Carb manifold to head gaskets...........

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jeffdavison

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What's a better choice of material for the gaskets between carb manifolds and the head?
I've seen two types, Paper and Phenolic.
If paper, then is it well to put a gasket grease susch as hylomar on them? or just plain?

Thanks

JD
 
I don't use sealers on carb to manifold gaskets. I have seen what amateurs do though when they put too much on.
 
Hi,

I always understood that the purpose of the gasket was to provide heat insulation to the carbs from the head so use phenolic.
paper and sealant will not give the same insulation.

Regards,
Sean
 
Paper.... ???? You mean gasket material made up of "paper like" substances to create a cardboard gasket material readily available in various thicknesses for oil and petrol from most auto outlets... or newspaper, weeties packets, toilet paper or A4..

Good quality commercially rated "paper" gasket material cut to size or whatever you received from supplier, with a smear of "plain" grease is all i have ever used.. In that situation and other places i may use silicone/hymalar. Horses for courses...
 
olChris said:
Paper.... ???? You mean gasket material made up of "paper like" substances to create a cardboard gasket material readily available in various thicknesses for oil and petrol from most auto outlets... or newspaper, weeties packets, toilet paper or A4..

Good quality commercially rated "paper" gasket material cut to size or whatever you received from supplier, with a smear of "plain" grease is all i have ever used.. In that situation and other places i may use silicone/hymalar. Horses for courses...
Click to expand...

If I were to use the soft toilet paper that I use -Im pretty sure it wouldn't last 10 minutes :!: :shock:
 
They were phenolic when the bikes were new and no sealer was used. Mine were about 1/8" thick. I bought some replacements fairly recently and they were only half the thickness so I kept my old ones on there.
 
batrider said:
They were phenolic when the bikes were new and no sealer was used. Mine were about 1/8" thick. I bought some replacements fairly recently and they were only half the thickness so I kept my old ones on there.
Click to expand...

Sorry Bat, but i can lend you a copy of this if you want.... cant help myself sometimes....

Carb manifold to head gaskets...........
 
Player#3 said:
Hi,

I always understood that the purpose of the gasket was to provide heat insulation to the carbs from the head so use phenolic.
paper and sealant will not give the same insulation.

Regards,
Sean
Click to expand...

+1

Slick
 
I dont ever recall ever seeing a carb bolted directly to a head.... Then i could be wrong..

I can only recall them bolted to a manifold, same or similar to Commando type in principal. Generally having surface area heat ditributing "fins" moulded in to alloy. Or made of cast iron (or alloy) which doesnt transfere heat readily.
Therefore i dont believe that the phenolic/plastic/composite gasket will do SFA for heat insulation in the big picture unless its an inch or more in thickness as i seen in places..

It will have some insulation properties agreed, but irrelevant.. were nearly almost off topic here once again :lol: :lol: :lol: :lol: :lol:
 
Starting with the earliest norton heavy twin in 1949 thru 1975, they all use hard fiber insulators against the head.
Most earlier manifold are very thick and rigid, even through atlas.
If you put paper, which is compressable, you often ruin the early commando mainifolds 06-0509 by warping the flange. I see this quite frequently. These are a quite poor design.
The later stronger commando manifolds (guess why they upgraded the design :oops: ) could still be bent by using incorrect gaskets and over tightening.

Carbs go directly on the manifold and are sealed by the oring. Nothing more should go here.
 
On one of my cars I substituted a paper intake manifold gasket for one made of 3/8" phenolic and with a laser thermometer, at idle on a warmed up full operating temperature engine, I recorded a 100* drop in the temperature of the exterior surface of the intake manifold.
 
I like the extra thick paper composite type at head for the insulation and bit of crush to hold sealing clamp force w/o distorting the carb flange. Between carb and manifold I like softer rubbery thick one I cut myself for a bit more instulation and vibe dampening plus clamp force sealing retaining w/o all that much torque applied. I was very suprised by a crude expedient head gasket whose surround intruded roughly into air flow thinking good enough to break in on for 1000 miles then got to WOT and decided I liked against the grain path there.
 
I've noticed that the 32mm (850/Combat 750) insulators are about half the thickness of the 30mm (750) type.

From past experience, pretty much all the nasty warped carbs I've scrapped have been removed from bikes which were missing the insulators when I got hold of them.
 
B+Bogus said:
I've noticed that the 32mm (850/Combat 750) insulators are about half the thickness of the 30mm (750) type.

From past experience, pretty much all the nasty warped carbs I've scrapped have been removed from bikes which were missing the insulators when I got hold of them.
Click to expand...

Are you sure about that?
J
 
I have taken apart a couple different bikes with phenolic spacers that have a thin layer of softer gasket material on each side for sealing. Anyone else seen these?
 
B+Bogus said:
I've noticed that the 32mm (850/Combat 750) insulators are about half the thickness of the 30mm (750) type.

From past experience, pretty much all the nasty warped carbs I've scrapped have been removed from bikes which were missing the insulators when I got hold of them.
Click to expand...

I just pulled my inventory of hard - head/manifold spacers, over a dozen. I seem to only have 28.5mm or 32mm. I have a single pair of 30mm spacers, but I made them myself for my RH-10 heads. All the original ones and my copies are .125" (1/8") thick.

I do have one lone pair of thin spacers.
 
I looked in my parts and found one 30x32 piece; 30 on the head side and 32 on the carb side.
It has more fins on the casting and a screw in nipple for the balance tube.
Somebody painted it blue long ago.
Carb manifold to head gaskets...........
 
Bob Z. said:
I looked in my parts and found one 30x32 piece; 30 on the head side and 32 on the carb side.
It has more fins on the casting and a screw in nipple for the balance tube.
Somebody painted it blue long ago.
Carb manifold to head gaskets...........
Click to expand...

FWIW
That is an early commando 28.5mm mainifolds 06-0509. It is an example of the thin flange type. They were produced before any 32mm 0r 30mm norton head existed. So it's larger size is a modification and not original.

I also have a set like yours, modified as per Dunstall on a hot rodded 71 commando. It had a huge assortment of the Dunstall catalog bits. but it was not a real Dunstall.
I prefer to use the later manifolds as being stronger.
 
dynodave said:
B+Bogus said:
I've noticed that the 32mm (850/Combat 750) insulators are about half the thickness of the 30mm (750) type.

From past experience, pretty much all the nasty warped carbs I've scrapped have been removed from bikes which were missing the insulators when I got hold of them.
Click to expand...

I just pulled my inventory of hard - head/manifold spacers, over a dozen. I seem to only have 28.5mm or 32mm. I have a single pair of 30mm spacers, but I made them myself for my RH-10 heads. All the original ones and my copies are .125" (1/8") thick.

I do have one lone pair of thin spacers.
Click to expand...

I should have qualified my original post - the ones I've got from Andover Norton in the last couple of years have been as I described - I'll dig out my old ones to see if they're different.
Just an observation based on my experience ;)
 
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