Need an "off the line" performance improvement
#41
05-15-2018, 12:05 PM
Veteran Member
Anyone here used one of Johns Cars Quarterbreed kits? Seems made for just this.
http://www.johnscars.com/qb/v12qb.html
http://www.johnscars.com/qb/v12qb.html
#42
05-15-2018, 12:10 PM
Veteran Member
I followed Grant's timing process. Given that it's 86 F in the shade here, the sun is out, and the engine is at operating temperature, getting my face right over the distributor was not a challenge I was up to.
I was able to loosen the nut, and then I turned the adjustment screw slowly clockwise (not sure if this turns the dizzy cw or ccw, will check when things cool off). Anyway, just listening to it at idle it was happier the more I turned it clockwise.
I was able to loosen the nut, and then I turned the adjustment screw slowly clockwise (not sure if this turns the dizzy cw or ccw, will check when things cool off). Anyway, just listening to it at idle it was happier the more I turned it clockwise.
I floored it from a stop... there was a noticeable increase in "liveliness" 
. It still didn't chirp the tires, but it felt like it was trying. Didn't hear any pinging.
So I continued this process until the adjustment screw wouldn't turn clockwise any longer. Stomped on the gas over and over, and no pinging. I did check to see that the locking bolt hadn't tightened, but still couldn't turn any more clockwise.
I serviced the mechanical advance per Palm's recommendation, and replaced the vacuum advance about 5 years ago.
I'm a little concerned why I would be up against a "stop" on the dizzy adjustment. I would think (but am no expert) that by continuing the turn the adjustment I would have peaked at some point, then noticed less engine happiness
...
Thanks!
John
. It still didn't chirp the tires, but it felt like it was trying. Didn't hear any pinging.So I continued this process until the adjustment screw wouldn't turn clockwise any longer. Stomped on the gas over and over, and no pinging. I did check to see that the locking bolt hadn't tightened, but still couldn't turn any more clockwise.
I serviced the mechanical advance per Palm's recommendation, and replaced the vacuum advance about 5 years ago.
I'm a little concerned why I would be up against a "stop" on the dizzy adjustment. I would think (but am no expert) that by continuing the turn the adjustment I would have peaked at some point, then noticed less engine happiness
...
Thanks!
John
Last edited by JigJag; 05-15-2018 at 12:20 PM.
#43
05-15-2018, 01:24 PM
Veteran Member
Join Date: Jul 2010
Location: Austin tx and Daytona FL.
Posts: 7,362
Received 1,231 Likes
on
939 Posts
Vancouver - I replaced the O2 sensors when I first got the car, about 4 years ago. I drive it a lot, but most of that driving is local, so I've not put 5,000 miles on it. I think the sensors are supposed to last much longer than that...but it seems easy enough to test them, so I will.
ronbros - did you buy the Dana in one piece (i.e., housing and all, and it just needed to be bolted on) or did you do (or have) the gears only swapped? I've been looking at justdifferentials.com and the nitro catalog, and removing and installing gears seems like quite a process.
Thanks!
John
ronbros - did you buy the Dana in one piece (i.e., housing and all, and it just needed to be bolted on) or did you do (or have) the gears only swapped? I've been looking at justdifferentials.com and the nitro catalog, and removing and installing gears seems like quite a process.
Thanks!
John
my 1978 XJS came standard factory with 3.07 ratio powerlok(not the 2.88) , so my diff is stock original, when i had it apart i took the ring and pinion gears to a local diff. shop, guy looked at them and went in back supply room ,came back with a set of gears , made some measurements, and said there you go ,3.73 ratio fits a JEEP truck,i fit them into the casing with new bearings &seals. i use a standard HD GM yoke on pinion input shaft,Aluminum driveshaft, less rotating weight!
#44
05-15-2018, 02:08 PM
#45
05-15-2018, 02:36 PM
Veteran Member
ronbros - did you buy the Dana in one piece (i.e., housing and all, and it just needed to be bolted on) or did you do (or have) the gears only swapped? I've been looking at justdifferentials.com and the nitro catalog, and removing and installing gears seems like quite a process.
