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#1 |
Old Duffer
![]() Join Date: Mar 2003
Location: Maine
Posts: 1,821
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Inline six carbs
Maybe this should go in the "Engine" section, but it's related to the "Post Your Straight Six Pictures" thread, and I didn't want to hijack that thread with a question.
Having said all that, I noticed a lot of 4BBL carbs on the engines. Some of them had the primary's facing forward, and some were facing outboard (to the left). I mounted mine with the primary's facing left because my manifold is a dual-plane, and I reasoned the primary's would service one plane, and the secondaries would feed the other. I'd like to read some idea's as to which way is better, or if it even matters, and why...... Thanx!
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'68 Short C20 Flatbed Dually w/ 292 4bbl, Langdon cast headers, and WC T5 trans. '81 G10 Shorty Van "Good judgement comes from experience, and a lot of that comes from bad judgement." Will Rogers "Under promise, then over achieve." |
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#2 |
I am a Referee of life.
Join Date: Jun 2000
Location: Greensboro N.C.
Posts: 13,993
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Re: Inline six carbs
I've seen posts claiming the sideways mounting "should" create a more equal distribution of Fuel/air.I've seen others claim it makes no difference.I would like to see a photo of your intake since I was under the impression that all inline 6 cyl intakes were basically a single plane design.
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The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil" Last edited by PanelDeland; 06-05-2010 at 02:23 PM. |
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#3 |
Registered User
Join Date: Nov 2006
Location: Springfield/Kansas City
Posts: 1,842
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Re: Inline six carbs
I really don't think there would be much of a difference but I can see a slight variation on the spark plug colors in my engine. On my Holley and Offenhauser setup it would be difficult to run it sideways with the linkages and I imagine that's why most people do the four barrels that way. However looking at the carb, I can see mounted sideways will equally space the barrels side to side. Maybe I'll give it a try..
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#4 |
Registered User
Join Date: Mar 2009
Location: USA
Posts: 255
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Re: Inline six carbs
One thing to keep in mind when mounting the carb sideways is how making a sharp turn (u-turn) will affect it. In other words some times the engine can stall if the fuel were to slosh to one side and uncover the jets or go temporarily rich (high fuel level) if it were to slosh towards the jets. Some carbs are more prone to this than others.
I can remember the 76 Impala my Dad had, would stall durning a panic stop (sudden red light) as the Rochester 2 barrel had the float bowl on the front of the carb, and all the fuel would slosh forward away from the jets and kill the engine. Holley 4 barrels used on the drag strip would also bog down pretty bad when they launched, as fuel sloshed towards the rear uncovering the secondary jets. You can get jet extensions from Holley to fix this though. |
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#5 |
Registered User
Join Date: Jan 2008
Location: Anmore BC
Posts: 78
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Re: Inline six carbs
I've got an intake from a 67 Pontiac sprint motor that cam stock with a Q-jet. The primaries are close to the head, with the secondaries on the outside.
I've got my Holley/Offenhauser in the same configuration. went with a Lokar cable throttle, and it works good. |
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#6 |
Registered User
Join Date: Nov 2009
Location: stoddard nh
Posts: 693
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Re: Inline six carbs
do u have pics of the pontiac intake installed? thanks!
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#7 |
Registered User
Join Date: Apr 2010
Location: So Cal
Posts: 1,442
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Re: Inline six carbs
Old Bluey you should take fresh look at that Pontiac OHC Six you said you have. Chokes and primaries are outboard away from the engine on all of them that I have ever seen or seen pictures of and it's pretty hard to turn a Q-jet around. I hope no one is confusing the secondary air valve plates with the chokes.
Before I mounted the Carter AVS and Clifford, I measured the differences between the longest and shortest runners with a tape measure run through the passages. By mounting the carb with primaries to the front, the distance from the primaries to cyl #6 was about 15" longer than right primary to #3 cyl. By putting the primaries inboard the distance between the longest and the shortest was reduced to about 13". By putting the primaries outboard, the differences in distances between the longest and the shorted runners is reduced to about 8". I am a little fuzzy on the exact numbers because it was about five years ago that I did it. I liked the idea of putting the primaries outboard and the fuel line, vacuum hose, PCV hose, mechanical choke cable worked best that way. I had already decided to use a cable throttle so that wasn't a problem. |
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#8 |
Fun Stuff
![]() Join Date: Jan 2010
Location: Sedro Woolley, WA
Posts: 400
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Re: Inline six carbs
Be carefull, the primarys are just that the primary source of flow to the cylinders and the secondaries only function when you are accellerating hard. If infact it is separate planes, it could cause a lean condition on half your cylinders when driving normally. Just my $0.02
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Jay 68 C10(project) 88 Honda Accord(DD) 93 Chevy Astro EXT 2wd |
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#9 |
Six in a row makes it go...
![]() Join Date: Mar 2009
Location: Vacationland: Maine
Posts: 1,346
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Re: Inline six carbs
I did it like this. It worked. Can't say that I thought about it a lot.
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#10 |
Registered User
Join Date: Jan 2008
Location: Anmore BC
Posts: 78
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Re: Inline six carbs
RichardJ, My bad, You're of course correct. Hadn't looked at it in a while.
Although the ports on the Pontiac line up to the 250 head, the mounting holes & flanges do not. After a bunch of modification, i was still left with a lot of vacuum leaks. So I yanked it out, ran the stock Rochester for a while and replaced it with the Offenhauser. Before: ![]() After: ![]() |
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#11 |
Registered User
Join Date: Nov 2009
Location: stoddard nh
Posts: 693
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Re: Inline six carbs
sweet thanks for the pics yeah i found out they wont work, but never seen a good pic and was curious what they looked like, how was the q-jet performance?
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#12 |
Registered User
Join Date: Jan 2008
Location: Anmore BC
Posts: 78
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Re: Inline six carbs
The look is a lot like the Clifford intake. The weight of the cast iron Pontiac on the other hand is impressively heavy. Especially compared to the aluminum Offy.
I never used the Q-jet, I used a Holley (same carb on both setups) with an adapter. The stock single barrel was a Rochester Monojet. It's new home is on the shop shelf. |
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#13 | |
Old Duffer
![]() Join Date: Mar 2003
Location: Maine
Posts: 1,821
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Re: Inline six carbs
Quote:
RichardJ, thanks for the numbers, it never occured to me to measure distances. In the stock configuration, and using a single bbl carb, the numbers would be scary! I'm guessing that's why the guru's recommend a heated manifold thereby keeping the fuel mixture atomized while it's trying to decide which way it's going to go. ![]()
__________________
'68 Short C20 Flatbed Dually w/ 292 4bbl, Langdon cast headers, and WC T5 trans. '81 G10 Shorty Van "Good judgement comes from experience, and a lot of that comes from bad judgement." Will Rogers "Under promise, then over achieve." |
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