J head porting

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EL5DEMON340

EL5DEMON340

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Just getting started on a set of 1972 j's, milled the guide down .200 and about to profile the guide. was there a long thread about porting j/x heads? I can't seem to find it. anyway, can the guide tail be removed completely? This will be going on a somewhat stock appearing 6 pack, intake has been deep port matched. I know aluminum heads would be much better but the 6 pack intake don't flow all the great anyway, plus the looks on their faces when they see they got smacked by a SB with stock heads is fun.
 
EL5DEMON340 said:
Just getting started on a set of 1972 j's, milled the guide down .200 and about to profile the guide. was there a long thread about porting j/x heads? I can't seem to find it. anyway, can the guide tail be removed completely? This will be going on a somewhat stock appearing 6 pack, intake has been deep port matched. I know aluminum heads would be much better but the 6 pack intake don't flow all the great anyway, plus the looks on their faces when they see they got smacked by a SB with stock heads is fun.
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I never shorten a guide. You need to contour the front edge of the guide boss (manifold side) and the back side of the guide boss.

Removing the guide may look good to the eye but it causes turbulence right there.
 
EL5DEMON340 said:
Just getting started on a set of 1972 j's, milled the guide down .200 and about to profile the guide. was there a long thread about porting j/x heads? I can't seem to find it. anyway, can the guide tail be removed completely? This will be going on a somewhat stock appearing 6 pack, intake has been deep port matched. I know aluminum heads would be much better but the 6 pack intake don't flow all the great anyway, plus the looks on their faces when they see they got smacked by a SB with stock heads is fun.
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Pittsburgh racer sent me this old article.
The 6 pack flows a lot better than you think and a deep port matching helps a good bit on any intake. You can one up on the intake by making sure the throttle bores are the same size of not ever so slightly larger than the carb size is. Then stick your burr or cartridge roll in there and contour what you can under the carb.

Mopar Small-Block Intake Manifold Flow Test
Rat Bastid said:
I’d bet 23 years later he wouldn’t use a 30 degree seat. If he would he is way behind in his thinking.

Shape matters more than flow. Way more.
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Agreed! Even more so after he got done learning something from David Vizard.
 
Rat Bastid said:
I never shorten a guide. You need to contour the front edge of the guide boss (manifold side) and the back side of the guide boss.

Removing the guide may look good to the eye but it causes turbulence right there.
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I’ve never heard this before, in fact a few on here have said they do it.
 
EL5DEMON340 said:
I’ve never heard this before, in fact a few on here have said they do it.
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If you’re not sure, put your head on a flow bench. Forget the flow numbers. Use your senses and see what they tell you. How does it sound? Flow the head in reverse. See what that tells you.

Then look at ANY head today that makes HORSEPOWER and see how many take the guide boss out.

The quick answer is NOT ONE.

Do what you want but make damn sure you do your due diligence before you pick up a grinder.
 
I’m just starting, will cut to 2.02. Here is a pic of the guide cut down about .200, and just starting to blend. I’d like to have them flow enough to make 450/475HP so I don’t think I need to get to nuts on them, maybe 240cfm ?

317761A6-7131-498F-A3B6-2D3B67C0C403.jpeg
 
EL5DEMON340 said:
I’m just starting, will cut to 2.02. Here is a pic of the guide cut down about .200, and just starting to blend. I’d like to have them flow enough to make 450/475HP so I don’t think I need to get to nuts on them, maybe 240cfm ?

View attachment 1716033637
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Go for it and have fun !!!!
But keep your crash helmet close by !!!! LOL
 
EL5DEMON340 said:
I’m just starting, will cut to 2.02. Here is a pic of the guide cut down about .200, and just starting to blend. I’d like to have them flow enough to make 450/475HP so I don’t think I need to get to nuts on them, maybe 240cfm ?

View attachment 1716033637
Click to expand...

I know what I’d do and that’s start with a valve job. How do you know how big the throat will end up without establishing the valve job?

Learning to port on the interweb is no different than learning to port reading car magazines.

If you have access to a flow bench us it. The FIRST thing you’ll learn is most everything you read in magazines and forums like this WRONG.

