[TinjunTribe]

Filling Crossovers:

If considering Cotronics products heat riser filler.....!don't consider 907GF!, as sold by Cylinder head abrasives for this purpose. Look into the other types that people say they ARE having success with, possibly the 940.

I got my passages sterile....filled. 5-6 weeks later after letting them sit in a +100 deg garage results follow:

Noticed small air pocket near edge in bowl when blending down surface
Ground into void with 3/8" ball stone and was going to fill this pocket with more 907GF
907 GF hard 3/8" thick at surface, beyond this point, consistency of SOFT clay
Check at intake surface, same story, 3/8 in, mush

Might work if filled in sections. But in one fill, crust forms at surfaces, trapping in the water component, cant evaporate, stays soft. Heat cure will cause the water component to steam, push out and crack the hard outer surfaces.

I personally don't like the "fill in sections idea", if the final section near the bowl could have any fissures between it and the one before it.....I want a constant plug.

My porting is done....I am contacting SD to perform valve job, and FILL X-OVERS WITH ALUMINUM, and recommend cam based on flow #s of my work. I want drive the hell out of this particular car, so I want the filler that is tried and true in high engine hour environment, not some limited use street stripper that gets taken apart and checked every few months.

Anywho, wasn't all that bad getting it all out at least......

[BVR421]

well thats crappy for you but maybe save someone else from headaches
my 265cfm 6x heads were ported and filled by SD, thats the way to go. Very happy with that.

"I am contacting SD to /snip.........snip/ and recommend cam based on flow #s of my work"

You mean you would rather have a professional recommend a cam rather than rely on random opinions from an internet forum audience?

[Murf'sDad]

Originally Posted by BVR421

You mean you would rather have a professional recommend a cam rather than rely on random opinions from an internet forum audience?

Who are you calling "random"? Beside, everyone already knows that if something is said in an internet forum it is absolutely, undisputably true and that every forum member has intimate, indepth, knowledge of all aspects of the subject being discussed! Who needs a professional opinion?

Stewart

[TinjunTribe]

Theoretically, there are several members here I'd trust to pick a cam for me, but even they can't make an informed recommendation without some idea of the cam my heads want (or don't want) based on what I've done to them.

We can, however, recommend to stay the He!! away from 907GF

[lust4speed]

Sounds like you possibly went way too light on the catalyst. I thought you might have had some operational problems with the mix not holding up to exhaust flow or something, but not hardening just about has to be not enough hardener mixed in (or a really screwed up batch of material).

[Half-Inch Stud]

Whatever I bought from Cotronics has held-up: I did a "Visual Inspection up the Exhaust ports yesterday and all 4 Valvebowls show the Cotronics stuff holding up well after 1 month.

Search & Post the Thread that I documents the conversation I had with the Cotronics Materials engineer, and the stuff I bought. HIS

[Half-Inch Stud]

Here's what I said in that Thread http://forums.maxperformanceinc.com/...led+crossovers

""""""I'm going to try the 940 HT for it appears to offer the best adhesion & strength because it is a 2-part, whereas the 904 & 907 are water-based so they are less dense, lower thermal conductivity, and don't really wett to the cast iron like the 940 does.

Resbond compositions:

904: Zirconia powder in water suspension, suitable for thin gasket-like filler with mild adhesion. Water-evaporation, causes minor shrinkage, weaker bond and porosity. A low-strength filler.

907GF: More putty-like, yet relys on water-evaporation for 'cure', thus again poor adhesion to cast iron due to poor wetting. Probably stronger than 904.

940: Zirconia powder in thin epoxy suspension (I don't know about the water content) so it is a 2-part (pint can of powder & activator tube). Has excellent strength suitable for thick fill sections.

940HT: Alumina powder in thin epoxy suspension (I don't know about the water content) so it is a 2-part (pint can of powder & activator tube). Has excellent strength suitable for thick fill sections. Has higher thermal conductivity & CTE than 940, as is deemed most suitable for the Exhaust-crossover fill application.

Discussion: the Cotronics Resbond engineer says they have not tested any of their products in this sort of application, and they remain hopeful that it can hold-up to the fire exposure in the valve bowl. Our discussion revolved around how aluminum survives fire due to having ability to conduct the heat away rapidly, and avoid glowing orange. In that regard the tech engineer said the 940HT is the best bet for that application, and re-iterated that they have not evaluated nor tested their products that way.

HIS""""""

Therefore I bought 940HT. I recommend the 940HT. But I'm a nobody so it is still your choice.

[TinjunTribe]

[QUOTE=Half-Inch Stud;4041985]Here's what I said in that Thread http://forums.maxperformanceinc.com/...led+crossovers

940HT: Alumina powder in thin epoxy suspension (I don't know about the water content) so it is a 2-part (pint can of powder & activator tube). Has excellent strength suitable for thick fill sections. Has higher thermal conductivity & CTE than 940, as is deemed most suitable for the Exhaust-crossover fill application.

QUOTE]

FWIW, HIS I don't think you're a nobody.....you're really proving yourself here. I just chose to go with a product sold by a Cylinder Head tool supplier who told me it has been used successfully and they sold it for some time now for this purpose....and thus seemed to possibly have more "testing their products this way" vs. the HT which no one is selling for this purpose, and there is minimal info to suggest it's viability.....although maybe that will change.

Your discussion with the engineers is invaluable, and should carry more weight than a vendor (people don't necessarily put the best item on the shelf). Hopefully yours (and others) testing the product in use will reveal it is a viable alternative.

[taff2]

I considered going with the Resbond until I found out how much the stockists over here wanted for it,it was around the $200 mark if I remember right. I went with the molten ali fill ,and,considering how easy it was to do ,I can't see why anyone would want to use an untried product like Resbond.