It's easier/cheaper to buy a 3.54 diff out of a later XJS than to regear a 2.88. The reason is the carriers are different between a 2.88 and 3.07 and up due to the crown gear thickness, so you need the carrier as well as the gears from a 3.54.
Rebuilding a diff isn't that bad, it requires patience, willingness to read the manual and follow the directions and specifications exactly plus some special tools. In terms of clearances, this is a place where "good enough" really isn't good enough. It needs to be within spec.
If you're not comfortable measuring accurately to thousandths of inch, don't tackle this job. There was one measurement that took me about 6 hours to make until I was confident that I had it correct, and I could repeatably get the same number.
The following users liked this post:
ronbros (05-15-2018)
#46
05-15-2018, 05:42 PM
Veteran Member
There are 3 things you can do to fit 3.54 on a 2.88 hemisphere.
1 install the crown wheel on a spacer. This has been done here on 2 taga XJS race cars and works.
2 Jeep have thick crown wheels available for just this reason.
3 source an XJ40 LSD and swap the internals, this is what I did.
1 install the crown wheel on a spacer. This has been done here on 2 taga XJS race cars and works.
2 Jeep have thick crown wheels available for just this reason.
3 source an XJ40 LSD and swap the internals, this is what I did.
#47
05-16-2018, 04:51 AM
I followed Grant's timing process. Given that it's 86 F in the shade here, the sun is out, and the engine is at operating temperature, getting my face right over the distributor was not a challenge I was up to.
I was able to loosen the nut, and then I turned the adjustment screw slowly clockwise (not sure if this turns the dizzy cw or ccw, will check when things cool off). Anyway, just listening to it at idle it was happier the more I turned it clockwise.
I floored it from a stop... there was a noticeable increase in "liveliness"
. It still didn't chirp the tires, but it felt like it was trying. Didn't hear any pinging.So I continued this process until the adjustment screw wouldn't turn clockwise any longer. Stomped on the gas over and over, and no pinging. I did check to see that the locking bolt hadn't tightened, but still couldn't turn any more clockwise.
I serviced the mechanical advance per Palm's recommendation, and replaced the vacuum advance about 5 years ago.
I'm a little concerned why I would be up against a "stop" on the dizzy adjustment. I would think (but am no expert) that by continuing the turn the adjustment I would have peaked at some point, then noticed less engine happiness.
If I go with a new torque converter, I see a jump from 2400 RPM to 3000 RPM. Is the 3000 too much?
Thanks!
John
Hitting a stop with that adjuister is normal.
The screw is rotating a peg in a groove adjuster.
The distributor rotates Anti Clockwise looking down at the top. Rotating that adjuster so the casing moves Clockwise will advance the timing.
You have simply run out of adjustment, and now the base section needs to be "released" to manually move it Clockwise a few degrees, so that the adjuster CAN be turned the other way to match that base movement, then you can run the engine and turn that peg again to get a few more degrees out of it.
Once done, you may need to "trim" the ECU fuel POT a small amount.
These might help some more.
Adjusting the ECU fuel pot.pdf
Refitting the V12 distributor.pdf
The following 2 users liked this post by Grant Francis:
Greg in France (05-17-2018),
J_C_R (05-18-2018)
#48
05-18-2018, 09:13 AM
The following users liked this post:
Grant Francis (05-20-2018)
#50
05-19-2018, 06:05 PM
Veteran Member
#51
05-20-2018, 01:57 AM
Veteran Member
Hard to be 100% accurate without timing wheels etc, but definitely under 7 secs using the speedo, the last time we tried it, stick in position 1.
#52
05-20-2018, 04:01 PM
Veteran Member
The following users liked this post:
Daim (05-21-2018)
Thread
Thread Starter
Forum
Replies
Last Post
Newjag
XK8 / XKR ( X100 )
9
02-04-2019 12:10 AM
princemarko
XJ XJ8 / XJR ( X308 )
8
04-07-2014 08:08 AM
avos
S-Type / S type R Supercharged V8 ( X200 )
7
08-17-2012 04:54 PM
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)