Cam Selection for Weber DCOE carbs

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Captainslow42
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Cam Selection for Weber DCOE carbs

Post #1 by Captainslow42 » Wed Dec 27, 2017 12:15 am

Does anyone here have experience with running 3 Weber side draft carbs on a 300? I'd be interested to know if there are any rules I ought to adhere to for selecting a cam. I have been led to understand that DCOEs perform best with high lift, moderate duration cams, with a high LSA due to reversion problems with overlap. But I'm just an amateur with an ambitious project! I'm not looking for anything too radical, as this engine is going into a car which will be frequently driven around town, and which will most likely never see a track or a drag strip, and I don't want to be stalling at stop lights and getting 5 MPG. I have been looking at a selection of comp cam and isky products, but I'm not sure where to start, so I'm open to suggestions! Thanks!

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Re: Cam Selection for Weber DCOE carbs

Post #2 by rbohm » Wed Dec 27, 2017 2:50 am

it really doesnt matter what cam you choose, so much as how you tune the carbs. reversion can be a problem with individual runner carb systems, even using holley carbs. we had the problem with pro stock cars and reversion running tunnel rams and holley dominator four barrel carbs. it usually happens though as you noted with large overlap cams, and usually at higher rpms, and even then usually in a narrow rpm band.

so pick a cam that operates in a wide rpm band, and get the tuning for your webers right, including the tuning of the air horns. as i recall, longer air horns means reversion happens at a higher rpm. its been a while since i have tuned an IR system.
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Re: Cam Selection for Weber DCOE carbs

Post #3 by Captainslow42 » Wed Dec 27, 2017 10:06 pm

Thanks for that! It's one thing in this build that I just haven't been able to get my head around. When someone says a "low" LSA I'm not quite sure what qualifies as "low" and whether or not I even need to worry about it. I'm not planning to spin this think much past 4500 rpm. Good to know! Now onto my next challenge, Getting Chokes, venturis, jets + tubes right : :)

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Re: Cam Selection for Weber DCOE carbs

Post #4 by Captainslow42 » Wed Dec 27, 2017 10:36 pm

Also, I see one of your cars is a Falcon?? I'm hoping this engine will eventually find it's way under the hood of my 61 Falcon. I'm currently short on shop space though so that'll have to wait for a bit.

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Re: Cam Selection for Weber DCOE carbs

Post #5 by pmuller9 » Wed Dec 27, 2017 11:02 pm

What year engine and compression ratio?

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Re: Cam Selection for Weber DCOE carbs

Post #6 by Captainslow42 » Wed Dec 27, 2017 11:13 pm

pmuller9 wrote:What year engine and compression ratio?



Came out of an 83 F150. Pretty sure its got the 8:1 compression, although I can't say with 100% certainty.

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Re: Cam Selection for Weber DCOE carbs

Post #7 by pmuller9 » Thu Dec 28, 2017 3:05 pm

Are you rebuilding the engine or just adding the carbs, cam and headers?

I looked at a set of these 3 weeks ago at the PRI trade show.
https://store.jenvey.co.uk/throttle-bod ... e-tdt40-48

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Re: Cam Selection for Weber DCOE carbs

Post #8 by Captainslow42 » Thu Dec 28, 2017 6:44 pm

pmuller9 wrote:Are you rebuilding the engine or just adding the carbs, cam and headers?

I looked at a set of these 3 weeks ago at the PRI trade show.
https://store.jenvey.co.uk/throttle-bod ... e-tdt40-48



I'll be doing a total rebuild top to bottom, Hyper pistons, overbore only if I need it, Cam, port and polish, 3 angle valve job, new intake, 2 into 3 exhaust headers, yet to be determined ignition mods, etc. And I'm still not sure what sort of condition the crank is in. I am mostly still in the saving and planning phase, I hope to start building in spring.

Wow, did you have something in mind for those injector units?

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Re: Cam Selection for Weber DCOE carbs

Post #9 by pmuller9 » Thu Dec 28, 2017 9:11 pm

Looks like a good plan.
The 4 highest compression Hyper pistons are:

5/64 x 5/64 x 3/16 piston ring set:
Speed Pro/Sealed power H519P
KB/Silvolite 1186H

2mm x 2mm x 4mm piston ring set:
Speed Pro/Sealed power H674P
KB/Silvolite 3171H

All have a 22cc "D" dish.
The metric ring set has less cylinder drag.

