V12 engine mods, cheap

jenko wrote: sectioned Jag v12 flat head

Back when I had my own vertical mill it was simple to bore out and straighten the intake port and then hand blend the two passes required per port. The advantage was time, it took less than 10 hours to do both heads and bring the valve size out to 2.00 inches. My flow bench numbers went with the car when I sold it, but it was a significant improvement. I focused on the intake because the exhaust port already flowed well. The exhaust port only required one nearly vertical pass with a Ball mill and then resize the seats to the exhaust valve I used.
I never did the port work alone so I can't tell you how much power it gained, rather I always did it in conjunction with a bigger bore, offset ground (stroked) crankshaft using narrowed Chevy aftermarket connecting rods, and Aries pistons with 13.0-1 compression

In reply to jenko: Like anyone who has lifted a Jaguar V12 crankshaft I understand the weight loss potential and the resulting benefits. However I noted Group 44's crankshafts all had full counterweights as they got ready to run LeMans. In addition they had bigger/heavier vibration dampeners.I had assumed it was for harmonic reasons since they are at peak RPM for so long going down the Mulsane straight at LeMans

The aftermarket Chevy Connecting rods I use are massively lighter than Jaguar's and since they are used by NASCAR teams who rev their engines to over 9500 RPM for well over 1100 miles (2 events) before they are allowed to replace them I felt it was an easy and cheap replacement, not to mention the stroke gain potential. With the Jaguar rod bearing at 2.300 and the Chevy Rod bearing down to as little as 1.94 it's an easy and cheap way to gain stroke.

How long do you keep your engine at peak rev's?

Second The Kent camshafts I've used are made from a billet and don't have any of the roughness the stock Jaguar cams do.

In reply to jenko: You are right, my racing knowledge was gained a long time ago and I've not kept up with currant thinking or trends.. Please don't think I want to be the final authority. I learned a very long time ago to appreciate others who have different approaches.

I especially noted that you placed a squish pad opposite the spark plug to reduce detonation. Have you gone to the heart shaped combustion chamber used by MG (and others) back in the early 1950's (of course in the piston rather than the head)? If so the irony isn't lost on me.. (Jaguar switched to the H.E. head in 1980 which basically copied GM's Fireball head of the 1940-50's)

It's exactly that sort of knowledge that I appreciate. In the past I used alcohol fuels to prevent detonation and never explored compression ratios above 13.0-1. Since many who use alcohol fuel are currently working around 15-16.0-1 I wonder how much power I lost compared to the real potential..

The use of alcohol fuels is why I bothered to enlarge the intake port and valve size, I'm not sure the gain would be worth the effort on the street where gas is the normal fuel. Due to the angle of the intake port over the valve there seems to be sufficient swirl but that would be an area to explore if I ever was to return to racing again.

Motage wrote: Dear frenchyd, how do I recognize an early head if it is on an assembeled engine?

Look at the transmission.. If it has a Cast Iron Borg warner transmission hooked to it, the heads will have flat heads.. From about 1977 to 1980 things get a little harder.. I've been looking at external markings and frankly I can't see anything that indicates H.E. from flathead, on the other hand I never find Waldo in where's Waldo.

Okay, correct me if I'm wrong. The Jag 12 bolts up to a GM slushbox, yes? Therefore the bellhousing pattern should be fairly well known and an acceptable clutch bellhousing or adapter should be available, right? Anyone know what that is?

stroker wrote: Okay, correct me if I'm wrong. The Jag 12 bolts up to a GM slushbox, yes? Therefore the bellhousing pattern should be fairly well known and an acceptable clutch bellhousing or adapter should be available, right? Anyone know what that is?

i want to say the jag th400 uses a jag-specific bellhousing bolt pattern that isnt the same as the GM pattern, i might be wrong though

edizzle89 wrote:

stroker wrote: Okay, correct me if I'm wrong. The Jag 12 bolts up to a GM slushbox, yes? Therefore the bellhousing pattern should be fairly well known and an acceptable clutch bellhousing or adapter should be available, right? Anyone know what that is?

i want to say the jag th400 uses a jag-specific bellhousing bolt pattern that isnt the same as the GM pattern, i might be wrong though

This is my foggy-memory too. Also I seem to remember it's a non-separatable bellhousing, so its not really that useful for MT swaps.

^This is 100% correct. Bellhousing from the TH350 Jaguar is quite different from the GM lines. Also trying to convert to a 4L60E or 4L80E is challenging.

There are a few threads using everything from a R154, Borg Warner T5, etc. with adapter plates and what have you over on the Jag boards. I've been a long time fan and had cash in hand for a XJS until it overheated (while idling) while we discussed maintenance, so I walked away. Haven't found one cheap enough or in good enough condition since to purchase.

If you really want one, there's a several HUNDRED page .pdf with all the info you need to know about owning an XJS. It's INCREDIBLY comprehensive and detailed. I'd highly suggest reading the entire thing before purchasing a XJS.

Here it is, quick search pulled it up. It's 731 pages long and includes anything and everything you'd ever need to know about owning the XJS.

http://www.jag-lovers.org/xj-s/book/XJS_help.pdf

Just get a full manual valve body for the th350 then?

