Chevy VS Jaguar V12

Thanks for the quick reply and all the info.  Yes, I have thought about the roots blower also but didn't know how hard the manifold would be to come by.  I'm not looking for every ounce of power so my question is could I use say a 1992-1994 6.0 and cut a dish in the crowns to lower the compression to like 8.5:1 for either a turbo or blower?

Should I look for an engine under 100K?, 80K, 60K?

I want air but will get rid of the big compressor.  Probably use vintage air.

Will the rear ends from 1992-1994 adapt as easily?  Do you remove the cage?

I've actually built a few Jag TH400's and 4L80E's back in the day but plan to use the TKO 500 in this build

I'm in the middle of building a house and shop but want to know what I should be looking for so to keep my eyes open for it.

I hope you don't mind but I'll have a bunch more questions I'm sure.  You seem to love Jags so I bet that's not a problem lol.

This thread just went from zero-to-awesome in 2.7 seconds...

Robbie said:

This thread just went from zero-to-awesome in 2.7 years...

FTFY

frenchyd said:

 

First it has more torque than the Chevy big block even though most were only 326 cu in  The reason?  A V8 will have two con rods at or near 90 degrees while a V12 has three!  

 

 

I would love to know your source for this statement.  And yes, I realize this thread gets bumped from the dead now and then, but you throw the above around a fair bit, from what I've seen. 

From a cursory google search, the most torque any factory Jag V12 ever made was on the 6.0 HE, at 336ft-lb at 3750rpm.  hardly stump-pulling, and pretty high in the range.
pretty much the worst big block ever, from the height of the fuel crisis, a 1975 Monte Carlo 454 made 350ft-lbs at 2400. 
I wonder if you may be mis-remembering, or cherry picking to suit your narrative.  Maybe you mean a low compression 402, like the 1972 LS3?  But even that made 345ft-lb, despite 210net hp rating.

Might be time to update the old fact sheet?

Ask away Glad to help!

First no you cannot  dish the stock pistons in a 6.0 or a 5.3 at least not enough to use the early flat heads.

Second don’t focus on a 6.0.  The 20 or so extra horsepower just isn’t worth the premium. Turbo or supercharged you’ll come close to twice the power as stock.  

Yes later rear ends work fine and like the early ones you’ll want to keep the cage unless you love fabrication work.  Keeping the cage almost makes it a bolt in proposition.  

My experience you’ll want to keep the engine to under 300,000 miles if it’s been well maintained.   More than that an you might start to see a ridge in the cylinder liners. Seriously I’ve never pulled one apart that has had any sort of ridge. 

The engine is so under stressed I’d bet it would go a million miles if properly maintained.  Great big giant oversized bearings, short little stroke,  massive oil pump, fantastic quality of parts. Brilliant engineering. Timing chain rather than belts. Plenty of water all around the cylinders.  Where most companies put one bolt Jaguar will use 4.  Head studs not bolts, Something like 27 or is it 33 per side where most companies would use 14 

The all aluminum engine block looks like it came out of  9000 horsepower top fuel dragster only with 12 cylinders instead of only 8 

Imagine the eye candy of  all that aluminum polished up! You can do it yourself, it will just take some time. 

In short no shortcuts taken.  

In reply to frenchyd :

Yes I plan to do the vast majority of work like that myself.  This is a take my time and have fun project.  Out of curiosity do you know the cam specs for the 5.3?  Lift - Duration - LSA - Intake and Exhaust centerline - Overlap?

Also could I use the 6.0 heads or are they just not worthy?

In reply to MARKUSA :

Nope not of the top of my head. Total lift 375.  Yep .375  

cams will add power how much do you want?  But it won’t lope and idle rough even if you throw the biggest nastiest camshaft  Kent or Piper make.   They have better camshafts than Isky or Crower can grind from the stock cam lobes. 

As for the 6.0 heads,  they are very poor for performance. Valves too shrouded for power. Designed to get better fuel mileage.  Realize this engine goes in a big heavy 4 door sedan designed to carry 4 fat guys and their golf clubs.  

The best heads for power are the early 1971-1980 flat heads.  

When Jaguar came out with the HE it was designed to meet California emission standards which the Flathead ( early head ) never would. The better fuel economy claimed actually was the result of other things 

PS  valve event timing.

Intake opens 17  BTDC   Intake closes   59 ABDC.  Exhaust valve opens 59  BBDC  Exhaust Valve closes. 17 ATDC 

the HE has slightly different numbers for the camshafts but the part numbers are the same.  It’s believed that they just changed the method used to report events. Like .050 measurement instead of actual numbers.  

