With the number of cracked 360/401 cylinder heads that I have been finding lately, I thought I would try to use 304 heads with bigger valves in them for the full size Jeep 360's that I build. The idea is to use the chevy 2.02" / 1.60" valves in the 304 cylinder heads and hope that we can get the flow numbers to come close to a stock 360/401 head. The first thing that I wanted to do was to just have them machined in and then measure the differences in flow between a stock 360 head, a stock 304 head and a modified 304 head with 2.02"/1.60" vlaves. To do this we had to install new guides which have to be replaced about half the time anyway. Our results for the stock 304 head is really close to what Mr. Parkman has recorded here so, I know that my numbers are fairly accurate. users.erols.com/srweiss/tablehdc.htm#AMC
The 360/401 cylinder head is a 1977 #3231475-1 and the 304 head is a 1978 #3233324-2.
I am really happy with the intake side. The exhaust side is not as close but is getting there. This is with no fancy work or anything. It is just what the cutter can do under normal machining. I didn't want to have to do any more than that but to get the Exhaust flow numbers up I guess that I will have to. IMG_2836 by Rick Jones, on Flickr
304 head 2.02"/1.60" left side, 1.787"/1.406" right side IMG_2828 by Rick Jones, on Flickr
Klvn8r’s brother has a set of early small chamber 304 heads that parkman did with ( if i recall correctly) 1.87/1.50 chevy 305 valves. Now they were ported pretty extensively, and i dont remember exact numbers, but we noted they exceeded edelbrock performer head numbers. The 304 heads are limited mostly by the tiny valves and the ports for the most part are comparable to the big valve heads. I have a set of 1977-ish 304 heads with the bigger chamber modded with nicer manly 305 chevy valves that i ported the exhaust and blended the bowls ready to go for 304 fun. Not like a 304 eats much but they shouldnt hurt? Well who knows. I didnt want to overdo the intake because im using the low end of the rpm range and trying to enhance the torque response. 304 heads are winners. I have used stock 304 heads on 360’s and they work awesome with a stock or mild cam in a jeep or a truck and get better milage. I built a 360 for a j-10 that with late 304 heads . The original engine had cracked heads and i donated the 304 heads cuz the old man was low on cash and just needed a runner to haul his fishing boat. He was quite happy with it and said it pulled better than ever.
I will add the part numbers of the heads but they are all late bridge rocker heads in my test. All in all I am really happy with the numbers and I should leave well enough alone at this point. At this stage, it will cost less to put the chevy valves in the 304 head vs new stock valves in a 360 head.
Its a very economical strategy. The factory 304 has some quite disturbing areas just under the valveseat. Putting in larger valves cuts this hideous transistion out. If you notice your intake flow numbers, the amc valve has a fair amount better flow off the seat to about .300 lift, thats the advantage of the 30 degree seat. You actually get better flow earlier and increased cylinder filling due to that, the chevy valve is the same from 300 up. The chevy valve surpasses the amc valve extreme lifts due to its 45 degree seat. So my point is if your running a street cam with less lift, you will do better with an amc valve. If your moving ahead to a hi lift roller a chevy valve has advantage. Not trying to go negative just adding to the conversation. I have been flip flopping on buying a pair of “ aeroheads” 304 heads modded with 202/160 chevy valves, they are early small chamber 304 heads. But since i actually want them for a 304 the 202’s are kind of a deal breaker. I dont want those in a small bore 304. I just want the small chambered early head. Recalling info from dills forum, i forget the name jcisworthy i think built the hot 304, ( the start of our monster 304 topic) i think he used 202/160 valves, but dont rule out the 196/155 , 196/150, 187/150 or and combo of 196, 187 intake, 155 and 150 exhausts in your 304 heads, they are all cheap and theres not a dimes worth of difference in what they flow in a correctly seated 304 head. The 304 head can flow better than a big valve head when ported, even with stock 178/140 valves as has been proven in garret ghezzis 290!
