XJ6 & XJ12 Series I, II & III 1968-1992

XJ6C Mechanical restoration and upgrade to 700R4

 
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Old 11-18-2018, 07:35 AM
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Default XJ6C Mechanical restoration and upgrade to 700R4

This spring, the XJ let me down for the first time in my ownership... On the way to cars and coffee, the crappy BW transmission started slipping and 3 miles later had only reverse. I never liked that transmission anyway, gearing was not good for anything over 50mph either. I'd been looking at 5 speed conversion kits for a while, even bought a Manual console, shift boot and knob on Ebay because I was sure I would go manual. In the end I decided that I liked having the auto in this car, shifting gears just didn't seem to fit the character. Also the cost of the manual conversions are quite a bit more, and I had to factor in the cost of an engine rebuild due to the prodigious leaking of oil and alarming amount of blow-by. I decided to go with John's Cars 700R4 quarterbreed kit. I sourced a freshly rebuilt late injection cylinder head with tappet hold downs already installed for $300, and found a set of very lightly used .030 over 9 to 1 pistons to use for the bottom end.
 
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Old 11-18-2018, 07:40 AM
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Here is the engine about to come out.

 
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Old 11-18-2018, 07:47 AM
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New engine back from the builder. The 3 week timeframe he gave me sounded too good to be true. Turned out it was. It took THE ENTIRE SUMMER and that was with me calling to bug him constantly. Dropped the engine off on Memorial day, picked it up on Labor Day. Apparently it had actually been rebuilt before (car shows around 110K miles on it and P.O. gave me a reciept for a $3500 engine rebuild from 10 years ago but given the amount of leaking and low compression I didn't believe it.) Builder said there were no thrust washers in the motor at all -- not even chunks. No metal, just not there. Crank had been wiping against the block webbing and managed to chew itself up pretty bad so it needed significant welding.



 
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Old 11-18-2018, 07:50 AM
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Here is the engine mounted to the locally sourced 700R4 with the John's cars kit block adapter.

Huge motor and very heavy. I think I read that the engine and trans are close to 900lbs. But man it is beautiful.
 
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Old 11-18-2018, 07:53 AM
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Nice Jag, fun project

Looking forward to following along.

Cheers
DD
 
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Old 11-18-2018, 07:55 AM
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While the engine was out, I took the opportunity to clean, simplify and paint the engine compartment.



I used a single stage urethane after doing some sanding and priming with red oxide primer. There was significant de-greasing needed, the car must've never had the engine bay cleaned. Muck was thick everywhere.
 
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Old 11-18-2018, 07:57 AM
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Here's the engine going in.




 
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Old 11-18-2018, 08:04 AM
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Using triple SU's from a 420G, not sure if there will be much more performance, but they look awesome.


They definitely are not a simple bolt-on affair, and thanks to RustfreeMike for the details on the mods to make them fit the car. Still have to get the dashpots machined down by Joe Curto, but I want to hear it run before I send them off. Don't need to hood on just yet. Looking to fire it up for the first time this week after I re-wire the distributor.
 
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Old 11-18-2018, 01:55 PM
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Awsome work!

The 700R4 gearing with a 3:31 diff is ideal for the torque curve of the XK. You're in for a GREAT driving experience.

I spy an early 928. I'm also a XJ coupe and 928 owner. Ive got a 1986,5 5 speed. LOL



.
 
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Old 11-18-2018, 03:13 PM
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Originally Posted by icsamerica View Post
Awsome work!

The 700R4 gearing with a 3:31 diff is ideal for the torque curve of the XK. You're in for a GREAT driving experience.

I spy an early 928. I'm also a XJ coupe and 928 owner. Ive got a 1986,5 5 speed. LOL



.
Small world! My 928 is an early 78 5 speed with black/white pasha and sunroof delete. It was in a barn with busted fuel pumps for 25 years. Got it roadworthy last year... wasn't easy.
 
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Old 11-18-2018, 08:00 PM
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There is a special place in my heart for 1st year cars, The 1st 928 with it's low weight, clean styling and no frills design is focused representation of the designers original intent, I love that, same with the 1969 Series 1 XJ, the 1976 XJS and 1988 BMW 735i. As time passes. the market place speaks and dilutes the designers original intent.

I had a 1978 Euro import 5 speed... Long ago. All the instruments were in German. I though it was the coolest thing. I Almost have the same story with my current 928. It's sat for years, I had it towed home. It had a bad fuel pump, 1 bad plug and 1 bad injector, a bad fan clutch, After all that, it's great.
 

Last edited by icsamerica; 11-18-2018 at 08:44 PM.
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Old 11-19-2018, 10:06 PM
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Thumbs up Clean Machine

SableXJ6C,

As a fellow XJC owner, I'm amazed and impressed how clean your engine bay was BEFORE you cleaned it! If I could stand up & salute you while keyboarding, I would!

Much of what I've seen on Jaguar Forum inspires me. Some of what I see makes me hang my head in shame!

Aren't these XJC's beautiful cars?
 
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Old 11-20-2018, 06:22 AM
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Coventrywood -- those pics of the engine bay were taken after much de-greasing and scraping of muck. Guess I didn't take a true BEFORE shot.

Update on running situation: Have spark now (re-wired pertronix distributor), have fuel (pump jumper wire was unplugged). Still won't start. Been cranking the fresh engine way too much. I suspected that maybe the distributor was 180 degrees off so I flipped it, no change. It has popped a backfire or two and tried to start a couple of times, but no luck yet. Hate to keep cranking the motor without lots of oil pressure. Gonna do some more investigation today.
 