In reply to stylngle2003 :

The numbers you are using are likely 49 state SAE numbers for the Chevy Big Block in 1975. Now look at numbers from the 1980’s for California which is  the numbers Jaguar uses. 

I’m looking at the Haynes manual 1980 edition  page 20 chapter 1

284 HP 5750 rpm. 294 Torque  4500 rpm  that was the older 5.3 v12  

from 1975-1980, you could get a "400" in a K20/K30 chevrolet.  Rated at 185hp and an even 300ft lb.  so that gets close to your haynes manual numbers, but still not less.  but the 454 of the same vintage was still a 205-210hp and 335-340ft-lb workhorse.  specific output is greater in the jag, but with 50% more moving parts, i'd hope so.  

http://www.chuckschevytruckpages.com/73-87specs.html

http://brochures.slosh.com/1979/pickups11.jpg

In reply to frenchyd :

Thanks for the specs -

I just just wanted the cam specs to play with my Desktop Dyno LOL

I've been looking around and the best deals I can find are the 1984-86 Jags.  The only custom pistons I've found are Ross at $2000 a set. 

MARKUSA said:

In reply to frenchyd :

Thanks for the specs -

I just just wanted the cam specs to play with my Desktop Dyno LOL

I've been looking around and the best deals I can find are the 1984-86 Jags.  The only custom pistons I've found are Ross at $2000 a set. 

The square headlight xj sedans are generally considered the ugly ones, and I find them the cheapest usually. Less common for them to have v12 than xjs, but they're out there I think.

Robbie said:

MARKUSA said:

In reply to frenchyd :

Thanks for the specs -

I just just wanted the cam specs to play with my Desktop Dyno LOL

I've been looking around and the best deals I can find are the 1984-86 Jags.  The only custom pistons I've found are Ross at $2000 a set. 

The square headlight xj sedans are generally considered the ugly ones, and I find them the cheapest usually. Less common for them to have v12 than xjs, but they're out there I think.

Years and models don’t matter when you are buying rusty  scrap non-running ones.   My favorite deals are guys who buy a Jag to put a chevy in it and give up  because it’s so much harder than it sounds. 

Yet the V12 engine can be fine or need only minor repairs. They just can’t figure out the wiring or hoses.  

MARKUSA said:

In reply to frenchyd :

Thanks for the specs -

I just just wanted the cam specs to play with my Desktop Dyno LOL

I've been looking around and the best deals I can find are the 1984-86 Jags.  The only custom pistons I've found are Ross at $2000 a set. 

 The most common camshaft spec is Isky’s XM3 but there is more power in either Piper or Kent’s camshafts.  Because they are new camshafts rather than regrinds the lift is greater and not compromised by the existing profile the way others are.  I used to get Crower to weld up the lobes to get a greater lift and better profile than the stock cam could be ground to. Plus it avoided the need to have those really thick custom made shins required. 

That’s why I avoid replacing the pistons.  The good thing is usually the pistons are fine.   

When I bought pistons I called around and one time Aires would get me the best price another time Venolia  but those were forged racing pistons custom compression and valve relief. 

Right now the best Jaguar pistons are made by Cosworth  they are much lighter and yet the combustion chamber is reported to be worth a significant power increase over the usual dish. 

The last time I looked I found an off the shelf piston I could make work by boring the sleeves out.  which I could do on my lathe, and fly cutting a valve relief. Which I could do using my drill press and a home made jig.  

But my computer dyno showed a gain of only 12 horsepower for all that work so I never bothered. 

There is one other possibility if you use the 7.8-1 compression pistons from a 5.3 on a 6.0 engine you can remove enough of the squish area ridge to bring the compression up to around 13.5-1 using the early flatheads. I say around because it depends on what size valves you use and how much lift/duration. 

MARKUSA said:

In reply to frenchyd :

Thanks for the specs -

I just just wanted the cam specs to play with my Desktop Dyno LOL

I've been looking around and the best deals I can find are the 1984-86 Jags.  The only custom pistons I've found are Ross at $2000 a set. 

Oh, when reverse engineering to calculate power etc. don’t forget there is a decent amount of power lost by Jaguar to make the engine civilized.  

For example the intake on the air cleaners is choked down a lot so the passengers can’t hear the sound of air sucking in.  We racers pick up a significant increase by removing that air horn and going to a 5 inch duct picking air from in front of the radiator.  Jaguar picks the air up behind the radiator  because air heated by the radiator gets slightly better fuel mileage than the colder air in front of the radiator.  

