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getting more out of a 304 with a STOCK bottom end. (Read 854 times)
gschuld
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getting more out of a 304 with a STOCK bottom end.
11/24/16 at 15:43:36
 
For those who need a mental break from Thanksgiving activities(mother in law, etc Wink ), here is a little distraction.
 
First off, I fully understand that 304s are not the ideal engine choice where power is a consideration.  I have a nice 360 and a 401 and love them.  But I'd like to keep this about 290/304s
 
Specifically, late 70s dead stock vintage jeep cj 1.07 venturi 2100 Motorcraft 2bbl, free flow manifold, Motorcraft ignition/distributor motors.  Let's say that I own a few of them Roll Eyes
 
I'm curious, for giggles, how much an improvement can be made while retaining the dead stock bottom end, including the cam. I have found, consistently, that the dead stock 304, plus the restrictive factory single cat converter exhaust downstream, they are set up to perform fairly well(for a choked down Malaise era V8) from 1500 or so through 4000 or so (when valve float appears to kick in).  
 
My goal would be to increase overall power/torque with a peak of 5000 or just over and in an ideal world, retain a factory stock appearance.  The idea is to retain it's general function.  Favoring torque over hp with a wide power band for good manners with a 3spd trans.  It will be used in a pretty stock late 70s Jeep cj, T150 3spd toploader, Dana 20 transfer case, 3200 lbs.  No extreme rock crawling planned, so the power band doesn't have to start at 1200 or anything.
 
My thoughts:
 
-Retain 2bbl manifold, with some blending of the sharp edges into the runners from the carb throat and misc touching up.
-Upgrade to a Motorcraft 1.21 venturi 2bbl (1.07 stock) or possibly the more rare 1960s 1.33 venturi Autolite 2bbl.
-rebuild the heads, possibly a set of 1970 #517 small chamber 304 heads to bump the compression to +/-9:1 along with a porting job on the bowls, gasket match, good valve job, minor chamber work, etc.
-valve springs.  Clearly I'd need a bit more than the old self limiting 304 springs. Factory stock 360/401 springs would likely be enough I'd think.
-possibly go with an MSD ignition box/MSD coil/factory distributor combo for a bit better spark.
-retain the free flow manifolds, but port the air bosses down, open up the exit, and put in a full dual 2 1/2" exhaust with a pair 20" Walker Super Turbo mufflers to keep things quiet.
 
So theoretically:
 
More intake flow with bigger cfm 2bbl carb
Bump in compression  
Better head flow from porting
More spark
Better springs to combat valve float
Better flowing exhaust.
 
I'm NOT looking for a race engine here, clearly.  Just a bit more umph out of a 304, mostly for the entertainment of the challenge.
 
I'm curious to get an idea as to whether the factory cam would respond well with something like the above mods considering the goals.  Otherwise, new cam recommendations are welcome.
 
FWIW: I believe the factory cam specs for the 2bbl 304 are as follows:
 
.266 lobe lift(.426 overall lift) 
263.50 duration intake and exhaust  
Intake opens 14.75 BTDC 
Intake closes 68.75 ABDC 
Exhaust opens 56.75 BBDC 
Exhaust closes 26.75 ATDC 
Valve overlap 41.50
 
Thanks for playing.... Smiley
 
George
 
P.S.  I am interested in picking up a set of small chamber #517 304 heads if anyone has a set on hand.
 
 
 
 
 
 
 
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« Last Edit: 11/24/16 at 20:33:48 by gschuld »  
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matadorman 401
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Re: getting more out of a 304 with a STOCK bottom
Reply #1 - 11/24/16 at 17:18:36
 
i am running a 343 cast iron 4 barrel intake and an eldo 600 electric choke in a 72 matador motor is a 304 it ran better but the big improvement was a set of shorty headers that really woke up the little 304 still running single exhaust my y pipe bolted right up  hopefully going to duals next year i am also looking for the early 304 heads
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72 matador 401 aka "THE BEAST"
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tufcj
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Re: getting more out of a 304 with a STOCK bottom
Reply #2 - 11/24/16 at 17:22:35
 
I know this isn't quite what you're looking for.  Back in the early 80s I had a CJ7 that I mud bogged.  Factory 304/3speed/Dana 20.  The class I raced in had to have original block/trans, but the engine could be modified.
 
The crank was stock.  Rods were original, but I had them shot peened.  Block bored .030 w/forged TRW flat top pistons with custom cut valve reliefs (about 10:1 compression).  Rotating assembly was balanced.  Heads were 304, done with Chevy 1.5 and 1.94 valves and Isky dual valve springs, mild port/polish (stock valves are 1.4 and 1.78).  I ran an Isky cam with .488 valve lift on stock bridged rockers.  Distributor was a Mallory Unilite.  I ran a Performer manifold and Holley 600 w/vacuum secondaries.  I ran Alumacoat fender well headers.  I revved this engine regularly to 6500 RPM, it put out well over 300 HP.  I raced it for many years with no failures, drove it daily on the street.  I used to get called out all the time for running a SBC conversion in the class I was running, easily dis-proven by lifting the hood.
 
