225 Slant Six Manifold

[chinze57]

I've got a 225 chrysler slant six in my '64 Dart. I'm having a bit of an issue with the car stalling out in drive, which it seems is due to a slight vacuum leak (when i first got the car it stalled if not constantly revved, after a clean up and new gaskets and such, it started only stalling in drive when idling, there are some cracks my mechanic plugged on the intake manifold).

What should I do about this? I'm thinking that I should replace the intake manifold, but I don't have the faintest clue what the best will be. It looks like aussie speed makes a manifold for /6 with either 4 barrel carbs or 2 barrel carbs (I believe mine is 2 barrel).

Any thoughts or ideas? Y'all have years more experience with this than I do so I appreciate anything.

 

[my68barracuda]

I've got a 225 chrysler slant six in my '64 Dart. I'm having a bit of an issue with the car stalling out in drive, which it seems is due to a slight vacuum leak (when i first got the car it stalled if not constantly revved, after a clean up and new gaskets and such, it started only stalling in drive when idling, there are some cracks my mechanic plugged on the intake manifold).

What should I do about this? I'm thinking that I should replace the intake manifold, but I don't have the faintest clue what the best will be. It looks like aussie speed makes a manifold for /6 with either 4 barrel carbs or 2 barrel carbs (I believe mine is 2 barrel).

Any thoughts or ideas? Y'all have years more experience with this than I do so I appreciate anything.

Concerning your current intake manifold, there is a two piece die cast aluminum intake in two bbl and one bbl versions that have leak issues at the seams. But they can be successfully repaired be either welding the seams or sealing the seams with epoxy.
So unless you want to go with a different intake manifold, you do not need to.
It would be helpful if you could post a photo of your current intake manifold. So we can better understand the issue.
If you do change the intake manifold, that change should be made in conjunction with other engine component upgrades. With a 4 bbl you should also consider raising the compression, maybe a better cam and improved exhaust to get your money’s worth out of the larger carb.

 

[1963dartgt]

I went the 4bbl route,if you do be prepared to spend more money than you think you will(alot more). If its stock its most likely a 1bbl carb with cast iron manifold. Pics would really help.

 

[chinze57]

I went the 4bbl route,if you do be prepared to spend more money than you think you will(alot more). If its stock its most likely a 1bbl carb with cast iron manifold. Pics would really help.

I believe it’s stock, so most likely 1 bbl then. I’ll post pictures later

 

[chinze57]

Concerning your current intake manifold, there is a two piece die cast aluminum intake in two bbl and one bbl versions that have leak issues at the seams. But they can be successfully repaired be either welding the seams or sealing the seams with epoxy.
So unless you want to go with a different intake manifold, you do not need to.
It would be helpful if you could post a photo of your current intake manifold. So we can better understand the issue.
If you do change the intake manifold, that change should be made in conjunction with other engine component upgrades. With a 4 bbl you should also consider raising the compression, maybe a better cam and improved exhaust to get your money’s worth out of the larger carb.

I’ll post pictures later today. I don’t believe I want to go the route of a 4 bbl carb at the moment, as I’ve got so many other things to upgrade and fix before I can even think about that

 

[krazykuda]

If you upgrade to a 2 or 4 barrel, you will also have to change the gas pedal linkage over to a cable vs the solid rod...

 

[pishta]

if you need a good iron 1bbl intake, I can mail you one for cost. Probably <$22.00

 

[chinze57]

Quoting all of you so you can see the pics.

I think these are good photos. If you want to see something else or see it a bit better, please let me know. As I understand it, this is not a stock manifold (based on what my mechanic told me probably 8 months ago).

If it’s looks like it’s the manifold that’s the issue, then I’ll probably take you up on the offer pishta

Concerning your current intake manifold, there is a two piece die cast aluminum intake in two bbl and one bbl versions that have leak issues at the seams. But they can be successfully repaired be either welding the seams or sealing the seams with epoxy.
So unless you want to go with a different intake manifold, you do not need to.
It would be helpful if you could post a photo of your current intake manifold. So we can better understand the issue.
If you do change the intake manifold, that change should be made in conjunction with other engine component upgrades. With a 4 bbl you should also consider raising the compression, maybe a better cam and improved exhaust to get your money’s worth out of the larger carb.

I went the 4bbl route,if you do be prepared to spend more money than you think you will(alot more). If its stock its most likely a 1bbl carb with cast iron manifold. Pics would really help.

If you upgrade to a 2 or 4 barrel, you will also have to change the gas pedal linkage over to a cable vs the solid rod...

if you need a good iron 1bbl intake, I can mail you one for cost. Probably <$22.00

 

[my68barracuda]

Quoting all of you so you can see the pics.

I think these are good photos. If you want to see something else or see it a bit better, please let me know. As I understand it, this is not a stock manifold (based on what my mechanic told me probably 8 months ago).

