I started thinking about what you said about loosing velocity and now I'm thinking weather I should touch the runners or not.

I really wanted to get rid of the divider as it looked restrictive and seemed to block the runner.




Now that I took it out and knife edged it. it no longer directly obstructs the runner. I'm starting to think that if I port match the runner to the head without opening it all the way up to the blower I'll be loosing velocity? Right? Should I leave it alone?

 

The ONLY reason the splitter/divider is there is because on the end there was supposed to be that flap that blocked off one side of the ports. Thats why it's so obstructive.
The flaps were dropped and the dividers stayed as a bad hangover from a stinking deal.

For port velocities, you need to directly measure where you are- theres an old equation that relates engine capacity, engine speed and port local cross sectional area to local velocity. An easy way for you would be to measure the volume of the port itself with fluid- you know the length- it's between 100- 120mm so the local cross sectional area is easy to find from this. This is painstaking but is what differentiates an engineered approach from a mechanics approach.

 

I decided to step it up a bit

 

A Knife edge isn’t automatically better than a more rounded edge…
Would wait until you have had a chance to speak to Count Iblis...

Flow dynamics is something on its own, not easy or something to take uneducated guesses on, and as far as I understand it, it was his area of profession.


My biggest mistakes where done when I didn’t give a thorough thought/enough time to perform a certain task.

 

He did say he would knife edge the divider in one of the above posts.

 

Was just a heads up, nothing more.

 

Gotcha Thanks for looking out.

I figured no matter how I screw it up, anything is better than that big *** divider. I'm also using the AJ26 heads as a rough guide.

 

One school of thought in porting is to open up the far end at each successive transition but not the near end. This aids in promoting anti-reversion.

For example, at the intake runner to head transition, hog out the intake port, but only do minor adjustments and polishing at the intake runner. The resulting lip helps keep the air charge from going back up the runner.

This has been seen to work better than a full port match ... and is less work

YMMV greatly, because this is based on experience with carbureted, naturally aspirated engines. But ... it's still air flowing through those passages.

 

 

 

One side is done. Here are the before and after shots. I'll touch up the heads to match perfectly too before assembly. I'm thinking about making my own gaskets also.







They were all done with 3/4 sanding drums. The drum goes under the injector easement.
Be careful in that spot thou and try to get the opposite side as even as possible before tackling that as the wall gets real thin over there.

BTW this one side took up my whole Sunday. Now I'm thinking about the TB, Elbow, Inter-coolers and SC.. I need to stop this madness.

What do you guys think?

 

I think do it cus once its together if you dont you'll be thinkin wonder how much better it coulda been if you had.

 

There’s no stopping Adam anyhow as far as I can see


Adam, not sure what can be done in the intercoolers that could matter, but the intake elbow iirc does have some spots that could be improved.


Wouldn't do porting on the SC, chances are it will only make it louder, and you will not gain (but IU guess this is another incentive to start the work right )

Maybe mating the 4.2 blower to the 4.0 intake would be good if you go that route.


There is something good to be done about the TB, as I am sure you can bore that one out to 79mm (from stock 75mm), make a new blade and done.

 

I think I'll just do the elbow, custom gaskets and fit the newer SC. I've been thinking about opening up the inlet to the elbow size on the SC.

Now I really need sleep

 

By doing the TB as described, you increase the area for airflow by almost 12% (this becomes almost 15% when going to 80). Once you are planning to move more air than stock, this part of the full intake will become a bottleneck (amongst others).

The more vacuum you have before the SC, the more power this will consume from the engine (and of course hinders more airflow, so double penalty).

Of course this is a mod that can be done later, here is just 1 company in the US that does this, (I’ll bet there are much more):
http://www.maxbore.com/index.html

 

Good Link! I'll look into it down the line. At this point I want to do things that are hard to get to once the engine is in the car and I need to get this thing running. Any idea how I can disable/ bypass the downstream o2 sensors to run cat-less?

 

Did you get that from Smokey Yunicks hot rod book or David Vizard?

When advocating a lip you're bascially reccomending is an area ratio expansion although not dissimilar to vena contracta. This will simply impose a further flow loss proportional to the inlet manifold to inlet port area ratio.

 

OK, so I had to take a break from the Jag past two days. Anniversary with my GF and a fuel pump on a Nissan Quest (300,000miles) were more important.

Here's today's work.






I'm ready to start swapping accessories and the lower sump.

 

I tried digging some info on the knock sensors but it looks like the earlier are made only for Jaguar...

 

OK, so my humble goal is to have it started by the end of day Sunday....however...


Today I started swapping the oil pan and sump and some of the accessories. I'm going to try to retain the 4.2 front cover, ballancer/pulley as it is bigger than the 4.0 one= more boost plus it's newer with less miles and I've learned how important balancers are, especially on boosted cars. The bottom pulley upgrades are $500 so it's worth the trouble on my low budget project. (anyone know the size of the upper pulley? would a Cobra pulley work?)


Anyway, I've run into the first hickup:



So the 4.0 bracket for the power steering and the ac is blocked by the front cover provisions for the 4.2 brackets. The block has all the necessary openings so it's just a matter of cutting off a part of the front cover to make this fit.