In  addition the ignition timing is set for low emissions not maximum power.   

The stock mufflers also hurt power.  Going to 1/2 inch larger tailpipe and a high flow muffler will make significant power increases as well. 

Get rid of the heavy fan  and a few other minor bits also make a real difference in power output.  How much?  

Enough to say that 350 rear wheel horsepower is possible from the stock 284. 

Couple of other things, since you’ll have a lot of room for a radiator try to use the Jaguar radiator if possible.  It’s remarkably well engineered and complex.

 In a big engine bay like a truck you might have the problem of the engine running too cool.  The Jaguar engine compartment is so tight a mouse fart would have trouble fitting in, let alone any  cooling air. 

stylngle2003 said:

from 1975-1980, you could get a "400" in a K20/K30 chevrolet.  Rated at 185hp and an even 300ft lb.  so that gets close to your haynes manual numbers, but still not less.  but the 454 of the same vintage was still a 205-210hp and 335-340ft-lb workhorse.  specific output is greater in the jag, but with 50% more moving parts, i'd hope so.  

http://www.chuckschevytruckpages.com/73-87specs.html

 

http://brochures.slosh.com/1979/pickups11.jpg

 

 

I understand you think I’m attacking Chevy. Nothing is further from the truth  I’ve driven Chevies almost all of my life.  They are good value.  If a bit ordinary.  I hope you don’t find that perjoritive It’s not the intended  to be.  Both have their place in the world. Chevy most definitely have their supporters, heck I’m one.  But there is real value in Jaguar especially at the level of us GRM people. 

With regard 50% more parts?  Did you count how many pushrods a Jaguar has? Rocker arms? Hmmmm  none compared to 16 of each  for a total of 32.   Look pushrods and rocket arms make it easy. But once you’ve done a Jaguar valve train it makes the Chevy look complex.  

PS

I’ve been looking to repower my cruiser and was offered a very low hour  mercruiser Chevy Big block (7.4-454) to replace my 5.7-350   

Looked it up ,  the 454 has 310 horsepower at the prop.   Now my 350 has a target master engine with Vortex heads and  a roller camshaft claimed horsepower is 330    Replaced when the marina failed to properly winterize the motor when I paid them to do it. 

I know the Mercruiser 350 has 300 horsepower  at the propeller .  So 104 more cubic inches only nets 10 more horsepower?   

Oh and a 350/5.7 weighs 880 pounds while a 454/7.4 weighs 1158 pounds.  But I don’t know if those weights  includes the outdrive or just the engine marinized. 

markwemple said:

In terms of sound, I hate a US v8, other then a gt40 for some reason, and all v12s are wonderful. Chevys are cheap but Im biased against them. Personally hate the old LS swap. I think either you like one or the other. Don't think many would like both. Opposite ends of the scale.

Srsly.

Cammed up LS sounds nasty and I mean that in a good way.  

93gsxturbo said:

markwemple said:

In terms of sound, I hate a US v8, other then a gt40 for some reason, and all v12s are wonderful. Chevys are cheap but Im biased against them. Personally hate the old LS swap. I think either you like one or the other. Don't think many would like both. Opposite ends of the scale.

Srsly.

 

Cammed up LS sounds nasty and I mean that in a good way.  

For the GT40?  180 degree header design (aka bundle of snakes) along with downdrafts and other internal engine changes makes a huge difference.

In reply to frenchyd :

How far do the pistons sit below deck on a 5.3? or 6.0?   Combing 7.8:1 pistons with a late 5.3 block and early flat heads would give what compression ratio?  Thanks again for all the info.

MARKUSA said:

In reply to frenchyd :

How far do the pistons sit below deck on a 5.3? or 6.0?   Combing 7.8:1 pistons with a late 5.3 block and early flat heads would give what compression ratio?  Thanks again for all the info.

The 7.8-1 pistons in the 5.3 have a dish and sit slightly below the “deck”  the longer stroke of the 6.0  moves the pistons up ( the bore remains the same ) I don’t remember for sure how much has to come off the squish land  but you still have some dish left in the pistons.  

Then chuck a 1&5/8ths fly cutter  in a drill press to notch the pistons. I make a simple block of wood with a 3 1/2 inch hole in it to act as a jig. Then drill a hole through it to locate the piston pin.  Slide two pins together and meet in the middle will properly locate the piston. It’s a simple matter to clamp the jig drop the piston in place line everything up and cut the valve reliefs.  In fact it takes less time to do than describing the process.  About a 1/2 hour and all of the pistons are notched. Set the depth stop based on how much lift the cam has. 

