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Edelbrock DP Modification

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old28racer
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Edelbrock DP Modification

Post #1 by old28racer » Mon Aug 19, 2019 10:21 pm

I have an old DP intake that I am not going to use, had it for years, not much tied up in it. As I may want to run my Holley 2300 2bbl for a while, I am looking at milling the 4 port holes out so it is an open feed area. I would install a 4x2 adapter to the modified DP intake.

One guy on the site sent me a picture of how he did modified a 4 port square bore setup as shown in picture #1. It leaves the center material & knife edges the material left inside. I would like to do mine a little different.

In picture #2 all the red area would be removed down to the Pimary & Seconary runners. The same adapter would be mounted to this modified DP intake.

I know it is not a C or Clifford but I have it on hand. Comments please, will it work out?
Image
Image
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Re: Edelbrock DP Modification

Post #2 by MechRick » Tue Aug 20, 2019 4:06 pm

So you are going to completely remove the dividers?

The only problem I forsee is you *might* create mixture distribution problems. If you can make the plenum and intake floor appear like a known configuration (like an Offy 'C' or Clifford), you should be able to avoid that.

If you remove the dividers you could bolt a flat plate to the intake with two holes for the carb venturi.

If you can cut away the dividers from the head face a few inches, with a looooong carbide burr bit, along with what you have in mind for the dividers in the plenum, it *should* make it function like a 'C'...
Last edited by MechRick on Wed Aug 21, 2019 12:02 pm, edited 2 times in total.
1994 F150, 4.9L/ZF 5 speed, C-Vic police driveshaft
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Re: Edelbrock DP Modification

Post #3 by BigBlue94 » Tue Aug 20, 2019 7:28 pm

How tall is the adapter plate? Pics?

I ask because if it is an open bore, it will effectively negate the dual port aspect of that manifold.

If it were me, I'd remove all the red portion, and the floor of the higher side of the dual port design. Leaving the dual port dividers in the runners themselves may prove beneficial, as it should in theory, increase the velocity of the intake charge. However, the dividers add friction, so it's all hearsay unless tested. Not sure how you'd remove them anyway.
1985 Bronco. 309ci I6, NP435, 4.56 gears, Detroit locker and tru-trac, 4" lift, and 37" swamper tires. The 309 is 9.75:1 CR with a Schneider 140H cam, 4bbl, roller rockers, larger valves, and headers.

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Re: Edelbrock DP Modification

Post #4 by old28racer » Tue Aug 20, 2019 11:42 pm

MechRick --- Thanks for the reply and information. Still in the planning stage. I have not seen a picture of A "C" or Clifford Plenum floor. Will have to find one to see what you are talking about.

BigBlue94 --- The 4x2 adapter is one inch thick, I plan on running a 1" open spacer with the adapter. Yes it will not be a dual port intake any more, Will be more a pour mans "C" or Clifford. Like I said above it is still in the planning stage, any & all comments welcome. This is my first time trying something like this.
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Re: Edelbrock DP Modification

Post #5 by BigBlue94 » Fri Aug 23, 2019 5:19 pm

Here ya go, my Clifford without any adapter plates.

Image
1985 Bronco. 309ci I6, NP435, 4.56 gears, Detroit locker and tru-trac, 4" lift, and 37" swamper tires. The 309 is 9.75:1 CR with a Schneider 140H cam, 4bbl, roller rockers, larger valves, and headers.

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Re: Edelbrock DP Modification

Post #6 by old28racer » Fri Aug 23, 2019 8:26 pm

BigBlue94 ---- Thanks for the picture of your Clifford intake plenum floor. As the DP has primary & secondary runners at different levels the floor will not be flat as in the Clifford.
I do not know if the upper runner in the DP can be milled down to the same as the lower runner so the bottom plenum would look more like the Clifford bottom. What do you say?
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Re: Edelbrock DP Modification

Post #7 by BigBlue94 » Sat Aug 24, 2019 10:39 am

Without investigating a DP, it's hard to say. However, I think it should be feasible to remove the upper step without issues.
1985 Bronco. 309ci I6, NP435, 4.56 gears, Detroit locker and tru-trac, 4" lift, and 37" swamper tires. The 309 is 9.75:1 CR with a Schneider 140H cam, 4bbl, roller rockers, larger valves, and headers.

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Re: Edelbrock DP Modification

Post #8 by wallen7 » Sat Aug 24, 2019 12:13 pm

If you cut the 4 hole divider out I think you will find that the runners have 2 levels. I think if you polish and blend the 2 levels in the plenum it will work fine, especially with a open adapter on top. It wont be a C but it should be close.

