Porting Big Block Heads

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JGC403

JGC403

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I don't know what magazine the articles were in originally but its in the Hot Rod Magazine Archives now. Back in 1998 they did a 3 part article on porting Mopar Big Block heads. Here are the links if anyone hasn't seen them before:

Part 1: https://www.hotrod.com/articles/cylinder-heads/
Part 2: https://www.hotrod.com/articles/cylinder-heads-ii/
Part 3: https://www.hotrod.com/articles/cylinder-heads-iii/

Has anyone on here copied what they did with a set of heads? I am really interested if anyone is running around with the 30* intake seat that they liked so much in the article, they claim that the 30* seat gains a considerable amount of low lift flow and doesn't hurt high lift flow, says it would make a good street head.
 
It rarely makes sense to port cast iron heads these days. I don't think it even made sense back in 1998 but Steve probably needed some money so he got a few articles published. These days you just buy some Stealth heads or step up to Edelbrock or Trick Flow if the wallet is a little thicker. Cast iron heads are all 50 years old and most of them are used up. I haven't seen a customer with ported cast iron heads for at least 10 years.
 
Why does anybody run anything but an LS? Maybe a Gen III Hemi if they weren't so EXPENSIVE! I wish they made motorhomes with new Hemis, if they did, imagine the MARKET for engine builds in 2050!!!
 
Bighead440 said:
Why does anybody run anything but an LS?
Click to expand...

Because I'm not a Chevy guy, if I was I wouldn't own Mopars. Chevy Engines don't belong in Mopars, I don't like Chevys, I don't want anything to do with Chevys. Hemis are expensive I am working on a 1st Gen DeSoto Hemi now. I would like to build another 1st Gen Hemi some day. Mopar Big Blocks are cool.

Anyone out there that can actually answer the original post?
 
I wouldn’t use a 30 degree seat on any head. Ever. There is more to making horsepower than just looking at flow numbers. A 30 degree seat is a power loser. Every single time.

I’ll read the links because I don’t remember reading them at the time.
 
JGC403 said:
Because I'm not a Chevy guy, if I was I wouldn't own Mopars. Chevy Engines don't belong in Mopars, I don't like Chevys, I don't want anything to do with Chevys. Hemis are expensive I am working on a 1st Gen DeSoto Hemi now. I would like to build another 1st Gen Hemi some day. Mopar Big Blocks are cool.

Anyone out there that can actually answer the original post?
Click to expand...

I wouldn't put an LS in anything but a dumpster. My post was satire in support of you RUNNING iron heads. I threw the "motorhome" jab in to protest the latest craze of postings and hysteria about anything "motorhome." Like real MoPar faithful haven't been doing the same thing for 40+ years and NOT caring. LOL
 
So, from what I’m reading (should have known Vizard was involved...he just loves the 30 degree seat) they went to the 2.14 valve and used a 30 degree seat, but didn’t use the 2.14 and a 45 degree seat to compare the 30 and 45 with the same valve size. That makes ZERO sense, unless I missed something.

I’ll say it again...even in Vizard’s porting book he points out how much pressure drop there is at low lifts...as high a 200 inches! So how does testing a port, at 28 inches and .025 prove anything? The case can be made increasing the low lift numbers in that range, when the exhaust valve is still off the seat and the header is pulling on the port all you are doing is pulling the new air/fuel charge right out of the exhaust port.


That’s how you end up with lean reading spark plugs, and dirty, wet exhaust ports.

Also, back cutting looks awesome on the flow bench, but isn’t always the cool deal in real life.
 
AndyF said:
It rarely makes sense to port cast iron heads these days. I don't think it even made sense back in 1998 but Steve probably needed some money so he got a few articles published. These days you just buy some Stealth heads or step up to Edelbrock or Trick Flow if the wallet is a little thicker. Cast iron heads are all 50 years old and most of them are used up. I haven't seen a customer with ported cast iron heads for at least 10 years.
Click to expand...
I read and reread those articles when they came out. I think the Stage 6 head was the only street type aluminum head available at the time and not a lotta "bang for the buck". I did a bowl port on a set of 346s and tried to copy the guide boss mods shown in the articles. This was in 2000-2001 for a mild 400. Shortly after I build the motor, the Edelbrocks came out. I typically wouldn't fool with old iron heads now, but a few years ago I did a quickie bowl port on some heads off of a 75,000 mile 318 that was just getting a Summit cam stab, used intake and headers.
 
