Let's talk about custom made intakes and runner lengths for a second.

[Psychoholic]

For those playing the home game or who haven't seen my previous posts we've been working on doing a turbo 472 for my '72 M-M hearse but that project got put on a different burner while we finished building our permanent shop. I have fallen in love with the idea of switching to a set of Boogieman heads but between whatever intake I'm using (which generally are 4-5" taller than stock) and the added 1" of height the Boogieman heads provide I'm genuinely concerned that I won't have enough room for the blow through hat through the throttle body.

This has lead to a discussion amongst me and my friends about possibly fabricating our own intake for the project. Thinking that something with a front mounted throttle body would be ideal (LS style) for the turbo piping. Obviously I'm not trying to invest 10's of thousands of dollars on R&D especially when most design flaws can be overcome by forcing atmospheres through a motor.

So first question is: Has anybody here fabricated their own intake?

Second question: How worried would you be about runner length and overall plenum volume? The anecdotal knowledge I have about intakes is that the longer the runner the higher the power curve and that short runners are generally better for torque.

 

[gordon]

What I am doing is using the Boogieman manifold(looks like short tunnel ram with out a top) and I will be fitting the top from a holley snipper multipiece manifold to mine to end up with forward facing throttle body. Holley does sell the separate parts lots of versions to choose from. and will be way lower that any top entry set up. The thing that is slowing me down the most is the Boogieman heads . All the corrective machine work I am having to do . As delivered they do not bolt on and run. The manifold will most likely need the injector bosses re done as there looks like not enough meat to machine to accept the normal size injectors to feed 600-700 lbft. torque. but other wise I like it. I like that it is very low, the runners are a bit short and the plenum a bit big but I know how to deal with that. It is a good starting point.

 

[Psychoholic]

What I am doing is using the Boogieman manifold(looks like short tunnel ram with out a top) and I will be fitting the top from a holley snipper multipiece manifold to mine to end up with forward facing throttle body. Holley does sell the separate parts lots of versions to choose from. and will be way lower that any top entry set up. The thing that is slowing me down the most is the Boogieman heads . All the corrective machine work I am having to do . As delivered they do not bolt on and run. The manifold will most likely need the injector bosses re done as there looks like not enough meat to machine to accept the normal size injectors to feed 600-700 lbft. torque. but other wise I like it. I like that it is very low, the runners are a bit short and the plenum a bit big but I know how to deal with that. It is a good starting point.

I'm definitely looking at the Boogieman but given how much you'd have to remove it might be easier for us to just cut something on the plasma for the flanges and weld runners (my math has it needing 5.2 cm of runner diameter and 32 cm of runner length). The plenum volume of that Boogieman intake has me a little worried about it wanting a lot of RPM to be ideal so a tapered 'log' might be good to keep velocity up for the rear runners.

What needs to be done to those heads to get them to run?

 

[gordon]

Going with fuel injection I think the runner length and plenum are not as critical as on a carb combo due to lack of vacuum needed for fuel signal. I also plan on reducing the volume of the plenum after I see how it runs. As far as the heads go , right off the bat the intake face was not cut correctly. It is supposed to be 90* to the deck surface on a Cad. This one was cut at an angle giving a .062 gap at the bottom of the port inlet and touching at the top. It would have sucked oil out of the lifter valley into the ports and would have been a massive vacuum leak. I had to make a .063" cut on that port face of the heads. Now that cut makes the intake manifold fit up off a bit which I will deal with by using a different thickness intake gasket. Next the cyl. head dowel pin holes looked like they were drill with a broken drill bit in a drill press with worn out spindle bearings. Cads use standard Gm block/head dowels .309" , these holes measured .325" were not round and were tapered all the way down and not drilled in the right place . They were too far apart. I am in process of reaming to a size that I plug with aluminum dowel then get drilled and reamed in correct place and size for alignment dowels in block. On each head one of the lower head stud holes did not get spot faced. This is a partial list. I am very disappointed in the QC but on the other hand I am glad that they are available. It is not a cheap undertaking to make these available. In Several months I will post all that I had to do and how well it turned out. Like I said I am glad I was able to buy them but the QC is way below what it should be. Sending them back is not an option for me so I must take care of this stuff here .

 

[Darius]

For those playing the home game or who haven't seen my previous posts we've been working on doing a turbo 472 for my '72 M-M hearse but that project got put on a different burner while we finished building our permanent shop. I have fallen in love with the idea of switching to a set of Boogieman heads but between whatever intake I'm using (which generally are 4-5" taller than stock) and the added 1" of height the Boogieman heads provide I'm genuinely concerned that I won't have enough room for the blow through hat through the throttle body.

This has lead to a discussion amongst me and my friends about possibly fabricating our own intake for the project. Thinking that something with a front mounted throttle body would be ideal (LS style) for the turbo piping. Obviously I'm not trying to invest 10's of thousands of dollars on R&D especially when most design flaws can be overcome by forcing atmospheres through a motor.

So first question is: Has anybody here fabricated their own intake?

Second question: How worried would you be about runner length and overall plenum volume? The anecdotal knowledge I have about intakes is that the longer the runner the higher the power curve and that short runners are generally better for torque.

Psycoholic, Howdy Brother!

About that last paragraph above you have it backwards: long runners aid low end torque while short ones aid high rpm HP.

Hope that helps,
bro. d

 

[gordon]

Darius has it correct on the long and short of runner length trends.

 

[Psychoholic]

@gordon That quality control sounds horrific! I'd love to see some good pics of the heads if you have them or wouldn't mind posting a few?

Psycoholic, Howdy Brother!

About that last paragraph above you have it backwards: long runners aid low end torque while short ones aid high rpm HP.

Hope that helps,
bro. d

That was always my understanding too but heard otherwise the other day. Probably still accurate.

I used to have a '97 Cobra that had Intake Manifold Runner Control (IMRC) plates that would open up at 3250 RPM to switch between the short runners down low and long runners. When I took those plates off it was a total pig down low.
Doing the math on all of this is super fun actually. Currently researching on if doing Helmholtz resonators or velocity stacks inside the plenum makes more sense and generally what the optimum runner length is for a turbo motor. Plenum size and design is a bit more challenging.

 

[gordon]

If I can figure out how to post pictures on here I will . Otherwise it will have to wait til around the first of Aug. I need to go spend some time with the elders that are not doing well . Dang I am an elder but these are my elders. If you want to see some of what I am talking about youtube video by Eric Weingartner called (cyl head development) . He actually is grinding on an unfinished boogie man head and tests it on the flow bench.

 

[gordon]

 

[gordon]

 

[gordon]

Ok I fumbled my way into inserting the pictures. The two pictures of the intake face are to show what I had to contend with as far as the angle being off . The picture showing the adjustable square was just to simulate the angle found on the heads intake face as purchased. The one with the machinist square shows the correct 90* face angle. There is one picture that shows lack of spotfacing for a corner headstud on both heads. The CNC program needs a slight edit on that line of G-code. The pictures showing the rough cuts in the chamber are just not acceptable to me. Looks like some one is trying to shorten machine time by using less moves and faster feed rates. I still like these heads , I will keep working on them until I am satisfied. I would like to see the finish work be to higher standards for the money paid but I don't run the business. When I get done I will post all that I did and how well they fill the bill for making bigger power on the Cad 472/500.