different carbide that will help in that area.

I went with the short injectors to be sure I had plenty of clearance for the TPI throttle bracket. It looks like there will be lots of room.

On a side note, these injectors are unlike any I've ever seen before. I've worked professionally with factory EFI vehicles since 1992 and I've seen every variation of injector from every manufacturer many times over. These PICOs from Edelbrock are tiny. Not just short but iddy biddy. About 1.5" long and 1/2" round. I guess they'll work just fine though.

BTW, sorry about the crappy blurry photos. Try not to get dizzy looking at them. Promise I'll do better on the next ones.

Re: Porting the Edelbrock Pro Flow XT
 

Here are some better photos.

Re: Porting the Edelbrock Pro Flow XT
 

Very cool stuff. Glad to see different things still being played with.

Re: Porting the Edelbrock Pro Flow XT
 

It's a cool project. Look forward to getting it done.

Re: Porting the Edelbrock Pro Flow XT
 

The XT's been at the welder's for a few days now getting the plenum edges built up where it was cut too close to the runner entries. I actually picked it up yesterday. It looked good at a glance, but after looking it over more closely, I see one area where it still needs more. So, it will be going back to the welder before it goes to the machinist. It looks good so far though.

Talking to the welder, I picked up some new ideas also. The sides, rather than being bent from flat bar, will be cut from 3" aluminum pipe. Schedule 40 is .22 thick and just the right in/out diameter to fit and will provide a little more inside volume and clearance for the 58mm throttles. It will create a more oval shaped plenum.

Rather than a bolt on TB adapter, we will be welding a new throttle flange in place to accept the dual TB. The existing flange will be cut away to allow the 3" pipe side walls to join the new TB flange. We're reusing the plenum top with the Edelbrock emblem and ribs. It will be shorter than the walls. The gap will be filled with flat bar. I'll post more photos soon.

Re: Porting the Edelbrock Pro Flow XT
 

Photos

Re: Porting the Edelbrock Pro Flow XT
 

Looking real good doc.
Curious to see the tb mod.
Subscribed

Re: Porting the Edelbrock Pro Flow XT
 

Thanks bro. Hoping to make some progress soon. Need to get this phase of welding done. Wish I did TIG myself so I wasn't dependent on others for it.

Re: Porting the Edelbrock Pro Flow XT
 

Got the XT back from the welder today. Very pleased with his latest work. I removed the upper portion of the throttle flange, cutting down to match the sides of the plenum. I may rough out the opening also to save the machinist some time milling it to match the plenum walls. Getting pretty exciting now.https://cimg4.ibsrv.net/gimg/www.thi...3c0c884268.jpg

Re: Porting the Edelbrock Pro Flow XT
 

Off to the machinist on Sunday. It will look a little different, especially the front, when I get it back. Then, I'll finish the porting and fine tuning the runner entries before we start assembling the throttle flange, walls and roof of the plenum.

Re: Porting the Edelbrock Pro Flow XT
 

No news yet from the machinist. He's a busy guy so I'll be patient. The machinist and I talked about a removable plenum top. I had abandoned the idea over concerns with sealing and general logistical issues. After more research, I think I may have come up with a solution. This will work well with the dual throttles and provide a removable top for future access to the plenum floor and runner entries.

Here is a photo of a Hogan's intake with a removable top plate. Our design will look something like this.
https://ls1tech.com/forums/attachmen...take-hogan.jpg