Port epoxy life

[NeilRoshier]

Is there an expected life span of epoxy used in intake ports? The original ali would be 'roughed' up with 60 grit paper or by a burr, then cleaned with acetone, prior to the epoxy being used. Epoxy is JB weld 'steel'. The epoxy will be exposed to fuel and may also be in quite large amounts/thicknesses ie more than 5mm in places.

 

[willeng]

NeilRoshier:
Life of epoxy in intake ports is dependant of a certain number of things, eg:

Reversion: It won't last long unless controlled. The smell in your nose lasts awhile though---about 3weeks from memory.

Temp

Application of mix.

Surface preparation etc etc.
Check it from time to time.
I take it there aluminium heads you say ali i would recommend using an aluminum epoxy --Try DEVCON they have what your after.
Make sure you get a good key to the parent material.
It pays to make small opposed direction holes at either end of the fill to make certain the epoxy will stay put, force the epoxy into these before filling the rest.
Don't be afraid to rough up the area.
Try to avoid very thin sections.
Blend in all the edges---carefully.
Acetone is a good cleaner-- let it dry.
Let the mix cure by itself-----don't heat.
Hope this helps
Not sure what fuel your using, or for that matter what affects different types of fuel will have on this. I'm sure someone else could help with that.

 

[NeilRoshier]

Willeng thanks for taking the time to reply. Yes the heads are alloy and we would like to explore different port shapes by machining and filling where necessary to improve a short turn radius and also increase port angle relative to valve etc. So although initial port will only see a flow bence the shape will be replicated and used, hence the query. I am not sure if the devcon epoxy is available locally (australia), I will check.
Where the epoxy attaches can be roughed out with a carbide ali burr...which should provide an adequate key...reversion amounts are unknown.

 

[willeng]

NeilRoshier
The DEVCON is available here--AUSTRALIA through outlets such as BSC & many engineering suppliers.
When roughing surface make sure it has more of a coarse dull finish. Most good burs cut a little smooth for this.
I use modeling clay or similar to experiment with, it's cheap,quick & easy. The final port shape is then moulded & finalised ready for Epoxy, for aluminium use DEVCON (F).

 

[NeilRoshier]

Willeng I will try a few places in Melb then for the ali filled-epoxy. When you say moulded do you mean using a silicone material poured into the final shape port? (I have used such materials for FGI etc)...I was tempted to cut the head to have a look at the final shapes (given the secondary purpose of the head was as the basis for a club-mag type article).
How do you find the epoxy holds up to the thermal loads ie the heating/cooling over time?

 

[willeng]

NeilRoshier:

Any of the air curing rubber or silicone moulding compounds will do the job as long as it is not to rigid to remove from the port, theres on old book
(The Chevrolet racing engine)
by Bill Jenkins that would be worth a look, this shows port moulding.
Whenever we have used Epoxy fill it has been for testing or for our own application & in both cases it has only been to see if were on the right track before welding in more permanent pieces.
I know for the short term it has worked for us but as for a permanent fixture i'm not sure how long it would last.

Maybe Larry or someone else has used this for longer periods of time, it would be good to hear there thoughts on this.

 

[NeilRoshier]

there is a step by step guide in Dalton's Practical Gas Flow and I have used the product for some sculptural work in the past. The silicone is easy enough to use and perhaps preferable to the reusable heat softened material.
Welding may or may not be problematic as one port idea was to macine away a large section of the top of the port and inset 2mm wall thickness ali tube to create a semi-down draft type port.

 

[patprimmer]

Neil

I use charmac Pipe Jointing Compound.

it is avaliable from plumbers supplies and is intended for jointing and repairing cast iron pipes, particularly sewer pipes. It is also known as Hydro Epoxy. it is a two part epoxy putty that can be mixed in the presence of water, and disperses in water untill it cures, so you can use water to control viscosity and to wash surfaces clean.

I have used it to repair heads and in some cases exhausts and manifolds. It stands up use as a filler to block exhaust crossover ports in V8 inlet manifolds, and also to repair water passages in aluminium manifolds used in boats with raw (salt) water cooling. I have seen manifolds bogged up with this still working in my Ski Boat after 25 years.

If I do inlet ports, I try to put mechanical pegs in the port, as well as all the roughing up, I try to get a small aluminium bolt and drill and tap the port floor from the valley side and screw the bolt in so the thread protrudes into the port to a significant degree.

Regards
pat

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[willeng]

patprimmer

Pat what do you think would be the max temp range for the HYDRO-EPOXY if subjected to continuous heat.

 

[patprimmer]

I don't know. The resin is probably rated to about 250 deg C

I started useing it, because my brother, who was a plumber, had some in his Ute while we were on holidays for some water skiing, and the manifold started leaking. As we were in a relatively remote area, in the middle of the Christmas break, we used what we had. As it is still going about 25 years later, we have developed some confidence.

In one spot it fills the passage that is directly attached to the exhaust port in a small block Chev.

For many years now, I have used it as a matter of course in any boat or high performance engine to block exhaust heat to the inlet manifold. None has ever burnt out.

I would never consider useing it in the actual exhaust port, but I don't hesitate to use it in the inlet, so long as there is a good mechanical key to hold it in place during thermal cycling.

Regards
pat

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[NeilRoshier]

Pat have you found similar durability when placed in contact with alum?

 

[patprimmer]

Yes

The heads are cast iron, but the manifolds are aluminium.

I must emphasise that the holes were irregular shape, and fully blocked with a large plug, so it was very well keyed in or retained in all cases, but it has withstood many years in a ski boat where we regularly barefoot, so it sees relatively long spells of high load.

Also, on thre water crossover to the thermostat housing, it sees salt water at up to 100 psi. The original Chevrolet LT1 manifold corroded to a leak in about 6 years. The repair has lasted over 20 years.

Regards
pat

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[NeilRoshier]

Thanks for that Pat, my only other query is the fuel resistance, given that if I go this way it will receive fairly constant exposure to PULP.

 

[patprimmer]

Mine have only been exposed to Avgas, leaded super and unleaded over the years.

Regards
pat

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[patprimmer]

Mine have only been exposed to Avgas, leaded super and normal unleaded over the years.

Regards
pat

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.