[jrgoffin]

It was definitely a relief that it smoothed out so fast (probably needed a bit more priming!), but had there been the very slight "tap" at each cold start, I would have been okay with it. No matter, it sounds now as if the PTW tolerances are near factory-spec.

On that note, these pistons went in with 0.0035" PTW clearance. Ed had mentioned that OE spec was tight - right about 0.001", which keeps the noise down and the masses happy. No worries here now!

On to John's Vampire next...

 

[Edmisten1]

On that note, these pistons went in with 0.0035" PTW clearance. Ed had mentioned that OE spec was tight - right about 0.001", which keeps the noise down and the masses happy. No worries here now!

Yikes....mine are at .0045"! It should have sounded like marbles rolling around in a tin can that loose lol

 

[Wicked46]

Yikes....mine are at .0045"! It should have sounded like marbles rolling around in a tin can that loose lol

I'm at .0045 with my Gibtec pistons as well. I went with what Gibtec recommended

 

[jrgoffin]

My mistake - it is 0.004" - sorry about that!

The shop that did the machining was sure that 0.0045" was too much and didn't want to go any more than 0.0035". Based on a conversation with Nick at Gibtec, they compromised on 0.004". My fault for getting the numbers a bit jumbled. In any case, it worked out perfectly.

 

[Edmisten1]

My mistake - it is 0.004" - sorry about that!

The shop that did the machining was sure that 0.0045" was too much and didn't want to go any more than 0.0035". Based on a conversation with Nick at Gibtec, they compromised on 0.004". My fault for getting the numbers a bit jumbled. In any case, it worked out perfectly.

Roger that...half a thou on a diameter (which is ony half of that on a radius) should not have any ill effects. Everyone has their preferences for sure. Some machine shops want to go tighter....others looser.

 

[P49Y-CY]

:rock: awesome, congrats!

 

[eschaider]

A few words of clarification on PTW clearances for everyone reading this thread;

The original OEM pistons can get away with very tight PTW because of the aluminum stock they are made out of. Even with their low coefficient of expansion, Ford has chosen to use an anti friction coating on the skirts for insurance. The OEM piston alloy is a relatively low expansion alloy that while expanding little, also does not have the toughness/durability of the 2618 alloy Joe's pistons are made of. The increased PTW that the 2618 piston has is used to provide clearance space so the piston will have a proper operating clearance after it has warmed up.

Pistons, although they look round are in fact eliptical when they are cold. As the piston warms up it's elliptical shape grows into a round shape. The extent of the ellipse is a function of the material used, the piston's various cross-sections, the bore size and the experience of the piston designer with a particular n/a or supercharged application. All this gets mixed into the recipe for the piston design and shape. The elliptical shape of a piston skirt is sometimes described as the cam that was built into the skirt or piston. It can vary not just from manufacturer to manufacturer but from application to application within a single manufacturer.

One of the reasons I chose Arias originally and Gibtec later, when the Arias forgings I needed ran out, is that both these firms live in the supercharged piston design and application space and I had decades of good supercharged experiences with Arias. The Gibtecs (and the older Arias) designs were not just a piston somebody drew up out of the clear blue. Both pistons represented a piston from an experienced long standing supplier of supercharged pistons for use at the top of the blower motor food chain. Both these firms design and offer among the very best of pistons available for supercharged applications.

If you attempt to fit one of these blower motor pistons the way the OEM pistons were fit you will have an unhappy experience. If you fit them from 0.0035" to 0.0045" you will have a happy experience. If you fit them at 0.0035" and attempt to operate the engine like it's showroom counterpart that was in the car when you originally bought it from Ford you will have an unhappy experience. An engine at 200˚F+ will begin to scuff the pistons in the bores. If you are a little frisky or just plain wrong with your fuel system, at 200˚F+ operating temperature you are playing a dangerous game that will most likely not end well.

If you operate your engine at 180˚F or cooler use a 0.0035" to 0.0045" PTW and do not get a lean is mean sort of mentality into your tune you will be very happy. Do not attempt to do a destructive testing routine and your engine will make good power for you and importantly, treat you well.

Ed

p.s. Do not listen to your machine shops. Listen to your piston manufacturer. They are very different information sources. If you choose to go to 0.0035 keep the engine temp down and the tune conservative.

 

[Edmisten1]

^^^ As usual, great info. My pistons came from Gibtec with a card that said specifically to set them up at .0045". Since they were the designer of the piston, it was a logical assumption that they knew best how to set up their product.

 

[eschaider]

It is amazing how easy this stuff is, Jeff, when you just follow the yellow brick road from the manufacturer's install map


Ed

 

[4vFoxx]

Great to finally hear the beast run congrats. Can't wait to order up my Gibtecs.

