intake manifold variations (FAQ)

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Elder Statesman
Supporting Vendor
Apr 14, 2004
The question was posed in a separate thread, but I thought it would be easier to find this info later if it was posted directly on topic in it's own thread.

58-9/66: F135 Engine [3.9 liter] 1bbl cast iron intake standard, 2bbl optional. 4 bolt attachment to exhaust manifold

9/66-9/69: F145 Engine[3.9 liter] 2bbl aluminum intake with wide runners standard. 3bolt attachment to exhaust. 4 bolt bosses on the side of the intake for oil filter bracket, which attached via an adapter plate.

10/69-1/72: F145 Engine[3.9 liter] 2bbl intake with narrow runners. 69 and 70 models had one vacuum port only, for the 4wd shifter. 71 had one port on the side for the brake booster. 72 added a second one in front of the carb for filtered manifold vacuum.

1/72-12/74: F155 Engine[ 3.9 liter] 2bbl intake with narrow runners. 74 Cali intake is distinguishable because there is a large hole in the side of the intake under the carb for the Cali-spec EGR system.

1/75-1/79: 2F [4.2 liter] 2bbl intake with 5 bolt attachement to exhaust. Port behind carb for brake booster, port under carb for PCV, port in front of carb for filtered vacuum source.

1/79-9/87 2F [4.2 liter] 2bbl aluminum intake with 5 bolt attachment to exhaust. Main distinction from earlier 2F intakes is that EGR ports into the side of the intake underneath the carb, alongside the PCV system.
In the F A Q

Thanks Mark man!

:beer: :beer:
WOW! My first FAQ on MUD. I'm somebody now!;p
good info Mark

brian said:
yes, but nobody will ever see it:D as it seems nobody uses the faq.

50 points for the man with the sodium pentathol!:rolleyes:
I have a 66-69 with the wide runners and a 72 with the narrow runners. Both have all the vacuum ports I need.

I am running SOR headers, along with a Holley 350 carb. Is there any preference for the narrow vs wide runners for air/fuel flow on the intake side?

I've been running the intake with the wide runners for 2 years on a 77 2F engine.
Well, at first glance, a Holley 350 would seem to suggest that you are motivated by a need for speed!

Rather than just making the assumption, I'll offer this. The narrower runner manifolds are going to keep manifold vacuum higher at lower rpms, but become somewhat restrictive at high rpms. The wider manifold isn't gonna have quite as much vacuum at the lower rpms, but will obviously move more air for higher rpm operation.

I use the narrower manifold on my '68, which is pretty well built. I notice a little drop off in power above 4000 rpm because of the manifold. But I get in that RPM range so seldom, I can more than live with the trade off; I like the higher vacuum and torque at slow speed that the 'smaller' manifold gives.


Mark A.
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I take the other side of the arguement. I feel that the gain in mid range and top end on a built engine is noticable.

For most stockish engines, this manifold won't gain you anything.


I've been having the same argument with myself. I actually have the Holley with a 2 stage power valve for high altitude performance, not necessarily for speed, though it does provide that also. In fact, I put in a Downey cam for more mid-range/low-range torque. I have the engine balanced, so 3,400 - 3,600 or more rpm is not a problem, but I rarely am above 3,200 rpm.

I'ts a daily driver, but also gets some serious offroad work in rough country at 10000 ft elevation when I'm hunting elk.

Based upon your observations, I think I'll try the narrow runner intake, at least for now. I've had the wide one on for two years, so I know what it does.

Thanks, Mark.
Thought I'd add a couple of pics. The top one is a 9/66-9/69 wide runner intake and the bottom one is, uh later, I guess? EDIT: I meant the wide runner is on the RIGHT!

Intake 001.jpg
Intake 002.jpg
Intake 003.jpg
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That's cool that the wide runner has the firing order stamped into it.
In the first pic you can see how deep the sparation of the runners actually is. The side view shows the relative thickness of the two. you need the firing order stamped on the intake. s***, that's on the wrong side of the motor! What good would that do?!?!?!?!:D
AFAIK, the firing order of all 6 cylinder motors is the same. At least the Toyota F/2F is the same as my BMW.

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I ended up going back to the wide runner manifold, after I had cleaned up and prepped the narrow one. I guess it came down to "the devil you know versus the devil you don't."

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