FCar2000TA

iTrader: (7)

I'm not sure that I am thinking about heads correctly. Does a decreased valve angle increase or decrease the available Piston to Valve clearance? i.e. does a 13.5° valve angle have more or less Piston to Valve clearance than a 15° valve angle? Assuming the valves are the same size.

G Atsma

If the chambers are the same volume, I would say the flatter valve angle would afford more clearance.

wannafbody

iTrader: (2)

G Atsma, that's the way I understand it. That's why the LS1 went from 23 to 15 and TF to 13.5

FCar2000TA

iTrader: (7)

Ok. That is what I thought. I assume that larger valves cut into that extra P2V? Since TFS is 13.5° with 2.02"/1.575" valves, the P2V is back to stock, or really close to stock? I think I read somewhere that TFS heads give you .006" more Piston to Valve, or enough to bump compression by .1.

rotary1307cc

iTrader: (5)

All depends on the head. With a shallower valve angle you gain PTV clearance

But you could have a 15* head with more PTV that a 12* on the same valves depending on the valve drop

93Polo

iTrader: (5)

I understood the low angle typically flowed better at all lift points possibly due to less shrouding. I'd love to hear from some of the guys in the industry with more knowledge.

Agreed with valve size being the same. Valve size would impact the clearance.

00pooterSS

iTrader: (40)

Shrouding is in relation to how close the valve is to the cylinder wall. The angle doesn't change it's relative location to the cylinder wall, it changes the valve's angle in relation to the deck of the engine. The more straight up the valve is (lower angle number) the more the valve can go down before the edge of it will tap the piston. You're likely seeing the increase in flow because the better angle valve has a port with more of a straight shot to the valve, not because shrouding was down.

It's not just valve size. Some heads offer more valve drop alone. Then angles and valve sizes also come into play.

Summitracing

FCar2000TA

iTrader: (7)

What about TFS LS1 215 heads? How much more clearance to those get compared to stock LS1 heads?

Summitracing

the 243 heads have about .157 intake and .167 exhaust valve drop. The TFS 220 as cast is .157i/.211e. The 215/225/235/245 will vary about .010, but are similar to the 220.

FCar2000TA

iTrader: (7)

So, the TFS 220 and 215 could be shaved .075 shaved off, and still be at recommended LS1 minimum piston to valve (080 Intake .100 Exhaust)?

Summitracing

Usually .030 is about the limit before requiring modifications to get an intake manifold to fit. Generally we use .060 intake and .090 exhaust as our minimums, but it would really be dependent more on what cam you're running. As an example, our Pro LS Stage 4 SUM-8709 has .061 intake and .091 exhaust clearance. This was with .045 piston to head clearance and .128 valve drop.

FCar2000TA

iTrader: (7)

Can the FAST LSXR 102 intake have the bottom shaved any to allow more to be shaved off of the heads?

Summitracing

A Machine shop can correct the intake face of the cylinder head. Then the bolt holes in the Fast would need to be slotted. Port Matching will be required.

00pooterSS

iTrader: (40)

It doesn't work that way because you are picturing the valve drop as what you can have before making contact with the piston but forgetting that the valves are open a little when the piston is up. So the valves may be down say .100 or so at TDC (just throwing a number out for ease of understanding) so you now have .75 left before piston contact not factoring in milling, headgasket thickness and piston out of the hole. So picture the piston all the way up. Now picture the total distance the valve can travel before hitting the piston. For conversation thats stated to be .157, but with the piston at TDC the cam is holding the valves open a little during overlap so however far the cam is holding them open is taking away from drop. So as said if they are open .100 and you have .157 total drop measured before piston contact you now only have .57

So obviously the valves are not open .100 during overlap but it's just a number for easy understanding.

Valve drop is measured by having the valve all the way in the seat and seeing how far it can go down before contacting the deck. However the best way to do it is to do it with the cylinder head installed and measure the drop from the valve fully seated to how far it can go down before hitting the piston. Since LS motors have the pistons sticking up out of the hole a little you lose a little of that depth, however you also have a head gasket in there that adds to it. So you have to calculate all of that to get the true number that YOU have. But to compare heads to each other the advertised drop to the deck is fine. Gives you what you need to know to compare heads.

Also summit stated the stock LS head and the TFS have the same .157 intake drop so no you can't mill the TFS any further than the stock LS head before running into problems, since the valve drop is the same.

For several other reasons you couldn't cut the heads that far anyway

You can cut the heads on the intake plane to make them match up to the intake better, that's the more common route. But you can cut anything. The cutting makes the angle line up but as you remove material you can only go so far because if you go too far the intake wont be wide enough to reach both sides and make full contact so it's a delicate dance there.

FCar2000TA

iTrader: (7)

So, unless I want to spend a lot of extra money, removing .030 from the head is the max. The price of TFS 215s over AI 226s is starting to become not worth it, since I won't be able to get more than 11.1 compression, and I won't want a cam larger than low-mid 230s duration.

TXsilverado

iTrader: (18)

it's not as simple as looking at duration to determine valve clearance. it's about valve events.

00pooterSS

iTrader: (40)

There are more benefits. The TFS has a better valve angle, thicker decks, a higher ceiling/hp potential than ported OE castings if you want to compare them full out. I would think the better valve angle would show in the valve drop. I find it odd the TFS and the OE head have the same valve drop. I wonder if summit can confirm that and make sure it wasn't a typo.

I think he just means he wants to stay around 230's cause that's the size he wants

Summitracing

Yes, unfortunately this comes from the head engineer at Trick Flow. It's unfortunate, but that's the case with them. Part of it is because of the larger intake valve diameter offsetting some of the gains of rolling the angle. The LS3's have more though. It's a bit more work, but going with some domed pistons would be helpful and solve this piston to valve issue entirely.

Summitracing