I actually have a second project that I want to use a pair of 1970 304 heads on a 360 for slightly high performance street car so, I am listening to what you are saying. The Machinist and I both think that we cam help them out quite a bit by cleaning up the short side radius. Right now, there is a sharp transition in that area. I will spend more time on this second set but, I am not going to spend days on them. Fun stuff though.
it doesn't take much time to blend in the new throat area to the as cast bowl area. i did mine in a couple hours. I had the exhaust ports completely done before i took the heads to my machinist to cut seats for the new 305 valves, he gave them back and i blended the bowls and took them back to him for finishing. he also install springs for the small crane hydraulic roller cam and machined the pedestals for screw in studs and guideplates. i kinda wish now i left the pedestals alone so in could have tried the bolt on LS rocker trick. i think your flow numbers reflect more improvement in the seat/ throat transistion and improvement in developing a short side radius more than the chevy valves alone i dont think the chevy valve offer advantages in flow on any of their design features, well except weight... i have read information by a guy named davad vizard [WOW!!! you gotta read this guys shit!real lightbulb on stuff based on his own research}on cylinder head development which indicates the valve angle, seat angles, and angles and contours leading into the intake seat and into the exhaust port, " the window " areas are the most critical items in improving flow. the 304 stock vave seat is not good atall. the pictures of before and after tell a tale of a sharp 90 degree corner with a 30 degree seat cut and little else on the factor seat. your new seat is a masterpiece compared to that. blending and enlarging the deeper bowl area will surely pick up flow. not as much as the your new seats, which are going to be the most profound improvement, as gains beyond that will be smaller. on a street application i would consider starting with a amc valve and gain back the flow at low lifts. or a new chevy valve recut to 30 degrees. get back the flow boost at lower lifts. starting the flow momentum sooner. the flow bench is a fine tool,and its whispering something there. big numbers at higher lifts are fine, but closing your eyes to big losses at lower lifts is not. all flow counts and getting it going sooner counts big on smaller cams. smaller cams and better flowing heads are really fun things to have in your engine. what makes the 304 so disgusting to most is it doesn't respond so good to the " bigger is better" thinking we throw at bigger engines. when you hurt low end torque you really feel it with a 304. which .. makes it a great r&d tool in its own right. but think about it, making any engine have more low end, and part throttle power is going to give it a more effective range of torque, and that wide flat torque is power, and it accelerates the car more of the time, ultimately doing work when a hotrod engine is "lazy"... and thats streetpower you can really use.
Yes David Vizard is a very knowledgable internal combustion engine researcher. Reading his books,many,makes you avoid many common mistakes,saving time and money in the process. What I have learned from only one day of class at Joe Mondello a few years ago, is that a good air flow gain can be had doing port work at home with simple tools,as long as you keep it simple.
I picked the heads up from the Machine Shop today. Chuck spent 45 minutes on each head blending in the short side radius. Looks to me that it was worth the effort. This basically exceeds my hope of matching the flow of a stock 360 head with minimal work. IMG_3102 by Rick Jones, on Flickr My man Chuck helps a brother out every once in a while. He didn't charge me for a hour and a half for porting time because these are for me. He also charge me a quarter of what he should have for all of the flow bench time. I guess I owe him a few more beers. One minor thing that I will ask about tweaking the next time is the valve stem heights. I was hoping that they would end up at the stock height of 1.97". These ended up at 2.050" for the intakes and 2.025" on the exhausts. Not a huge deal, it just means that I will have to shim the rocker arms up by the difference. Pretty cool little project all in all.
Yep. I had a second set of 304 heads reworked with the 2.02"/1.60" valves. These are the 1970 304 heads so the combustion chamber is a little smaller which will bump the compression up a little. Chuck told me that he spent 45 min each on hand blending and porting. They came out really nice. IMG_3611 by Rick Jones, on Flickr IMG_3610 by Rick Jones, on Flickr IMG_3609 by Rick Jones, on Flickr
This time the valves ended up .100" less in height than the stock stuff so, I will have to use adjustable rockers. I thought that I ordered the exact length valve as the AMC valve but guess not. Now I know that I need to order +.100 valves to get it to work out perfectly. Still learning..
67roguexcode: Come on guys, don't despair, your guy will be sworn in soon, and the heavens will open up and FREE stuff will be dispensed to everyone... the world will hold hands and we'll watch in awe as Plugs leads us to Nirvana.
Jan 8, 2021 7:11:40 GMT -8