i do think that this v12 inlet manifold is the best idea ,YET!

we dont have to stick to the Grp A rules for our cars.

this type is is used by many race cars starting with the 1954 M/Benz(maybe earlier),

it has a large plenum, and larger and longer runners, if the heads were opened as far as possible along with larger valves, i betting it would work, better than anything i'v seen yet for a jag V12.

i'm not sure that fiberglass on engine manifolds would be durable enough!donno.

 

that intake was made by aj6 at one point. and although im not sticking with the group A rules I want a somewhat stock looking manifold.

btw bmw has intakes with fiberglass runner cones

 

That looks like the AJ6 intake. I think the design has merit long equal length runners and large plenum.

Loads of cars these days use plastic manifolds, the LSX for one use injection molded plastic.

I also like the idea of the dual plenum like Audi use in their R8, they also used it in their Group B rally cars. Google Lehmann intake. Here is a good writeup on the Honda Forums.

Dual Plenum Intake Manifolds - Honda-Tech

 

There are a couple of cars on ebay in OZ at the moment that really fit this discussion.

Jaguar XJS from Tom Walkinshaw Racing Jaguar XJS From TOM Walkinshaw Racing in Melbourne, VIC | eBay

JAGUAR XJS 1977 V12 TWIN TURBO Race car - CAMS LOG BOOK Jaguar XJS 1977 V12 Twin Turbo Race CAR Cams LOG Book in Sydney, NSW | eBay

 

 

yes injection molded hi-temp plastic, not home brew resin and glass fibers

 

As it seems this conversation has turned toward intakes, and someone mentioned the AJ6 Engineering manifolds, I decided it might be worthwhile to take a couple measurements, and shoot some photos of both my stock intake manifold runner openings, and those on my AJ6 Engineering Plus-Torque intake runner openings. I also measured the intake openings of the heads my Gran Turismo Jaguar motor, and those on the original motor I had in JagZilla, which I ported myself.

MEASUREMENTS

GTJ (and also probably stock) Intake Port Opening - 33.40mm diameter
My Ported Heads Intake Port Opening - 38.00mm diameter
Stock Intake Gasket Opening (New) - 38.00mm diameter
Stock Intake Manifold Runner Opening - 34.08-34.22mm diameter
AJ6 Engineering Plus-Torque Manifold - 34.52-34.75mm diameter

Side-by-side comparison (notice how much larger the opening is on the intake gasket, as indicated by the ring left by the gasket around each manifold opening)


Stock intake manifold has a ledge just below the injector


AJ6 Engineering Plus-Torque intake manifold has been smoothed from the injector, down to the opening, eliminating the ledge that the stock manifold has. I believe the slightly larger opening is nothing more than an unintentional by-product of this process


This photo shows where AJ6 Engineering cut and re-welded the intake plenum in order to install their bellmouths inside the plenum to equalize the length of the intake runners. The phillips head screws on each of the intake runners is used to help secure the bellmouths within the upper runner openings


****EDIT****

After mentioning the size of the intake ports on my heads, I thought I should probably post comparison pix of them as well.

This is looking inside the un-ported GTJ 1B intake


This is looking down into the ported 6B intake from the original motor I had in JagZilla. Notice that the size of the port matches the 38mm opening on the gasket. It is that size all the way down to the valve. You'll also notice that I cut off the exposed portion of the bronze valve guide. I'm not sure if that weakened the valvtrain or not. I've wondered if the shorter valve guide might have allowed the valve stems to flex at high RPMs, but, I haven't found anything whiich says shortening them would cause flex.

 

Great info on the AJ6 manifolds

 

I've edited my last post in order to show a couple comparison photos looking down inside both ported, and un-ported intake ports on two of my motors.

 

I also did the gasket matching and ported.the ports to be completely the same diameter all the way through, but I also worked the inside of the curve which is ideal for bettee flow, and made sure there were.no sharp turns in the ports.

 

Yeah, the curve in there is pretty tight, and it is located right where the valve guide & it's buttress protrude into the port. The combination of those two things in that area creates a serious bottleneck, and is probably the single greatest restriction in the entire intake/exhaust process. I, too, straightened it out as much as I dared, and gave it a much larger inner radius so the air had a straighter shot into the heads. The key is to resist the urge to straighten that curve out too much, because there is a coolant passage directly under that inner radius, and if you break through to it, you'll be tossing that head into the dumpster, and finding a replacement.

