FE-FC Holden Discussion Forum

Hey guys ... have just re-built and re-kitted two standard BXOV-1 Strombergs and about to mount on a Lanspeed Twin Manifold ... wondering if I should fit heat insutator/spacers ... any thoughts ?  Experiences ?

Thanks, Dave.

Good question Dave,

I've been running twins for a while without them and I've seen sets with and without them, I've got a few spacers hanging in the shed just never bothered to see if it makes a difference or not ???
Then again I don't have a choke on my carbies either as I'm happy to sit there and let it warm up with my foot on the gas ;)

Will be interesting to read the responses.

Mick 8)

It is a good idea to fit the insulators ;D the idea is to keep as much heat out of the carby as possible  to stop vaporising the more dense the fuel the bigger the bang .......FC427.....

Mark, thanks for that info, but are there any other benefits of fitting a spacer? What effect (if any...) would a longer inlet tract have??

cheers, jack

Jack are you talking about increase in velocity because of the height  ??? ???......FC427....

Not sure, Mark... I think I recall some theory about a longer inlet tract possibly giving increases in mid-range torque in modified red sixes...

But then again, I AM an old bastard, and increasingly find myself thinking of the 'hereafter'...

(as in walking down to my shed to do a job and when I get there thinking "WTF am I here after"...  :D)

Hi Dave,

I asked a similar question an number of years back. See link below-

http://fefcholden.org.au/forum/index.php/topic,9443.msg56553.html#msg56553

I had read a book on small block chevs and it indicated that a small increase in Hp can be gained by increasing the size of the spacer. Unsure how but would be something to do with atomisation I would suggest.

I didn't put spacers in mine because it would mean getting the studs replaced.

Have a read of the thread listed above.

Cheers

Rod

Thanks gents for the responses so far ... I read somewhere that extractors can reduce inlet manifold temperature ... I am fitting them too so does that make any difference ?

Cheers, Dave.

Hi Dave,
The insulator is there to help prevent heat transfer from the manifold to the carby.
It "could" help mid-range flow, but because it is so short the results would probably be immeasurable.

As you are running twins the manifold almost certainly does not have a hot box, so the inlet manifold is not heated by the exhaust anyway.

The same applies to extractors.
As there is no hotbox, the exhaust does not heat the inlet manifold, so it (the inlet manifold) will run cooler.

I have seen old racing greys develop ice on the manifold where twin carbs are mounted. (TRUE!!!)
With triples the carbs are closer to the head, therefore warmer, and this would rarely occur.

However, some older multi-carb manifolds had a rudimentary hot-box of sorts.
The manifold metal was thicker where it passed over the second and third exhaust pipes, and in fact actually touched in most instances depending on style of extractors.
We had to file a little (or big) bit of clearance depending on the application.

I hope this helps,
Cheers,
Gaz

I'm getting the idea that the insulator was always fitted on the standard manifold with hotbox but I never seem to see them fitted on twin or triple manifolds ... What thoughts ???

many of the twin carb manifolds actually curve up and sit much higher than the standard manifold. With the carbs and reasonable air cleaners on top you can start to get pretty close to the bonnet. I suspect that many people leave spacers off for this reason i.e. to actually gain a bit of space (I did).

Jon