17 replies to this topic

[LXCHEV]

Hi guys,

What are your thoughts and experiences from using phenolic, wood, or plastic carb spacers? The idea is to reduce the amount of heat transfer from the intake manifold to the carb. This can only be a good thing - the cooler you keep that carb and fuel bowls, the more power - or more consistent power you should be able to make - especially in hot conditions.

If you browse the various speed shop websites, there are endless choices - open, 4-hole, divided, etc, plus different heights.

I'm very keen to fit one to my 383 small block. My reason is purely for the heat transfer advantage, I don't actually need the added height or anything as I already have plenty of plenum area, and I'm happy with my rev-range etc.

So I have a specific question - I want to know which style of spacer I should choose to suit my manifold/carb. I'm running a BG Mighty Demon 4 barrel (squarebore). The manifold is an Edelbrock 7501 - RPM Air-Gap Dual Plane. If you look at this photo below, you can clearly see the dual planes, and also note the cut-out section of the middle dividing wall (this cut-out is the main reason why I'm asking this question):



Ok, so spacer choices:

Firstly, height-wise, I'm leaning towards 1/2" tall (as small as possible).

This is a 1/2" phenolic 4 hole:


This is a 1/2" phenolic open:


This is a 1/2" wood fibre laminate 'Divided Plenum':


Check this one out - 1/2" wood 'Divided Wall' - very strange shape - what on earth for???


THOUGHTS????

[Heath]

I like the concept for the material choice, but I really think you need to test different combos and see what actually works, there is no 'right and wrong'

[76lxhatch]

Not many of the two-hole ones around, but they would certainly be good in some instances, perhaps even here. Maybe that one has an odd shaped hole to suit specific carb throttle butterflies?

As I understand it the wood ones have a pretty short life, you need to keep replacing them.

Judging by the gap between the manifold planes its not intended to be entirely open, so I'd be looking at a separator of some sort. Usually the four hole spacer is sticking on the safe side, you can't go too far wrong.

[FastEHHolden]

I really think it makes stuff all difference...also take into account you need heat for vapourisation and that the venturi's drop the temp to the point that its possible to get ice.

Yes the manifold gets hot...but does the air have long enough to?

[V-SLR5000-P]

Wooden spacers are effective, cheap and easy to make. I have used an open MDF spacer on a
Victor Jnr with no issues. A cheap kitchen cutting board is also a good source of spacer material.

[FastEHHolden]

Infact reading that back...it's really not related

[76lxhatch]

A cheap kitchen cutting board is also a good source of spacer material.

That does work but they have a very short life. Before making one I checked out the melting temps and resistance to fuel/solvents and it all seemed good, but it still came out very warped and yellow after only a few months.

[lxsstorana]

I had a little problem with my 383 chev hatch early last year when it would sometimes develop a miss on hot days or when stuck in traffic.

Took it to my mechanic who said the fuel was getting too hot. He fitted a 1/2 bakerlite spacer (4 holes I think) and he recommended changing air filters.

I got rid of the edelbrock solid metal top air filter(was 3 inch) and went for a K & N 4inch filter with extreme top that allows air flow through the lid.

Problem solved. Car runs great and can handle hot days and city traffic. Here's a couple of photo's.

Mick.

Edited by lxsstorana, 03 March 2010 - 05:37 AM.

[ls2lxhatch]

The Kostecki carburettor vibration dampener has been reported to deliver results on the dyno. It reduces vibration and heat transfer.

It was discussed in your previous thread.

[LXCHEV]

Great feedback, thanks for ALL the replies. As always, excellent discussion.

Firstly - yes I have been suffering from heat issues in warm weather. It seems the fuel is getting too hot. If you touch the carb bowls they are scorching hot. Exactly what lxsstorana described above - "it develops a miss on hot days or in traffic" - is exactly what I have too. So I am rapt to hear that this fixed up your problem, it gives me hope!

It sounds like the 4 hole spacer is a safe bet. The divided spacers seem very unknown to anyone I chat with.

I'm not hoping for / or expecting to see any gains or improvements here, I purely want to try and cool the fuel down. (My previous thread from 2006 was more about trying to get performance improvements). It was good reading over that again though.

It's very interesting about making your own from MDF / Kitchen cutting boards etc.... LOL... that's pure old-school hot rodding at it's best

PS. Just for interests sake, as follow up to my other old thread - I did end up trying a 'Street Sweeper' (Super Sucker style aluminium 1" shaped spacer) to suit dual plane, on my 383 a year or two back. It went backwards on the dyno which surprised me, but it was only at a club dyno day, with no specific tuning done for that spacer. So it's possible with tuning, it may have improved, but from a quick 'bolt-on' it didn't anything spectacular at all.

Either way, it looks like I'm now on the look-out for a 1/2" 4 hole spacer - just need to decide on what material to use.

[myss427]

I had a bad problem of fuel vaporisation, before I made a Marine ply spacer. Cured it straight away! Coated it with a marine varnish that was petrol proof and has lasted over 10 years now with no problem at all. Cost $35 all up to make!