Click Here -> Please Consider Making a PayPal Contribution to the FordSix Forum!
2018 Contributors:
StarDiero75, curts56, DannyG, B RON CO, wsa111, Captainslow42, falconcritter
Econoline, THE FRENCHTOWN FLYER, 95FordFleetside, turbo6, Max_Effort, WorldChampGramp
cr_bobcat, C.S.Designs, pmuller9, gus91326, rwbrooks50, rocklord, drag-200stang, Big64my79Effie, CNC-Dude, gb500

2019 Contributors:
NJwpod, 1strodeo, mightynorseman, maxtrux, 6d7coupe, broncr, Phase3, 68Flareside240, bmbm40,
mustang6, WorldChampGramp, justintendo, BigBlue94, ags290, motorsickle1130, Rooster, ousooner919, ethanperry

Unknown->> M.Ketterer, T.Smith, J.Myers, P.McIntire - Please PM me (1966Mustang) and lemme know who you are!

Carb options

Moderator: Mod Squad

Supervan66
Registered User
Posts: 7
Joined: Sat Feb 09, 2019 10:23 pm

Carb options

Post #1 by Supervan66 » Tue Feb 12, 2019 1:44 am

Hi guys, thanks in advance. I’ve been lurking for awhile and you folks have givin me a whole lot of useful information.
I’m putting together an engine for my 1966 econoline camper van and I need to pick out a good carb. Here’s my engine build.
-77 300 engine with a 240 head
-Bored 0.060
-Decked to 0.020
-Silv-0-lite 3118h pistons ( 25cc )
-comp cam 260h kit
- hartland sharp 1.6 roller rockers
- clifford truck headers
- Offenhauser C series intake.

Anyways, I’m looking at 2 different holley carbs , both have a $250 price tag and are in almost new shape.
Option 1 - Holley 390cfm ( #6299-1 )
Option2 - holley 450cfm (#4548)
Both have vacuum secondaries and will need to be jetted.
Just looking for some opinions.
Thanks

User avatar
THE FRENCHTOWN FLYER
VIP Member
Posts: 5865
Joined: Sat Nov 09, 2002 9:25 pm
Location: FRENCHTOWN

Re: Carb options

Post #2 by THE FRENCHTOWN FLYER » Tue Feb 12, 2019 8:40 am

I think either will work fine. For some reason the 390 seems to be a little problematic in terms of getting the adjustment right.
Plan on a low restriction exhaust to complete your build. If it were me I'd go with a bigger cam to take advantage of your increase in compression while avoiding the chance of detonation on premium gas at low rpms.
FORD 300 INLINE SIX - THE BEST KEPT SECRET IN DRAG RACING

Supervan66
Registered User
Posts: 7
Joined: Sat Feb 09, 2019 10:23 pm

Re: Carb options

Post #3 by Supervan66 » Tue Feb 12, 2019 10:48 am

THE FRENCHTOWN FLYER wrote:I think either will work fine. For some reason the 390 seems to be a little problematic in terms of getting the adjustment right.
Plan on a low restriction exhaust to complete your build. If it were me I'd go with a bigger cam to take advantage of your increase in compression while avoiding the chance of detonation on premium gas at low rpms.



Any recommendations on cam , I’m trying not to loose any low end grunt. This van gets heavy, especially all loaded up with camping gear. Or my other option could be to go with the 300 truck head I have bringing my compression down to about 8.5/1.
As far as carburetors go, both look identical but with different Cfm ratings, could one really be more problematic to tune. Thanks for everything, it’s nice to get feedback from people who have real experience not just in theory.

BigBlue94
Registered User
Posts: 249
Joined: Wed Mar 07, 2018 6:38 pm
Location: Hoyt, Kansas

Re: Carb options

Post #4 by BigBlue94 » Tue Feb 12, 2019 11:24 am

Had a 390 Holley on my 300. Worked pretty okay. New engine is getting a Holley style 450 quickfuel carb. Either should be just fine.
1985 Bronco. 300-6, NP435, 4.56 gears, Detroit locker and tru-trac, 4" lift, and 37" swamper tires. 300 has a 4bbl and headers.

pmuller9
Registered User
Posts: 2941
Joined: Tue Aug 06, 2013 12:33 am
Location: Columbus, Indiana

Re: Carb options

Post #5 by pmuller9 » Tue Feb 12, 2019 12:19 pm

Supervan66 wrote:Any recommendations on cam , I’m trying not to loose any low end grunt. This van gets heavy, especially all loaded up with camping gear. Or my other option could be to go with the 300 truck head I have bringing my compression down to about 8.5/1.