If you machine the block for Zero piston to deck clearance the compression ratio will be 8.8:1

I'm sure your build plan included screw in studs for the rocker arms which will let you use roller rockers that will easily accommodate valve lifts around .500" lift or more.

A cam with 0 +/- 1 degrees of overlap based on the .050" cam duration using the stock 110* LSA will give you a very slight lope at idle but deliver reasonable fuel mileage and plenty of power.
Here are three examples:

Crower Cams 284HDP (19205) .509”/.517” 220/222 284/290 110deg
Howards Cams 280996-10 .501”/.501” 221/221 275/275 110deg
Schneider Cams 140H (13912) .496”/.496” 220/220 280/280 110deg

With only an 8.8 compression ratio you can afford to raise the Dynamic compression ratio by using less advertised duration while decreasing the advertised duration overlap as well.
That would be the Howards cam with 275* of advertised duration
If the compression ratio was higher then the Schneider or Crower would be the better choice.

Nothing from Crane, Comp, Clifford or Isky matches.

I like to stay with a 1.6 ratio rocker arm.
The higher ratio arms increase the pressure on the lifter to cam lobe contact surface which increases the chance of losing a cam lobe.
I also prefer steel rocker arm over aluminum for longevity.
This is the last set of roller rockers I used on a build.
https://www.summitracing.com/parts/cca-1826-12
https://www.dropbox.com/s/dlwsfdl82ziie ... 4.JPG?dl=0

I was looking at Jenvey's line of throttle bodies with the hopes of finding an easy way to make Stack Injection for EFI gas street and mechanical alcohol for track use.
After looking at what most of the injection companies have to offer I'm pretty much settled on making the units myself as a single throttle body unit with six butterflies on a common shaft.

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Re: Cam Selection for Weber DCOE carbs

Post #10 by Captainslow42 » Fri Dec 29, 2017 11:56 pm

pmuller9 wrote:Looks like a good plan.
The 4 highest compression Hyper pistons are:

5/64 x 5/64 x 3/16 piston ring set:
Speed Pro/Sealed power H519P
KB/Silvolite 1186H

2mm x 2mm x 4mm piston ring set:
Speed Pro/Sealed power H674P
KB/Silvolite 3171H

All have a 22cc "D" dish.
The metric ring set has less cylinder drag.

If you machine the block for Zero piston to deck clearance the compression ratio will be 8.8:1

I'm sure your build plan included screw in studs for the rocker arms which will let you use roller rockers that will easily accommodate valve lifts around .500" lift or more.

A cam with 0 +/- 1 degrees of overlap based on the .050" cam duration using the stock 110* LSA will give you a very slight lope at idle but deliver reasonable fuel mileage and plenty of power.
Here are three examples:

Crower Cams 284HDP (19205) .509”/.517” 220/222 284/290 110deg
Howards Cams 280996-10 .501”/.501” 221/221 275/275 110deg
Schneider Cams 140H (13912) .496”/.496” 220/220 280/280 110deg

With only an 8.8 compression ratio you can afford to raise the Dynamic compression ratio by using less advertised duration while decreasing the advertised duration overlap as well.
That would be the Howards cam with 275* of advertised duration
If the compression ratio was higher then the Schneider or Crower would be the better choice.

Nothing from Crane, Comp, Clifford or Isky matches.

I like to stay with a 1.6 ratio rocker arm.
The higher ratio arms increase the pressure on the lifter to cam lobe contact surface which increases the chance of losing a cam lobe.
I also prefer steel rocker arm over aluminum for longevity.
This is the last set of roller rockers I used on a build.
https://www.summitracing.com/parts/cca-1826-12
https://www.dropbox.com/s/dlwsfdl82ziie ... 4.JPG?dl=0

I was looking at Jenvey's line of throttle bodies with the hopes of finding an easy way to make Stack Injection for EFI gas street and mechanical alcohol for track use.
After looking at what most of the injection companies have to offer I'm pretty much settled on making the units myself as a single throttle body unit with six butterflies on a common shaft.



Wow! Thanks pmuller9 for all your help :) I've got a lot of thinking to do now. Are the screw in studs something which is available specifically as an upgrade for the 300 head or are they sourced from a different engine? I've been looking all over for them online and can't seem to find exactly the set I need...Also, would you recommend going to a 7/16" stud? thanks again!