If it’s looks like it’s the manifold that’s the issue, then I’ll probably take you up on the offer pishta

View attachment 1715525627 View attachment 1715525628 View attachment 1715525629 View attachment 1715525630 View attachment 1715525631

That looks to be a rather common cast iron intake manifold. Those are about as durable as concrete. What makes you think there is an issue with the intake that you have on the car? Your first post mentioned that you thought it was cracked,,,and your mechanic repaired cracks in the intake,,, what exactly did the mechanic do? The cast iron intakes do not have a history of cracking. The cast iron exhaust manifolds have a cracking issue, but not the intakes.

 

[Ian McCrimmon]

Well from what I see the triangular washers look like they are backwards. And it also looks like there is a regular washer and nut on the last stud (cannot see the first one). It should be a brass washer and an expansion nut.
Read this article about slant 6 washers and check all of yours against this info.
Slant 6 Exhaust Manifold Washers

 

[chinze57]

That looks to be a rather common cast iron intake manifold. Those are about as durable as concrete. What makes you think there is an issue with the intake that you have on the car? Your first post mentioned that you thought it was cracked,,,and your mechanic repaired cracks in the intake,,, what exactly did the mechanic do? The cast iron intakes do not have a history of cracking. The cast iron exhaust manifolds have a cracking issue, but not the intakes.

I frankly don’t know much about the intake/exhaust manifolds. When I got it, as i understand it, there was a massive vacuum leak. After that was mostly fixed, my mechanic told me there was still a slight issue with it sealing, he mentioned he thought it might be an issue with the manifold itself. Amen with it’s stalling at lower Rpm’s (when idling in drive or reverse) I figured the issue might be the manifold.

 

[chinze57]

Well from what I see the triangular washers look like they are backwards. And it also looks like there is a regular washer and nut on the last stud (cannot see the first one). It should be a brass washer and an expansion nut.
Read this article about slant 6 washers and check all of yours against this info.
Slant 6 Exhaust Manifold Washers

Interesting. I will be reading that now and seeing what I can discern. Thank you!

 

[chinze57]

That looks to be a rather common cast iron intake manifold. Those are about as durable as concrete. What makes you think there is an issue with the intake that you have on the car? Your first post mentioned that you thought it was cracked,,,and your mechanic repaired cracks in the intake,,, what exactly did the mechanic do? The cast iron intakes do not have a history of cracking. The cast iron exhaust manifolds have a cracking issue, but not the intakes.

Upon rereading your post, it is entirely possible he was talking about the exhaust manifold. I’ll check that.

 

[chinze57]

Well from what I see the triangular washers look like they are backwards. And it also looks like there is a regular washer and nut on the last stud (cannot see the first one). It should be a brass washer and an expansion nut.
Read this article about slant 6 washers and check all of yours against this info.
Slant 6 Exhaust Manifold Washers

That was a great read. I’m now interested in the possibility of getting those correct studs and nuts and a better gasket and then cleaning everything up and and mounting it.

 

[1963dartgt]

http://catalog.remflex.com/MOPAR_Header_Exhaust_Manifold_Gasket_p/6008.htm
Heres the only gasket ill ever use again.

 

[chinze57]

MOPAR Header/Exhaust Manifold Gasket
Heres the only gasket ill ever use again.

I will definitely be picking one up when I fix whatever is going on with my manifold

 

[chinze57]

if you need a good iron 1bbl intake, I can mail you one for cost. Probably <$22.00

If you upgrade to a 2 or 4 barrel, you will also have to change the gas pedal linkage over to a cable vs the solid rod...

Quoting y’all to ask a question. I was reading about the “Dutra Dual”. What is the point of it as an exhaust manifold?

 

[pishta]

Just spending $600 for a dual exhaust thatll need another $200 in exhaust work to get it operational. Money well spent on other items in my opinion. If you need an intake let me know: flat rate game box should cover it. Ill have to check length. You sticking with EGR? As i got both versions.

 

[chinze57]

Just spending $600 for a dual exhaust thatll need another $200 in exhaust work to get it operational. Money well spent on other items in my opinion. If you need an intake let me know: flat rate game box should cover it. Ill have to check length. You sticking with EGR? As i got both versions.

I’m sticking with EGR. My mechanic said that the issue was where the two manifolds met, they weren’t sealing properly because the exhaust manifold wasn’t back quite flat like it should be. Would I be best off replacing both manifolds and investing in better gaskets?

 

[pishta]

your issue is not the intake. Its the warped exhaust, that stuff happens. Is your issue possibly where the heat riser is on the exhaust (bright silver gasket)? There is a rectangle gasket that seals them with 3 long skinny bolts. You can take your exhaust off and lay it on a flat surface and check each runner if it sits flat on the surface ad are inline with each other as well. IIRC there is a 1/8" variance allowed (anyone confirm this?) on the runners but the heater must be flat as well as the intakes stove underside. The triangle washers allow the exhaust to expand in length and slide on the gasket so there needs to be clearance on the triangle washers between them and the raised portion of the exhaust flange. I got an exhaust too. PM me. Thats more bulky and cannot ship flat rate. You should be able to find that locally. Ebay even has them reproduced new for ~$130. Exhaust leak wont cause it to stall just make it loud and stinky.