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Old 11-20-2018, 09:31 AM
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Originally Posted by SableXJ6C View Post
Still won't start. Been cranking the fresh engine way too much. I suspected that maybe the distributor was 180 degrees off so I flipped it, no change. It has popped a backfire or two and tried to start a couple of times, but no luck yet. Hate to keep cranking the motor without lots of oil pressure. Gonna do some more investigation today.
​​​​SableXJ6C If you have the ignition working and fuel in the carbs and the starting carb is functional it should start quick - mine started in 1 or 2 cranks after total engine rebuild. I think you mentioned you had someone rebuild the motor? If you find nothing obvious pull the cam covers before cranking again and be sure the cams are in the right place with #6 at TDC. I hope your rebuilder knew how to set up a Jag motor!
 

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Old 11-20-2018, 10:52 AM
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I guess if you can get a POP or backfire, then you have your plugs wired wrong, double check that. you've got fuel and spark, just not timing. Had the same problem on my first start, I was one off on the dizzy.

good luck geneo
 
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Old 11-21-2018, 06:21 AM
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Good news-- it runs! Bad news is it only runs for a few seconds on starting fluid and my freshly rebuilt 700r4 leaks bad at the pan gasket. I'm also not showing any oil pressure on the gauge. Needle doesn't move at all. Wire is on the sender. I know the builder bench tested the pressure on the short block before he finished the engine so I suspect a broken wire or bad sender.

After sleeping on it, I verified TDC on cylinder number 1 with compression and found the rotor pointed at number 1. When I swapped leads on the cap yesterday, I got a few misplaced -- that's why it backfired a couple of times. I had to remove the dizzy clamp bolt at the block so I had more rotation on the distributor to find the timing sweet spot. Will have to loosen the clamp now and re-orient so I can put the bolt back in.

I'm removing the carbs to go through them once again to make sure the jets are centered and there is no crud in them. My starting carb is spitting fuel everywhere and the solenoid will not tighten down with the screw on top... something is amiss there. I may buy a rebuilt one but they are expensive. If all else fails, I will send the whole set to Joe Curto for a proper rebuild and setup but may have to win the lottery first.
 
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Old 11-21-2018, 07:50 AM
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Consider a new pan. For many reasons including servicing, consider an aftermarket pan with fresh unbent rails and a drain fitting. There are many for the 700r4...stamped and billet. I'd get the billet, check it for flatness and put it up with a felpro seal.

You're deep in project hell, been there, keep at it, one step at a time.
 
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Old 11-21-2018, 08:38 PM
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Originally Posted by icsamerica View Post
Consider a new pan. For many reasons including servicing, consider an aftermarket pan with fresh unbent rails and a drain fitting. There are many for the 700r4...stamped and billet. I'd get the billet, check it for flatness and put it up with a felpro seal.

You're deep in project hell, been there, keep at it, one step at a time.
Got the new pan from Summit today with Felpro gasket, and yes it has a drain plug! Nice feature to have. Not looking forward to spilling 5 quarts of ATF outta there when I remove it (didn't finish filling).
 
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Old 11-22-2018, 01:27 AM
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Good that it runs - at least you have ignition. You may already know this but Jag numbers the cylinders opposite from most companies. Number 6 is the front cylinder.

If you use a 1-5/16" socket to turn the engine so that the timing pointer is at 8-10 degrees BTDC and then use the lightbulb method to ensure that #6 is just in firing position you're in the Jag sweet spot for timing without guesswork... Although if you have a pertronix or pertronix conversion you'll have to eyeball it - should be able to get it close though. There is a method using a lightbulb with pertronix but it's hard to see the pulse.

If you remove the carb suction chambers, pistons and springs you can use the tail end of a caliper to adjust each jet to .090" below the bridge. Then turn the slow idle screws all the way in and back them out 2-1/2 turns. This'll start the car.... probably a little rich but that's easy to adjust when you get it going.

The starting carb is the simplest device - you can save yourself alot of money by just checking that it's clean below the jet and the needle isn't bent. Also really important that the solenoid operates and that the disc valve seats well. There's not much else to go wrong with it. They will spit back if the car backfires or dies while it's open but that's normal - that's one of the reasons they have that little rain hat. BTW you should hear the starting carb hiss when it's operating and the car is running and it's energized. Alot of people call them 'hissers' because of the sound.

If you set it up this way and there's nothing wrong with engine, ignition or carbs the car will start and run.
 

Last edited by rustfreemike; 11-22-2018 at 08:30 AM.
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Old 11-27-2018, 11:44 AM
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Update: Got the car running pretty nicely this weekend, and it started quite easily with the newly-hooked-up starting carb. I chased minor leaks for a while and started to add more trans fluid while the car idled. Temp came up and starting carb clicked off just like it should, idle dropped nicely. Running 30W break-in oil and the oil pressure was not quite as strong as I expected with a newly built motor -- 40psi cold at idle dropped to around 20 when warm. Do you guys use thicker oil? Temp sender still not working, must have the wrong wire on it. I suspect I have it and my oil light swapped because the oil light stays on despite decent oil pressure.

Had a major scare when I pulled the car out of the garage for the first time... car started running really rough and quit. I investigated and continued to try to start it but it wouldn't stay running. Looked everywhere for issues and discovered that the NEEDLE IN THE FRONT CARB WAS GONE!!!!! NOWHERE!!! I immediately assumed it was sucked into the motor and destroyed valve seats etc. After about an hour of inspecting the cylinders and ports with my trusty tiny color camera on a flex line, I found no evidence of it. I was about to remove the front exhaust manifold to see if it was stuck in the exhaust port when I wondered if the needle could completely fit in the bottom of the carb. I pulled the banjo off the bottom of the front carb and the needle fell out. Disaster averted. Amen.
 

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