|
Motor won't rev over 4,000 rpm. Valve springs?
#1343224
11/30/12 12:04 AM
11/30/12 12:04 AM
|
Joined: Feb 2007
Posts: 649
Davis, California, USA
MrBelvedere2
OP
mopar
|
OP
mopar
Joined: Feb 2007
Posts: 649
Davis, California, USA
|
Hey guys, I got my 383 engine running really nice, just seems to drop off at 4,000 rpm. The tach will not go over 4,000 rpm no matter what I try to do to it. Brand new holley carb custom built for the motor as well. My question is, it has a crane cam hi intensity hydraulic 226 duration. cam card says max lift at 109 ATDC, 119 BTDC. Loads are 95 lbs closed, 244 lbs open. I have been trying to figure out what it could be. In my research it seems to point to valve springs. I am not sure if they are matched for the cam when the motor was built. The receipt I have for the motor is just "HP Springs". I am wondering fit this cam needs more than just HP spec springs? I can't find the part number for it which is 644321. It is an old cam so they probably don't make it anymore. What do you guys think?
1965 Plymouth Belvedere II hardtop
|
|
|
Re: Motor won't rev over 4,000 rpm. Valve springs?
[Re: MrBelvedere2]
#1343226
11/30/12 12:26 AM
11/30/12 12:26 AM
|
Joined: Dec 2004
Posts: 1,548
DC, MD Suburbs
440PURSUIT
pro stock
|
pro stock
Joined: Dec 2004
Posts: 1,548
DC, MD Suburbs
|
You'd prob get the engine loaded up and stall if trying to rev it. When the springs float the fuel just floods all cylinders and car wont run until cleared out. Any evidence of a POP when revving?.
You may look for low voltage in ignition system or bad coil. Another likely culprit.
1969 Hemi Charger R/T,
1970 Charger 472 Hemi 6 Sp
1969 Charger Pro Tour Project
1971 Barracuda Convert
1970 440 6pack Superbird,
1968 Fury I Police Pursuit 440 Super Commando 2 door sedan (Black/Blue)
1967 Barracuda Convert
1968 Barracuda Coupe
1972 Charger w 383
1972 Sebring Plus 440-6 Clone
1969 Coronet Pro Street
2009 Challengeer SRT8 stick
1992-1986 Body 2500 4x4 440 stick
1982 Ramcharger 318 Sniper- getting enhanced.
1997 Ram B3500 Van 5.9
1991.5 W250 Cummins- Big Chief
|
|
|
Re: Motor won't rev over 4,000 rpm. Valve springs?
[Re: 67Satty]
#1343229
11/30/12 12:35 AM
11/30/12 12:35 AM
|
Joined: Jan 2003
Posts: 10,714
North Dakota
6PakBee
I Live Here
|
I Live Here
Joined: Jan 2003
Posts: 10,714
North Dakota
|
What does the engine sound like at 4,000 rpm? If you have weak valve springs it'll sound something like a rev limiter, a lot of missing and popping. If this is not happening and the engine is smooth at 4,000 rpm but won't go further, something else is awry.
"We live in a time when intelligent people are being silenced so that stupid people won't be offended".
|
|
|
Re: Motor won't rev over 4,000 rpm. Valve springs?
[Re: Dunnuck Racing]
#1343231
11/30/12 01:31 AM
11/30/12 01:31 AM
|
Joined: Jul 2003
Posts: 3,377
Rancho Cordova, CA
Exit1965
master
|
master
Joined: Jul 2003
Posts: 3,377
Rancho Cordova, CA
|
Another possibility is piston/valve interference. I once had a 383 that wouldn't rev past about 3500, and that was the cause. I found out about it once it took out a valve and ate a piston. I hadn't checked the P/V clearance and it bit me hard. So, has the piston to valve clearance been checked? 
|
|
|
Re: Motor won't rev over 4,000 rpm. Valve springs?
[Re: Kern Dog]
#1343233
11/30/12 02:02 AM
11/30/12 02:02 AM
|
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert
Circle Track
|
Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
|
As said how does it act at 4K? For a start I'd try to pin it down to inadequate fuel delivery or to ignition. Will it rev past 4K in your driveway? (fuel requirements then are minimal as it ain't under load).
live every 24 hour block of time like it's your last day on earth
|
|
|
Re: Motor won't rev over 4,000 rpm. Valve springs?
[Re: Kern Dog]
#1343235
11/30/12 02:57 AM
11/30/12 02:57 AM
|
Joined: Feb 2007
Posts: 649
Davis, California, USA
MrBelvedere2
OP
mopar
|
OP
mopar
Joined: Feb 2007
Posts: 649
Davis, California, USA
|
Hey guys thanks for the responses so far. I am running new Firecore wires, and brand new autolite 85 plugs gap set right. The exhaust is almost straight through with classic chambered mufflers. The distributor however is a stock points type that is a couple years old that did run fine on the old motor. I have a low deck distributor with a pertronix kit in it on the shelf, I might switch that out and see what happens. The motor sounds like it's revving fine and everything, but when your in the car and revving it, you look at the tach and as soon as it hits 4,000 it just doesn't seem to want to go over that at all. No sputtering,maybe some popping noises.
