Intake manifold construction

[Bernd Felsche]

Sean W Walsh writes:

>Can anyone give me a reason why I shouldn't construct an intake
>manifold using Glass Reinforced Plastics?

You might not have the skill to actually do the work.
There's also the cost of materials, but if neither of those applies,
go for it. A large number of OEMs are going for plastics.

>I have an older 4 cyl lancia engine with a dual throat single carby
>and 4 branch manifold. I'm converting this to EFI and want to
>create a port injection rampipe style intake with a small plenium
>etc. GRP lends itself to "backyard" techniques and since I have a
>bit of experience with boat construction I thought I'd give it a go
>myself rather than getting something fabricated.

The only problem area would be at the interface with the head. A
short alloy tube (about 50 mm long) with flange to suit the head
should provide enough thermal and mechanical isolation to prevent
the plastic from melting. It can also provide machined seats for
fuel injectors should you want to fit them there.

Depending on your skills and resources, you might be able to bond
the manifold directly onto the alloy section.

>What are the problems I'm likely to face : different temperature
>expansion rates of the inlet manifold (grp) and the head (alloy)?
>fatigue from vibration? high temperatures breaking down the epoxy?
>I know there are epoxy resins available that are rated to 150
>degrees celsius so that should be enough (?) any other suggestions?

Don't know about fatigue; chemical ageing may be a problem at
elevated temperatures. You might want to fit a small 12V fan at one
side of the manifold with thermoswitch to prevent heat-soak turning
your craftsmanship into a work of art. :-)

-- 
Real Name: Bernd Felsche
    Email: nospam.bernie at perth.DIALix.com.au
     http://www.perth.dialix.com.au/~bernie - Private HP
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