Porting intake

[ftl]

Here is another view of the intake, this time looking down the ports. The only thing I was not sure about in shaping the insert was whether I made it too pointy at the top. The guys I showed it to that spend a lot of time porting 2-strokes and some time on 4-strokes thought it would work well.

[RallyBob]

A billet piece is simply a solid chunk of aluminum, usually extruded or forged rather than cast.

Regarding the welding of the insert. If you haven't done it yet, I suggest you bolt the intake solidly to a junk head. Welding that much will warp the intake enough that it may not line up with the intake ports/bolt holes afterwards.

Bob

[opelenvy]

When I got my 73 GT it still had the Solex on it. I, like so many others was skeptical about changing it. Well I came across a good deal on a used Weber that came off a parts car, so I jumped. Wow! What a difference! Now fast forward a couple years...
I have been following everything about porting the intake. I recently decided to take off my Weber 32/36 to do some work on it. Originally I just basically pulled the Solex and slapped on the Weber. I later got a jet kit from racetep with minimal improvements.
So, anyway, I pull off the Weber and realized how missmatched the gaskets, spacer, and heatshild are with the Weber. I am surprised about the original improvement over the Solex with this mismatch. I have not really seen anything about opening up the gaskets and heat shield. I am guessing that they all need to be matched to the Weber. Does the space between the open thick gasket and the two holes of the heat shield restrict air flow at all? Should the material be removed from the heat shield or is the turbulance good?

[namba209]

The pointy tip of the insert you made is actually better than a rounded wider edge. I used to polish transfer ports and knife edge them on 2-strokes way back when. The knife edge helps get more air flow into the transfer ports when the piston coming down pressurizes the crankcase for the incoming charge to go to the top of the piston. I've also match ported and polished 4-strokes, polished the tops of pistons, the combustion chambers, valve faces and the back of the valve up to where the stems go into the guides. There has been a controversy about highly polishing everything in the intake and exhaust tracts, but I feel just getting rid of as much boundary layer air as possible without increasing the bore of the ports too much actually opens the ports by as much as 30% depending on how rough cast the port is to begin with. Using this method, I got a Honda 90cc up to 70 MPH and the RPM was way out of site with a 13:70 final gear ratio. I did the same with an old CL-72 Honda that I made into a 350cc and on a quarter mile oval flat track it got 90 MPH in second gear at 14,000 RPM. Of course both bikes had some serious cam shafts in them.

Ron

[opeldean]

aren't engine blocks cast? like the way an artist makes a wax sculpture..then buries it in a sand (investment)mold. heat the mold..
the wax melts out to leave a void,into the void molten aluminum or bronze is poured in the replicate the shape.I believe the intake was made in this manner.we dont want to make a whole intake...just a SMALL PIECE.

what if someone made a master copy of the metal piece as pictured..make a rubber mold of it and split it open into 2 halves(like a waffle iron)..from the rubber mold we pour in wax to make a wax copy...now you have patterns..that could be easily cast into aluminum with out machining.

I saw a demo of this in a shop class. the instructor used a sand /oil mixture to form a mold around a metal pattern..(in this instance there was no wax pattern). this sort of casting is rougher than lost wax casting as is used in jewelry and dental crown casting.

Has anyone cast aluminum of this size.?(we dont want to make waffles) ..but we could churn out a dozen or so "intake -tented pieces" to be placed into the ported intake

maybe its easier to machine it..I think you could cast a very complex shape..complete with a floor...that would fit very precisely
so that the edges would just need to be welded.

[GTJIM]

That is the most elegant (machinist's!) solution to getting the shape at the bottom of the plenum even and balanced from side to side. No more welding down inside a wee hole, then trying to grind it out evenly - down through the manifold flange.

For small numbers, machining the part from billet stock is probably less time consuming than making up a pattern and casting the bit - and also more accurate.

you could even fix the divider in with epoxy - test run it and then try other shapes. The exhaust manifold heat would fry the epoxy so the final shape would have to be welded in with the manifold clamped to an old head or a special jig to minimise warping as previously mentioned.

This method opens up potential for much easier experimentation.

NICE ONE ftl !

[kwilford]

And to add to John Warga's (aka ftl, a fellow Calgarian) accomplishments, here is a picture of the exhaust manifold that he modified to make it "Sprint-Like". It smooths out the exhaust gas flow, and eliminates the heat stove effect of the stock set-up.

