Warren is this with the In 38/70 Ex 74/34 Cam and revised plenum or just the In 38/70 Ex 74/34 cam?

 

That includes IM mods as well. This would work better with shorter rear gears.

Bigger valves would also give more power right through the rpm range, but I wanted to see what I could get out of a stock setup.

I'm planning on putting the 2.88 gears back in the diff after I swap to the big engine. With a tight converter somewhere around 1800rpm it should be awesome out of the blocks with 470ft/lb at 2000rpm, I know this is in the ball park.

 

I have just finished CCing the heads, I recon it took about an hour per chamber, but I did get them all between 31.2 and 31.3cc ±0.05cc. Repeatability was the biggest issue. CC's changed with temperature. I CCed the A head last weekend when the temp was 10°C warmer when I checked them again today CC's were up 0.1cc.

Just waiting for the cams now, it's a 600km round trip to pick them up, good outing for the XJS.

 

Nothin ever goes completely without issue, when the studs were removed so the head could be machined all but 2 came out without issue, but 2 had to snap below the face of the head. The broken studs were removed and the head was welded.

I had to make a jig to hold the head at the correct angle to redrill and tap the holes. I have the digital level on the manifold surface to ensure it is level so the hole is at the correct angle. I plan on installing the collet chuck and using a 6mm end mill to drill the holes then I'll swap back to the drill chuck to drill the holes to the correct diameter.

 

.

warrjon , i would not give much thought to such small differences in CC's .

you could never measure it on a dyno anyway.

spend time on getting more air in and air out is the main considerations!

your on the right track , there is NO ONE on this site anywhere close to what you are doing!

altho you do amaze me in your attention to detail!!

 

Same here. Can only agree. Many people come here, say i'm going to make 500 hp out of my v12 and you never hear from them again. And then there is Warren, who not only says he's doing something, but pictures it all and is willing to explain everything.

I wish I had your knowledge and expertise, as well as tools

 

Following up on this, so, a shorter runner with say a separate throttle body would reduce these problems? Is it only the length between the valve and the TB or would the extension to the full air intake be a restriction?

For example, replacing both intake manifolds with say 12 short, stubby runners with individual TBs would allow for more flow with a reduction in restriction?

Somewhere along the lines, I remember that a longer runner will result in more air speed boosting torque where as a shorter runner will increase bhp. My C30 had a switchable intake manifold and you would feel the switching of it. It would be all of a sidden. Say around 3300 rpm and then it would switch to the shorter runners. But would that be a system for a V12? I mean it already has loads of torque in the lower rpms, so i guess it shouldn't require it.

 

As a rule short runners will make peak torque at high RPM and longer runners lower RPM.

Why is this so - when the valve opens air starts to flow, when the valve shuts there will be a reverse of the flow and an induction wave will flow back up IM runner until it reaches the entry to the runner, where it will reverse and head back to the valve (like a wave in a pond if it hits an object in the water the wave will bounce, air acts exactly the same).

At some RPM (this can be tuned by the length of the intake runner) the wave will hit valve just as the valve opens causing more air to be forced into the cylinder, this happens at peak VE of the engine.

In a road car to keep runners short enough to fit under the bonnet the 4th or 5th wave is generally used to keep peak torque around 3000-4000rpm as the less number of waves increases the length of the intake runner.

So to answer your question longer runners do not increase air speed they increase the time for the wave to travel the length of the runner. The longer the runner the lower rpm peak torque will be developed. The diameter of the runner will have effect on air speed or more importantly air acceleration, how long it takes for the air to start moving.

As an aside long runners and higher rpm cams if done correctly can fatten the torque curve of an engine.

 

Thanks for upping that Warren! I'll leave my V12 as is

 

Hey I want to build a 500hp V12 ��. I had expected to find a few modern (not Group 44 vintage) proven recipes for high hp V12s easily accessible on the internet but no such luck. I’m watching and learning. It’s facinating reading all the information here including the computer modeling. My thanks to Warren and all contributors.

Below is a flow chart for heads from a shop is Austin, TX showing flow for stock and modified pre HE heads. I was surprised they used such small valves. Intake 1.74 and exhaust 1.45. Also shows cam lift above 0.400” not doing much on the modified intake whilst above 0.400” has a significant effect on the exhaust.

