Wrong intake to head angle??

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rick1062

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Hi folks,

I am looking for a bit of help and confirmation.

I am helping my daughter in law with a 1965 Barracuda that has been in her family many years, but parked for about the last five years. I don't have a lot of MoPar experience, but I have turned a lot of wrenches. After replacing the rusted out freeze plugs and a bit more routine work we got it running. Problem is, it won't run well after warmed up (choke open). It has seemed to me like it had a vacuum leak. After rebuilding the carb and checking all the easy stuff I started suspecting the intake manifold gasket. I sprayed carb cleaner around the manifold where I could reach but of course I couldn't reach the bottom side. I didn't notice any change in engine speed while spraying around the intake manifold where I could reach it. As I looked closer I noticed it seemed like some of the intake bolts didn't have the lock washers squeezed down all the way. I checked and the bolts were not too long and bottoming out. I tried a new bolt with a flat washer. That is when I noticed that the flat washer was pinched down on the lower side (toward the center of the intake manifold), but not on the upper outside, so it looked at a glance like the bolt was loose,but that was not the case. So... now I am thinking somewhere along the line someone replaced the heads with later ones. By the way, yes the bolts are 3/8 not 5/16 as I believe they should be.

All of that said, to ask you all if I am on the right track, and if so, what is the best way for me to resolve this. I am thinking, if I could find a two barrell intake manifold that matched the heads I might be in business. I am not sure though, what years of manifold might work on this engine now. This car is not a beauty and is just going to be used for daily transportation at this time, but we do want it to run right.

Can some of you point me in the best direction as to what parts to get, or maybe I am way off base here.


Thanks as always,

Rick
 
A picture would help here.

The angle of intake manifold bolts was different for 64-65 engines compared to 66-92. So later intakes don't bolt well to early heads, and early intakes don't bolt well to later heads. From what you describe this is your problem.

A later 2 barrel intake shouldn't be too hard to find. They were about the worst manifold and carb combo known to man, so somebody nearby will have one on their junk pile.
 
Proceed cautiously here and know what you have before spending any money.

First, just because the bolt surface on the intake is not parallel with the machined surface of the head may not be what you think it is.

Are you sure that the bolt/thread is not cross-threaded?

The bolt angle is what changed, the center line of the bolt, not the angle of the block, head, or intake face. It's difficult to tell the angle by looking at it by eye...

You're referencing off of a cast surface, which is not as accurate as a machined surface. You may just have casting variation throwing you off.

I would take off the valve covers and look at the casting numbers on the heads first. Make sure that you have the proper casting numbers for 64/65. 64 & 65 have the same intake bolt angle and size.

If you not have the proper year heads, and the later ones with the larger bolts and different angle, then why not get a matching intake for it instead of changing the heads.

As already posted above, some pictures can help. We can spot some things that others may not.

Start there and let us know what is going on, then we can help you get this figured out better...


Here's a link to the head casting numbers:

http://www.mymopar.com/index.php?pid=68


Here's a link for the intake manifold casting numbers:

http://www.mymopar.com/index.php?pid=69


Also keep in mind that changing the heads to a later year will slightly lower your compression. The earlier heads had the smaller combustion chambers, so have slightly higher compression. Not enough to where it won't run, but just so you know what you will be affecting by changing the heads...
 
64-67 273 Heads 2bbl & 4bbl had the same stlye closed chamber. the 64-65 273's had the 5/16 bolt's & the 66-up had the 3/8 bolts'with a little diffrent angle on them. i just swaped an lb4b intake for 66-up 273-318 ports & it wasn't hard at all to "make" it fit the early heads.
 
Agreed with krazykuda - with that said it's more likely someone changed the manifold to a newer one then someone changing the heads? if I read your post correctly it doesn't say if you have a 2 barrel or 4 barrel? I put a LD4B on my girlfriends 66 Barracuda to replace the two bro and worked flawlessly but again I was just across the borderline of not having a 65 or older. again this is why I suspect someone change the manifold as this is the easiest upgrade. and you can rest assure your bolts are not bottoming out because they go all the way through the head into the oil galleys.please don't spend any money till we can get some pictures! probably going to be very simple.
 