Should be so much torque that a clutch pedal would really be needed.

In reply to stroker :

GM turbo 400 yes but not a chevy Buick or Cadillac housing. It's a Jaguar only housing. 

On the other hand the dowel location makes adapting manual gear boxes easy

Frenchy, you wouldn't happen to have some XJS interior laying around would ya? 

In reply to MugenReplica :

The last V12s all used a version of the 4L80E (except really heavy duty because of all the torque a V12 makes). 

Putting a 4/5/6 speed gearbox is simple if you can cut and drill aluminum plate. There are aftermarket aluminum and steel flywheels all that's left is drill out a crankshaft bushing to the size of 1st motion shaft you will be using. 

Frenchy, do you know of a link for the nickel list of the parts necessary?  Or a list off the top of your head?  Just for estimating/awareness purposes?

In reply to stroker : list? what for? 

Oh Ok I looked back a couple of years and found you asking about a manual transmission 

you'll need an aftermarket scattershield. Capable of using a center release hydraulic bearing. I use Tilton but there are cheaper ones 

flywheel 

pressure plate

clutch disk 

pilot shaft bearing 

transmission 

driveshaft 

everything I've done is for racing so I use triple disk clutches and the like. However I shop aggressively for used parts wherever I can find them and adapt or make a lot of the pieces myself 

In reply to frenchyd: 

How thick does the plate need to be?  Where's the best place to get the flywheels?

MARKUSA said:

In reply to frenchyd: 

How thick does the plate need to be?  Where's the best place to get the flywheels?

Depends on which transmission  to determine the thickness. If you want I can walk  you through the process once you’ve got things sorted out.  The process has to be followed even if you buy a kit.  Several/many engines have been ruined  from  having the  transmission shoved to hard into the engine. If you get the transmission too far away  the clutch won’t work properly.  

My numbers likely will be wildly different than yours. My last one was a triple disk on a custom made tiny diameter flywheel. Using a Tilton scatter shield. 

I also did one using a steel scattershield and a M22 4 speed 

As for flywheels there are several sources.  I’ve heard a whole lot of different prices quoted.  Plus some sources seem to have multiple prices for the same product.   You’ll have to check around for a street model. I’ve never bought one.  Incidentally  Jaguar made a steel flywheel for their own 4 speed  so there might be several around at various Jaguar shops/ junk yards 

In reply to MARKUSA :

Mark I don’t know where you live but a Jag message board I’m on has a 1975 Jaguar XJ12 for sale in Joliet ILLINOIS  ASKING $800 his name is Brad Curlett, but if not sold in a week it’s going to the scrap yard where he might get $150 if he had tittle. Which he doesn’t.  It’s almost too nice to part out but without tittle it’s parts.  The parts you’ll need including a nice set of seats and complete instruments.  

It will have the Flatheads and the 7.8-1 compression pistons  plus the front and rear suspension.  It likely will have a 3.07 positraction. A few might be 3.31.* Don’t worry you can get a 3.54 pumpkin and plop it in plenty easily. 

*  3.31 would  be usable with a tire less than 28 inches tall and a 5 -6  speed   

Rules differ but in the past I’ve accepted a hand written bill of sale.  Then I pay him with a check which I cash for him after he signs the back of it.   

I check with local police  explain that I want to buy a car for parts  the owner doesn’t have the tittle. to see if they’ve had any issue with the person. 

I know some people will go on line and check the person out see if he has a record.  I haven’t done that but you might want to.  Others avoid cars without tittles completely. 

In reply to frenchyd :

What's your formula for calculating compression on these engines?

In reply to frenchyd :

What's the best type of coolant to use?

In reply to frenchyd :

I'm about 7 hours away from him (Southern KY).  What message board is this on?  

MARKUSA said:

In reply to frenchyd :

What's your formula for calculating compression on these engines?

Depends on what I’m doing. Talking about choices?  I use factory numbers.  Planing on building a race motor?  Use estimated numbers Actual building of a race motor?   I start measuring.  With no combustion chamber you have to measure how far the valves actually intrude. Off the top of my head assuming stock valves with a really good multi-angle valve and seat grinds I think I remember 8 cc’s  but it’s been too many years.  

there are 3 well accepted head gaskets and each is slightly different.  I prefer to use cometic.  In my race motors.  Extreme compression ratio or boost situation I have used a gas filled o ring.  But the Jaguar gasket is fine for normally aspirated engines built for the stock compression.  

MARKUSA said:

In reply to frenchyd :

What's the best type of coolant to use?

 

For the street?  50% water, 50% antifreeze. Flush every two years

race track?  Water, with water wetter if allowed . Drained after the race.  

MARKUSA said:

In reply to frenchyd :

I'm about 7 hours away from him (Southern KY).  What message board is this on?  

I’m so poor with the internet. The simple way would be to copy the message board and set it up as a link.  I’m not able to do that. 

It’s a JaguarXJS owners board.  But there isn’t any more information, no phone numbers.  On the other had there are pictures. 

In reply to frenchyd  I can't find anything by searching google on it.  What is the website address - maybe I can search it?