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Re: Cam Selection for Weber DCOE carbs

Post #11 by pmuller9 » Sat Dec 30, 2017 2:00 pm

There aren't any rocker studs that are specific for the Ford 300.
If you use the 1.6 Ratio BBC rockers I recommeded then you will need a 7/16" upper end.
I used a 1.75" long rocker stud.

Are you looking at larger intake and exhaust valves?
The 1.910" long SBC 1.94" intake and 1.60" exhaust valve work well.
The non-EFI heads has 1.810" long valve.
All stock valves are 1.780" intake diameter and 1.559" exhaust diameter.

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Re: Cam Selection for Weber DCOE carbs

Post #12 by Captainslow42 » Sat Dec 30, 2017 11:40 pm

pmuller9 wrote:Are you looking at larger intake and exhaust valves?
The 1.910" long SBC 1.94" intake and 1.60" exhaust valve work well.
The non-EFI heads has 1.810" long valve.
All stock valves are 1.780" intake diameter and 1.559" exhaust diameter.


I had thought about the larger valves, I was unsure of the cost of milling the head to accept the new valve seats, and I haven't got pricing from anyone in my area. I would if I could do it without breaking the bank. Although I guess it would be pointless to send the head off to a shop to get New stock valves and seats installed and modified, stick the thing back together, drive for a few months then pull it apart and move to enlarged valves, might as well just do it. Will I need a matched set of pushrods with the taller bbc valves? Valve train geometry is a subject I am not well schooled in...

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Re: Cam Selection for Weber DCOE carbs

Post #13 by pmuller9 » Sat Dec 30, 2017 11:50 pm

Captainslow42 wrote: Will I need a matched set of pushrods with the taller bbc valves? Valve train geometry is a subject I am not well schooled in...

SBC valves

I needed longer pushrods for my set-up.
The roller rocker tip needs to ride across the center of the valve stem tip.

In theory at mid valve lift, the line through the center of the roller rocker tip and the center of the roller rocker shaft or pivot point should be 90 degrees with the valve stem.

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Re: Cam Selection for Weber DCOE carbs

Post #14 by WorldChampGramp » Sun Dec 31, 2017 10:27 am

It is so refreshing to see all this knowledge shared openly among likeminded inline Ford enthusiasts. EVERYONE on this Forum should be thankful to those contributors like P. Muller who in my opinion is one of the most knowledgeable engine builders I have ever had the privilege to converse with. Now To the point. I vividly recall some 45 years ago when we went through the rocker arm geometry issues with Preparation H. Using an adjustable pushrod available for many sources like Summit, Comp cams etc. the near perfect length can be determined using a black Magic Marker or machinist’s layout dye on the tip of the intake/exhaust valve stem. With adequate spring tension [even with a lighter ‘checking spring’] the roller rocker will clearly show you just where the center of its force is on the valve stem tip. Too short a pushrod will make an impression to far toward the “toe” of the valve toward the spark plug side of the head. The reverse is true of a too long pushrod. Order your custom 3/8’ pushrods based on the above SUGGESTION and you “should be good to Go” pun intended. Just my 2-cents Bruce Sizemore

:beer: HAPPY NEW YEAR To All

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Re: Cam Selection for Weber DCOE carbs

Post #15 by Captainslow42 » Sun Dec 31, 2017 6:41 pm

Thankyou all for taking the time to share your expertise with me! I've got so many more questions floating around in my head, but what I really need to do next is get the thing on a stand and start tearing it down and cleaning/measuring everything so I know exactly what I've all got! Hopefully 2018 is going to be a busy year :D

Happy New Years!!

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Re: Cam Selection for Weber DCOE carbs

Post #16 by pmuller9 » Sun Dec 31, 2017 8:56 pm

What size are your Weber DCOE carbs?

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Re: Cam Selection for Weber DCOE carbs

Post #17 by Captainslow42 » Sun Dec 31, 2017 9:35 pm

pmuller9 wrote:What size are your Weber DCOE carbs?