If you find you need a 64/65 2 barrel intake, I have one on my 65 Barracuda that I can pull.
 
If they swapped just the intake then he would still be using the 5/16 bolts to bolt it down then. He said it is using the later 66-up 3/8 bolts! The front 2 & rear 2 intake bolts will bottom out. they go into a pocket into the head! So 4 of the 12 can bottom out. My LD4B intake i had to reem the hole a little to fit it to my early 5/16 273 heads. he's rite my intake bolts if not ground a little will sit **** eyed a little. Had i found a D4B intake (made for 64-65 273 heads) no mods would have had to be done.
 
krazykuda said:
Are you sure that the bolt/thread is not cross-threaded?

I would take off the valve covers and look at the casting numbers on the heads first. Make sure that you have the proper casting numbers for 64/65. 64 & 65 have the same intake bolt angle and size.

If you not have the proper year heads, and the later ones with the larger bolts and different angle, then why not get a matching intake for it instead of changing the heads.
Click to expand...

Thanks to all for your input.

None of the bolts are cross threaded or bottomed out. I put some new bolts in with my fingers, then snugged down with a wrench.

I probably was unclear at some point, but I never considered changing the heads, but maybe the manifold.

Here are my head and manifold casting numberes:

Head 2843675 273/318 1968-74

Manifold 2463252 Not on chart, but by the numbers looks like it would be 1965 or earlier.

The manifold is for a 2 barrel.

Below is a pic I took of the left front of the manifold with a new bolt and new flat washer (for visual purposes). It is snugged down and you can see the bolt is only making contact at the inboard area of the washer. This the same for all of the bolts.

It seems to me like I might be looking for a newer 2 barrel manifold. The other thought I had is that who ever put the heads on, machined the manifold to match the angle and just drilled out the bolt holes so the 3/8 bolts would work. Sounds kind of hinky to me, but maybe it was common practice for some. I sure don't know that is what happened, just trying to stir up some ideas.




Thanks again to all for ideas and suggestions,

Rick
 

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Yes it seems you are now looken for a 66-67 273 or 67-up 318 intake. Mine is the opposite way with the bolts (seating on the top vs the bottom) If your not worried about being correct id look for the later 318 dual plane 2BBL. You will pick up a little bottom end torque with the dual plane 2BBL over the single plane intake. I've got $50 sayen at some point the heads were swapped out & just drilled the stock intake out a little to fit them.
 
Get some angled engineers washers, I think they are machined at a 6 degree taper.
 
Do you know the difference between a single plane and a dual plane intake manifold?

I would recommend using a dual plane intake as it will give better performance for your application than a single plane will. The factory made both dual plane and single plane 2 bbl intakes for the 318.

Below are some pictures of a dual plane 2 bbl 318 intake, I believe from the mid 70's from the electronic choke thermostat. This is the kind of intake that I recommend using. Note how there are two "H" shaped patterns for the ports. This is how you tell a dual plane intake manifold.

View attachment 318 2bbl Int E02 B.jpg

View attachment 318 2bbl Int E02 B2.jpg

View attachment 318 2bbl Int E04 B.jpg

View attachment 318 2bbl Int E05 B.jpg

View attachment 318 2bbl Int E07 B.jpg

View attachment 318 2bbl Int E08 B.jpg

Here's some pictures of a single plane intake. Notice how all of the ports are on the same level, not one on top of the other. Don't use this kind, use the kind above.

View attachment 318 2 bbl single plane.jpg

View attachment 318 2 bbl single plane b.jpg
 
If you are going to change intakes, I would recommend you look for a 4bbl intake and carb (~500cfm, no more) while you're at it. You will be MUCH happier with it's performance.
 
Wow, thank you all for the help and the single/dual plane lesson.

Ok, so I get what I need to do to fix this, but my head needs a bit more for understanding.