Bob
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gschuld
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Re: getting more out of a 304 with a STOCK bottom
Reply #3 - 11/24/16 at 17:55:07
 
Matadorman,
 
Thanks for the thoughts.  I believe a set of ported free flows stack up pretty well against shorty headers in the 5000 and under range, especially up to 4000.  Anyway, I'd really like to stick with a factory appearance for personal reasons.
 
I have plenty of parts if I was inclined to skip that route, headers, early/late cast iron and performer 4bbl intakes, Holley and Carter carbs, etc.  Bigger engines for that matter.  But it's not my intention here.
 
Tufcj,
 
Yeah, your build would be WAY overkill for my interests.  I want to have something that I can toss the keys to my nephew when he gets his license.  It's more of a stock layout cj.  No lift, 31s, reasonably stable, front hoop roll cage add in, decent seatbelts, tightened up suspension slop, etc.
 
George  
 
 
 
 
 
 
 
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gschuld
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Re: getting more out of a 304 with a STOCK bottom
Reply #4 - 11/24/16 at 23:22:28
 
A few reference points from various forum posts.  
 
 
304 dyno results and holley tune
 
Finally got that darn Holley 470 TA tuned right, took a dyno to do it. Mains for primaries went from .57 to .51, secondaries from .57 to .54. Power valve now a 7.5, was 2.5. Squeezed out a RWHP of 193 and Trq maxed at 250. Should get ~200 as soon as I change secondary mains to .56. Then we order the headers and hope for 220
 
It's a stock long block, 85 oct pump gas. Edelbrock performer intake, 470 truck avenger, MSD distributor, wires, plugs, fuel pump. And a bunch of adjusting and dyno runs to squeeze that out. 
 
 
 
Pirate4x4 Addict!
 
Another:
 
With Edelbrock EFI on a bone stock 304 with 90,000 on the clock, my CJ 7 made 138 hp. Valve float was a big problem. The Jeep wouldn't rev beyond 4,000 rpm successfully. It had single exhaust and an open element air cleaner. This was with a t-150 and model 20 t-case.
 
With efi, shorty headers, 3" exhaust with SDT muffler and a performer cam, lifters, valve springs and a new timing chain it made 201 at the rear tires. NP435 and d300. The motor was not rebuilt other than these items.
 
George
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Re: getting more out of a 304 with a STOCK bottom
Reply #5 - 11/26/16 at 16:07:48
 
have you thought about going to a 500 holley 2 barrel it bolts right up i had one on at 78 concord with the 304
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72 matador 401 aka "THE BEAST"
72 matador 401 aka The Grasshopper
79 Power Wagon stepside

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gschuld
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Re: getting more out of a 304 with a STOCK bottom
Reply #6 - 11/26/16 at 18:36:56
 
Yes I have actually.  Those 500cfm 2bbl Holleys are very well respected and developed carbs.  Since many restricted engine  racing series require these carbs, many have been modified to put out serious power.   And even race ready Holleys 500s are available pretty cheap used.  
 
The old 2100/2150 Autolite/Motorcraft carbs have also shown surprising capability in the larger venturi (cfm) sizes.  Especially the harder to find mid 60s 2100 that had the 1.33 venturis, which is the same exact venturi size as the Holleys 500cfm carbs.
 
I'd prefer to use the larger venturi versions of the factory Autolite/Motorcraft carbs though if possible.  The 304s came with the tiny 1.07 venturis, quite a bit more restrictive than their bigger venturi (yet otherwise identical looking) brothers.
 
I have always favored the modified stock looking approach, or modest "sleeper" look.  It's just a personal preference thing.  I like the "goes faster than it looks" kind of thing.  Holleys 500 carbs look like half a full race 4bbl carb.  It is a dead give away the motor may have been modified.
 
My interest is to see what is attainable without straying from the factory original look under the hood.  But I'll keep other options in mind.  As I said before though, I have my share of higher performance non stock parts on hand if I wanted to go down that path.
 
A few baseline chassis dyno runs for a dead stock 304 chassis dyno would be a given before making any mods, just to compare.
 
George.
 
 
 
 
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matadorman 401
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Re: getting more out of a 304 with a STOCK bottom
Reply #7 - 03/19/17 at 12:19:14
 
any updates on the little 304 ?
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72 matador 401 aka "THE BEAST"
72 matador 401 aka The Grasshopper
79 Power Wagon stepside

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