 

If you remove the injectors you can remove the hump inside the inlet manifold to advantage. We found a significant increase in flow by doing a proper valve job. By this I mean triple cut of the head seats ensuring the 45 cut was 40thou on the inlet and 60 on the exhaust; no more. Ensure the 45 cut mates to the edge of the valve so the internal 60 cut makes the port as large as possible through the seat. It also makes it quite clear just how large you can get the port near the valve.
On the valves cut them to match the width of the seats and right out to their edges. then reduce the width by back cutting at 60 which will reduce weight and improve the flow.
Tools from Neway do a great job and the time you put in will reap rewards, no machine shop does this unless its a real specialist who will charge loads.
expect 10-15 % without too much effort here

 

on the pre.he heads, the exhaust was actually larger than the intake gasket so I couldn't port much more than to smooth it out.

after you port the heads have them pressure tested before putting them on any engine

 

How far do you back cut? I know in some instances back cutting too much can effect high lift flow.

Do you grind the stem to reduce width? if so how much.

In your experience does removing the protruding valve guide in the port reduce longevity?

 

cutting the 45 angle increases the width of the seat on the valve. the more you cut the wider the seat; the back cut is done to reduce the width of the seat back to where you want it and this just happens to increase the flow at the same time.
We use std length guides but the section that protrudes into the port is tapered to reduce flow losses. No more than that; but bear in mind the race heads have much larger ports, much larger than the std gaskets.
The size of the exhaust gaskets was mentioned; bear in mind that I know of 3 styles, the original Cooper Payten type which is grey with an internal metal mesh. A later type with outer metal skins laminating a grey core held together with 'z' like hole stampings/stakings; and a very late type similar to the later but with an internal sealing ring bit like a head gasket compression ring. All have different ID's. There may be more std types never mind the custom ones for the race heads be they round , raised or 'D' port.

 

Yep I understand this bit

So you are saying cut the 60deg to reduce the valve diameter and set the 45deg to thew seat. Do you cut a 30deg on the top of the valve?

Thanks again for all your input.

 

Your guess!

testing

testing

testing

testing

testing

testing

testing

 

man that is.so freakin cool, I wish I was lucky enough.to have access to engines like that

 

I know I'm a bit late to the party here fellas, but I thought this would be the best place to ask.

First of all thanks xjr5006 for the pics!

Now it seems that the biggest obstacle to making power is the intake manifold. So why not ditch it all together and go for individual throttle bodies?

I see a "simple" way to do it, but it's not the cheapest that's for sure.

Webcon UK Ltd - 5.3 V12 6 x Weber IDF

"Cast Aluminium Inlet manifolds set (6 off) to fit 6 x Weber 40 IDF Carburettors to Jaguar V12 engine"



£575+VAT for the set of six.

And then use six of these

PRO-RACE throttle body IDF 45/43/40

IDF 40 EFI Throttle Body



£223-£306 each +VAT depending on which ones you go for.

OK there is more to spend on the trumpets, injectors, ECU, tuning, etc.

But it seems to me that this will eliminate any restriction in the intake tract.

The Pro-Race 40mm throttle body is rated at ~50HP, so x12 = 600HP

Assuming (oh yeah, get ready to make an *** out of me) that the heads will flow enough, and you get the compression, cams and exhaust sorted, then it doesn't seem to much a stretch for 500HP.

 

Not necessarily. According to Allan Scott

5.3L with GpA Exhaust Manifold and large bore exhaust with XJR-S cold air intakes and K&N filters (stock intake manifolds) added 40hp

GrpA inlet manifolds lost power in the 3000-4000rpm and did not make power until 6500rpm. Larger butter flies were also tried with poor results.

If HE heads cam choices are limited in duration because of the flat top pistons. This limits power. Pre-HE (FLAT) heads can run much bigger cams.

HE heads will limit power to around 450hp (NA) but can make a ton of torque and much flatter torque curve than pre-HE.

If you constantly run the V12 above 6000rpm without significant oiling mods you will almost certainly be rebuilding the engine.