Intake manifold "leans"

[Redmond49]

I got my cleaned up manifolds back today, and at the shop we noticed that the intake manifold "leans" to the right. It seems to have been cast that way. Is that normal?

 

[Plymouthy Adams]

it almost appears that the downward inline of the engine has been taken into account to keep the fuel bowl level...I have to admit I do not recall looking that close at mine...something to muse for sure..others may have support photographs...

[casper50]

my offy dual carb setup does the same thing.

 

[PT81Jan]

“Is that normal ?“ – short answer: not really …

There are two possible sources where this can come from:

1. machining: If your intake flanges / bolt bores matches to the motor and there is an angle deviation between the machined flange of the intake and exhaust (picture1, yellow marked) when both elbows are mounted to the motor, it likely is a machining fault.

2. casting process: When looking on the shape of the casting surface, I believe that hte cast part itself is deformed. A pattern for cast parts needs a mold draft of 1°+ on vertical surfaces starting from the parting line (red horizontal line). This is needed to get the part formed. Then the shape looks like the yellow line on the left of picture 2. The yellow line on the right shows an inverted draft angle. This let me suppose that the cast part is distorted. If the flanges of the intake elbow fits to the motor and to the exhaust without any stress or gap, the issue is only cosmetic -> carburetor leans a bit forward. If you can live with that, everything should be o.k.

Hope my explanation attempt is comprehensible ...?

Edited December 3, 2016 by PT81Jan

[PT81Jan]

Supplement:
There is a third possibility as Plymouthy Adams wrote and casper50 just confirmed: Intention ! -> the design engineers wanted to have a slight angle due to installation reasons.
(Mine doesn`t have it by the way. But there might be different intake elbows for different applications)

[oldodge41]

Do the intake and exhaust ports line up with the ports on the engine? If the exhaust manifold is sitting level and the intake is canted I think it would have to be specially cast to get the ports to line up correctly. If it is amachining error I don't think the ports are going to align properly.

[Young Ed]

Not quite the same side shot photo but the one for my 48 appears to have the same lean. I would suspect its to level the carb

[DrDoctor]

   Well, that was interesting . . . I just had to look, so I’ve just returned from almost literally crawling into the engine compartment of our car to “have a look-see”. And, what to my wondering eyes did I see? The planes of the intake and exhaust manifolds are roughly parallel to one another, keeping in mind they’re castings. And, the “tower” (for the lack of a better term . . .) upon which the carburetor mounts is roughly perpendicular to the plane of the intake manifold, and NOT angled towards the front of the engine as depicted in the photo provided by Tyson. So, what does that tell us? I don’t have a bloody clue what it tells us, other than Tyson’s intake manifold has a unique “bow” in the carburetor mounting tower than mine. So, I’m going to endorse PT81Jan’s cogent explanation – something occurred during the casting process, most likely when the part was still red hot, and it became canted as it now is. I can only assume (and we know the dangers of doing that) that the machining phase of the process milled the mating surfaces between the manifolds and the engine together on the same plane, as well as the boring of the mounting holes. But, that doesn’t address the issue of misalignment of the engine’s intake and exhaust ports to those of the respective manifolds.  Interesting, to say the least. What will be discovered next?  Thx.

[DrDoctor]

   Oh, I just saw the photo as sent by Young Ed. His arrangement looks more like what we’ve got here, altho’ his is much cleaner/nicer looking. Ours is just semi-rusty. And, ours doesn’t have anything on the outside, which I’m guessing on his to be an automatic choke (ours has a manual choke).  Thx.

[DrDoctor]

   Oh, and  I just saw the comment from oldodge41 about the potential misalignment of the engine’s intake and exhaust ports to those of the respective . Great minds – same channels . . .  Thx.

[Redmond49]

It seems to line up nicely on the studs.

[DrDoctor]

   If everything aligns, and the car runs OK, I personally wouldn’t lose too much sleep over the “leaning”. Instead, look at it as you having a one-of-a-kind manifold arrangement, and then just cruise happily down life’s hiway.  Thx.

[Andydodge]

Maybe the extra lean towards the front means that this manifold is a special early Nascar part, gets more weight over the front axle to assist with turn in..........oops..........forgot my meds this morning.............lol............back in my corner I go...........andyd 

[maok]

Way off Andy. Its the 1st of the leaning tower of power slant 6 engine parts....:)

[Plymouthy Adams]

26 minutes ago, maok said:

Way off Andy. Its the 1st of the leaning tower of power slant 6 engine parts....:)

right thinking...wrong slant

[Dave72dt]

Believe it's to compensate for engine inclination to ease driveshaft angles, usually to about 2 -3 degrees.  A close look at many aftermarket manifolds, V8 included will show a similar inclination.  Since many engine installations show them to be lower  in the rear and pinion angles to be up a bit, that casting angle tends to level the carb at the base.  That's the theory I used when mocking up mounts for the truck, vehicle at ride height, level surface.

[DJ194950]

How about putting the 4 bolts in the intake manifold when apart from the exhaust manifold to see if they are parallel to the gasket flange of the intake.?

If so and you stated mounting bolts align with motor mounting holes, I say run it.

Just leave the 4 joining bolts loose as both manifolds are installed for to allow them to fit the motor and each other with the least pressure between the two parts. Tighten the 4 bolts last.

[Redmond49]

Thanks for all the replies, all!

Will do on the final assembly to motor. The machine shop that decked the two manifolds also told me to loosen the four bolts holding the units together and then tighten them after the manifolds are bolted to the engine.