The thing that’s almost never discussed when talking about the 30* seat is, it allows for easier port reversion during the overlap period, especially when there is any restriction in the exhaust system(mufflers), and can make it so the motor has to turn a few hundred more rpm before really overcoming the reversion and getting up on the cam.
It’s more of a “problem” as the cam starts getting “bigger”.

Really it comes down to this......
Does the 30* increase low lift flow?
All else being equal....... basically..... yes.
Is that something you want?
Maybe......maybe not(usually not......even if you don’t know it).
 
AndyF said:
It rarely makes sense to port cast iron heads these days. I don't think it even made sense back in 1998 but Steve probably needed some money so he got a few articles published. These days you just buy some Stealth heads or step up to Edelbrock or Trick Flow if the wallet is a little thicker. Cast iron heads are all 50 years old and most of them are used up. I haven't seen a customer with ported cast iron heads for at least 10 years.
Click to expand...

That's because you and your customers are all rich and don't know what's it's like to have to used old stuff. Maybe you did......a long time ago.
 
PRH said:
The thing that’s almost never discussed when talking about the 30* seat is, it allows for easier port reversion during the overlap period, especially when there is any restriction in the exhaust system(mufflers), and can make it so the motor has to turn a few hundred more rpm before really overcoming the reversion and getting up on the cam.
It’s more of a “problem” as the cam starts getting “bigger”.

Really it comes down to this......
Does the 30* increase low lift flow?
All else being equal....... basically..... yes.
Is that something you want?
Maybe......maybe not(usually not......even if you don’t know it).
Click to expand...

Totally agree--I have tried 30* seats exactly twice (not including Pontiac builds) and both times the engine was WAY "cammier" and also WAY down on power. I have flow tested 30degree seats backwards and they FLOW like gangbusters up to .400"--like 20-30cfm more backwards than they do "forwards". This totally explains (at least in my mind) why the engines respond the way they do. Only old diesels should use 30* seats. Vizard was and is wrong on this one. J.Rob
 
RAMM said:
Totally agree--I have tried 30* seats exactly twice (not including Pontiac builds) and both times the engine was WAY "cammier" and also WAY down on power. I have flow tested 30degree seats backwards and they FLOW like gangbusters up to .400"--like 20-30cfm more backwards than they do "forwards". This totally explains (at least in my mind) why the engines respond the way they do. Only old diesels should use 30* seats. Vizard was and is wrong on this one. J.Rob
Click to expand...



Exactly. This is one reason why a 50 degree seats has advantages over the 45. It has less reverse flow. And the shape is better.
 
Murray said:
Why are we going back over 20 year old technology? Stay current.
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Well then buy a new Hellcat Demon & get it over with,....I'll be at the yard when You haul that heap of Yours in for scrap, :D .........
Airflow is 20yr. old tech?? The basic MBB head architecture is actually 62-63yr. old technology, the quest to get as much out if them almost exactly as old, many have spent countless hours making them actually work well. What's wrong with discussing it?
& there was supposed to be a part 4 which is missing....
 
PRH said:
The thing that’s almost never discussed when talking about the 30* seat is, it allows for easier port reversion during the overlap period, especially when there is any restriction in the exhaust system(mufflers), and can make it so the motor has to turn a few hundred more rpm before really overcoming the reversion and getting up on the cam.
It’s more of a “problem” as the cam starts getting “bigger”.

Really it comes down to this......
Does the 30* increase low lift flow?
All else being equal....... basically..... yes.
Is that something you want?
Maybe......maybe not(usually not......even if you don’t know it).
Click to expand...
But We always get the chance to discuss it here,....so the few times We do may sink in.......
:thumbsup:
 
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