Porting intake

[jordan]

what would be the best way of heating it up? we have a 1.5 million btu forge, 200k btu forge, and several rose bud torch tips. Im afraid of melting it with the big forge, and our pyrometer isnt fast enough to detect the temp. we have an infared thermometer but it only goes to 500ºf. we have a 55 ton press but I don't see where that would help, but I do have a porta-power that may help.

[RallyBob]

Knowing the low temp aluminum melts at, I think the forge is risky. But if can get your hands on some Tempilaq (temperature-sensitive paint) and use a rosebud tip, that will work just fine. The key is to heat at the radii and gently pry the flanges apart with some sort of tool....as I said I have a simple spreader made from threaded rod and a coupler nut. I think you have wayy more tools than you need, the tough part is deciding what to use! Good luck.

Bob

[GTJIM]

A LPG/air torch is probably best - the flame temp is much lower and you will hear the casting creaking and moving, if it has some pressure on it, long before melting starts!

[RallyBob]

A little late, but this was my solution today for jigging up multiple intakes for welding without warping. I used a piece of 3/8" steel plate, and fitted dowels for the flange alignment, with steel welded pads to keep the inner mounting flange edge from moving inward. Lastly, the intakes are bolted together at the outer flange edges.

I will be welding them tomorrow, so I'll let you know if it doesn't work out.

[RallyBob]

Originally Posted by Crusher You really get the most out of porting the head...lots of metal to ground out there under the valves were its restricted.

This is a blanket statement that does not always apply. Unless larger valves are installed, Opel heads often flow worse when ported. I've seen some really bad stuff over the years on my flowbench, especially with home-ported heads, although plenty of machine shops have ported heads badly as well. I feel that most people could port their own heads effectively IF they had the specific (Opel) knowledge to do it correctly. If you port it like it's a Chevy you'll only hurt performance.

[RallyBob]

Per some suggestions from other members of these forums, I tried a different method of instituting a 'tented' plenum floor on an intake manifold. This required cutting the plenum floor out completely, which made it easier to port the manifold too BTW. I then welded in a piece of .060" thick aluminum from the underside of the plenum which was bent into the 'tent' shape.

[BQS4]

Bob;
This is kinda the idea I was thinking. Now that manifold can be use with or without a sprint manifold, or header.

[RallyBob]

Originally Posted by BQS4 Now that manifold can be use with or without a sprint manifold, or header.

In this case a stock exhaust manifold couldn't be used, I trimmed some material off the bottom of the intake. Plus, I think a thicker material would be necessary for heat resistance, maybe 1/8" or so.

[Crusher]

The manifold is a good place to start.
The intake and exhaust ports in the head are badly restricted and there's alot of metal there to be removed. Just by looking at a strippled head you can see how restricted it is..A stock intake manifold actually has better airflow than the head.

[BQS4]

Bob;
This looks like a "do-able" mod for $$, especially if the customer sent you their manifold. What do you think? How much? Did you do this on a '74 manifold? I, myself, am looking to have this mod done, but, I don't have a sprint manifold. I would like to finish out the header flange I bought from you to go with this type of intake, but, I'm running the the stock "bolt together" manifolds.
Gene

[RallyBob]

Originally Posted by Crusher A stock intake manifold actually has better airflow than the head.

Uh...wrong. I have flowbench data to prove it, the intake restricts the head by a LOT. The head can definitely be improved, but only with big valves. Porting with the stock valves is a general waste of time. One only needs to look at the valve area-to-port area relationship to see the ports are actually decently sized for the intended rpms and engine displacement.

Bob

[jordan]

Bob, how did you weld the center divider in charle's manifold? The fella who is welding the divider in mine can't figure out how to get the tig torch that far down in the plenum to weld, I believe it is a cover gas issue because the ceramic guide will be too far away from the point where the welding is occuring.

[RallyBob]

Originally Posted by jordan Bob, how did you weld the center divider in charle's manifold? The fella who is welding the divider in mine can't figure out how to get the tig torch that far down in the plenum to weld, I believe it is a cover gas issue because the ceramic guide will be too far away from the point where the welding is occuring.

I didn't weld that intake....I didn't even own a TIG back then. The guy who welded it is a professional aerospace industry welder. He used a short tungsten without a back-cap (just some sort of plug). He got the whole torch head down inside the plenum that way. That's the reason I weld my own intakes from underneath, doing it from the inside is beyond my capabilities.

Bob

[Tru-Craft]

Has anyone just tried bolting the "divider block" in the manifold.
Make the "triangle" block out of AL, drill and tap 2 holes in the bottom of it.
Drill 2 holes thru the manifold.
2 bolts from the bottom, a little gasket sealer.
?

[yellaopelgt]

So if I understand this all.....(not really) dont bother porting the intake unless you have installed larger valves??? Its GOT to help some even without oversized valves!!!

[RallyBob]

Originally Posted by yellaopelgt So if I understand this all.....(not really) dont bother porting the intake unless you have installed larger valves??? Its GOT to help some even without oversized valves!!!

Intake manifold porting....good.
Intake port porting w/stock valves....bad.

The ports are already too big relative to the size of the valve. Sure, you can blend the bowls a bit, but enlarging the ports gains no airflow, reduces port velocity, and reduces power and torque.

HTH,
Bob

[oldopelguy]

Originally Posted by yellaopelgt So if I understand this all.....(not really) dont bother porting the intake unless you have installed larger valves???

Go ahead and port the manifold, just don't bother porting the head without the bigger valves.

[Tru-Craft]

OK just got back from the shop. Was working on things to fit my new 38DGES carb. I rough ported the the intake manifold, made up an aluminum spacer.
I was thinking about the tent in the plenum and came up with a different type of plenum floor insert!
It is made from a 1-1/2 round aluminum sawed in half, milled flat and (2) 1/4-20 tapped holes. Then I drilled and counter bored 2 holes thru the plenum floor.
It will reduce the volume of the plenum and split the air equally to both sides, like the tent design.
No welding, easy to make and you can change it easily!
Think it will work?
Lyle

[opelgt73]

Wouldn't it be better if the inser had a concave curve instead of a convex one?

[hrcollinsjr]

Anyone remember the "turtle" inserts that Brodix sold for V-8 intake plenums? I had wondered if cutting them in half and experimenting with them if one of the patterns might help to more evenly distribute the fuel between the cylinders.

Harold

[Tru-Craft]

I don't know what is better for flow, Bob probably will!
The convex will seperate each side of the runners more!
The air flows smoothly over either type of radius.
Never saw the Turtle inserts, have one or a picture?

[hrcollinsjr]

Here is a link with pictures of different ones.

http://www.brodix.com/Turtles.html

Harold