 

You weren't meant. They come and go in regular intervals. I remember someone 'making' a quadturbo V12... That died off quietly...

 

Daim I didn’t think you were talking about me. The smiley face I put didn’t show up... cheers.

 

all things relative: if anyone TODAY is really serious about making an IC engine make more usable power ??

enter FORCED INDUCTION, many of the ways of making more power NOTHING is better at it than SUPERCHARGING !

stop and think about it, you want power, so in the inlet manifold(of any engine), have instead of a vacuum suckin air in , force feed the air into the cylinder.

a quick study, if you can increase the manifold positive pressure just 1 BAR,(like atmo of 14.7 psi), theory says a 100% increase in power ,(altho in practice dont quite workout that way,but HEY i'd settle for a 75% more).
been there done that, but you havent lived,until you feel the boost of a good turbocharger comin on line, and torque increasing double amounts!

with out all that cam stuff,porting, polishing, fancy types of internal engine modifiecations.

just my thoughts, but to each his own, because its the FUN and knowledge that is most important, about any type endevor we attempt , that gives you reason for exsistence.

 

.

longjoun; because the JAG V 12 is not a performance engine, its a docile street engine, that does not lend itself well to performance mods.

may i ask who in Austin TX, has done those flow charts??
also Austin does not get the recognition it deserves, we had some of the worlds first 200mph after midnight street cars around the area, there are some old videos of that stuff, and it seems they were mostly Nissan Skyline, SUPRAS 93/95 being super/supercharged.
being modded by ordinary people, not knowing what would happen! austin and its computer nerds/geeks.
Ron

 

Ron, I've seen a quadturbo Jag V12. But not in an XJ-S. Efficiently placed would require a lot of body work. People put them nowadays at the rear of thr car. But then it has soooo much lag... But I agree, forced induction a way to go.

 

Ron, Classic Jaguar in Austin. 5k per head but you may get a discount if you order two... Are you now Austin based?

Pretty hard to put a positive displacement supercharger on a V12 but someone was talking about it on the other forum. A centrifugal supercharger would be easier but they don’t provide much boost until they get to the top end of the rev range.

 

The base line flow in those head does not look right to me. When I flowed my heads flow dropped away after 10mm 0.400" lift due to port sizing so the increasing flow to 0.450" lift looks wrong, unless the heads already had larger ports.

If you want 500hp talk to Norm, he has built many 500+hp NA V12's and knows what is needed. You will need flat heads as the valve diameter is limited in the HE.

Basically the biggest intake valve you squeeze into the head 95mm, bore also increases the max valve diameter. You will need to rev to 7500rpm to make 500hp.

 

Could the difference with your heads be because these are flat heads?

I will speak to Norm when the time comes. I’m still in Venezuela and probably won’t move back to Perth until Apr next year. I’m not sure I need to rev to 7500 rpm, Using one of his 7.5L setups as a base I think 500hp at 6000rpm should be achievable. That’s only 67hp per liter. In theory Classic Jags head should be good for 600hp.

 

.

sorry for the wording , i'm saying turbochargers only, Not mechanicly driven superchargers, actually turbo's were/are exhaust turbo-superchargers.

later on to save words/ink they were called simply turbo's!

with todays electronic turbo technology , we can make boost pressure setting still ,like 20psi in neutral not moving.

lag gone forever.

brings up my neighbor just bought a new M Benz 550 twin turbo, driving the car you cannot feel any lag whatsoever!!

i offered to drive it and do some DONUTS, but he declined, DARN, just wanted to have fun, to me thats what SPECIAL cars are all about FUN!

Ron

 

I wouldn't have thought the intake port and bowl were too much different from the flat head but as I've not measured them I am not 100% sure.

The intake runners are the same diameter and the pinch point at the valve guide is what restricts flow. Ideally you want flow to peak just above max valve lift which is what my heads do.

In fact they flow the almost the same at max lift as they do with no valve. I did this just to see what happened.

You can make +500hp with HE if you go FI, otherwise you will need flat heads and BIG valves. A 5.3L will make 500hp with twin turbos and very smooth power delivery.