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304 Power and Potential

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DaemonForce View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DaemonForce Quote  Post ReplyReply Direct Link To This Post Posted: Sep/21/2016 at 12:19pm
Ken has this spot on. Here's the thing, I come from a world of L6 AMC. Not that fond of V8s of any kind since my family is so big on Ford FE garbage. Seriously, 390 after 390 is junk and I've never seen these in any decent shape. Considering that my grandfather was a journeyman mechanic that knew what he was doing with big Caterpillar engines most of his life, I'd say he knew what he was doing with the Fords, but even I don't understand what he really wanted.

My first taste of an AMC V8 is currently sitting in a 1970 Ambassador with a Holley carb that likes to flood and puke itself after the first minute of use. Doesn't sputter or misfire, just drowns the engine with extremely rich mixture. I'm still thinking of buying this vehicle from a guy North of the capitol but until he gets this issue under control, probably a non-runner. Which is a shame considering that it's a really great powerplant despite sitting for 12 years. It's a big bore skinny stroke engine which I immediately relate to the 232's design made into a V8 reality. The square is about 84% which makes this a nice revver and feels about as torquey as my L6 stroker. I'm tempted to say it's a preferred engine but it can be better.

The current V8 I'm messing with comes from a Javelin SST that I bought earlier this month and it is in fact a 304 2v. That's a medium bore skinny stroke engine that is the most square of the entire AMC lineup at 92% and I'm still struggling to get it to stop misfiring but this thing is absolute gold. I'm honestly not a fan of V8s but something about this 304 feels exciting and I'm directly comparing that to the 360. I wonder if a 290 would be the same but seeing how my one trouble spot with these engines is their age, I'll have to find a later 304 from a Grand Wagoneer or start swapping distributors, intakes and cranks just to get this mated up to a more modern transmission like a torqueflite or TH400. The stock Borg Warner 3spd has to go, that's the first line of business with this thing.

The most unmentioned thing I think about these engines is the flow rate in the heads. The stock 304 heads are appropriate for what it is and I wouldn't change anything about it unless there's some sort of design issue I don't know about when I finally put on a 4 barrel intake. These are great performing heads that can BREATHE. It's the crossflowing pattern that I find to be appropriate engineering and it's probably the exact same kind of heads that I find on the 1 year earlier 360 that seems to hit some kind of flow limit but with all these tuning issues going on, it's hard to say.

Maybe I'll give it Indy heads.
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53w View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote 53w Quote  Post ReplyReply Direct Link To This Post Posted: Sep/21/2016 at 1:14pm
Over 20 years ago i had a really hot 304 built. Balanced, Ported heads, cam,intake,headers, 600 carb. All good parts. Shifted it at 6000. This was before internet and had no manual or amc expert. Had a ford buddy that built hot ford 302 in local street racing. Used his ford recipe on my 304. Was very fast won alot of street races even took down some mild 350 with it. Problem was the rods we lost 2 engines in 2 years do to rod failures. Both times it looked like the rods fell apart..... remains of rod bearing where perfect, crank perfect. We gave up on the 304/360 and i parked the car for 15 years. As years went by ran into amc engine guys and internet and had amc experts to ask about my 304 build and failures. All said same thing stock 304/360 rod and bolts are good only in stock rpm range they will fail if constantly ran over rpm limit.
That was years ago. Currently arp makes rod bolt kits and there is good aftermarket rods advailable. If you get the rods setup right you can build a dam good 304/360. The rods are the weak spot on a 304/360 build, fix that first and build away.

Edited by 53w - Sep/21/2016 at 6:59pm
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mixed up View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mixed up Quote  Post ReplyReply Direct Link To This Post Posted: Sep/21/2016 at 1:28pm
Im with everybody on this forum 290 and 304 are vey reliable engine for performance I have a 290 in a rambler running 12.30 all day 6000 rpm launch and true the traps yes it has after market rod bolt and piston .030 over but other than that its just a amc im sure with a little work on any engine you can get the performance you desire I have a saying theirs no replacement for displacement
69 amx 290 auto
65 220 290 4spd
80 ford fairmont
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Rambler Mexicano View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rambler Mexicano Quote  Post ReplyReply Direct Link To This Post Posted: Sep/21/2016 at 2:30pm
Thanks everyone for your responses.