The 300 head will let you run 87 octane with the Comp 260 cam.
The Dynamic Compression Ratio will be right around 7:1
Plus the 300 head has better flow below .350" valve lift than the 240 head.

Use the Summit 500 cfm Carburetor with annular discharge boosters.
Much better cold intake manifold response.

What are you using for rocker studs?

User avatar
THE FRENCHTOWN FLYER
VIP Member
Posts: 5865
Joined: Sat Nov 09, 2002 9:25 pm
Location: FRENCHTOWN

Re: Carb options

Post #6 by THE FRENCHTOWN FLYER » Tue Feb 12, 2019 2:43 pm

Supervan66 wrote:
THE FRENCHTOWN FLYER wrote:Any recommendations on cam , I’m trying not to loose any low end grunt.


I think it is a common misconception that one will lose low end performance when adding a bigger cam and more carb. In fact the bigger carb and head work will allow you to go pretty radical on the cam and not lose any bottom end compared to a stock 1V and stock cam. My experience is with a cam in the 280* range (don't have the exact specs handy) and multi carbs allows me to rip the tires off the pavement virtually at will.

Image
FORD 300 INLINE SIX - THE BEST KEPT SECRET IN DRAG RACING

Supervan66
Registered User
Posts: 7
Joined: Sat Feb 09, 2019 10:23 pm

Re: Carb options

Post #7 by Supervan66 » Tue Feb 12, 2019 6:45 pm

pmuller9 wrote:
Supervan66 wrote:Any recommendations on cam , I’m trying not to loose any low end grunt. This van gets heavy, especially all loaded up with camping gear. Or my other option could be to go with the 300 truck head I have bringing my compression down to about 8.5/1.


The 300 head will let you run 87 octane with the Comp 260 cam.
The Dynamic Compression Ratio will be right around 7:1
Plus the 300 head has better flow below .350" valve lift than the 240 head.

Use the Summit 500 cfm Carburetor with annular discharge boosters.
Much better cold intake manifold response.

What are you using for rocker studs?


That summit carb looks pretty appealing,
Which carb do you think is least likely to have fuel boiling over due to the high heat of my doghouse ?
I’m planning a trip this summer where I will be starting at sea level and going to Telluride, CO where the elevation is 8.5k feet. Which carb is easier to re-jet for a leaner mixture? Also as far as parts go,do you think the holley stuff would be more available?
. As far as rocker studs go, I was under the impression that my stock ones would be fine for that hartland kit I have.

The 300 cylinder head is at the machine shop and they are saying that it’s in good shape , all valve are sealing and very little play in the guides. But are saying the guides are original and recommd new bronze guides a valve job and hardened seats for the exhaust valves only. Would this be worth the extra $500 ?

pmuller9
Registered User
Posts: 2941
Joined: Tue Aug 06, 2013 12:33 am
Location: Columbus, Indiana

Re: Carb options

Post #8 by pmuller9 » Tue Feb 12, 2019 10:45 pm

The Summit Carb comes with a thick insulated spacer to help with heat transfer from a hot intake manifold on a V8 engine.
In your case the heat is coming from the exhaust manifold and heat soaking everything inside the closed engine box so I'm not sure if one carb would do better than another. It would be worth while wrapping the exhaust system to lower the temps in the box.

The Summit Carb was designed to use Holley parts so jets, power valves and other tuning components are not a problem.

The Summit Carb has a one piece body so you simply lift the top to get to the jets and floats so you don't have to drain the carb or spill gas.
There are plenty of youtube videos.

As long as you are going to use the low lift Comp 260 Cam with the Comp 903 valve spring the stock press in rocker studs should not pull out.
Any more than that I would convert to screw in studs.

