Adam's Homemade Plenum chamber thread

[Eliot]

Yep not surprised the splitter above the first four trumpets makes a gap of 55mm whilst the front ost trumpets have a gap of 90mm, not good in my limited knowledge of this subject.

And they used the totaly standard trumpet heights. So when you look down the throttle all you could see was trumpets.

[adamnreeves]

Yep, I have that picture, I think you sent me a few! Anyway, now that you have drawn my attention to it I can see what you mean but not sure if this makes a big difference. Have you checked the spark plugs at all?

twin thottles, yes, I thought it might circum-navigate this issue! but only to be replaced with more complex issues like space, lnkages etc!

I had looked at a couple of pictures of the ACT plenum chamber from the inside and cannot see any guides or splitters. Can anyone shed light on this.

It is not easy to see but the guide on the ACT Westfield plenum is the way it is shaped more than having deflector plates inside.
This picture may show it to a certain extend. Look at the back were the plenum is shaped outwards towards the back (which is the front on the photo)


If you could get your hands on one it would be a lot easier to see as the photo does not show it well.
As for a twin throttle in your Westy, front and back, you are having a laugh surly?

[adamnreeves]

Even worse than I thought!

Yep not surprised the splitter above the first four trumpets makes a gap of 55mm whilst the front ost trumpets have a gap of 90mm, not good in my limited knowledge of this subject.

And they used the totaly standard trumpet heights. So when you look down the throttle all you could see was trumpets.

[adamnreeves]

Just to let those of you that are interested know that I am still getting on with this. Probably at a slower pace because I actually have a plenum chamber now. Once I have finished this then I intend on replacing the ali plenum chamber with this.

Still making the pattern, latest is:





The grey bits on the main part of the chamber is where I have sprayed with left over paint to highlight low spots to fill. It is absolutely smooth just doesn't look it!

[adamnreeves]

general shaping finished and spray gloss to highlight surface imperfections and I couldn't resist taking a photo with it placed on the trumpet base!

I have just bought a 72mm jaguar throttle body of ebay. Hope that will work.

[chodjinn]

mate that lokos awesome! I want one, pretty please!!!!!!

[adamnreeves]

Cheers mate. I am pleased with it so far. I still need to do some minor work on this, fill in some minor surface imperfections which is why I sprayed it to show them up. This of course is only the pattern/model. From this I can then make a GRP mould and then I can produce the object from that. Of course the design and fabrication of pattern/model is the most labour intensive part of the entire process.

I think I could be persuaded to sell a few of these once I get to that stage or swap for other parts that I need.

Thanks for the feedback.

mate that lokos awesome! I want one, pretty please!!!!!!

[adamnreeves]

This is the finished pattern for the plenum. Spent hours filling slight imperfections, sanding. Tweaked the design a little and made a radius edge on the end of the chamber. Next I need to fabricate a flange on the intake end to suit my jag 72mm throttle body. I also need to make a weir board so that I can make the mould in two halves.

[ihatesissycars]

I'd be chuffed to bits if i'd managed to make that! Well bloody done!

[adamnreeves]

I am chuffed to bits. Thanks mate. I have spent hours and hours on it at one point I almost threw it because when I sprayed it the first time it managed to go through the thinner parts of the filler and into the foam and reacted and craters formed and this took a long time to re-work. Glad I stuck with it. Suffice to say when I sprayed it today I was watching waiting for another reaction, thankfully didn't.

I'd be chuffed to bits if i'd managed to make that! Well bloody done!

[SC500]

Hi Adam
New to this site and have read your thread with interest, looking good by the way. I work in GRP and have made a few plugs and moulds over the last few years. It can be hugely rewarding as well as extremely frustrating and slow sometimes.

I probably have some good advice for you before you start laying up the mould.

Where are you going to put the split line in the mould? Only two obvious ways I can see but I'm only working from the pictures so its hard to be sure. Are you going to use gel-coat?

[adamnreeves]

I could do with some advice before I start laying up the mould, yes. I have not done any grp stuff before. I have spent hrs and hrs on the pattern. I was thinking of splitting the mould on the top middle, what do you think?

Also bear in mind that the front intake of the plenum is going to have a square flange also, I have yet to make this mod to my pattern. I have the throttle body now so can do this next.

Only problem is with the split on the top then this will a visible line but I am happy to spray black. Some goodies arrived today via courier.

I have tissue, glass fibre, flow coat which shold have black pigmentation premixed. I have resin which is specifically for mould making. I have some PVA which looks black and nasty, I was expecting white glue type stuff! I also have some kevlar matting for when I produce the plenum chamber itself.

