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360 Kinda Slow? |
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wantajav 
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Joined: Sep/04/2009 Location: PA Status: Offline Points: 1150 |
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 Topic: 360 Kinda Slow?Posted: May/31/2018 at 6:15pm |
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Other things to consider here:
1.check engine vacuum 2.are you getting a good spark (coil, bad ground - I ran a second ground on a Javelin once, etc) 3.bent push rod(s) 4.Carb not opening all the way 5.balancer slipped (wrong timing marks) 6.compression check
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WhatISit
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Joined: Aug/07/2017 Location: Phoenix, AZ Status: Offline Points: 0 |
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Posted: May/31/2018 at 8:53am |
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Well, it could have been a lot worse. I bought the engine rebuilt and mostly assembled for a pretty good price. If I did it myself I would have gone with a different cam for sure.
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amcenthusiast
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Joined: Jul/02/2012 Location: SW Atlanta GA Status: Offline Points: 1778 |
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Posted: May/31/2018 at 5:33am |
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By tradition, with stock type diameter tires, 3.54 to one rear gear will give the Javelin much better acceleration from a dead stop.
IMO, you've learned an expensive lesson; compared to all the money spent to hop up the engine, a gear ratio swap is one the best 'bang for the buck' mods a person can make to their car. ~especially by buying the expensive tall tires. *you can do the 'rope trick' to install new valve seals... |
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443 XRV8 Gremlin YouTube video: https://www.youtube.com/watch?reload=9&v=2DmFOKRuzUc
XRV8 Race Parts website: http://amcramblermarlin.1colony.com/ |
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WhatISit
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Posted: May/30/2018 at 12:34pm |
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I'm definitely thinking it's a timing/carb tuning issue at the moment. Gonna see if I can get it a little more sorted out this weekend. You guys are probably right that the intake/carb is a little restricting, but I'm just gonna have to live with my combo for now. I'll probably just get it running as best I can with what I have and start saving for a 401 build lol
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Red Devil
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Posted: May/30/2018 at 11:38am |
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There are several dyno tests on Thumpr cams that seem to show they do pretty well compared to traditional grinds. Expect the tight LSA helps. Where they typically suffer is low vacuum and off-idle, so power brakes won't work well.
With a 3000 stall, I'd be curious if the converter is stalling to where it claims? Should make up for any loss in bottom end and the small runner Performer intake should help low-end torque, but drop off quickly on top end. Tune it first, but expect intake, gears and a bigger carb ... or just go with less cam to suit the rest of the combo and keep it a nice cruiser ... or if otherwise happy with the Thumpr, just run it and have fun. |
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PHAT69AMX
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Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5919 |
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Posted: May/30/2018 at 12:05am |
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- I'm sorry, this in no way helps with the original question posted, I got distracted, but I'll leave it here...- I would really like it if someone made and ran a CAM LIKE THIS... I got one like this ~1990, Stock AMC Cam Re-Ground by Chet Herbert. It was a very good cam imho... The "magic", -IF ANY-, is in using stock lobe centers... Does look "different" when mapped out as a double 360 graph... ( maybe later ) Chet Herbert AMC V8 A4B 7.0k Max ?, late 80's... '69 AMC Stock Camshaft Reground, Straight Up, Self Degree Wheel Measured, not guaranteed... .512" Lift Intake 280* @ .005 227* @ .050 (? 58* ramps) ( assumed symetrical ) 112* ATDC = Intake CL .529" Lift Exhaust 295* @ .005 246* @ .050 (? 61* ramps) ( assumed symetrical ) 112* BTDC = Exhaust CL IN opens .050 @ 2* BTDC - .005 @ 31* BTDC IN closes .050 @ 45* ABDC - .005 @ 73* ABDC (DynCR) .050 @ 227* - .005 @ 284* EX opens .050 @ 53* BBDC - .005 @ 77* BBDC EX closes .050 @ 13* ATDC - .005 @ 39* ATDC .050 @ 246* - .005 @ 296* Overlap .050 @ 15* - .005 @ 70*
Edited by PHAT69AMX - May/31/2018 at 12:00pm |
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jpnjim
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Posted: May/29/2018 at 9:48pm |
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^Intake lobe is not terrible for what you're doing, neither is the intake lift (could be better, but for what is probably a Chevy lobe it could be worse), the big lazy exhaust lobe is where it gives up everything for sound. My (probably way too deep) thoughts of why this cam is mismatched with itself: overlap is normally helpful (and this cam has decent overlap), it lets the strong exhaust signal pull fresh intake charge into the cylinders under the right conditions & RPMs. With that big exhaust lobe (compared to the intake lobe), exhaust velocities are still lazy at the RPM's the much smaller intake lobe is really starting to work, and could use the benefical scavenging you would otherwise get from the overlap if you had good exhaust velocities. The cam likely does ok up high because when you get to the RPM that the 241 exhaust is finally flowing great, the 227 intake is having trouble keeping up. ^and the scavenging can finally help the small intake keep up. But in your case, the small intake manifold and carb probably limit you at that point. Big exhaust lobes work better with big intake lobes, and mid size intake lobes work better with mid size exhaust lobes. Going a little bigger on the exhaust can help, but might give up some torque, but the 14* more exhaust duration is just there because it sounds better. |
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71 P-code 4spd Javelin/AMX
some Jeeps and some Fords |
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WesternRed
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Posted: May/29/2018 at 8:27pm |
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For the sake of comparison:
Thumpr Intake Duration (gross): 279 Exhaust Duration (gross): 296 Intake Duration (.050”): 227 Exhaust Duration (.050”): 241 Intake Valve Lift*: .491" Exhaust Valve Lift*: .476" Lobe Separation: 107 RPM Range: 2000-5800 |
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one bad rambler
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Posted: May/29/2018 at 7:06pm |
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 68 AMX 390 4 Speed,68 American,64 American 2 Door Wagon Altered Wheelbase,78 Concord Build 360,727,8.8
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one bad rambler
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Posted: May/29/2018 at 6:53pm |
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i agree with the thumper cam choice..to me it`s a snake oil circle track cam.... a comp. 270 or 280 and a little more gear will help pull a little more down low
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68 AMX 390 4 Speed,68 American,64 American 2 Door Wagon Altered Wheelbase,78 Concord Build 360,727,8.8
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WesternRed wrote: