TheAMCForum.com Homepage
Forum Home Forum Home > Competition > Drag Racing
  New Posts New Posts RSS Feed - 360 Kinda Slow?
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Click for TheAMCForum Rules / Click for PDF version of Forum Rules
Your donations help keep this valuable resource free and growing. Thank you.

360 Kinda Slow?

 Post Reply Post Reply Page  <123>
Author
Message
PHAT69AMX View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jul/07/2007
Location: West Virginia
Status: Online
Points: 3380
Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: May/29/2018 at 1:15pm
Be sure valves properly adjusted.
Confirm and nail down the Ignition, Timing, and Advance Curve.
Borrow a known good working 750 Holley Double Pumper.
Bolt it on, set it up buy someone who knows how.
Car all warmed up and run-in a bit with the Holley....
Fuel delivery and regulated fuel pressure nailed down.
Creep up... stop... light foot on brake pedal ( fronts only )...
a tiny little bit of step-in on the carb, then hard to the floor...
using the really light brake pedal with the left foot...
and it'll smoke those tires and walk sideways....
When it's all workin' right how the driver uses his right foot
on the accelerator is what determines the best 0-60 times
because it's his right foot controlling the tire spin throughout the 0-60 run...
Borrow a known good running working Holley 750-800 Double Pumper and TEST...
Or....  the drag launch type test.
creep up... stop... hard on the brakes...
squeeze into that gas pedal and bind that thing up into a tight knot,
that converter, like a rubber band wound up in a model airplane...
wind that converter up hard, knot that car up on those brakes...
then let off the brakes and floor the gas... 60 Feet in 1.8x seconds maybe...
-IF- it bites...

All nothing more than some crazy frustrated car-less internet forum dude's opinion(s)...


Edited by PHAT69AMX - May/29/2018 at 1:19pm
Back to Top
WhatISit View Drop Down
AMC Apprentice
AMC Apprentice
Avatar

Joined: Aug/07/2017
Location: Phoenix, AZ
Status: Offline
Points: 115
Post Options Post Options   Thanks (0) Thanks(0)   Quote WhatISit Quote  Post ReplyReply Direct Link To This Post Posted: May/29/2018 at 1:44pm
Well, that brings up an entirely different issue, now that you mention it. I believe I have a bad valve seal on the passenger side (smokes a little at startup and slows down or stops altogether after it's warmed up). Could a bad valve seal affect performance that acutely? 
'74 Javelin AMX-- Mildly built 360 V8/998 auto
Back to Top
PHAT69AMX View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jul/07/2007
Location: West Virginia
Status: Online
Points: 3380
Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: May/29/2018 at 2:40pm
A bad valve seal alone, no, but "incorrect valvetrain" yes, performance acutely affected.
What kinda valve seals?  Fresh build, why'd it go bad?.... 
There's a whole buncha stuff to an overall correct properly working valvetrain...
Especially if the motor has been "re-built"... lotta "error opportunities"...
Back to Top
one bad rambler View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jan/09/2008
Location: On The Island
Status: Offline
Points: 1598
Post Options Post Options   Thanks (0) Thanks(0)   Quote one bad rambler Quote  Post ReplyReply Direct Link To This Post Posted: May/29/2018 at 7:53pm
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
68 AMX 390 4 Speed,68 American,64 American 2 Door Wagon Altered Wheelbase,78 Concord Build 360,727,8.8
Back to Top
one bad rambler View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jan/09/2008
Location: On The Island
Status: Offline
Points: 1598
Post Options Post Options   Thanks (0) Thanks(0)   Quote one bad rambler Quote  Post ReplyReply Direct Link To This Post Posted: May/29/2018 at 8:06pm
Part Number:30058
Grind Number:LSP-58H
Intake Duration (gross):284
Exhaust Duration (gross):294
Intake Duration (.050”):224
Exhaust Duration (.050”):230
Intake Valve Lift*:.510"
Exhaust Valve Lift*:.510"
Lobe Separation:110
Intake Valve Lash:.000"
Exhaust Valve Lash: .000"
RPM Range
2500-6500
I`m running the same compression in my sons 360...with a 750 dp ...Performer rpm air gap...3,000 stall..3.73 gears..and this Schneider cam....The car was doing a consistent 19.1 1/4 mile before the swap...We can only get better lol
68 AMX 390 4 Speed,68 American,64 American 2 Door Wagon Altered Wheelbase,78 Concord Build 360,727,8.8
Back to Top
WesternRed View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Aug/03/2010
Location: Australia
Status: Offline
Points: 3380
Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: May/29/2018 at 9:27pm
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
Back to Top
jpnjim View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Nov/25/2007
Location: New England
Status: Offline
Points: 1761
Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: May/29/2018 at 10:48pm
Originally posted by WesternRed WesternRed wrote:

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

^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.



71 Javelin AMX P-code Go pac 360/4spd/3.91's
was Green/green now T/A red w/blk leather

88,89&98 Jeeps
Back to Top
PHAT69AMX View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jul/07/2007
Location: West Virginia
Status: Online
Points: 3380
Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: May/30/2018 at 1:05am
- 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 1:00pm
Back to Top
Red Devil View Drop Down
AMC Addicted
AMC Addicted


Joined: Jul/10/2007
Location: Canada
Status: Offline
Points: 1475
Post Options Post Options   Thanks (0) Thanks(0)   Quote Red Devil Quote  Post ReplyReply Direct Link To This Post Posted: May/30/2018 at 12:38pm
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.
Back to Top
WhatISit View Drop Down
AMC Apprentice
AMC Apprentice
Avatar

Joined: Aug/07/2017
Location: Phoenix, AZ
Status: Offline
Points: 115
Post Options Post Options   Thanks (0) Thanks(0)   Quote WhatISit Quote  Post ReplyReply Direct Link To This Post Posted: May/30/2018 at 1:34pm
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
'74 Javelin AMX-- Mildly built 360 V8/998 auto
Back to Top
 Post Reply Post Reply Page  <123>
  Share Topic   

Forum Jump Forum Permissions View Drop Down



This page was generated in 0.063 seconds.
All content of this site Copyright © 2012 TheAMCForum unless otherwise noted, all rights reserved.
PROBLEMS LOGGING IN or REGISTERING:
If you have problems logging in or registering, then please contact a Moderator or