Lost top end speed - Page 3 - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep CJ Forum > Lost top end speed

Introducing MONSTALINER™ UV Permanent DIY Roll On Bed LineFS: Jeep Fog Light LED Bulbs! Several Brightness Options! Clayton Off Road JK Short Arm Suspension Kits

Reply
Unread 04-23-2013, 11:11 AM   #31
firemanjim7
Registered User
1983 CJ7 
 
Join Date: Dec 2010
Location: Giddings, Tx
Posts: 150
Quote:
Originally Posted by Matt1981CJ7

No. Total advance is purely mechanical, and is not based on load.

Initial timing is based on the rotation of the distributor, and centrifugal is based on RPMs. Engine load doesn't change either of those.

Matt
10-4 gotcha!

Sent from my iPhone using JeepForum

firemanjim7 is offline   Reply With Quote
Unread 04-23-2013, 12:33 PM   #32
I6CJ7
Registered User
1984 CJ7 
 
Join Date: Aug 2009
Location: Virginia
Posts: 873
I've had my CRT hei for a couple years now. And I have the same problem. The low end and midrange performance is great. And I have smooth idle. But the top end it's a dog.. I have 3.54 gears, sm465, weber 38, hedman headers, Dui live wires. And when I'm in fourth at cruise and punch it to accelerate... It just sort of gets faster after awhile.
I know it's not the weber, I have that thing tuned perfectly thanks to Swatson454! Hey Shawn it's been awhile!
So what can I do? My grasp of how distributors and timing isn't very strong. I think my 258 runs strong everywhere except top end, it's not real comfortable going over 65mph power wise at all. And it seems I could be getting better mileage, I get around 15-16mpg
But it does tow pretty good, twice a year I tow a trailer with an Atv, Dirtbike and full camping gear, that trailer must weigh 2000 lbs fully loaded.
Any suggestions on where to start?
I6CJ7 is offline   Reply With Quote
Unread 04-23-2013, 12:50 PM   #33
firemanjim7
Registered User
1983 CJ7 
 
Join Date: Dec 2010
Location: Giddings, Tx
Posts: 150
Quote:
Originally Posted by I6CJ7
I've had my CRT hei for a couple years now. And I have the same problem. The low end and midrange performance is great. And I have smooth idle. But the top end it's a dog.. I have 3.54 gears, sm465, weber 38, hedman headers, Dui live wires. And when I'm in fourth at cruise and punch it to accelerate... It just sort of gets faster after awhile.
I know it's not the weber, I have that thing tuned perfectly thanks to Swatson454! Hey Shawn it's been awhile!
So what can I do? My grasp of how distributors and timing isn't very strong. I think my 258 runs strong everywhere except top end, it's not real comfortable going over 65mph power wise at all. And it seems I could be getting better mileage, I get around 15-16mpg
But it does tow pretty good, twice a year I tow a trailer with an Atv, Dirtbike and full camping gear, that trailer must weigh 2000 lbs fully loaded.
Any suggestions on where to start?
I hear ya I6CJ7. I went from poor low end with idle issues to poor top end. I feel like a dog chasing his tail.

Sent from my iPhone using JeepForum
firemanjim7 is offline   Reply With Quote
Unread 04-23-2013, 12:52 PM   #34
Matt1981CJ7
Web Wheeler
 
Matt1981CJ7's Avatar
1981 CJ7 
 
Join Date: May 2011
Location: Elbert, CO
Posts: 10,123
Quote:
Originally Posted by I6CJ7 View Post
I've had my CRT hei for a couple years now. And I have the same problem. The low end and midrange performance is great. And I have smooth idle. But the top end it's a dog.. I have 3.54 gears, sm465, weber 38, hedman headers, Dui live wires. And when I'm in fourth at cruise and punch it to accelerate... It just sort of gets faster after awhile.
I know it's not the weber, I have that thing tuned perfectly thanks to Swatson454! Hey Shawn it's been awhile!
So what can I do? My grasp of how distributors and timing isn't very strong. I think my 258 runs strong everywhere except top end, it's not real comfortable going over 65mph power wise at all. And it seems I could be getting better mileage, I get around 15-16mpg
But it does tow pretty good, twice a year I tow a trailer with an Atv, Dirtbike and full camping gear, that trailer must weigh 2000 lbs fully loaded.
Any suggestions on where to start?
I think John's and my suggestion to Jim applies to you, as well.

Plot your advance curve and post it up. Then we'll go from there.

It sounds like the CRT's factory curve doesn't suit the 258 very well.

Matt
Matt1981CJ7 is offline   Reply With Quote
Unread 04-23-2013, 01:12 PM   #35
firemanjim7
Registered User
1983 CJ7 
 
Join Date: Dec 2010
Location: Giddings, Tx
Posts: 150
Well I left CRT a lengthy email with everthing i did and asked for their help. We'll see if they get back with me.

Sent from my iPhone using JeepForum
firemanjim7 is offline   Reply With Quote
Unread 04-23-2013, 01:19 PM   #36
swatson454
Mall-crawlin' Hot Rodder
 
swatson454's Avatar
1983 CJ7 
 
Join Date: May 2009
Location: Dripping Springs, TX (soon)
Posts: 4,868
D.U.I.s come with a 24* curve. If 86 is right and the CRT has a 20* curve, I wonder if that's what you're seeing? What rpm are you at when it peters out in 4th?

Like Matt said, you need to find out where you are and we can go from there.


Shawn

Edit: Jeff!
__________________
Live in a way that those who know you but don't know God will come to know God because they know you.
swatson454 is offline   Reply With Quote
Unread 04-23-2013, 01:20 PM   #37
firemanjim7
Registered User
1983 CJ7 
 
Join Date: Dec 2010
Location: Giddings, Tx
Posts: 150
Quote:
Originally Posted by swatson454
D.U.I.s come with a 24* curve. If 86 is right and the CRT has a 20* curve, I wonder if that's what you're seeing? What rpm are you at when it peters out in 4th?