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Re: Edelbrock DP Modification

Post #9 by bubba22349 » Sat Aug 24, 2019 12:38 pm

:hmmm: I have to wonder though if you wouldn't get much better results in Economy / Performace by just mounting a Autolite / Motercraft 4V carb so that the primaries are facing towards the valve cover as these DP intakes were designed for. Good luck on your experiment. :thumbup: :nod:
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Re: Edelbrock DP Modification

Post #10 by pmuller9 » Sat Aug 24, 2019 1:48 pm

old28racer wrote:
In picture #2 all the red area would be removed down to the Pimary & Seconary runners. The same adapter would be mounted to this modified DP intake.

I know it is not a C or Clifford but I have it on hand. Comments please, will it work out?

Image


I would just cut it out as shown all the way down to the bottom of the manifold and open up all runners to the new plenum.

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Re: Edelbrock DP Modification

Post #11 by old28racer » Sat Aug 24, 2019 8:07 pm

pmuller9 --- Thanks Paul for the reply. If I remove all the red material all the way to the bottom of the intake plenum I think the corners can be removed also. Is this correct?

If all material is removed to the bottom of the plenum will the square cut runner that are open to the plenum need the edges knife cut/ground?
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Re: Edelbrock DP Modification

Post #12 by pmuller9 » Sun Aug 25, 2019 12:36 am

I would leave the upper corners round and just remove the material shown as red.
You can cut the corners sharper down in the plenum.

Air does not approach knife edges as well as round edges. Knife edges are for trailing edges. Round off the square edges.

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Re: Edelbrock DP Modification

Post #13 by old28racer » Sun Aug 25, 2019 12:00 pm

pmuller9 --- Thanks for the additional comments. I never really looked at knife edge as for trailing edge, make lot of sense. I will round off all the edges inside the plenum and leave the corners.
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Re: Edelbrock DP Modification

Post #14 by old28racer » Sun Aug 25, 2019 7:37 pm

If all the red material was removed in picture #2 all the way to the intake bottom the cubic inches would be as follows:
New open DP intake plenum = 33.49 cubic inches
1" 4x2 adapter = 12.25 cubic inches
1' open spacer = 12,25 cubic inches
Total open plenum will be 58.19 cubic inches.

As the rule of thumb for a open plenum for a 300" 6 cylinder is one half the cubic inches so that would be 150. My 58.19 is about 1/3 of that. Will this setup be OK for a mild street F250?
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Re: Edelbrock DP Modification

Post #15 by BigBlue94 » Thu Aug 29, 2019 6:44 pm

old28racer wrote:If all the red material was removed in picture #2 all the way to the intake bottom the cubic inches would be as follows:
New open DP intake plenum = 33.49 cubic inches
1" 4x2 adapter = 12.25 cubic inches
1' open spacer = 12,25 cubic inches
Total open plenum will be 58.19 cubic inches.

As the rule of thumb for a open plenum for a 300" 6 cylinder is one half the cubic inches so that would be 150. My 58.19 is about 1/3 of that. Will this setup be OK for a mild street F250?


By that calculation, a 460 would have a 240i6 for an intake manifold... that just doesnt sound right.

I can tell you right now my Clifford is no where near even 100 ci. Probably about 40... The edelbrock EFI intake on my old 351w was maybe 100ci. But efi is quite different. And I've never seen any v8 manifold sized that large (100ci+/-) until you get into bored and stroked big blocks with 1000 cfm carbs.

I would say you'll see a significant improvement and it will be plenty sufficient for mild towing/hauling/roasting tires.

On my Clifford, the 4bbl adapter is a 4-hole plate, 3/4" thick.
1985 Bronco. 309ci I6, NP435, 4.56 gears, Detroit locker and tru-trac, 4" lift, and 37" swamper tires. The 309 is 9.75:1 CR with a Schneider 140H cam, 4bbl, roller rockers, larger valves, and headers.

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Re: Edelbrock DP Modification

Post #16 by old28racer » Thu Aug 29, 2019 10:46 pm

BigBlue94 -- Should have said for a race motor, my buddy has built a 2x2 plenum intake off of a EFI lower intake with two 2150 1.08 carbs and the plenum is 145 cu in. As in the above information my adapter has a 1" open plenum along with a 1" open spacer
33.49+12.25=12.25 = 58.19" I agree it should work out real good.
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Re: Edelbrock DP Modification

Post #17 by old28racer » Mon Sep 16, 2019 11:24 pm

pmuller9 & others ---- After I mill out all the red area on my DP intake do you think my Holley 2300 350cfm 2 bbl carb will still work with a 1" spacer and a 1" thick 4x2 adapter. Not building a performance setup just a nice mileage cruiser. Really don't want to step up to a 500-600 cfm 4 bbl at this time.
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Re: Edelbrock DP Modification

Post #18 by pmuller9 » Tue Sep 17, 2019 9:09 am

If you mill out the red area you will not need the 1" open spacer.

