intake port molds

[tpepmeie]

Got the port molds done. Pretty neat to see an LT5 port from the inside out. Also helped me confirm the cross-sectional areas.

here are primary and secondary head port (right), and also primary and secondary injector housings (left). Pay no attention to the lengths... I didn't get a "full pour" on a couple of them. In this pic, you can't see just how unfortunately large the bowl is behind the valve, as cast. We discussed seriously about welding that or using some epoxy to reduce the volume there, but didn't do it.




Todd

[Locobob]

Originally Posted by tpepmeie

You can see a lot more in some other pictures, but afraid those angles might be giving too much I.P. away. A lot of time and much $$$ went into these.





Todd

It's your stuff and therefore your choice whether or not you want to share the details but if you choose not to then the discussion is over before it can begin. Kinda nullifies the value of the thread if you're not willing to share the details don't you think?

[tpepmeie]

Originally Posted by Locobob

It's your stuff and therefore your choice whether or not you want to share the details but if you choose not to then the discussion is over before it can begin. Kinda nullifies the value of the thread if you're not willing to share the details don't you think?

Not trying to offend anyone. Yes, I paid for these heads, but I don't think it is fair to show the finer details of a professional's work, developed from his years in the trade. I am sure he would consider that his trade secrets. He earns a living that way, so I was just trying to respect that, that's all.

Other than that, I'm happy to talk about the subject (as we did in the other thread), as much as anyone wants to. I love talking about the topic, and have a genuine interest in how this stuff works.

I'll edit the original post to remove the reference to I.P.

Todd

[Locobob]

I enjoy these technical discussions as well. I can certainly respect your concern regarding the person who did the work for you, perhaps you should ask him if he minds the details of his work being discussed here.

[tpepmeie]

Some basic info/observations about the ports: As I said before, they are small...about 35mm for the most part. Not a great deal of taper, but pretty uniform. The taper is provided by the plenum runners, as they are larger at entry before the bifurcation. Shape is not round throughout, and also has to be larger in some spots due to the turns in the tract. Pretty standard stuff for a four-valve, the min csa is before the turn and that dimension was basically set by the casting...could have been even smaller otherwise. A lot of focus was put on the short side radius, as you would expect. Very little if any material was removed from the long-side and bowl. The port shape adn dimensions were determined on the flow bench with a velocity probe. The valve job must be killer, as the low and mid-lift flow is quite strong. 39.5mm valves w/ thin stems and tapered bronze guides.

Also interesting to note that the valve center is offset from the port, as designed by Lotus. Presumably this creates quite a bit of mixture motion in the chamber.

[Polo-1]

just watch which " professional " you choose.

B.K. special


Just needs a little silicone to seal up

[limey]

Originally Posted by Polo-1

B.K. special

Is that as in Burger King or the Bearing King?

Oh *&^%(&^^ it, don't get me wound up!

[Locobob]

Originally Posted by tpepmeie

.
Also interesting to note that the valve center is offset from the port, as designed by Lotus. Presumably this creates quite a bit of mixture motion in the chamber.

Often referred to as port biasing, my LPE heads were like that, I kept with the theme when I went through them again recently. I'm a bit surprised by how small your runners are given you are building a stroker. It'll be very interesting to see how it does in relation to the current "bigger is better" builds. The relatively smaller runners you are going with are not necessarily new, most of the early LPE builds I've seen are pretty conservative in the porting department too. The chamber shape on the other hand is something I've not seen before on an LT-5, LPE stuck with the clover.

[tpepmeie]

Originally Posted by Locobob

I'm a bit surprised by how small your runners are given you are building a stroker. It'll be very interesting to see how it does in relation to the current "bigger is better" builds. The relatively smaller runners you are going with are not necessarily new, most of the early LPE builds I've seen are pretty conservative in the porting department too.

Conservative in size, yes. However, they move a ton of air, and as much or more as the LPE big valve heads. The housings only lose less than 10 cfm airflow, which is quite good. Took a little extra effort, though...the first pass through resulted in a 20 cfm drop! We're going to test them on Greg's bench too, just to confirm the results and add the plenum to the system.

Todd

[LGAFF]

When you said that the ports were small, I was thinking 34 or so.....my 92 had around 35MM ports and produced decent power(391rw) considering no tune. The 36MM ports I have done have produced power similair to those of 92, but I assumed some benefit on the 92 due to cam timing, as the 92 had lower miles than the other intakes I have ported.

Recently did a 36MM for a 368, wil be interested in results.