1965 Plymouth Belvedere II hardtop
|
|
|
Re: Motor won't rev over 4,000 rpm. Valve springs?
[Re: MrBelvedere2]
#1343236
11/30/12 04:06 AM
11/30/12 04:06 AM
|
Joined: Feb 2003
Posts: 4,796
Castlegar, BC, Canada
That AMC Guy
master
|
master
Joined: Feb 2003
Posts: 4,796
Castlegar, BC, Canada
|
If you're still running points, check the condensor.
Years ago, on my Gremlin I had the same issue only at 2,000 rpm, it would fuss and fart and break apart.
Asked on here and somebody said change the condensor. .75 cents later and the car ran perfectly again!
Bloody Mary, Full of Vodka, Blessed art thou among cocktails....
|
|
|
Re: Motor won't rev over 4,000 rpm. Valve springs?
[Re: 68KillerBee]
#1343238
11/30/12 11:19 AM
11/30/12 11:19 AM
|
Joined: Jan 2006
Posts: 587
IL . usa
cjs69mope
mopar
|
mopar
Joined: Jan 2006
Posts: 587
IL . usa
|
What kind of timing are you running ? a 383 bone stock in 66 charger with a good tune and 600 Holley DP carb my buddy had in high school was faster than any of the late 80's cars my other friends had at that time a rusty old charger wupin 305 camaro and mustangs on the street HA HA!
Retarded timing , broken vacuum advance , Clogged fuel Filter .
These things i would look at closely first.
Last edited by cjs69mope; 11/30/12 11:22 AM.
1969 Dodge Charger
1969 Dodge Superbee
|
|
|
Re: Motor won't rev over 4,000 rpm. Valve springs?
[Re: Firepowerflyer]
#1343240
11/30/12 12:41 PM
11/30/12 12:41 PM
|
Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
70Cuda383
Too Many Posts
|
Too Many Posts
Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
|
if this is a problem that just started out of nowhere, and it was previously running fine, then I'd look at valve springs.
however, I had a mishap once... mis-read the timing marks on the gears when I installed them. cam ended up about 30 degrees advanced. engine fired right up and ran great. but it would NOT rev over 3,000 rpm.
so don't be afraid to check cam timing either if you find that it's not in your ignition anywhere, and the valve springs are ok. although it's unlikely, I suppose it could be possible somehow if the chain is old and very slack, to have jumped a tooth or 2...but if it was that loose, I would also think that your timing would be eratic as the slop in the chain allowed the cam to lag behind, then get yanked forward, then lag behind...giving you a tick-tock back and forth on your spark timing.
**Photobucket sucks**
|
|
|
Re: Motor won't rev over 4,000 rpm. Valve springs?
[Re: MrBelvedere2]
#1343241
11/30/12 03:36 PM
11/30/12 03:36 PM
|
Joined: Mar 2008
Posts: 5,746
Ontario, Canada
Dodgem
master
|
master
Joined: Mar 2008
Posts: 5,746
Ontario, Canada
|
Adjustable Rockers or pushrods??
Last edited by Dodgem; 11/30/12 03:38 PM.
|
|
|
Re: Motor won't rev over 4,000 rpm. Valve springs?
[Re: 70Cuda383]
#1343242
11/30/12 04:24 PM
11/30/12 04:24 PM
|
Joined: Jan 2003
Posts: 27,468
So Cal
autoxcuda
Too Many Posts
|
Too Many Posts
Joined: Jan 2003
Posts: 27,468
So Cal
|
Quote:
if this is a problem that just started out of nowhere, and it was previously running fine, then I'd look at valve springs.
however, I had a mishap once... mis-read the timing marks on the gears when I installed them. cam ended up about 30 degrees advanced. engine fired right up and ran great. but it would NOT rev over 3,000 rpm.
so don't be afraid to check cam timing either if you find that it's not in your ignition anywhere, and the valve springs are ok. although it's unlikely, I suppose it could be possible somehow if the chain is old and very slack, to have jumped a tooth or 2...but if it was that loose, I would also think that your timing would be eratic as the slop in the chain allowed the cam to lag behind, then get yanked forward, then lag behind...giving you a tick-tock back and forth on your spark timing.
I saw that in a Mopar that someone took to shop about 6 monthes ago. Aligned the marks and all was good.
|
|
|
|
|
I currently use 150+ on the seats and 350 to 375 opened and shoot for the spings to be within .100 of coil bind at max lift 
I was looking into a whiplash cam, but just bought a 2010 challenger and the car fun is a little low. Snowball effect otherwise. 