Is the difference between the early and late intake manifolds just the angle of the bolt holes and 5/16 vs 3/8, or is the angle of the machined surface and manifolds and heads also different. This brings me back to my original problem and how I noticed the manifold bolt problem. The engine won't idle well after the choke fully opens, like there is a big vacuum leak and the choke butterfly being closed or close to it allows the engine to run, but when the butterfly opens, and allows more air in, it seems like there is way too much air (I am thinking because of a vacuum leak) and runs rough and it dies. If i put my hand over the carb air intake and mostly cover it, the engine smooths out and will run fine. So I guess what I am asking is, with the mismatch of early intake manifold and late heads, am I more susceptible to a vacuum leak at the mating surface between the manifold and heads and possibly on the bottom side where I can't see it or notice any affect when spraying brake cleaner around the visible upper area of manifold/head mating surface?

I hope that makes sense. Thank you all for being so much help.

Rick
 
I would say "yes", you have a greater risk of a vacuum leak using the mismatched heads and intake. The actual intake surface and head surface are the same, early to late...the difference IS in the bolt size and angle. I'm assuming nothing has been machined over the years Ie: intake or head gasket surfaces. With the bolts not clamping evenly, or straight down, this could possibly be your problem. You can either have your intake machined at the bolt hole area to correct the mismatch, or, install a later style intake with the correct bolt size and angle for your heads. Either way, use some sealer on both sides of the intake gasket at the ports (ie: silicone), not just at the water ports.
 
rick1062 said:
Wow, thank you all for the help and the single/dual plane lesson.

Ok, so I get what I need to do to fix this, but my head needs a bit more for understanding.

Is the difference between the early and late intake manifolds just the angle of the bolt holes and 5/16 vs 3/8, or is the angle of the machined surface and manifolds and heads also different. This brings me back to my original problem and how I noticed the manifold bolt problem. The engine won't idle well after the choke fully opens, like there is a big vacuum leak and the choke butterfly being closed or close to it allows the engine to run, but when the butterfly opens, and allows more air in, it seems like there is way too much air (I am thinking because of a vacuum leak) and runs rough and it dies. If i put my hand over the carb air intake and mostly cover it, the engine smooths out and will run fine. So I guess what I am asking is, with the mismatch of early intake manifold and late heads, am I more susceptible to a vacuum leak at the mating surface between the manifold and heads and possibly on the bottom side where I can't see it or notice any affect when spraying brake cleaner around the visible upper area of manifold/head mating surface?

I hope that makes sense. Thank you all for being so much help.

Rick
Click to expand...

The only difference in the 64-65 intake/heads and the 66 & later intake and heads is just THE BOLT DIAMETER AND ANGLE only...


You can go with a 2 bbl or a 4 bbl intake for it.

A 2 bbl will be easier to just bolt on.

A 4 bbl will require a few other "adaptions" to get it to work, but is a nice option, especially with an electric choke.

Which ever you choose, get a dual plane intake, they are made in 2 bbl and 4 bbl.


The best 4 bbl for what you have is an old Edelbrock LD4B, but are not made anymore and can be hard to find.


Another good choice is the wiand Stealth part # 8022

https://www.holley.com/products/intakes/dual_plane_manifolds/parts/8022


And top it off with one of these:


Holley electric choke:

http://www.manciniracing.com/homo41noflca.html

Edelbrock electric choke:

http://www.manciniracing.com/ed600cfmelch.html


And use this thick base gasket and stud kit with the center divider to keep the split signal all the way to the carb base:

http://www.summitracing.com/parts/edl-9266


Then you will need to change the throttle bracket and modify the trans kick down linkages to work with the 4 bbl....


That's why I originally suggested the dual plane 2 bbl intake, but it's your choice, those are a couple of options...
 
Heres a simple test for a vacuum leak originating inside the motor;
The crankcase has to be sealed, except for one east-to-access point.Then you simply start the engine,let it idle, and check the access point for vacuum.
Sealing the crankcase means if you have a PCV or road-draft tube, it has to be plugged. Same with any breathers.The dipstick can be used as the convenient access point, but I like to use a bigger hole, such as a breather port or the PCV port.A vacuum gauge can be connected to the dipstick tube pretty easily. When using a larger port,a thumb placed over it instantly reveals the vacuum.
 
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