[DeTomaso] Epoxy in Injector Pockets????

Wed Jan 20 18:30:45 EST 2010

epoxy will all be removed in a press fit except on the surface as a fillet this is ok to ensure a seal and a mechanical fillet . 
if you are goint to press fit  then use a shrink fit with loctite  648 press fit on the injector tube as this will ensure a gas tite seal all around the injector tube.  the tube design for a pressfit should be shapped differently than a weld or glue fit part. It should have thick walls and a shoulder that contours to the manifold at the hole or the hole should be spot faced square with the drill axis and the tube shoulder can be now square to the tube axis.This ensures no cocking at seat as well as that a seal with a sealant can be done on the shoulder so that a lapped finish is not needed. 
The problem with a press fit in this case is that; the manifold walls are thin , non uniform and that the hole for the injector , due to the sloping of the castings , is not a straight round hole except in the direction of the axis that it was drilled at . What this means is that unless the injector tube is very thick walled to allow a very large circumference as well as the hole and the tube , then one cannot guarentee that a press fit will stay in place over the temperature range that the manifold will be operating over . If the manifold wall is only .1inch or less thickness any where along the pressfit circumference as well ; then uneven expansion of the manifold will cause the hole to get bigger than the  tube and will leak air if a sealent or a lapped hole and tube are not used. Then when one trims the injector tube inside the manifold to be smooth with the runner wall  (or close to it) the tube can easily be dislodged because of the thin
 sections involved. 

 if you are worried,  thread the od of the tube and the id of the manifold  clean and wash real well , coat the tube with epoxy,  screw it in  let it dry. cut the extra length inside the runner off with a die grinder and porting setup. This requires a thicker wall tube than a weld or glue in. 
If the tubes are made from 6061 t6 alloy and the manifold is A356 (more than likely) 
the expansion coefficient for a356  t7 is 21.5  compared to 23.4 for 6061 t6 (both metric units) so as long as the fuel is not cooling of the tube at a rate that is the ration of the 2 numbers then the tube will stay put and will not crack the epoxy nor will it seperate if enough surface is at the press fit uniformally distributed .

jg 

--- On Wed, 1/20/10, Ken Green <kenn_green at yahoo.com> wrote:

From: Ken Green <kenn_green at yahoo.com>
Subject: Re: [DeTomaso] Epoxy in Injector Pockets????
To: detomaso at realbig.com, "Tomas Gunnarsson" <guson at home.se>
Date: Wednesday, January 20, 2010, 4:23 PM

Tomas,

    I wondered about a press fit and epoxy.  I need to understand epoxy better.  It seems like a press fit would scrape all the epoxy off the mating surfaces, unless the surfaces have scratches that hold some of the epoxy?  Is this an issue or is there a small residue that remains that bonds the parts?  I know that it's good to have a minimum amount of glue between surfaces in most instances, but does that extend to press fits?

    The holes will be milled not drilled, so they will be a very good fit.  But, the injector pockets will not be perpendicular to the roof of the runner, so that may affect a press fit?

Ken    

--- On Wed, 1/20/10, Tomas Gunnarsson <guson at home.se> wrote:

From: Tomas Gunnarsson <guson at home.se>
Subject: Re: [DeTomaso] Epoxy in Injector Pockets????
To: detomaso at realbig.com
Date: Wednesday, January 20, 2010, 1:36 PM

I share your feelings regarding epoxying metal to metal in an engine application. How about a loose press fit with the epoxy acting more as a sealant? The loose press fit could be achieved by drilling the holes and/or turning the injector holders to zero press fit, then scarring one of the surfaces for a small interference fit. I haven't seen the parts so I don't know if this is practical though.

Tomas

----- Original Message ----- 
From: "Ken Green" <kenn_green at yahoo.com>
To: <detomaso at realbig.com>
Sent: Wednesday, January 20, 2010 12:31 AM
Subject: [DeTomaso] Epoxy in Injector Pockets????

> I'm having a manifold converted to EFI and the shop thinks it's better to epoxy the injector pockets into the manifold than to weld them. I bought MSD pockets, and they say "epoxy in" on the label. It's a little scary, but there in no structural issue, and it's not like adding epoxy inside ports that can break loose. Is it a waste of $s to have the pockets welded in?
> 
> Ken
> _______________________________________________
> 
> Detomaso Forum Managed by POCA
> 
> Archive Search Engine Now Available at http://www.realbig.com/detomaso/
> 
> DeTomaso mailing list
> DeTomaso at list.realbig.com
> http://list.realbig.com/mailman/listinfo/detomaso
_______________________________________________

Detomaso Forum Managed by POCA

Archive Search Engine Now Available at http://www.realbig.com/detomaso/

DeTomaso mailing list
DeTomaso at list.realbig.com
http://list.realbig.com/mailman/listinfo/detomaso
_______________________________________________

Detomaso Forum Managed by POCA

Archive Search Engine Now Available at http://www.realbig.com/detomaso/

DeTomaso mailing list
DeTomaso at list.realbig.com
http://list.realbig.com/mailman/listinfo/detomaso