 

[jrgoffin]

Thanks for posting that PTW info, Ed.

I know from personal experience that the owner of the shop I used got a little cantankerous about the "loose" clearance, but I'm glad he called Nick at Gibtec anyway - that settled him down. I can live with 0.004" since it's pretty close to the card, and I know I won't be running this engine on the hot side.

 

[eschaider]

I recall that journey of passage Joe. Your machine shop guy was a hardboiled egg


Ed

 

[gt347mustang]

Sent an email to gibtec a few weeks back and haven't heard back.

Anybody have direct contact info for Nick(I think that's his name) there?

 

[jrgoffin]

Sent an email to gibtec a few weeks back and haven't heard back.

Anybody have direct contact info for Nick(I think that's his name) there?

I think that info is somewhere in the original Gibtec piston thread, but if not, Ed will surely have it!

 

[408Stang]

303-243-3340 is Gibtec's direct number. Nick often answers, but not always.

 

[eschaider]

Thanks Mike. Beat me to the draw

BTW Joe is right, it is also in the original thread which is now an article.


Ed

 

[jrgoffin]

A little bit more play time today, so I got started on the Vampire. It was only a matter of laying it out and getting the knock sensor run, but it gave me an idea as to how I'll set it up. The wiring is really straightforward, and John's instructions make it as simple as can be. The instructions are also printed and included, but here are the details right from the J&S site (I'll expand on them later as I get in to the PCM harness): http://www.jandssafeguard.com/VampirePage/Vampire.html

Also, just to show the simplicity one more time, here is a picture of the wiring diagram:

For my short day today, I got started by un-bolting my passenger seat and leaning it back so I could set the control box underneath it. Since I have Recaro seats that are both powered, there is a harness under the passenger seat, but I set the box just about on top of where the wire bundle ran out. This still gives me access to the Vampire, while also not getting in the way of the seat power:

John includes a real nice harness with 10' of wire, one bundle for the knock sensor (black), and the other for the coils, power, ground, and nitrous control if you have gone that route. Here is the harness laid out and ready to go:

You have to remove the kick panel and the scuff panel to pull the carpet up, and after that was out of the way, I cut two small slits in the carpet (in the shape of an 'X') right behind the forward seat crossmember so I could feed the harness in. Before I get the engine running to test this, I'll probably put a small strip of Velcro under the box at the back edge to grip the carpet, but with the wire harness plugged in, it should sit fairly steady.

Since the knock sensor was already bolted on the block, that was one step out of the way, but running the wire was simple enough. I chose to feed it under the carpet, up under the shifter bezel, then down in to the transmission tunnel. Since I have a wideband sensor connected to my Aeroforce gauge, the routing of the knock sensor followed it (the wideband controller is in the glovebox so it makes it easy to access for occasional recalibration). Here's both wires in a piece of wire loom poked in the lower shifter seal and dropped down:

John makes it easy to do this since there is no plug on the sensor wire, but once you are under the car, you snap the wire ends in, push in the retaining clip, then plug it in to the sensor. As I pulled the wire down, it was fed along the wideband cable and transmission harness, starting above the transmission mount bracket that is spot-welded to the tunnel (on the right side in the picture). Here's the wire fed forward, and already with loom on it:

From there, I zip-tied it to the rest of the wideband harness after I figured out how much loom was needed, then dropped it down slightly near the clutch fork cover to keep it farther away from the mid-pipe.

Plugged in and ready to go:

After this was all done, I jacked up the body slightly to remove the ramps, then dropped the front tires on the ground for the first time in a few months (the engine bay almost looks unusually low after sitting up so high all winter!). I'm getting a temporary tune for it that I'll install tomorrow so it will idle a bit better (once it is open-loop, it is hard to keep running now that I have the 60# injectors), then I'll be back with the rest of the Vampire in a few days or maybe sometime next week.

 

[MattP]

I put my J&S box in the glove box. You will need to see the light on the box to set up the sensitivity. Im a at about 10:30 position on the sensitivity knob. Or if you have the knock gauge your good. Or you can clip and extend the LED to your dash area so you can see it all the time.

 

[Wes Duenkel]

You may have mentioned it before, but where did you get that engine block plug (opposite side of the starter). Mine's just an open hole...

 

[jrgoffin]

You may have mentioned it before, but where did you get that engine block plug (opposite side of the starter). Mine's just an open hole...

Thanks for the reminder, Wes. I was asked about that and the p/n for the new rear main seal retainer plate and completely forgot to post them.

Inspection cover: F3LY-6C070-A (about $8)
Rear retainer plate: 6R3Z-6K301-AA (about $35)