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Re: Edelbrock DP Modification

Post #19 by old28racer » Tue Sep 17, 2019 12:40 pm

Thanks Paul for your reply, sorry I did not finish what I was asking. After I mill out all the red center and install the 1" thick 4x2 adapter will my Holley 2300 350 cfm 2bbl carb still work with this modified DP intake or will the intake require a bigger carb to run right. Seems like it will be like using a Clifford or C open chamber that work well with a 2bbl carb. Don't want to go to a 4v carb at this time.
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Re: Edelbrock DP Modification

Post #20 by F-250 Restorer » Tue Sep 17, 2019 3:08 pm

So, is modifying an Edelbrock DP the same as modifying an Offenhauser DP? Ha ha.

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Re: Edelbrock DP Modification

Post #21 by old28racer » Tue Sep 17, 2019 10:14 pm

What a sharp Dude :thumbup: :wow: :nod:

More or less the same :bang: LOL
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Re: Edelbrock DP Modification

Post #22 by xctasy » Fri Sep 27, 2019 2:24 am

For you, old28racer.I think you are onto something good with your plans.

I'm sure your healing up okay, and that you may have in the past seen this. Copy for your info while your on the mend.


http://fordsix.com/viewtopic.php?f=2&t= ... 29#p587329



Carloespo wrote:Image

IMG_20150321_123544506.jpg

This Moody intake was on a championship winning car on display at the International Motorsports Hall of Fame at the Talladega speedway in Alabama.


its311pete wrote:
82F100 wrote:
its311pete wrote:I run a H/M on my race car and I can say without a doubt the H/M intake performed better than a Clifford. This is using a
Holley 350 2 brl carb, 240ci. running up to 7k down the straights.

I modified a 2" carb. spacer the had 4 hole divider and dropped it down in the big intake plenum hole . A old timer told me this would give it signal. It dramatically helped low to mid rpm throttle response and didn't hurt upper RPM performance.


Do you have any pics of this mod?


No I didn't take any pics. Here is the spacer I bought.

Image


I cut the bottom lip, the part that would normally bolt up to the intake, completely off. I cut the connecting
pieces that went in between the upper and lower plates off . This allowed the spacer to drop down into the plenum
about 2".
Image
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FAZER 6Bi (M112 & EEC5) or FAZER 6Ti (GT3582 & EEC5) 425 HP 4.1L/250 I-6
FAZER 6V0 3x2-BBL Holley 188 HP 3.3L/200 I-6 or 235 HP 4.1L/250 I-6
X-Flow Engine Components Ltd http://www.xecltd.info/?rd=10

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Re: Edelbrock DP Modification

Post #23 by old28racer » Fri Sep 27, 2019 1:39 pm

Good information. Do you have a part number for this spacer?
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Re: Edelbrock DP Modification

Post #24 by old28racer » Sun Oct 06, 2019 7:05 pm

As a secondary thought I may mount a Autolite 4100 4V 1.08 venture carb on the opened up Offenhauser DP intake.This carb is rated at 480 cfm. Has anyone used one on a DP, C, Cliford 4V open intake on a 240/300 inline 6?

As I have found most say that they run 48-50F primary jets and 55/58F secondary jets with a 8.5 power valve that was stock. Does the jeting sound right? I will run a 6.5 power valve.

My feeling is that my Holley 2300 350 cfm 2V carb will be to small as a single unit on my opened up DP intake. The 300 inline 6's like 400-500 cfm carbs.
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Re: Edelbrock DP Modification

Post #25 by xctasy » Fri Oct 11, 2019 5:13 am

old28racer wrote:Good information. Do you have a part number for this spacer?



Either the shallow or real deep 1-1/2" H.V.H Super Sucker,

Shallow is like this


Image


https://www.carid.com/hvh/hvh-4150-supe ... 17240.html

Deep is HVH® - 4150 Carburetor Spacer image 12 of 13
more details on - https://www.carid.com/hvh/hvh-4150-supe ... 17240.html, butcha gotta look a lottle

Or the Wilson Manifolds Tapered Carburetor Spacer, 4150 or 4500 Dominator


https://www.summitracing.com/search/par ... or-spacers
Image
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FAZER 6Bi (M112 & EEC5) or FAZER 6Ti (GT3582 & EEC5) 425 HP 4.1L/250 I-6
FAZER 6V0 3x2-BBL Holley 188 HP 3.3L/200 I-6 or 235 HP 4.1L/250 I-6
X-Flow Engine Components Ltd http://www.xecltd.info/?rd=10

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