Again since you are going to use the Comp 260 with 903 springs the stock induction hardened exhaust seat will be ok so no need for exhaust seat inserts.

The stock iron valves guides wear very well with the stock valves so no needs for bronze guides.

This is a side note referring to what THE FRENCHTOWN FLYER wrote.
FTF is absolutely correct that a larger cam (up to a point) increases the torque everywhere along the power band in a 300 six.
The only difference is as the overlap increases the idle needs to be higher before the engine smooths out but after that it will break the tires loose on an empty pickup truck.

Case in point: Fully ported, big valve 300 head, .050" duration 232/232, advertised duration 288/288, .534" valve lift, 112 LSA.
9.75 compression ratio, Quick Fuel HR 650 cfm. Hedman Headers, T18 4 speed. Idles smoothy at 900 rpm.
In second gear from an idle put your foot in it and at 1200 rpms the rear tires break loose.
It gets 18+ mpg @ 70 mph highway 2400 rpm and 15 around town.

User avatar
broncr
VIP Member
Posts: 1096
Joined: Sun Apr 13, 2003 1:33 am
Location: Colorado

Re: Carb options

Post #9 by broncr » Tue Feb 12, 2019 11:28 pm

"I’m putting together an engine for my 1966 Econoline camper van"

There are a lot of CFM calculators out there. http://www.4secondsflat.com/Carb_CFM_Calculator.html

Be realistic - Get one that fits your needs.
'82 FSP Bronco. Just about every mod ever mentioned. ( Too much to list - or remember...)

pmuller9
Registered User
Posts: 2941
Joined: Tue Aug 06, 2013 12:33 am
Location: Columbus, Indiana

Re: Carb options

Post #10 by pmuller9 » Wed Feb 13, 2019 10:14 am

broncr wrote: There are a lot of CFM calculators out there. http://www.4secondsflat.com/Carb_CFM_Calculator.html
Be realistic - Get one that fits your needs.


These are fine for a V8 but do not take into account for individual cylinder size versus intake plenum volume for a big straight six.
The 300 six has a cylinder size equivalent to a 400 V8 and with the same "Gulp" volume requirments so on a 4 barrel intake with relatively small plenum volume the Carburetor can be larger to handle the peak cfm rather than the average cfm.
Last edited by pmuller9 on Wed Feb 13, 2019 10:28 am, edited 1 time in total.

User avatar
THE FRENCHTOWN FLYER
VIP Member
Posts: 5865
Joined: Sat Nov 09, 2002 9:25 pm
Location: FRENCHTOWN

Re: Carb options

Post #11 by THE FRENCHTOWN FLYER » Wed Feb 13, 2019 10:17 am

Instead of an 83% V.E. in the example given I think I'd plan on no more than 70% for a 300 at the power peak. That's more realistic if you're sucking through an air cleaner and snorkel and pushing through a muffler and vehicle exhaust system
FORD 300 INLINE SIX - THE BEST KEPT SECRET IN DRAG RACING

User avatar
Dr Jay
Registered User
Posts: 193
Joined: Sat Oct 05, 2013 6:12 pm
Location: North Alabama

Re: Carb options

Post #12 by Dr Jay » Wed Feb 13, 2019 12:41 pm

My personal experience is that I followed cam companies recommendation to be careful and not lose low end torque and have the truck go undrivable off the line. My first selections seemed fine but had detonation. As my overlap increased as I went more aggressive with my cam choices, detonation went away and gained low end (not losing low end, actually gaining).
I decided these cam descriptions are written by engineers and V8 guys with no 300 experience.
Now I make choices that sound like duration for a 350-400CID V8s. Be brave!
Blessings,
Dr Jay

1978 F100 Shortie, Lowered front and rear, 300 .030 over, 300 carb head, Clifford, Holley 390
268 Comp Cam, Cloyes, Fuel Inj. exhaust manifolds, MSD 6A, TOD, 9"

User avatar
broncr
VIP Member
Posts: 1096
Joined: Sun Apr 13, 2003 1:33 am
Location: Colorado

Re: Carb options

Post #13 by broncr » Wed Feb 13, 2019 12:57 pm

SV

Pm'd ya about a couple 390's I may be willing to let go.
'82 FSP Bronco. Just about every mod ever mentioned. ( Too much to list - or remember...)

