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Old 07-29-2018, 02:29 PM
RoadRacer_Al RoadRacer_Al is offline
232 I6
Join Date: Jun 18, 2018
Location: California
Posts: 38
AMC 327 Head Porting?

Hey there - new '67 Gladiator owner.

It's looking like I have to rebuild the cylinder head with hardened valve seats.

I've been looking at performance options for the 327, and they are substantially hard to get power out of -- in fact, I've seen several comments suggesting not even switching to a 4-barrel carb because the exhaust ports are the limiting factor.

Porting is never mentioned.

For background: I used to race motorcycles, and built all my own engines, but I've never built a car engine, much less a car engine with cast iron heads. And, I haven't got the heads out of the truck yet, in any case. Just trying to set expectations.

Is porting a cast iron head impossible or otherwise impractical? Are the water jackets too close to the ports? Why doesn't anyone port AMC 327s?
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Old 07-31-2018, 12:44 PM
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babywag babywag is online now
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Join Date: Jun 08, 2005
Location: Land of froot loops and cukcoo-nuts, CA
Posts: 9,569
In an old heavy Jeep I'd spend my time elsewhere.
Any gains(if successful porting a pair) would be very minimal IMHO and likely only @ high rpm.
It's your call, but I wouldn't even bother if it was me.

I'd look into possibly fitting larger valves, and stick to the basics.
Basics meaning good dual exhaust, and maybe 4bbl intake & small(like 450 cfm) 4bbl.

If it was me a newer throttle body TBI setup would be installed.
Holley has a 2bbl sniper that'd probably work well?
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Old 07-31-2018, 02:02 PM
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Cecil14 Cecil14 is offline
Join Date: Jan 22, 2001
Location: Carson City, NV
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There's nothing unique about iron heads, they port the same as aluminum (they're just harder, obviously). As far as what gains you would get? No idea. You'd have to do the entire package (valves in included, as Tony mentioned) to likely see any gains. You've got a 60+ year old engine design, without much in the way of aftermarket. I'm sure there are improvements to be made, but it's going to take a lot of time and engineering to get much.

1983 J-10 - 4.6L(MPFI)/CS130D/Hydroboost/NV3550/D300/44/44/3.54/Disc-Disc/32s/42 gallon 'burb tank
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Old 07-31-2018, 11:29 PM
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FSJunkie FSJunkie is offline
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Join Date: Jan 09, 2011
Location: Not The Hot Part, Arizona
Posts: 3,989
Jeeps except the Super Wagoneer got the low compression 2bbl 327 of 250 horsepower while most Ramblers and Super Wagoeners got the 4bbl high compression 270 horsepower 327. There is a noticable difference between them. Most of that difference is the carbruetor. Installing a 4bbl manifold and 4bbl carburetor that fits the manifold will make a noticable difference on it's own. It's not a life-altering difference, but you can feel it.

Porting the heads will get you nothing unless you change the cam. In fact, porting might ruin your low RPM torque without a cam change. The cam is your first hurdle to get over. The stock 327 cam is extremely mild. It's the same grind used on the early 1950's Nash sixes. Performance cams have to be custom made, usually by regrinding your old cam. There are limitations to that. Then after you have more cam you can look into porting the heads. larger valves are not really feasible because of the combustion chamber shape in the head. Fun fact: the valves are also shared with the early 1950's Nash sixes. The 327 is basically a Nash six with two more cylinders. The stock intake manifold can be ported, but otherwise a performance manifold must be made from scratch. Some people have modified a Torquer to fit. Headers must be custom made from scratch.

Old school hot rodding, not hot rodding from a Summit catalog. This gets really expensive really fast and takes a lot of work.

I suggest if you find your current power inadequite to install the 9.7:1 compression pistons instead of your current 8.7:1 pistons and find the stock 4bbl manifold and Holley 4bbl carbruetor setup to install. Those two things will put you at 270 horsepower instead of your current 250 and that should be plenty of power for any reasonable needs.
'72 Jeep Wagoneer Custom, 360 V8

I love how arguements end as soon as Ristow comments. Ristow is right...again.
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Old 08-02-2018, 12:33 AM
RoadRacer_Al RoadRacer_Al is offline
232 I6
Join Date: Jun 18, 2018
Location: California
Posts: 38
Thanks for the input! I'm not looking to spend a TON of money, but I'm not afraid to spend some if the results are good.

There's a well-known cam grinding place less than 30 miles from my house, so they might be getting a call from me.

The big exhaust valve might be do-able since I might have to get the head rebuilt anyway.

I have experience building headers, and it would be a fun project try my hand at an intake manifold. I have an idea about a cross-ram fed by a pair of 300cfm 2-bbls.
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Old 08-02-2018, 07:44 AM
440sixpack 440sixpack is offline
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Join Date: Jul 21, 2016
Location: oregon
Posts: 612
Porting would be a waste of time . unless you built a performance engine and operated it at WOT you'd never notice it.
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