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AMC 360 Limited RPM? |
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Lyle
AMC Addicted Joined: Jul/17/2014 Location: None Status: Offline Points: 772 |
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There is more information required to answer you question.
What is your torque converter stall and flash points? Your transmission and final gear ratio? The whole combination has to be looked at to determine your shift rpm's and what you may or may not want to change.
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73Gremlin401
Supporter of TheAMCForum Joined: Mar/02/2013 Location: Stmbt Sprgs CO Status: Offline Points: 946 |
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FWIW, I'm thinking the 3" exhaust is what's killing the output. motor needs some back pressure, and a 3" setup, especially if it is dualled, is giving the motor nothing to scavenge with. the rest of what's been described in the engine build up makes sense, and should make a very decent runner.
Edited by 73Gremlin401 - Jan/22/2018 at 10:10am |
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73 Gremlin 401/5-spd.
77 Matador Wagon 360/727. 81 Jeep J10 LWB 360/4-spd 83 Concord DL 4-dr 258/auto |
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dbomb
AMC Addicted Joined: Jul/22/2012 Location: new jersey Status: Offline Points: 705 |
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If you're running too much timing advance it won't want to rev. It will fight itself on top before it breaks the pistons or lifts a head If you've got loud exhaust you might not hear it or know it then boom
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rebuiling 73 amx need parts
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ruphianh
AMC Apprentice Joined: Jan/21/2018 Location: CA Status: Offline Points: 76 |
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This describes what I'm feeling, about 230-260HP and 4500 is about where its topping off. T. COMP CAMS makes a cam called XE256H that might have been a better choice when I had the engine built. This is in a CJ5 Jeep, so the power down low, torque, idle is great with the current cam when off roading, I just wish it could turn a bit more power everywhere, especially up top.
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Greyhounds_AMX
AMC Addicted Joined: Nov/14/2009 Location: Kansas City Status: Offline Points: 1268 |
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I have the Edelbrock cam in my 390 AMX, and it will rev to 5500 rpm pretty decently. On an inertia dyno it spins up pretty quickly:
That's with a Holley 600, cast iron intake, free flows, and 2-1/4" exhaust. I'd suspect that your TB is sized for off road work and not higher rpm use and probably a little small then.
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1968 AMX 390 w/T5
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ruphianh
AMC Apprentice Joined: Jan/21/2018 Location: CA Status: Offline Points: 76 |
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Do have the performer plus or performer RPM cam? Also, the TBI is 500CFM I believe and the same TBI used in the late 80s early 90s Chevy 350s. I had a 600CFM Edelbrock before the TBI, and the TBI runs better up top too hands down.
Edited by ruphianh - Jan/22/2018 at 1:26pm |
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Greyhounds_AMX
AMC Addicted Joined: Nov/14/2009 Location: Kansas City Status: Offline Points: 1268 |
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Ok, it looks like the Howell EFI for Jeep engines use a GM 305/350 TBI unit. Per the Harris Performance website:
"The stock 305 and 350 TBI unit has 2 (1 11/16″) bores which flow 450 cfm of air. Up to 230hp engines that air flow is fine. "
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1968 AMX 390 w/T5
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ruphianh
AMC Apprentice Joined: Jan/21/2018 Location: CA Status: Offline Points: 76 |
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Interesting. They have a holly 670 TBI upgrade, maybe i should look into that?
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Greyhounds_AMX
AMC Addicted Joined: Nov/14/2009 Location: Kansas City Status: Offline Points: 1268 |
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That might be a worthwhile upgrade for you. If you still have the Edelbrock carb I suppose you could pop that back on there and see if there's any improvement, but some of those also have alarmingly low flow capacities. You can check via the model number of course.
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1968 AMX 390 w/T5
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WesternRed
AMC Addicted Joined: Aug/03/2010 Location: Australia Status: Offline Points: 5798 |
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Maybe try an open spacer under the TBI if you don't already have one, might give you a bit more up top. XE256H is still a pretty small cam in my books if you want something to rev, probably the ticket for 4 wheeling and towing though.
Might want to look at something like the Holley Sniper if you are upgrading the injection side of things but a fair few dollars there. |
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