Supervan66
Registered User
Posts: 7
Joined: Sat Feb 09, 2019 10:23 pm

Re: Carb options

Post #14 by Supervan66 » Thu Feb 14, 2019 1:10 am

Lots of good advice, thanks.
Today my 300 cylinder head came back from the machine shop disassembled and I’ll be spending some time cleaning up its ports.
I ended up sending back my cam and went the next one up to a 268 and I decided to go with the summit 500cfm carb. I’ll keep you guys posted

pmuller9
Registered User
Posts: 2941
Joined: Tue Aug 06, 2013 12:33 am
Location: Columbus, Indiana

Re: Carb options

Post #15 by pmuller9 » Thu Feb 14, 2019 9:35 am

How much port work are you doing?

F-250 Restorer
Registered User
Posts: 656
Joined: Wed Jan 13, 2010 10:42 pm

Re: Carb options

Post #16 by F-250 Restorer » Thu Feb 14, 2019 11:06 am

I have used the Summit carb on my truck. I was running a Hedman header and a DP intake which put the primary bowl right over the header, and I could not resolve the boiling fuel issue. I tried a heat shield, wrapping the fuel line, turning the carb around, all while using the insulating thick gasket supplied with the carb, but the problem persisted. It only occurred during the summer months. If I used one again, I would wire my efan to run a few minutes after the key is turned off to dissipate the radiant heat. When I switched to a Holley 1848 (465 cfm) the problem vanished.

You will not have your primary bowl above a hot header, so you may not experience the problem that I did. I would reach out to other van owners and see if any are running the Summit carb. That small enclosure around the engine in a van would hold the heat.

Note: *The Summit carb is made by Holley. It is based on the old Autolite 4100 (the shoe box) that ford used. Holley bought the design and repackaged it as a Holley, but it didn't sell because it didn't look like a Holley. The Summit carb now is a Holley/Autolite hybrid, using Holley jets, choke, acc. pump, float mechanism, while retaining the 4100 annular booster assembly.

Supervan66
Registered User
Posts: 7
Joined: Sat Feb 09, 2019 10:23 pm

Re: Carb options

Post #17 by Supervan66 » Thu Feb 14, 2019 12:15 pm

pmuller9 wrote:How much port work are you doing?


Not a ton, really just smoothing out some casting lines , cleaning up the bowl area and runners. I don't have enough experience to go hog wild.

User avatar
THE FRENCHTOWN FLYER
VIP Member
Posts: 5865
Joined: Sat Nov 09, 2002 9:25 pm
Location: FRENCHTOWN

Re: Carb options

Post #18 by THE FRENCHTOWN FLYER » Thu Feb 14, 2019 7:27 pm

Supervan66 wrote:
pmuller9 wrote:How much port work are you doing?


Not a ton, really just smoothing out some casting lines , cleaning up the bowl area and runners. I don't have enough experience to go hog wild.

good
FORD 300 INLINE SIX - THE BEST KEPT SECRET IN DRAG RACING

User avatar
broncr
VIP Member
Posts: 1096
Joined: Sun Apr 13, 2003 1:33 am
Location: Colorado

Re: Carb options

Post #19 by broncr » Thu Feb 14, 2019 8:25 pm

I suppose, for the sake of discussion, I'd like to hear the logic of running a carb capable of supporting 6000 RPM, on an engine that may occasionally see half of that...

It seems driveability would suffer - remember the OP is talking about a warmed up 300, in a camper van.
'82 FSP Bronco. Just about every mod ever mentioned. ( Too much to list - or remember...)

pmuller9
Registered User
Posts: 2941
Joined: Tue Aug 06, 2013 12:33 am
Location: Columbus, Indiana

Re: Carb options

Post #20 by pmuller9 » Thu Feb 14, 2019 10:06 pm

broncr wrote:I suppose, for the sake of discussion, I'd like to hear the logic of running a carb capable of supporting 6000 RPM, on an engine that may occasionally see half of that...

