AMC 327 Head Porting?

[RoadRacer_Al]

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?

[babywag]

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?

[Cecil14]

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.


aa

[FSJunkie]

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.

[RoadRacer_Al]

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.

[440sixpack]

Porting would be a waste of time . unless you built a performance engine and operated it at WOT you'd never notice it.

[SC/397]

My Cuz and I built a hypo 327 a few yeas ago now. I did smooth out the runners and combustion chambers and blended them to a adapter plate for the later intake manifold. We installed SBC valves in them as well. Since then, he has been experimenting with the heads and actually had Ken Parkman (AMC head expert) port a set of heads for his next project. I will send you both of these guys information.

[FSJunkie]

Honestly if I was trying to get a 327 over 300 horsepower I would have it with sequential multiport electronic fuel injection and supercharging. AMC had an experimental multiport electronic fuel injected 327 in 1957. I was the same Bendix Electrojector Chrysler was using, only Chrysler actually sold a few and AMC's versions never left the engineering department.

An old school variable belt-driven centrifugal Paxton or McCulloch supercharger blowing into a four barrel throttle body with staged secondary barrels for precise throttle response. The intake manifold would be stock but I'd drill and tap it for fuel injectors. I could go to the wrecking yard and yank the EFI system off something like a Vortec 5.3 and adapt and reprogram it.

The engine internals would be basically stock. The lower compression 8.7:1 327 lends itself perfectly to this since the 9.7:1 versions are already prone to ping and would require water/meth injection to work. The stock ports, valves, and cam would work perfectly for forced induction. I'd probably upgrade my bearings and piston rings.

It would be a beautiful engine. It would still have the smooth, quiet idle of a stock 327 and the awesome low RPM torque of a stock 327 (because it basically is a stock 327 inside), but it would have more torque at all RPM's. The torque would be unbelievable. I think it could hit one horsepower per cubic inch. Something like 330 HP @ 4800 RPM and 450 ft-lbs @ 3000 RPM.

That would be the mild build. The wild build would be to bore and stroke it to around 400 cubic inches (which has been done before). Then some porting, larger valves, bigger cam, and headers come in. The EFI and supercharging stay. Now we're looking at over 400 horsepower and 500 foot-lbs of torque that still idles smooth and quiet.

Gives me a warm fuzzy feeling just thinking about it. One day I'm going to do it.

[44BZ]

I don't have the technical background that these other guys have, but I do have driving experience. My 68 has the 327. I added the stock 4bbl intake and a late model Holley carb, rambler driver side exhaust manifold to get rear exit, and 2.5" dual exhaust. It also has a Pertronix kit in it. It's a big, heavy pickup that drives like one but it'll spin the 35s on dry pavement and haul a load of gravel without any issues

[SC/397]

I don't have the technical background that these other guys have, but I do have driving experience. My 68 has the 327. I added the stock 4bbl intake and a late model Holley carb, rambler driver side exhaust manifold to get rear exit, and 2.5" dual exhaust. It also has a Pertronix kit in it. It's a big, heavy pickup that drives like one but it'll spin the 35s on dry pavement and haul a load of gravel without any issues

I will take experience over assumptions any day! On a vehicle like yours Torque is where it is at. 300 HP from a 327 takes a lot of work, more so than people think. The 270 HP 327 only existed in the books and calculations. If you built one today at those exact specifications it might make 225 HP on today's dynos. The key here is no one talks about torque. It would be fun to dyno one in stock condition and then add modifications to see what the improvements are.

[44BZ]

I will take experience over assumptions any day! On a vehicle like yours Torque is where it is at. 300 HP from a 327 takes a lot of work, more so than people think. The 270 HP 327 only existed in the books and calculations. If you built one today at those exact specifications it might make 225 HP on today's dynos. The key here is no one talks about torque. It would be fun to dyno one in stock condition and then add modifications to see what the improvements are.

I like my 327 a lot. I do have an "RV" type cam for it that I had ground a couple years ago. Just waiting for a reason to pull the timing cover and install it. I will add that previously I had a Holley Truck Avenger 470 on it and switched to a Holley 600 cfm, street style carb and it drives much better.