Hi fella's,

Well with my 351 turbo project underway, I've decided to attempt to build my own plenum to replace the upper Edelbrock manifold. I realise there's alot of math's involved and it's a tedious project, but why not!

Run down on the engine is, 351 block bored to 0.030", giving it a displacement of 357 ci. I'll be running stock camshaft with gt40x Aluminum heads and the Edelbrock 351w lower. With 'H' beams and Probe forged pistons. I'm just giving a run down of the engine to more accurately determine plenum volume and design.

I've attached some photo's of the Edelbrock manny.

Now I've done afew measurements with some vernier calipers and a measure tape. Sorry but this might be abit confusing.

Ok...

Runner size for the top of manifold. ( Part that bolts to upper ).
First measurement is smallest runner width and second is full size as it flares out towards top, as people with edelbrock manifolds will know.

8. - 46.12mm x 27.29mm
47.87mm x 29.84mm
7. - 46.82mm x 27.49mm
47.55mm x 29.70mm
6. - 46.14mm x 27.55mm
47.70mm x 29.71mm
5. - 47.06mm x 27.46mm
48.06mm x 29.91mm
4. - 46.36mm x 27.87mm
47.67mm x 29.68mm
3. - 47.88mm x 27.85mm
49.16mm x 29.66mm
2. - 46.19mm x 27.70mm
47.97mm x 29.66mm
1. - 46.96mm x 27.45mm
48.01mm x 29.55mm

FRONT

Measurements of dimensions for either bank.

1. - 45.92mm x 27.91mm 2. - 45.64mm x 28.75mm
3. - 46.26mm x 27.53mm 4. - 46.92mm x 28.13mm
5. - 45.99mm x 27.97mm 6. - 46.83mm x 27.89mm
7. - 45.77mm x 27.62mm 8. - 46.40mm x 28.06mm

Now length of runners ( both inside and outside of arc length )

8. - inside: 162mm Outside: 200mm
7. - inside: 160mm Outside: 200mm
6. - inside: 160mm Outside: 200mm
5. - inside: 160mm Outside: 200mm
4. - inside: 160mm Outside: 200mm
3. - inside: 160mm Outside: 200mm
2. - inside: 170mm Outside: 200mm
1. - inside: 170mm Outside: 200mm

Alright I'm hoping everyone can understand that? Now I'm asking for some feedback on design and best way to work out volume chamber etc.

any help would be great!

 

 

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Here are a few designs that may be promising..

 

 

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The last 2 look good. Front mount TB and smooth even distribution.

Brett

Brett, Yeh as this won't be a street car I think a front mounted T/B will be the way to go.

I've been looking through the interweb's resources and plenum size for turbo applications varies from half engine size upto double engine displacement. I'm thinking with a low boost '51, a plenum volume of about 6 Litres would be fairly well suited? Or should i go larger.

According to alot of people, shorter, larger runners are better for turbo engines. I could always get some meat machined off the top of the lower manifold if need be. Now settling on a design may be abit of a headache..

With it being a large V8, turbo lag won't be a problem, and therefore plenum size won't matter too much as it will always be under pressure, unlike an N/A setup. I spose it will be some trial and error.
I just need to settle on a plenum volume best suit to the engine.

Well i got bored today and this is what I've got to show for it.. one dodgy as f**k cardboard plenum!

 

 

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Why not just get a carby based manifold and use a 4 barrell EFI carby and hat on top??? much eaiser and look realy good.

that plenum isnt too bad man lol

Well to be honest this way will work out cheaper for me, as all i have to buy is a T/B and mounting bolts. It's also a good opportunity to have a go at building my own turbo plenum. I want to keep the Edelbrock lower i have atm. I reckon it could turn out really well if i take my time and do it right. It may easier with a EFI carby and hat, but the hard way is more of a challenge and a learning experience.

cheers for the feedback

Dont go cheap on me dude hahaha jks

Like i suggested to u with turbo manifolds i also think u should go this way with intake or other off the shelf EFI manfolds as they work. I'll post up or pm u some stuff about intake manifolds and u will soon understand that if its not done right in all aspects it will rob u of power and reliability.

Im have TFS track heat with over 650 rwhp.. No inlet issues..
Edelbrock, Holley would be the same...
On a 351 & forced induction I would like to see the TFS boxed inlet...
http://www.trickflow.com/partdetail.asp ... 150&orig=1
They are high rpm power band.. BUT with forced induction it all changes to much lower power band...

Mick, that would be good mate, I want to run a NOS system on the donk as well. So my edelbrock lower with a RPM2 upper should fit the bill? Then i can fit direct port injection to the lower manifold.
I can get the RPM2 upper from summit for a fairly good price. I just thought i could save abit of coin building my own plenum, but looks like off the shelf set-ups are the way to go.

What size T/B would be sufficient for such a set-up? 80 - 90mm?

How would the edelbrock RPM2 size up EBXR?

You already have an RPMII lower? I could be wrong, but I think I've read that the RPMII upper won't fit on the RPM lower.

Fabbed will be much more impressive to look at, but off the shelf is going to save you bulk-loads of time and probably money. Have you looked at the BBK SSI-R? I don't know how this performs against the TFS Box-R. Actully, it'll only mount to the driver's side anyway. May not be any good for you.

The Edelbrock will do fine.. Being forced induction... I would mill the runers on inlet alittle shorter giving larger plenum. Which is better for forced induction..
The is why the plate on plenum is there...

The RPM upper will fit that lower, I know because it is my old lower, and i fitted it to see if it would. The NOS polate i have is for that manifold. If you are interested in the NOS plate PM me for a price.

Brett

So both the RPM and RPM2 upper will fit the 351 lower??

PM sent Brett