Nelsonmxmarc 1993 GTSt Type-M Build / Tips-tricks for HCR32 (Skyleezy!)

[mitch32]

Check if your valves have excessive play in the guides. Use the intake as reference (intake usually is good since the air cools the valves/guides).

Nice good job, it's a good project...

BTW you don't need the polish the ports too much as being rough is actually better, not too rough but rough none the less. The roughness allows the air to slow down around the edges and creates a boundary layer, then on top of the boundary layer the air will flow smoothly and less chance for turbulance. Josh can back me up on this one!!!

[archaeic_bloke]

BTW you don't need the polish the ports too much as being rough is actually better, not too rough but rough none the less. The roughness allows the air to slow down around the edges and creates a boundary layer, then on top of the boundary layer the air will flow smoothly and less chance for turbulance. Josh can back me up on this one!!!

yeaaa.... he is correct! marc your build is going amazing man, cannot wait to driiiiive eh!?

[M13]

Check if your valves have excessive play in the guides. Use the intake as reference (intake usually is good since the air cools the valves/guides).

Nice good job, it's a good project...

BTW you don't need the polish the ports too much as being rough is actually better, not too rough but rough none the less. The roughness allows the air to slow down around the edges and creates a boundary layer, then on top of the boundary layer the air will flow smoothly and less chance for turbulance. Josh can back me up on this one!!!

what he said.

When I had my head ported out, the machine shop said you don't want it to be glass smooth as air needs boundary layer to flow smoother than smooth surface. Also the slight roughness in the intake tract atomizes fuel better.

[nelsonmxmarc]

Thanks guys appreciate the feedback!

Right you are; a smooth intake surface will result in the fuel clinging to the walls. My fathers friend decided it'd be best to polish his intake side and it was a pretty clear result as to what, not to do.

As for the exhaust side, its slightly less stringent. In my case i didn't plan to polish to a mirror finish, what i was more interested in was removing the grinding scores and basically sanding them smooth. I was concerned that THEY would hinder flow equally as bad as some of the castings i removed, so i figured it'd be best to smoothen them out as best as possible.

As for a mirror finish hindering performance though, i have heard both sides of the story;

A lot of race teams go through a process called extrude honing, which is simply done by passing an abrasive putty through your port, be it your exhaust manifold, turbo snail, head. The only place you would not be able to use this is in your intake side due to atomization of fuel. F1 teams use it, as do sport touring classes, as you can yield a large bump in CFM's per runner through one simple treatment. I remember a test was done on a Porsche forum whereby they measured the 3.2's (carrera) exhaust manifold to be 190CFM's per runner. After an extrude hone, they yielded 250 cfm per. They also tackled the exhaust housing on the turbo and even Garrett praised the idea in gaining a smoother curve/horsepower numbers. The reason is that it uniform's the surface area and removes any debris (castings) as well as removes a small amount of material. If you've ever looked into a cast product, be it the turbo housing or exhaust manifold, you'll see it's not smooth but quite rough, like sand paper. They say this creates too much friction and reduces performance. This being said, 3 points can be gained by doing this just on a turbo housing alone (exhaust only - no such gains on the compressor side). 1 point is about a 20% increase in rotating inertia.

So my theory on the "smooth polished" surface isn't really onset of mythical practice. Extrude honing resembles a mirror like quality once complete, thus why it cannot be used on any intake surfaces. Simply due to the fact F1 teams/sportcars/high end performance race groups rely on this for the few extra ponies says a lot in my books. Of course to do it would cost about 1500$ for the exhaust side, so the best we can do is to take a few hours and take extra care by hand!

[nelsonmxmarc]

-------------------------

So last night i returned to finish my head.. Figured i could get a 1 day turn around on this beast - 1 day is a slight underestimate unfortunately..

I can say this much, i have zero patience for installing collets and do not plan on doing this until my valve guides and seals give, or a valve breaks. (btw all guides are nice and snug, look to have been changed along with the seals)



First and foremost i had to lap my valves into the seats. This ensures a tight-closed fit and promotes a solid sealing surface. You can see after use that the finish has become almost like a mirror, shiny and even corroded slightly.