There are a few other tricks you’ll want to follow  before doing this. 

But if you do this you cannot turbo charge or supercharge the engine.  

So the question is, do you want the maybe 10% power increase of 13.5-1 compression 

Or the near doubling of horsepower turbo or super charging will provide?  

If like me you already have 7.8 -1 compression  pistons and a 6.0 engine  with a pair of early heads. There is no economic decision.  

If you have nothing to start with you’ll need to buy both a 1971-1980 engine for pistons and heads. And  a1992-1997 6.0 engine. 

Now there are many 5.3 early engines around and as a core they will be in that $300-$500 range.   A 6.0 engine core on the other hand will cost over $2000 last time I seriously looked for one.  ( and that one  lacked some major parts like a starter) 

Incidentally the starter on a 6.0 is one of those small gear reduction starters  that weighs less than 1/2 of what the earlier ones do and is so much more compact.  While providing faster starting and taking less out of the battery. 

Oops!!! 

I reread your question.  

Combing 7.8 pistons with any 5.3 block. Any5.3 block  and early flatheads will result in 7.8-1  compression.  

The only change comes when you put 7.8-1  pistons from a 5.3 in a 6.0 block.  Then you can use the flatheads and with the mods I mentioned wind up with about 13.5-1 compression ratio. 

Not what you want to do unless you are a racer like me.  Gas for that sort of compression is about $13.00 a gallon plus shipping and comes only in 55 gallon drums.  

In reply to frenchyd :

Yea, I was just trying to figure out the most economical way to get the compression low using the early heads.

In reply to MARKUSA :

Definitely going to turbo it (at least two or maybe four using Ko3 turbos)  Looks means a lot on this build.  Not so much power - but want plenty LOL

In reply to MARKUSA :

T3’s? Or Ko3’s?  

T3’s will do nicely up to about 3 liters  so a pair is perfect for  a V12. 

Ko3’s are pretty maxed out at 2 liters.   So a pair  is too small.  While you might be able to find a pair on a couple of junkyard cars they don’t have a sterling reputation.  

Plus I’m hearing good things about more recent Chinese Turbo’s. At a $127 each with wastegates they represent a nice entry point. Replacing the Chinese made ones with much more expensive American ones should the need occur is simplicity itself.  No doubt the early ones had plenty of issues.  Recently though they seem to be good value.  

MARKUSA said:

In reply to frenchyd :

Yea, I was just trying to figure out the most economical way to get the compression low using the early heads.

Buy two engines.  Shop around for an early one $300-500 tops. I’ve picked them up for as little as $50 from hot rodders  who want to put a V8 in a Jag. 

Then buy another car with a later HE engine.  Unlike American cars I’ve only rarely found any significant wear on a Jaguars pistons.    Doing it that way you likely will be able to rebuild a good one using all used parts.  Jaguar batch mixed parts when they were making the cars.

It’s been my experience that the sedans has slightly smaller  parts than the XJS  ( we’re talking by the ten thousands of an inch)  since race cars tend to use slightly increased clearances I tried to  use sedan parts in an XJS block You might try to put  XJS parts in a sedan block for greater longevity.  But given the tolerance you’re working with  it really won’t matter. Except for the need to significantly increase top  piston ring gaps if you intend to turbo charge your V12 

The early one with the flatheads and low compression pistons will be the hardest to find!  Some years they made less than a thousand and America got about 1/2 of them.  

Good news?  A flood engine or one that has had a fire won’t hurt the parts you want.  So shop the insurance sales, Craigslist for non running.  No tittle.  I’ve bought a number of them from shops with a mechanics lien.  

How to tell a HE engine from a Flathead.

The best way is if the engine is still in the car. Look at the back and see if it says HE. Or look at the serial number tag on the drivers door jam 1980 and earlier Flathead. 

If it has 4 carburetors  it is a Flathead.   If the oil pan is an aluminum casting that’s A Flathead and it may have the 9.0-1 pistons or the 7.8-1.  Only pulling the heads or checking the serial numbers will tell you which. 

Look at the transmission.  If the bell housing is aluminum but the transmission is cast iron that’s a Flathead.  If the transmission and bell housing is one piece aluminum that’s a GM turbo 400.   Now it might be a  Flathead or it might be an HE. Chances are best it’s an HE  serial  numbers will tell you.  Somewhere in there they went from a flat washer spark plug to a tapered spark plug. I’m almost sure the flat washer spark plug will be a flat head and there is only a slight chance that a tapered plug is a Flathead.  

In reply to frenchyd :

Do you know the weight of a stock V12 connecting rod?