I selected 45's, the 152 model

Main Venturi - 36mm

Aux Venturi - 45

Air ram tube- 62mm length

Main Jet - 145

Air corrector - 155

Emulsion tube - F18

Idle Jet - 55 F8

Accelerator pump Jet- 45

Accelerator pump valve - 40

Start Jet - 85 F9

Start Jet air corrector - 150

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Re: Cam Selection for Weber DCOE carbs

Post #18 by Captainslow42 » Sat Jan 06, 2018 12:54 pm

I've also been brushing up on some of the theory behind intake tuning in preparation for choosing parts, and I've been left a little bit uncertain about a few things. Is it possible to port out a 300 head too much? I don't know how much I would need to open it up before I would begin to see a detrimental loss in intake air velocity. The IR intake I plan on using has fairly long runners, and I don't want to disrupt the "intake ramming" this gives me at low/mid rpm by creating a large pressure drop right before the valve. Or is the stock head so restrictive that I can safely enlarge the ports and valves without much concern? Any advice would be appreciated :)

Another thing I've been wondering about is fuel atomization. I was talking to the manufacturer of this particular manifold (guess who :) ) and was told that one of the reasons production was originally discontinued was because of poor fuel atomization in the runners. I've also been led to believe that one downside of polishing intakes and heads is that while it improves total air flow volume, the elimination of the rough casting surface also eliminates the "boundary layer" airflow that normally prevents fuel from condensing and pooling in the walls of the intake runner. Is this anything I need to be concerned about? Again, I may be a little out of my depth here :? If anyone can shed some light on this for me, you have my thanks :D

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Re: Cam Selection for Weber DCOE carbs

Post #19 by pmuller9 » Sat Jan 06, 2018 1:21 pm

Even fully ported big valve 300 head ports are too small for 50 cid cylinders.
The port walls are thin and it is easy to hit water jacket so port enlargement is limited.
Most of the work is focused in the pocket area around the valve guide boss/

The Jenvey solution to the Weber atomization problem is delt with by installing fuel injectors in the body so it still looks like a Weber but has better fuel control.
https://store.jenvey.co.uk/throttle-bod ... e-tdt40-48

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Re: Cam Selection for Weber DCOE carbs

Post #20 by Captainslow42 » Wed Jan 10, 2018 11:23 pm

Thanks! I'll scale back my porting plans a bit. Rather not risk wrecking a perfectly good head if there isn't much room. Would you recommend De-shrouding the valves? If I go to the larger chevy valves will there be much room to do so anyways? I apologize if these questions have obvious answers, I haven't really had an opportunity to pull the head yet... Also, on another note, in the picture you shared with me of your roller rocker setup I noticed you installed pushrod guideplates. I had thought that guideplates were only necessary with the later pedestal-mount rockers/ efi heads? or does it have something to do with the fatter pushrods?

:thanks:

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Re: Cam Selection for Weber DCOE carbs

Post #21 by pmuller9 » Wed Jan 10, 2018 11:44 pm

The 1985 and 86 carb heads also had pedestal mount rockers. My head was an 86.
If your head is an 83 then you will not need guideplates.

I bolted the head on to the bare block and scribed the cylinder bore circle to the head surface.
Then I pulled the spark plug side of the chamber walls back to the scribe line and smoothed out the rest.
These are 2.02/1.64 SBC valves. I recommend staying with the 1.94/1.60 combination.
https://www.dropbox.com/s/5t7b6y8h5vdpu ... r.JPG?dl=0

Intake port: Notice that most of the work is in the bowl area around the valve guide. The port walls hade very little material removed.
https://www.dropbox.com/s/xklz27x77cvgh ... 3.JPG?dl=0

Exhaust port: Here the valve guide boss is ground flat across leaving a shelf before entering the port.
You can also see the undercut valve stem.
https://www.dropbox.com/s/pycdq6q58ecd0 ... t.jpg?dl=0

Ask any question you need to.

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Re: Cam Selection for Weber DCOE carbs

Post #22 by WorldChampGramp » Thu Jan 11, 2018 12:10 am

PMuller9 what bore size are the scribe lines attributed to. Bruce Opps Flight tomorrow AM better quit while I am a head. 240 rather than 300 :idea:

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Re: Cam Selection for Weber DCOE carbs

Post #23 by pmuller9 » Thu Jan 11, 2018 12:17 am

WorldChampGramp wrote:PMuller9 what bore size are the scribe lines attributed to. Bruce Opps Flight tomorrow AM better quit while I am a head. 240 rather than 300 :idea:

In this case it was 4.040"
I don't care for the 240 head, Too much shrouding with big valves.
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