A lapping kit includes;

Wooden dowel and suction cup
Lapping grease (sandy grease)

Theres 2 ways to get this one. Both require you put a small amount of lapping grease on the sealing surface of the valve, then put it into the guide and close it. Take your plunger and suction it to your valve face.

Method 1; fire starter, as i like to call it, as you'll be rolling the dowel between your hands vigorously. Every 4-5 twists, raise the valve with the plunger and smack it back down. This brings all the lapping grease back into contact with the seat. Do this 5 times approx, or until the coarse grinding sound fades to a light gritty noise.

Method 2; is the proper, original method (from what i hear), which requires the same technique, but instead of keeping the valve stationary and twisting, you lift and twist at the same time to continuously draw the grease out. It's hard, because the suction cup tends to let go and requires you stop, reattach, and continue. This was too time consuming IMO, and both methods should yield identical results.


Make sure the lapped surface is now clear of grit, and that its uniform. It should look like a rough piece of metal on a background of shiny metal, meaning the lapping has been done successfully, like such;

Before;





After;

[nelsonmxmarc]

Next; installing collets.

This took a lot longer than i had hoped; like 2 hours longer. It's really a tedious job, and unfortunately there is no physical way to speed up the process as it's just meant to be a long and tedious job.

With the spring compressor back in place, make sure you have ample room to move the collet into position. They are quite long, so make sure the springs are compressed quite a bit. Next, take a spray can extension (red plastic tube) and get a tab of grease on the end, as well as on the mating surface of your collet. Next, finagle your way in there and enjoying the quality hours spent screaming!

[nelsonmxmarc]

The piston went back home. The spring compressor revealed the mysterious cylinder scoring.



Whomever tackled the previous engine build decided to lodge this down inside the cylinder to facilitate the reinstallation of the piston. This would seem to most like the proper way to do it, however, it is far from proper.

First, line up the rings in their proper calibration. This is listed on page 223 of the FSM. The oil ring has 2 openings, upper and lower, and this one was not properly calibrated, so check to make sure everything is aligned beforehand. Once they are, get a good amount of oil on the piston, or engine storage spray, as well as on the surface of the piston ring compressor and pair the two. It's not stringent on how high or low the piston ring compressor is on the piston, as long as the two are together snug, and the ring compressor is not cocked.

Next, place the rod inside the bore. Best bet is to tape the rod end bolts so they dont score your journal. I didn't do this, but luckily when i replaced my piston, the con rod bearing fell directly onto the crank journal, so let that be a lesson!

Now, because its a snug fit, you can either use your own force to push/transition the piston from the holder to the cylinder. Other option is a piece of wood and a light hammer to slowly tap it into place.

MAKE SURE YOUR RINGS DONT CATCH THE CYLINDER.

Should flow pretty nicely if you've followed the above steps.. Just don't hammer the compressor into the bore.. Common mistake, obviously, and can easily be avoided..

[mikey]

It makes sense what Mitch said about the polishing of the intake. You can think of it as a golf ball, they have amazing aerodynamics because of all those dimples.

Anyways, Marc, I need to stop by your place and see your car some time. Apparently we've met before... Well according to my father.

[nelsonmxmarc]

Right, they vinyl wrapped last year or the previous years cup car with a dimpled vinyl wrap and it seemed to cut down lap times. That's disputible though, but at any rate, my point on extrude honing kind of outlines the reason for going to a perfectly smooth finish. There are arguments in either direction..

We've met?? Oh right through motocross right? Absolutely, pass by anytime!

[nelsonmxmarc]

FUCKKKKKKKKKKKKKKKKKK MEEEEE





Must acquire 1 inch headgasket...

Something weird going on here! lol

[nelsonmxmarc]

On lighter note, i went about disassembling my transmission..

I have YET to find a proper DIY on changing the input shaft bearing or swapping gearsets on the RB20 Transmission, so i'll likely write one when im done, but here are a few pics of the process;

Remove these 5 bolts to expose the input shaft bearing (Culprit of the whiny RB20 transmission noise)



Next, remove the rear housing. Simply undo all the bolts and attain leverage on the case by hammering on the intermediate plate, using a block of wood to avoid damaging the case.