It seems driveability would suffer - remember the OP is talking about a warmed up 300, in a camper van.

See post #10
Then add that most of the driving will be done on the 250 cfm primaries with vacuum activated secondaries for any additional flow needs
This particular carburetor has annular-discharge boosters which work far better on a straight six cold aluminum intake manifold.
The cam has been upgraded to a 218* 050" duration profile and before this is over there may be minor port work.

We have never seen driveability issues with up to 650 cfm four barrel carbs and still were able to break tires loose at 1200 rpm and get 18+ mpg at 70 mph on the highway.

Now look at post #6 and #12.
That is something that FTF has been preaching for a long time.
It holds true for both cams and carbs.
Last edited by pmuller9 on Thu Feb 14, 2019 11:07 pm, edited 1 time in total.

pmuller9
Registered User
Posts: 2941
Joined: Tue Aug 06, 2013 12:33 am
Location: Columbus, Indiana

Re: Carb options

Post #21 by pmuller9 » Thu Feb 14, 2019 10:49 pm

Here is a picture showing the Clifford shorty header with heat wrap.
This was done by "F-250 restorer"
https://www.dropbox.com/s/57cxy3rztr7e4 ... s.jpg?dl=0
Here is the link to the thread:
https://www.ford-trucks.com/forums/1565 ... -swap.html

User avatar
broncr
VIP Member
Posts: 1096
Joined: Sun Apr 13, 2003 1:33 am
Location: Colorado

Re: Carb options

Post #22 by broncr » Thu Feb 14, 2019 11:38 pm

pmuller9 wrote:See post #10

Now look at post #6 and #12.


I expected you could/would make more sense of it for me, Paul. Thank you.

I didn't realize that the 500 in question was a 4 BBL - 'makes far more sense. 250CFM primaries sounds like a very good match. The annular discharge is also obviously of great benefit.

I've had little difficulty or displeasure with the 390 4BBL on my heated up 300. A little finicky with our wide temp swings & altitude variations but basically very drive-able. I have to remind myself that 90% of my miles are driven at 6,000-7,000' altitude and the other 10% are from 7000-12,000'.

Thanks again. I may be getting old, but I'm still willing to learn.
'82 FSP Bronco. Just about every mod ever mentioned. ( Too much to list - or remember...)

Max_Effort
Registered User
Posts: 309
Joined: Sat Sep 29, 2018 12:26 pm

Re: Carb options

Post #23 by Max_Effort » Fri Feb 15, 2019 9:54 pm

Anyone else consider a street demon 1901 with composite bowl?
It’s basically an updated thermoquad.
625 CFM, small 1 3/8” primaries with larger vacuum secondaries. The composite bowl insulates the fuel from heat. (Which is why they were called a thermoquad)

Fordman75
Registered User
Posts: 990
Joined: Fri Nov 08, 2002 2:43 am
Location: Southern, Minnesota

Re: Carb options

Post #24 by Fordman75 » Sat Feb 16, 2019 11:06 pm

I'm a big 3rd gen Econoline fan so my dog house lay out is different then yours. But here's what I'm going to use to help with carb boiling issues on mine. I'm going with a pair of Phenolic carb spacers. With a heat sheild that's larger then the carb between them. That will help with the direct radiating heat from the engine. Then I'm ducting in outside air right to the carb area to help cut down the actual engine bay heat around the carb.

And if it's in your budget have the headers ceramic coated. It's not cheap to have done. But that will help cut down the engine bay heat a lot!


And on the carb sizing I've taken a lot of crap for it. But I've always found the 300's just like the bigger carbs. Really anything in the 500-650 cfm range just works. I've ran some 390 cfm carbs and a 450 or two. And just always find my way back to a larger carb. Now I leave the 390's for the 4 cylinder engines. They work quite well on a built 2.3L SOHC engine! :D For a modified 300 I always size the carb as if it was a 400 V8.