If you need more technical details of what I have just received let me know and I will dig it out the garage.

Hi Adam
New to this site and have read your thread with interest, looking good by the way. I work in GRP and have made a few plugs and moulds over the last few years. It can be hugely rewarding as well as extremely frustrating and slow sometimes.

I probably have some good advice for you before you start laying up the mould.

Where are you going to put the split line in the mould? Only two obvious ways I can see but I'm only working from the pictures so its hard to be sure. Are you going to use gel-coat?

[SC500]

I could do with some advice before I start laying up the mould, yes. I have not done any grp stuff before. I have spent hrs and hrs on the pattern. I was thinking of splitting the mould on the top middle, what do you think?

Also bear in mind that the front intake of the plenum is going to have a square flange also, I have yet to make this mod to my pattern. I have the throttle body now so can do this next.

Only problem is with the split on the top then this will a visible line but I am happy to spray black. Some goodies arrived today via courier.

I have tissue, glass fibre, flow coat which shold have black pigmentation premixed. I have resin which is specifically for mould making. I have some PVA which looks black and nasty, I was expecting white glue type stuff! I also have some kevlar matting for when I produce the plenum chamber itself.

If you need more technical details of what I have just received let me know and I will dig it out the garage.

Hi Adam
New to this site and have read your thread with interest, looking good by the way. I work in GRP and have made a few plugs and moulds over the last few years. It can be hugely rewarding as well as extremely frustrating and slow sometimes.

I probably have some good advice for you before you start laying up the mould.

Where are you going to put the split line in the mould? Only two obvious ways I can see but I'm only working from the pictures so its hard to be sure. Are you going to use gel-coat?

Ok Adam

My thoughts so far
You will need gel-coat for the mould and IMO for your parts as well. I would also get two different colours, white for the mould and black for your parts.
The good things about using gel coat on your parts is the split lines can be rubbed out quickly with 400 paper than work up, 800, 1200, 2000, making sure you get all the 400 scratches with the 800 and all the 800 scratches with the 1200 and so forth.

You don't need to be totally pedantic about it but you will be guaranteed to have a fantastic finish when you use a compound and buffer. Take the time to get the finish on your plug to as higher finish as you can to save any extra work.

PVA is good but ruins finishes, my advice would be get a mould release wax. Six layers of it over two days for a virgin plug or mould. Once used a couple of times just one fresh layer from then on is all that's needed.
If you have any complicated areas (you don't at the mo) then use PVA in that area to assist de-moulding.
Also as your part is quite a simple shape I would use a woven fabric instead on the chop strand. This will come through the gel and have a sort of carbon look to it.

I have never used Kevlar but if its anything like carbon than you will need to vacuum bag it which is serious stuff. Do you want a finish like carbon or are you thinking of spraying them? You won't need to spray them if you use gel.

Sorry if that makes no sense haha

[adamnreeves]

Cheers mate, some good tips there. I guess I will need to use the PVA around the throttle flange once I have that bit built as that will be tight and the the finish on the flange not so important.

Ok Adam

My thoughts so far
You will need gel-coat for the mould and IMO for your parts as well. I would also get two different colours, white for the mould and black for your parts.
The good things about using gel coat on your parts is the split lines can be rubbed out quickly with 400 paper than work up, 800, 1200, 2000, making sure you get all the 400 scratches with the 800 and all the 800 scratches with the 1200 and so forth.

You don't need to be totally pedantic about it but you will be guaranteed to have a fantastic finish when you use a compound and buffer. Take the time to get the finish on your plug to as higher finish as you can to save any extra work.

PVA is good but ruins finishes, my advice would be get a mould release wax. Six layers of it over two days for a virgin plug or mould. Once used a couple of times just one fresh layer from then on is all that's needed.
If you have any complicated areas (you don't at the mo) then use PVA in that area to assist de-moulding.
Also as your part is quite a simple shape I would use a woven fabric instead on the chop strand. This will come through the gel and have a sort of carbon look to it.

I have never used Kevlar but if its anything like carbon than you will need to vacuum bag it which is serious stuff. Do you want a finish like carbon or are you thinking of spraying them? You won't need to spray them if you use gel.

Sorry if that makes no sense haha

[adamnreeves]

Okay so I have made the mould from the pattern and had a bit of difficulty removing the mould from the pattern which resulted in having to destroy the pattern and got a few cracks in the mould. I am confident that I can repair the mould up to standard so not too worried about it.

Here's a picture of the mould halves before remedial work and trimming.