Right now you are just guessing.
 
LOL.....Here comes the Rat, launching a hostile takeover...better get that crash helmet ready.
 
Rat Bastid said:
I know what I’d do and that’s start with a valve job. How do you know how big the throat will end up without establishing the valve job?

Learning to port on the interweb is no different than learning to port reading car magazines.

If you have access to a flow bench us it. The FIRST thing you’ll learn is most everything you read in magazines and forums like this WRONG.

Right now you are just guessing.
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This would be about the 10th mopar head I have ported, bb and SB, Harley Davidson head, jap bike heads, some flathead old school mini bike stuff!! Why would I need to cut the bigger seat right now when I’m working on the guide? I will probably do one port and have it flowed to see if it’s going to be good. After 40 years of hot rodding everything I own I think I have a good handle on things. I have a pretty good reputation on this site for giving sound advice and sharing my builds and mods. And a quick small block Demon. But I will take your advice along with others because I know I don’t know it all and am always learning.
 
EL5DEMON340 said:
This would be about the 10th mopar head I have ported, bb and SB, Harley Davidson head, jap bike heads, some flathead old school mini bike stuff!! Why would I need to cut the bigger seat right now when I’m working on the guide? I will probably do one port and have it flowed to see if it’s going to be good. After 40 years of hot rodding everything I own I think I have a good handle on things. I have a pretty good reputation on this site for giving sound advice and sharing my builds and mods. And a quick small block Demon. But I will take your advice along with others because I know I don’t know it all and am always learning.
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Because I’m a nice guy, I’ll tell you EXACTLY why I said to start with the valve job.

Because thats where the most power is. Because it establishes the throat size. Because it is the biggest factor in how the rest of the port is shaped.

I’m all for working the guide but for the amount of time and effort spent the most power to be had is in the valve job. You’ll get very little in return working the guide boss (although I suggest you do do it, just not at first) compared to getting the valve job correct.
 
EL5DEMON340 said:
This would be about the 10th mopar head I have ported, bb and SB, Harley Davidson head, jap bike heads, some flathead old school mini bike stuff!! Why would I need to cut the bigger seat right now when I’m working on the guide? I will probably do one port and have it flowed to see if it’s going to be good. After 40 years of hot rodding everything I own I think I have a good handle on things. I have a pretty good reputation on this site for giving sound advice and sharing my builds and mods. And a quick small block Demon. But I will take your advice along with others because I know I don’t know it all and am always learning.
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I think that's one of the nicest " thanks, but no thanks" I've ever seen :)
 
EL5DEMON340 said:
No, they are 1972 j with 1.88
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I have a couple sets of Js, one with 1.88s and one with 2.02s. I think they have potential. Ive heard people say they are mediocre compared to the aluminum aftermarket offerings. I am ok with them for street/resto projects.
 
The OEM iron head only gets so good. It was after all designed as a people mover not anHP or race head. I don’t know what can be done as a max out of the head. I’ve heard some claims of flow numbers that I thought were pretty high in the mid 270’s. I really don’t know if that’s possible or not. Or if possible, what extreme mod must be done.

Regardless, if the head can flow 210 stock and you can find 240 cfm, that will allow for some nice street power. If you can find 250 or 260 cfm, you can get the car moving pretty well.

Head porters on here can tell you better of what the heads capable of. IDK if you want to bother with iron heads unless you want to do iron heads for a specific purpose.

In the MP “Speed Tips” section, they’re using ported 360 heads for 12 second recipes. Maybe 11’s as well, I forget, I would have to check to be sure. But, IIRC, they suggest a ported 360 head, 6 pack and a MP solid cam 296/.557 to get into the 11’s, again, IIRC.

Today I’d run the RPM-AG & a 750. It’s a lot cheaper that way.
 
Subscribed. Thinking about the same approach on my heads Mike @EL5DEMON340 . Been torn between aluminum and reworked stock heads. Looking forward to seeing the results. Holler if you need a second set of hands while working on the beast.

Be well man,
Pat
 
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I suppose if I was racing a 340, yes it would be aluminum heads a single plane intake and a 750 Holley carb. That would be my starting "recipe"
 
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