And I don't really care for running the Holley style carbs on 300's unless it's a race engine. Don't really care too much for the float bowls leaking fuel right above the exhaust headers/manifolds. That's why I really prefer the old Autolite 2100/4100 carbs. But if you want a new carb the Summit carb is a good choice.
Ted

54 Ford F100/F150 4x4
300, NP435 4spd, NP205 transfercase

Fordman75
Registered User
Posts: 990
Joined: Fri Nov 08, 2002 2:43 am
Location: Southern, Minnesota

Re: Carb options

Post #25 by Fordman75 » Sat Feb 16, 2019 11:11 pm

Max_Effort wrote:Anyone else consider a street demon 1901 with composite bowl?
It’s basically an updated thermoquad.
625 CFM, small 1 3/8” primaries with larger vacuum secondaries. The composite bowl insulates the fuel from heat. (Which is why they were called a thermoquad)


I prefer to leave the composites for the carb spacers. And I remember them being called thermobogs. :lol: Or as the Roadkill guys would say " the only carb that punishes you for going full throttle" . Or something like that.
Ted

54 Ford F100/F150 4x4
300, NP435 4spd, NP205 transfercase

Max_Effort
Registered User
Posts: 309
Joined: Sat Sep 29, 2018 12:26 pm

Re: Carb options

Post #26 by Max_Effort » Sun Feb 17, 2019 6:47 am

Fordman75 wrote:
Max_Effort wrote:Anyone else consider a street demon 1901 with composite bowl?
It’s basically an updated thermoquad.
625 CFM, small 1 3/8” primaries with larger vacuum secondaries. The composite bowl insulates the fuel from heat. (Which is why they were called a thermoquad)


I prefer to leave the composites for the carb spacers. And I remember them being called thermobogs. :lol: Or as the Roadkill guys would say " the only carb that punishes you for going full throttle" . Or something like that.


The Carter Thermoquad and the Rochester Quadrajet were both excellent street carbs. Both get a bad rap among performance enthusiast. They are sophisticated five circuit carbs with small primaries that deliver good ecomony and driveabilty if tuned for the application. The “bog” is from the secondary opening too quickly. This is easily adjustable.

Obviously I’ve never tried either on a 300-6. If I had heat soak /fuel boiling issues, I’d consider the Demon 625.
[The original thermoquad is 800 CFM... A lot of carb for a 300].

For power production, the Holley style carb is still king.

sandboxer
Registered User
Posts: 191
Joined: Mon May 23, 2011 4:34 am

Re: Carb options

Post #27 by sandboxer » Sun Feb 17, 2019 9:41 am

Max_Effort wrote:
Fordman75 wrote:
Max_Effort wrote:Anyone else consider a street demon 1901 with composite bowl?
It’s basically an updated thermoquad.
625 CFM, small 1 3/8” primaries with larger vacuum secondaries. The composite bowl insulates the fuel from heat. (Which is why they were called a thermoquad)


I prefer to leave the composites for the carb spacers. And I remember them being called thermobogs. :lol: Or as the Roadkill guys would say " the only carb that punishes you for going full throttle" . Or something like that.


The Carter Thermoquad and the Rochester Quadrajet were both excellent street carbs. Both get a bad rap among performance enthusiast. They are sophisticated five circuit carbs with small primaries that deliver good ecomony and driveabilty if tuned for the application. The “bog” is from the secondary opening too quickly. This is easily adjustable.

Obviously I’ve never tried either on a 300-6. If I had heat soak /fuel boiling issues, I’d consider the Demon 625.
[The original thermoquad is 800 CFM... A lot of carb for a 300].

For power production, the Holley style carb is still king.


I loved the Thermoquad. Nothing like the howl that happened when they opened up.

Fordman75
Registered User
Posts: 990
Joined: Fri Nov 08, 2002 2:43 am
Location: Southern, Minnesota

Re: Carb options

Post #28 by Fordman75 » Sun Feb 17, 2019 10:40 am

Max_Effort wrote:.

For power production, the Holley style carb is still king.