All of them have been very illustrative.

Now I have a picture of what the situation is like. The idea of of opting instead for a 360 is fiarly tempting but'd love to build up a 304.

Like you mention the bolt-ons are no problem (carburator, intake manifold, headers, exhausts, ignition), changing the camshaft and adding the 10.5:1 compression ratio pistons shouldn't be too. You already mentioned the solution to the small valve problem with the Chevrolet units and to find aftermarket conneecting rods and their respective bolts.

I think it would be a neat experience if done right.
Mauricio Jordán

Cuando no se es una empresa famosa se deben hacer mejores automóviles.
- Vehículos Automotores Mexicanos S. A. de C. V.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ken_Parkman Quote  Post ReplyReply Direct Link To This Post Posted: Sep/21/2016 at 4:28pm
Somewhat contrary to popular opinion (I do that) there is no problem with the 304 valve size, it's more or less perfect for the port size. It does help the ssr to put a little bigger valve in, but I would not overdo it, what is a nice combo is a 1.84/1.50 305 sbc valve set. One thing very often done wrong is too large a valve for the port, which can cause flow separation problems and poor efficiency. Of course this only matters in serious race use - a street application does not care much. Note that Ghezzi's absolute killer SS 290 must use a stock valve size.

No problems at all for bore. Properly prepped the 304 head can achieve efficiency levels approaching dedicated race heads - do that with a Ford. I did one set of fairly max effort heads for a CI limited race class - I repeat the 304 heads are amazingly good.

Part of the reason a 304 is capable of absolutely trashing a 302. But no one does it cause a 360 has 56 more inches.

The rod problem is easy now - reasonably priced billet rods available and no sense in using stock.
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53w View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 53w Quote  Post ReplyReply Direct Link To This Post Posted: Sep/21/2016 at 7:19pm
I still have my blown up 304 mod in my bro shed. Kept it to some day rebuild or salvage cam and heads. I really been thinking about a redo on it with good aftermarket rods and run it on a dyno to see what it was making hp wise back then.
with good aftermarket rods and other parts it would be worth doing a 304 or 360 if that is what you want.

I just went with a 401 cause after my 304 rod failures i did want to mess with the small stuff any more.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Traveller Quote  Post ReplyReply Direct Link To This Post Posted: Sep/22/2016 at 8:55am
The 304 and 360 rods are the same. Lightening the reciprocating parts will help them live longer.
I really like 1.94/1.5 for a larger overbore.   Reason being, the bowl can be blended the way I like.   The 1.84 is where I would go on a smaller overbore.   It's not hard to make the port go 230cfm@.500 lift. That's without porting the runner.   On the flow bench the flow characteristics are awesome.   Good flow right off the seat, smooth increase all the way up, no noise, no separation. Motor runs down the road very nice.
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DaemonForce View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DaemonForce Quote  Post ReplyReply Direct Link To This Post Posted: Sep/22/2016 at 10:59am
This is all great. I am about to have access to a Rambler parts car that just dropped. Possible 287 V8 + 3spd torque command combo. It would be a great temporary package for a Javelin while I build up a 304 or whatever else. Are the rods the only weak point? How many of us have dropped forged pistons into an early V8 or added speed parts?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Boris Badanov Quote  Post ReplyReply Direct Link To This Post Posted: Sep/22/2016 at 7:23pm
304s are excellent, just a bit heavy for the displacement.

4.75 bore centerlines on a 3.75 bore.....

On my bucket list is a 4" stroke 304 block engine.

I have a 304 saved for that purpose. I just have no time.....
Gremlin Dreams
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amcfool1 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/22/2016 at 9:49pm
hi, the 287 will not just drop in to a javelin, whole different beast, would be kinda cool though! good luck, gz
george z
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