I need a few opinions. I am building an NA 13B (S5 core) and would like to use the irons from a TII engine that I have torn down. I prefer the 4 port configuration. My dilemma is that there is about .002-.003 of wear on the endplates according to my dial indicator. The center housing has .004-.005 of wear due to a blown side seal so I know that it is garbage.



The question: Should I send the TII end housings out to be lapped even with the chance that they may be too far gone or should I just make due with the 6 port housings. Or does anyone know if taking .003" off is alright?

 

.003" will be fine.

 

We've went .004" without issue. There is a noticeable difference in the depth of the o-ring land and there was some concern when we re-assembled the engine. But it's done very well for about 10k miles now and is currently being daily driven. I wouldn't recommend it but we have gotten away with it.

 

Awesome, thank you both very much. I guess I will get to use 4 port housings. I just hope that the gain that I get from the housings isn't offset by using the TII intake manifold rather than the VDI one that I would use with the 6 port setup. Someday when my welding skills get a little better I may create my own lower intake manifold to bolt to the TII engine and the NA upper manifold.

 

You can keep lapping year after year. I used to grind them and then clean them up with solvent and a DA pad with 400 silcone carbide paper .



Eventually the engine will get short enough that the rear stationary gear face will start touching the back end of the rear throw. I found that during a build up, and shortend the rear stationary gear just a bit. No problem.



I found a young team at the Runoffs with that problem, and their starter would not turn the engine fast enough to start it. Imagine the load on the thrust plate.



I had them loosen the pulley bolt, and nothing changed, so it wasn't the spacer too short. I took off the front cover, and made a cardboard spacer to install under the front stationary gear flange, thus pulling the crank forward .025" and all was well again.



The nitriding is about .004" to .006" deep. So, even if you use all of it up, you can still use the irons. Nice to know if the port job is working well. Notice that the intake manifold will start to missalign at the bolt holes if you persist with this repair method. But it takes years to happen.



Lynn E. Hanover

 

hey lynn i have a question for u when u lapp housings how much u cut off to make it flat?

 

I have them ground, not lapped. I don't do anything until they get to about .006" deep. Then tell the operator to take it down until the line is just visible. So about .0055" off on the worst piece of iron. You can do that twice and then mix in a center iron that has not been cut and race a few more years.



Paul Yaw grinds them first, and then laps them to get the finish he wants. A good idea but more money.



If you race, or just use a lot of engine on the street, add a bit of premix for those hard weekends. The irons and side seals will just about stop wearing. Also change the oil at least every 2,000 miles. Real good Oil filters only go down to about 9 microns, and there is some nasty looking stuff below 9 microns (9 millionths of a meter) still in there.



Lynn E. Hanover

 

Correct me if I'm wrong Lynn but I'm sure you're talking about pre-86 irons that do not have the o-ring grooves cut in them. If you take .006" off a later housing you won't have enough meat left to hold the o-ring. Correct?

 

Correct indeed.



Those irons already suffer from some poor engineering that has pieces falling out of the groove wall.



One pass at .006" I doubt would hurt anything, but should involve a check for the "O" ring being hydrauliced ("O" ring material completely fills the groove) in the groove. There must be some volume left in the closed up groove after the irons are clamped. That would put a huge strain in an area known to have a problem. I only work on 12As, that have the groove in the housings as in the Renesis and as God and several thousand failures have indicated it should be.



When you torque up the stack you are applying several thousand pounds of force in that clamping action.

Although it seems impossible, all metals are plastic. ?????? Metals may be deformed by force. More force=

more deformation. Metals also deform themselves based on temperature. Metals get bigger as temperature goes up. So you torque up the stack, to stock specs. And then add some more, because if torque is good, more torque will be better, right? And that old torque wrench from the yard sale should be right on the money, right? So there it hangs on the stand, all torqued to hell and back. The case bolts are well into the working range. They stretch like rubber bands and if overdone (beyond the working range) will no longer return to there original size.



So what happens when you heat the engine up by running it?



It gets longer. Quite a bit longer. So if a properly torqued up stack should have about 6 tons of force holding it together, and you lay on another 5 pounds of torque, the total force applied becomes 8 tons. The bolts are at the end of the working range and quit stretching. The housings swell as though they were made of bread dough. The outer edges of the irons (out board of the groove) may crack off pieces. If you stress this engine hard, the front or rear iron will crack through the dowel hole. You can do this with detonation, an over heat, or too much case bolt torque. And if the grooves are in the cast iron, you snap off a piece. The end irons bow

outboard of the bolt holes. Because all materials are plastic. Even cast iron. Even a diamond.



Years ago my engineers boss at the bomb plant sent his son up to work on the race car, and get some "hands on" to go with his pre-engineering HS work. Were talking about working range and plastic and so on. I clamped a short length of 1 1/4" stressproof swaybar stock in my vice and invited trainee William to deform it. He pushed and pulled and then anounced that he could not generated the force to do any deforming at all on this stuff.



I said on the contrary, you have been doing a fine job deforming that stuff. Where we are falling short is our ability to detect the amount of deformation you are inducing. So we add the magnetic based dial indicater to the test and we can see several thousandths movement as he pushs and pulls on the short thick piece of steel rod. Next we clamp two pieces maybe 50" long spaced apart by a piece of lathe cutting tool.

Now you need no help seeing the deformation. With just your hands you can bend the rods so that the ends touch. Next I have him heat the outer sides of the bar stock for just short time, and he grins as the ends of the bar stock touch. So torque values and torque sequence, should be by the book. So evil engineers in Japan, and not you, are breaking your irons.





Grinding the face of the iron does not make the groove weaker. That problem was supplied by morons at Mazda. There is not enough material between the lower outside corner of the groove and the water jacket.

A slight radius at the corners could have saved it, and been cheaper to manufacture. Adding 2 cents worth of iron along the outside of the groove area. Or grooving the aluminum that is cheaper to do anyway,tooling life wise. Cutting small grooves in cast iron is a bitch tooling wise.



If further machining is required to save a set of irons, I would not hesitate to use an off the shelf, smaller than stock, "O" ring diameter from a packing house.





Lynn E. Hanover

 

the updated intake gasket for the 93-03 rx7's have you GREASING the gasket surfaces, i guess the papaer gaskets didnt slide well enough on a turbo