TFS pistons and Piston Notching

[Shawnski]

I aquired a long block 5.0 that consists of a never run 4.00 bore block, '86 flat top pistons, B-cam and TFS T/W heads. This was put together 5+ years ago and never ran.

This motor was "built" with the old rings, t/c, and I believe even the oil pump from the 86! Though it does have new bearings and ARP rod bolts. Anyway, I am going to reassemble this with new parts, Z cam (have one), and fit dome pistons that are compatible with the twisted wedge's unique wedge chamber and valve angle - however I cannot find std. size pistons!

Question 1. Is anyone aware of std. dome pistons for the TFS application?

Question 2. Failing no 1. I will more than likely use the flat top pisons, who makes a good notch cutter?

Thanks in advance!

 

[jrichker]

Cutting the pistions in place is not without problems.
1.) The balance will definitely be affected. You cannot remove metal from the pistons without changing the balance. A poorly balanced engine will shake itself apart, put out less HP and fail sooner.
2.) The pistion may be weakened by the cutting operation. There is almost no way to determine the amount of metal left and the strength of a piston when you cut it in place.
3.) Getting all the chips and debris out from the machining process can be difficult.

 

[Shawnski]

1.) The balance will definitely be affected. You cannot remove metal from the pistons without changing the balance. A poorly balanced engine will shake itself apart, put out less HP and fail sooner.
True enough regarding poor balance - however based on my research removing up to 10 grams per cylinder is acceptable in terms of not upsetting the balance - I will be using an SFI rated crank end balancer for RPM insurance
2.) The pistion may be weakened by the cutting operation. There is almost no way to determine the amount of metal left and the strength of a piston when you cut it in place.
Actually you can measure the thickness of the piston and based on my calculations the depth I need will leave plenty of material intact.
3.) Getting all the chips and debris out from the machining process can be difficult.
I am prepared for this - and I appreciate your concerns non-the-less

 

[bullitstang1313]

There is more to weakening a piston than just removing too much material. Once you start grinding away material from the piston you will start creating a lot of heat. This can affect the hardness of the piston and make it more brittle. Also, by removing material from the piston you will create localized stresses. It would be best to find the correct pistons.

 

[samickguy15]

ISKY sells notchers, but they're pricey. $125 per notcher plus $40 for the pilot tool. You would be better off buying some hyper pistons for about $200-300. I don't remember who makes them with the TW notches though. I tried hunting them down on Summit's site, but couldn't come up with it.

 

[PUNISHER RACING]

KB 312 is a dome piston, KB 311 is a flat top piston for TFS heads

 

[mike50sa]

Another solution would be to go with TFS pistons. I think they're made by Arias. I bought them to match my TW heads (and Stage 1 cam) so I won't have issues. They have a couple of diff compression ratios. I bought the 10:1. They're forged, and they're light weight. Not cheap though - about $500 for the set. However, you do get piece-of-mind knowing it's all engineered to work together. And these are top-shelf pistons.

I haven't put it all together yet so I can't tell you the piston-to-valve spacing. I could probably mill the heads and get more compression, but I might do a power-adder later. If you're going to add a blower or nitrous, be careful how much compression you add when you build it.

Hope this helps.

 

[Shawnski]

KB 312 is a dome piston, KB 311 is a flat top piston for TFS heads

The KB312 were what I was going to go with, however I need std. 4.00" as I have a fresh block - and those won't be available till some time next year...

I have decided to notch the '86 flat top pistons and have the heads milled to get my 10.1 compression goal.

Thanks all for the feedback!