Inside the front of the bellmouth, where the first step took place - there are circlips to remove. 1 is a small visible one on the shaft itself. Remove this then remove the spacer. Next, remove the large one holding the bearing in place (around the outside, hard to see). Once that's done, dislodge the intermediate plate from the bellhousing as you did to the rear portion a minute ago, and pull the 2 apart.







Now you have all your gears/synchros exposed.

If your transmission is noisy with your foot off the clutch, you likely have a worn input shaft bearing (one in the front). The reason i say this is because your throwout bearing is free, and when the car is at a stand still with the clutch engaged (foot off and in neutral), the only shaft spinning is your input shaft. Your intermediate shaft is free (holds the gears per se) and so is your output shaft. The only bearing spinning at this point is the large one you see in the first picture.

To change this, you'll need to strip the gearset down and have, from WHAT I CAN SEE, a new bearing PRESS FIT. This requires going to a machinist, or, tossing the input shaft in the freezer, and torching the inner race on the bearing to fit them, otherwise it may be a struggle.
I'll get into this more when i do it..


..............



FACKKKKKKKKK lol this is so gay.

[M13]

Damn that sucks... (now you know how I feel a bit )

As for the tranny, can you just drop in a different gear set that is stronger? or is that even possible? (ie Z32 tranny)

[Skym]

From what I have seen in articles on rebuilding gearbox (gearbox specialist), they heat the bearing up and fit over shaft.

You could fit a 300zx gearbox with an adaptor plate between bellhousing, engine. They do it with Nissan V8's, etc. Also I have noticed some use the front of a Silvia / 240sx? gearbox with 300ZX? gearbox. But from what can remember, have to remove some metal from housing for the gears inside to clear housing.

There are different gear ratio setups available from Japan for RB20DET gearbox. Also there used to be a option from Nismo, but don't think they make them anymore.

In Gibson GTS-R racecar with RB20DET, I noticed they used a Hollinger dogbox gearbox with custom bellhousing, reargearbox mount, etc. There's a photo of the Gibson GTS-R gearbox in one of the Australian magazines.

[nelsonmxmarc]

Damn that sucks... (now you know how I feel a bit )

As for the tranny, can you just drop in a different gear set that is stronger? or is that even possible? (ie Z32 tranny)

Lol fml

I'm not sure... I dont think so.

You could fit a 300zx gearbox with an adaptor plate between bellhousing, engine. They do it with Nissan V8's, etc. Also I have noticed some use the front of a Silvia / 240sx? gearbox with 300ZX? gearbox. But from what can remember, have to remove some metal from housing for the gears inside to clear housing.

Right, thats the entire bellhousing, however, which requires a modified mount and driveshaft. If i was able to replace the innards without modifying the actual fit of the transmission, that'd be great! The only known gearset that fits the RB20 bellhousing is that of a KA24.. Which is good, for acquiring spare parts!

We'll see how it lasts. All gears are in 100% shape.. I have two rb20 transmissions so sourcing parts atm is not an issue. As for breaking 3rd and blowing the gearset, i'm not worried just based on the sheer weight of the vehicle.

We'll see how she holds up!

From what I have seen in articles on rebuilding gearbox (gearbox specialist), they heat the bearing up and fit over shaft.

Awesome, thanks for the tip! I figured there'd be an easy way, without having to disassemble the entire gearset and take it to a machinist..

In Gibson GTS-R racecar with RB20DET, I noticed they used a Hollinger dogbox gearbox with custom bellhousing, reargearbox mount, etc. There's a photo of the Gibson GTS-R gearbox in one of the Australian magazines.

One GTSR part (along with their turbo manifold) that i'll never be able to purchase in my replica build But yes, one hell of a transmission..!

[nelsonmxmarc]

Input shaft bearing p/n - 32273-86w21.. Replaced by p/n 32273-86W70 . Same fitment for 1994 - 1998 240SX