King of fuel leaks too. :thumbup: If it's going to to sit unused for a period of time there's a good chance it's going to leak when you restart it. The more gaskets it has the more chances of leaks.
Ted

54 Ford F100/F150 4x4
300, NP435 4spd, NP205 transfercase

Supervan66
Registered User
Posts: 7
Joined: Sat Feb 09, 2019 10:23 pm

Re: Carb options

Post #29 by Supervan66 » Sun Feb 17, 2019 11:10 am

I still have a ways to go on this project , but I will try to keep you fine folks updated. The engine portion is really only half the battle. I need to reseal my transmission, find a bigger aluminum radiator that will fit, and customize my dog house so that I can fit Offenhauser intake, carb and filter. This is what I’m working on.... thanks again
You do not have the required permissions to view the files attached to this post.

Max_Effort
Registered User
Posts: 309
Joined: Sat Sep 29, 2018 12:26 pm

Re: Carb options

Post #30 by Max_Effort » Sun Feb 17, 2019 9:36 pm

Nice van.. that should be a lot of fun.

sdiesel
Registered User
Posts: 613
Joined: Fri Jan 06, 2012 12:33 am
Location: NW Oregon,Buxton currently

Re: Carb options

Post #31 by sdiesel » Sun Feb 24, 2019 1:21 am

Its impressive the number and variety of exceptional suggestions offered herein.
I especially like the outside air suggestion, goes a long way to avoiding problems.
And the q jet suggestion.
Except for single purpose carb, I cannot think of a better carb for you. Or me. Or any street rig.
They are a fundamentally intelligent design.
And they will power a 305 or a 501 without even a quibble.
I would go so far as to say theu are equal to many TBI designs.
They are heavy though.
a long love affair with the 300 six.
my lastest and final fling is a fresh 300 in an 88 ford f350 dually 4X flatbed

takehikes
Registered User
Posts: 90
Joined: Tue Nov 10, 2015 4:33 pm

Re: Carb options

Post #32 by takehikes » Fri Mar 01, 2019 7:31 pm

Was just reading about the old Pontiac OHC in-line 6. The optional engine cane with a Q Jet! Don’t know the size but it’s what they used.

Max_Effort
Registered User
Posts: 309
Joined: Sat Sep 29, 2018 12:26 pm

Re: Carb options

Post #33 by Max_Effort » Sat Mar 02, 2019 3:59 pm

takehikes wrote:Was just reading about the old Pontiac OHC in-line 6. The optional engine cane with a Q Jet! Don’t know the size but it’s what they used.


Most Quadrajets are 750 CFM , some are 800 CFM.
They will work on a small displacement engine because of the spread bore design. Small primary bores for regular driving and large secondary bores that open on demand, with flow controlled by the air door. The timing of the secondary air door opening can be easily adjusted. The secondary air door will probably never be fully open on a street driven 300-6.

The thermoquad Is similar in design.

sdiesel
Registered User
Posts: 613
Joined: Fri Jan 06, 2012 12:33 am
Location: NW Oregon,Buxton currently

Re: Carb options

Post #34 by sdiesel » Tue Mar 05, 2019 9:10 am

to keep up the drum beat for the "quads", I hesitate to use them on a six because of the weight.
with a longer runner intake, a heavy carb like the q jet, might stress the mounting points on the 6 . especially as a long term street driven rig.

maybe not too

heat shielding. ford did this, u can too.
a flat tin shield the entire length of your intske manifold held on by the bolts that are meant to secure the intake to exhaust, and toward the ends, slots cut in the sheet tin allowing for hose clips to pass thru to attach to runners.
if u csn direct a ducted flow of air to the bottom of that tin panel from outside. it should help to push the flow of air past , down, and out.especially if your tin panel extends to almost contact the walls of the doghouse, and a foam seal prevents heat leakage from going up because this foam seal.
another across the top to move the "shimmer heat" from around the carb.

I had a gig rig like that back in my music man days.
doghouse grew painfully hot. windshield, a greenhouse, my knees a first line of defence in a collision, and brakes that .....that werent.

ceramic coat, yes.
ceramic paint , touts temp reduction.
might be useful on the underside of the doghouse
last, word from me, is this, a hole or two cut and suitable vents installed helps immeasurably in heating the cabin on cold days.
allowing engine heat into the van, assumes no noxious fumes ....
a long love affair with the 300 six.
my lastest and final fling is a fresh 300 in an 88 ford f350 dually 4X flatbed

Who is online

Users browsing this forum: No registered users and 16 guests