[soybean]

Or this? Thanks, Jarrell

[oldopelguy]

Is this a question, Jarrell? Are you asking if you should port the manifold OR insert the machined piece in the bottom? If so, they are different parts of the same thing. The insert would be useless in a manifold that had not been ported, and a ported manifold would work better with the insert.

If you look a few threads back in this catagory you will find a link to RallyBob's old article on tips for porting you manifold. ( http://clubs.hemmings.com/clubsites/...ech/Intake.pdf ) In that article it describes the grinding required and the benefits to be gained from changing the shape of the floor of the manifold. Take a good look at the article and see if it doesn't answer your question.

Of course, if you're not asking a question, I have no idea what you want to get out of this post.

[soybean]

My ineptness of posting to a particular thread and attaching pictures is showing through. My second post and picture went through, but not the first. This is the first, sorry about the inconvenience. I am in the process of porting my intake and have a couple of questions. I have downloaded and printed the PDF from Hemmings and watched this thread, (hope I'm on the right one now) and have seen several manifolds ported. Which is better to leave the casting such as this picture, or the other picture?

[soybean]

I was unable to get down to my shop to take pictures yesterday and the question I was trying to ask was quite confusing. I have the pictures and here is the question. I have Rallye Bobs article in hand and was curious as to whether more benefit would be derived from cutting the casting, as in the bottom manifold. Or leaving it as in the top manifold. The article seems to favor the top casting, but I have seen both done and was curious to get a couple of opionions before I start on the interior of the manifolds. This is one of the few things I'm able to do right now, bundled up with a spaceheater blowing on me. Thanks, Jarrell

[GTJIM]

The important changes made with these intake mods are the reduction in volume to enhance response and the improving of the airflow into the individual runners.

The peak of the insert must be central for a start but could be moved a bit to even out fuel distribution - even " twisted" to improve mixture distribution!

It may be possible to either bend up a piece of 1/8th inch ali sheet and fit it down from the carb flange hole and weld it in place. Lots of scope for imaginative solutions to getting a raised portion into the bottom of the manifold.

The port entrances need to be blended too and the area into them kept open enough to flow but not too big to cause fuel seperation at low revs ...

Plenty of pics to look at just do what you have the resources for as fitting a bit through the bottom needs a milling machine or a very steady hand with a hacksaw!

[opeldean]

i am thinking about a heat proof -gas proof resin (biostar)that we use at work that could possibly used to make the diverter..instead of machining.

the resin is a thermoplastic sheet resin that can be molding into any shape .its a pressure forming process.

we form it into shape at 427 degrees F..will this with stand the heat of the intake? piece would have to be glued or sealed at the egdes...will high temp red rtv work? piece could be bolted in from the bottom ..but needs a tight seal at the edges.

all resins break down..what temp is safe?

[opeldean]

advise

[soybean]

Bucky, this is Bob was talking about, blowing thru the edges. This was were I did the same thing. Had it welded partway and was not happy with the welder. I am going to weld all 4 sides, then continue on.

[soybean]

This is the other side. Again it could have been welded better.

[soybean]

I started on another manifold and did not get quite as ambitious as the first one. This is what I ended up with. Jarrell

[RallyBob]

You're both right.

At the least, I always break through the casting at the 4 intake-to-exhaust holddown holes.

But usually I also break through at the junction from the top of the intake runners to the plenum rise. So there are another 4 points to be welded here.

[bq97]

Soybean, Where in NC are you? I'm in Fayetteville.

What I did with the bolt holes was I drilled them out to 5/16th inch and inserted a length of 5/16th inch aluminum rod in the now enlarged hole. With a steel punch and on an anvil I "seated" the aluminum rods with a few good hammer blows. The blows kind of squished the rod and filled the holes better. I then welded the top and bottom. After I ported the intake I could not tell where I broke through the bolt holes at but I know I did because the hump is completely gone. I think I have some digital pics around somewhere of the whole process. If I find them I'll post them. By the way I got the aluminum rod at HomeDepot.

BQ

[soybean]

Thank you BQ and Bob. I haven't broken through the plenum yet, but with my first attempt, I came close. BQ, that was a good idea with the aluminium rod, I'll get some when I go in town in the AM.
Between the two, I can probally get my first attempt correct. At least looking better. Jarrell