 

[chinze57]

your issue is not the intake. Its the warped exhaust, that stuff happens. Is your issue possibly where the heat riser is on the exhaust (bright silver gasket)? There is a rectangle gasket that seals them with 3 long skinny bolts. You can take your exhaust off and lay it on a flat surface and check each runner if it sits flat on the surface ad are inline with each other as well. IIRC there is a 1/8" variance allowed (anyone confirm this?) on the runners but the heater must be flat as well as the intakes stove underside. The triangle washers allow the exhaust to expand in length and slide on the gasket so there needs to be clearance on the triangle washers between them and the raised portion of the exhaust flange. I got an exhaust too. PM me. Thats more bulky and cannot ship flat rate. You should be able to find that locally. Ebay even has them reproduced new for ~$130. Exhaust leak wont cause it to stall just make it loud and stinky.
View attachment 1715535866

Yes, I believe the heat riser area Is where my issue lies. It definitely is loud and it can smell a lot more than other slant 6’s I’ve been around, good to know that’s likely where that’s coming from.

The stalling is incredibly strange to me. Sometimes, I can crank it, let it sit for a minute after revving it, and have no issue. Often times, however, i crank it and have to give it gas near constantly. I find that sometimes I can put it in neutral and not have to do that, the rpm’s will drop after idling for a few seconds, and all is good, but if it’s in drive it’ll stall after a few seconds of no gas.

 

[my68barracuda]

Yes, I believe the heat riser area Is where my issue lies. It definitely is loud and it can smell a lot more than other slant 6’s I’ve been around, good to know that’s likely where that’s coming from.

The stalling is incredibly strange to me. Sometimes, I can crank it, let it sit for a minute after revving it, and have no issue. Often times, however, i crank it and have to give it gas near constantly. I find that sometimes I can put it in neutral and not have to do that, the rpm’s will drop after idling for a few seconds, and all is good, but if it’s in drive it’ll stall after a few seconds of no gas.

my bet is that the carburetor needs to be gone through, thoroughly cleaned, rebuilt - reassembled then correctly set up,, choke adjustments, Idle mixture screws,,,
certainly the carburetor may also just be completely worn out, vacuum leaks around the throttle shafts, fuel bowl lid warped,,,

IIRC there is a 1/8" variance allowed (anyone confirm this?) on the runners but the heater must be flat as well as the intakes stove underside.

1/8 inch warpage seems like a lot, the stock gaskets could not seal that, with that much warpage I would think the sealing of the intake manifold to the head would be compromised. I don't deal with stock style exhaust / intakes, but I would think that flatness no greater that .030 would be max. The manifold flange faces are more critical to noise and engine performance than the stove faces....

A good machine shop could take the intake and exhaust manifold as an assembly, like they are mounted to the engine and mill the flanges so they are all in the same plane (flat). The mounting surface on the cylinder head also needs to be clean and flat.

 

[chinze57]

my bet is that the carburetor needs to be gone through, thoroughly cleaned, rebuilt - reassembled then correctly set up,, choke adjustments, Idle mixture screws,,,
certainly the carburetor may also just be completely worn out, vacuum leaks around the throttle shafts, fuel bowl lid warped,,,

IIRC there is a 1/8" variance allowed (anyone confirm this?) on the runners but the heater must be flat as well as the intakes stove underside.

1/8 inch warpage seems like a lot, the stock gaskets could not seal that, with that much warpage I would think the sealing of the intake manifold to the head would be compromised. I don't deal with stock style exhaust / intakes, but I would think that flatness no greater that .030 would be max. The manifold flange faces are more critical to noise and engine performance than the stove faces....

A good machine shop could take the intake and exhaust manifold as an assembly, like they are mounted to the engine and mill the flanges so they are all in the same plane (flat). The mounting surface on the cylinder head also needs to be clean and flat.

My carburetor was cleaned and rebuilt by my mechanic and adjusted a little, which greatly helped for the running versus when I first got it. I’ll read up on carburetors some more and might make some adjustments to see if I can help it any.

When I get my shocks and leaf springs replaced I’ll look at replacing my exhaust manifold at the least, but might replace both and the gaskets just to be safe, tighten it to factory spec and see how all of that does.

 

[pishta]

IIRC there is a 1/8" variance allowed (anyone confirm this?) on the runners but the heater must be flat as well as the intakes stove underside.

1/8 inch warpage seems like a lot, the stock gaskets could not seal that, with that much warpage I would think the sealing of the intake manifold to the head would be compromised. I don't deal with stock style exhaust / intakes, but I would think that flatness no greater that .030 would be max. The manifold flange faces are more critical to noise and engine performance than the stove faces....

yeah, I dont know where I pulled that from now, but the exhaust will draw in some under bolt torque as the runners are not connected at the ends like a V8 intake. I got an early exhaust that is totally smooth, no ribs at all, They put more and more ribbing into later versions to prevent cracking.

 

[chinze57]

yeah, I dont know where I pulled that from now, but the exhaust will draw in some under bolt torque as the runners are not connected at the ends like a V8 intake. I got an early exhaust that is totally smooth, no ribs at all, They put more and more ribbing into later versions to prevent cracking.

I have a suspicion that this is one of those times that buying a later version will be better long-term as it has those ribs to prevent cracking.