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Author Topic: 304 2V versus 258 2V?  (Read 9552 times)

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Offline tlake

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304 2V versus 258 2V?
« on: February 25, 2012, 04:59:04 AM »

  I was wondering if there is much of a performance difference between these two motors? Anyone have personal experience of driving 'em in the same kind of body e.g. Concord AMX, 1978/79 Pacer? Power rating they are only 5-10 hp different, but do they perform much differently in practice?  ???

  258 2V 8.0:1 comp ratio

Offline mudkicker715

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Re: 304 2V versus 258 2V?
« Reply #1 on: February 25, 2012, 08:23:34 AM »
Imo yes they feel noticeably stronger. compred in same 73 commando. my eagle is different i also changed axle ratio at same time

Current amc's
82 concord waggy 258 DD
84 eagle sedan stroker DD
86 eagle wagon sas 304 v8 toy
87 eagle wagon stroker

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Offline tlake

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Re: 304 2V versus 258 2V?
« Reply #2 on: February 25, 2012, 10:15:00 AM »
Imo yes they feel noticeably stronger. compred in same 73 commando. my eagle is different i also changed axle ratio at same time

 I recall Car and Driver speculated how nice it would have been to try the 304 in the Eagle wagon body, but they said they didn't want to give up even one CAFE 1 mpg, so they were happy with the 258. Not that they had a choice because the 258 was mandatory by 1980.

Offline Ohio AMX

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Re: 304 2V versus 258 2V?
« Reply #3 on: February 25, 2012, 10:44:20 AM »
I've had both in Hornets and Pacers. The 304 definitely feels like it has more torque. It also sounds a lot better!
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Offline 1OldFordMan

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Re: 304 2V versus 258 2V?
« Reply #4 on: February 25, 2012, 05:01:12 PM »
Have driven Gremlins with both (owned the 304) brother owned both & traded years ago. Think there were different gears in them, but the 304 was MUCH better!!!!
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Offline carnuck

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Re: 304 2V versus 258 2V?
« Reply #5 on: February 25, 2012, 08:51:44 PM »
Imo yes they feel noticeably stronger. compred in same 73 commando. my eagle is different i also changed axle ratio at same time

 I recall Car and Driver speculated how nice it would have been to try the 304 in the Eagle wagon body, but they said they didn't want to give up even one CAFE 1 mpg, so they were happy with the 258. Not that they had a choice because the 258 was mandatory by 1980.

There are a lot of CJ owners who got the 304 option till '86. No reason it couldn't have been put in the Eagle as it was passed off as a light truck. The same MC2100 carb on 258 as the 304 got pretty equal power to the 304.
   I had a '77 AMX 304 in my '73 J4000 (that I put in) and it was nearly perfect. 14 mpg in town (loaded) and 17-19 on the highway with TH400 Borg Warner Quadratrac part time converted with O/D and 3.73 gears (closed knuckle D44 front 5 lug and Dana 60 full float rear) running 33/12.50/16.5 BFGs with a 70 mph cruising speed. It pulled loads like my current '82 C20 with 454/TH400 but that's restricted to 60 mph and only 10 mpg. (I bought the Chev after I rolled my J4000 on my driveway when I almost hit a black horse wandering loose at midnight. I swerved into the ditch and back out, but caught a driveway, spun and rolled on the switchback by Sunset Falls)
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'82 Eagle Wagon (Brown Betty) 4.2L/727/NP229 and soon 8.25 rear axle and non-vacuum 3.08 front to match. 235/75/15 tires. It's down to minor body work (someone creamed my driver's door but I have another in good shape) almost rust free and interior work (seats are worn and carpet torn). $2000 but about to go up due to more work being done.

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Offline AMCKen

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Re: 304 2V versus 258 2V?
« Reply #6 on: February 26, 2012, 02:26:18 AM »
One of the biggest/easiest wake ups for the 79 304 is a jet change in the carb. Earlier ones had #47 jets. In 79 they were 45s. I use 52s and it makes a noticeable difference. 79 304s were about 15more hp (13%) and 10ftlbs (5%)  than the 79 258 2bbl.
39Master85w.partscar,67Marlin343,68AMX343,70Machine,73Matador2drht401,
73-74-75-76GremlinXs,75PacerX,76Hornet2dsd,76-77Matadorcpes,
2-77AMXs304,78AMX304,78GremlinGT,78Concordsw,79Concordhb,79PacerDL304,
2-79AMXs304/401,2-80AMXs258/401,80SpiritDL304, 80Eagle4dsdn,3-81SX4s,
81SpiritGT,2-81Concord4dsd,82Eaglesw,2-85Eaglesw,2-80J20/360,85J10/258,2-88Eaglesw,
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Offline j2sax

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Re: 304 2V versus 258 2V?
« Reply #7 on: February 27, 2012, 09:54:20 AM »
Having had both in stock form, you can really feel the difference on the interstate, however, taking off not as much.  the POTENTIAL for waking up the respective engines is much easier/less expensive with the V8.  AND it sounds better very easily! 