Like Matt said, you need to find out where you are and we can go from there.

Shawn

Edit: Jeff!
I'm thinking it was around 2500rpm.

Sent from my iPhone using JeepForum
firemanjim7 is offline   Reply With Quote
Unread 04-23-2013, 01:37 PM   #38
firemanjim7
Registered User
1983 CJ7 
 
Join Date: Dec 2010
Location: Giddings, Tx
Posts: 150
Let me ask you guys a question. First let me tell you how my duraspark was set up. Manifold vacuum. Initial timing was around 16* without any ping (I think my vacuum advance wasn't working that well). So I was thinking if I advance my initial timing some more and retard my vacuum advance maybe I can get the mechanical advance spinning alittle better. Just a thought.

Sent from my iPhone using JeepForum
firemanjim7 is offline   Reply With Quote
Unread 04-23-2013, 01:41 PM   #39
Matt1981CJ7
Web Wheeler
 
Matt1981CJ7's Avatar
1981 CJ7 
 
Join Date: May 2011
Location: Elbert, CO
Posts: 10,123
We're all kinda pi$$ing in the wind, here, without more accurate information. Seat-of-the-pants tuning will only get you so far. A 3-5 mph difference in top-end speed doesn't give us a whole lot to work with.

A quality timing light, with the ability to read advance (or a timing tape on the balancer), along with a vacuum gauge are two tools every wanna-be engine tuner should have. A wide-band A/F monitor pretty much takes the guess work out of it completely, but it's not necessary to achieve an adequate tune.

I'm curious to see what CRT has to say.....

Matt
Matt1981CJ7 is offline   Reply With Quote
Unread 04-23-2013, 01:51 PM   #40
firemanjim7
Registered User
1983 CJ7 
 
Join Date: Dec 2010
Location: Giddings, Tx
Posts: 150
Quote:
Originally Posted by Matt1981CJ7
We're all kinda pi$$ing in the wind, here, without more accurate information. Seat-of-the-pants tuning will only get you so far. A 3-5 mph difference in top-end speed doesn't give us a whole lot to work with.

A quality timing light, with the ability to read advance (or a timing tape on the balancer), along with a vacuum gauge are two tools every wanna-be engine tuner should have. A wide-band A/F monitor pretty much takes the guess work out of it completely, but it's not necessary to achieve an adequate tune.

I'm curious to see what CRT has to say.....

Matt
They just emailed me back and asked me to take a couple of pics of my dizzy and the setup.

Sent from my iPhone using JeepForum
firemanjim7 is offline   Reply With Quote
Unread 04-23-2013, 05:36 PM   #41
firemanjim7
Registered User
1983 CJ7 
 
Join Date: Dec 2010
Location: Giddings, Tx
Posts: 150
Ok they told me to adjust on the vacuum advance. Just didn't say which way. So I turned it in clock wise a 2 turns and test drove. Helped alittle. So I tried some more(ended up being only one turn) and it seems better. I can hit 75 now. Now I think I'm out of carb. Can I rich'en this thing up on top end?

Sent from my iPhone using JeepForum
firemanjim7 is offline   Reply With Quote
Unread 04-23-2013, 05:49 PM   #42
Matt1981CJ7
Web Wheeler
 
Matt1981CJ7's Avatar
1981 CJ7 
 
Join Date: May 2011
Location: Elbert, CO
Posts: 10,123
Quote:
Originally Posted by firemanjim7 View Post
Ok they told me to adjust on the vacuum advance. Just didn't say which way. So I turned it in clock wise a 2 turns and test drove. Helped alittle. So I tried some more(ended up being only one turn) and it seems better. I can hit 75 now. Now I think I'm out of carb. Can I rich'en this thing up on top end?

Sent from my iPhone using JeepForum
I'm sorry to say this, again, but the vac advance adjustment should have ZERO affect on your WOT top-end speed. Zero.

The CRT guys have led you down a path to nowhere.

Matt
Matt1981CJ7 is offline   Reply With Quote
Unread 04-23-2013, 05:59 PM   #43
firemanjim7
Registered User
1983 CJ7 
 
Join Date: Dec 2010
Location: Giddings, Tx
Posts: 150
Quote:
Originally Posted by Matt1981CJ7

I'm sorry to say this, again, but the vac advance adjustment should have ZERO affect on your WOT top-end speed. Zero.

The CRT guys have led you down a path to nowhere.

Matt
I hear ya. I'm not through tinkering with it yet.

Sent from my iPhone using JeepForum
firemanjim7 is offline   Reply With Quote
Unread 04-23-2013, 07:55 PM   #44
firemanjim7
Registered User
1983 CJ7 
 
Join Date: Dec 2010
Location: Giddings, Tx
Posts: 150
Well Matt. After reading that what you sent me I'm thinking my centrifugal spring or springs might be a bit too strong.

Sent from my iPhone using JeepForum
firemanjim7 is offline   Reply With Quote
Unread 04-23-2013, 08:04 PM   #45
Matt1981CJ7
Web Wheeler
 
Matt1981CJ7's Avatar
1981 CJ7 
 
Join Date: May 2011
Location: Elbert, CO
Posts: 10,123
Quote:
Originally Posted by firemanjim7 View Post
Well Matt. After reading that what you sent me I'm thinking my centrifugal spring or springs might be a bit too strong.

Sent from my iPhone using JeepForum
I'm thinking they may be too light.

Plotting your advance curve will confirm.

Matt
Matt1981CJ7 is offline   Reply With Quote
Reply
Thread Tools






Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.