The V8 is a little heavier, but swap on an aluminum intake and you are about equal.  Open the exhaust a little and play with the carb/install a 4 bbl and you are having fun.  You can find used intakes and appropriately sized 4 bbl's MUCH easier and more affordable  for the v8. 

That being said, I have had some great running 258's also with a Clifford Intake, header, performance cam and Holley 390 4 bbl.  Even sounded good.  If I had a 6 cyl car and just wanted a little pick me up in power I would work on the 6.  (4.0 head and cam works well too!) 

If I was looking for performance and hadn't bought a car yet and there were 2 choices of similar condition ,the V8 would be a good opening choice, imho. 

The whole V8 in an Eagle thing is a LOT of work though!

Offline 68AMXGOPAC

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Re: 304 2V versus 258 2V?
« Reply #8 on: February 27, 2012, 11:18:33 AM »
There is a stock ( meaning no internal engine work ) 304 in my AMX right now. It has a Holley street dominator aluminum intake and a edelbrock 4 barrell, ( and no I don't have that backwards ) ,lol.With headers and full exhaust.It has no problem smokeing them in first into second with the 4 speed T-10 and posi.They do wind up quicker I think than the I6.But like said , not much diff. in stock HP rateing between the 2. It's a 73 304 as far as I can tell.
The car stock was 390 wich is on the floor ( bummer) , next to the 401 on the stand now bieng built for it.
Click for Valatie, NY Forecast" border="0" height="100" width="150

1968 AMX GOPAC 390/4SPD.
1984 Eagle Wagon I6 258 auto
1983 Eagle Wagon I6 258 EFI convert ( Caroline)
1995 Cadillac Seville STS Norstar 32V 310 H.P. V8
1995 Cadillac Eldorado ETC Norstar 32V 310 H.P. V8
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Offline AMCKen

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Re: 304 2V versus 258 2V?
« Reply #9 on: February 27, 2012, 12:27:45 PM »
In 73 the 304 was rated at 150hp@4200 and 245ftlbs@2500. The only 1973 258 was a 1 barrell at 110hp@3500 and 195@2000. The first 258 2bbls were in 1977.
39Master85w.partscar,67Marlin343,68AMX343,70Machine,73Matador2drht401,
73-74-75-76GremlinXs,75PacerX,76Hornet2dsd,76-77Matadorcpes,
2-77AMXs304,78AMX304,78GremlinGT,78Concordsw,79Concordhb,79PacerDL304,
2-79AMXs304/401,2-80AMXs258/401,80SpiritDL304, 80Eagle4dsdn,3-81SX4s,
81SpiritGT,2-81Concord4dsd,82Eaglesw,2-85Eaglesw,2-80J20/360,85J10/258,2-88Eaglesw,
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Offline Blown7

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Re: 304 2V versus 258 2V?
« Reply #10 on: April 21, 2012, 08:05:04 AM »
Back in 1988 I installed a AMC 360 in a 1983 Eagle wagon.. it was way cool.

But you have to make a custom header for the left side of the vehicle to get the steering rod thru to the steering box.

And of course new custom engine/differential mounts.. I still have a pattern set.

Offline Sunny

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Re: 304 2V versus 258 2V?
« Reply #11 on: April 21, 2012, 09:40:29 AM »
No comments on power, but the 304 sounds a lot better.

Offline mudkicker715

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Re: 304 2V versus 258 2V?
« Reply #12 on: April 21, 2012, 10:41:50 AM »
Back in 1988 I installed a AMC 360 in a 1983 Eagle wagon.. it was way cool.

But you have to make a custom header for the left side of the vehicle to get the steering rod thru to the steering box.

And of course new custom engine/differential mounts.. I still have a pattern set.


I was able to use my stock 304 manifolds

Current amc's
82 concord waggy 258 DD
84 eagle sedan stroker DD
86 eagle wagon sas 304 v8 toy
87 eagle wagon stroker

Manitowoc WI

Offline 68AMXGOPAC

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Re: 304 2V versus 258 2V?
« Reply #13 on: April 21, 2012, 11:49:51 AM »
That's good to know Kicker, thnx.
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1968 AMX GOPAC 390/4SPD.
1984 Eagle Wagon I6 258 auto
1983 Eagle Wagon I6 258 EFI convert ( Caroline)
1995 Cadillac Seville STS Norstar 32V 310 H.P. V8
1995 Cadillac Eldorado ETC Norstar 32V 310 H.P. V8
Money Pit ll - 82 SX/4 Sport
1995 Triumph Speed Triple
1969 Honda CB350 - custom project

Offline standup650

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Re: 304 2V versus 258 2V?
« Reply #14 on: April 21, 2012, 09:05:18 PM »
if the output numbers were exactly the same: hp, torque, gears, tires, everything. the v8 would go a bit better and feel a bit better because it has more rotating mass. witch makes it harder to stop, thus feeling and being a bit better preformace wise.