High Compression 3400/3500 NA build

[02GT_SkyHigh]

Got the fly cuts done, did this about 3 weeks ago. went 0.060" into the pistons. I cleaned them up after pics with a sandpaper wheel. nice n smooth.

Im thinking about my tranny. going to a 4t65. either way its going to be ~$3500.
I dont think my S&S headers will clear the the 4t65..
Ill keep yall posted!

[sleepyalero]

So what's the benefitnor point of doing that to the valves?

[stewartfn18]

no benefit really. i do believe the reason that needs to be done really is because the quench is smaller than using factory pistons, so in order to prevent contact between the valves and the pistons , reliefs need to be cut

[sleepyalero]

Ahhhh

[geldartb]

Originally Posted by sleepyalero

So what's the benefitnor point of doing that to the valves?

from a guy on ls1tech

The point of flycutting pistons is to gain piston to valve clearance on cams with lots of duration and low LSA, i.e. Overlap. That is one of the problems with a LS1 design is that it limits piston to valve clearance with the stock slugs in the motor. Installing aftermarket pistons does the same thing as fly cutting because you have valve reliefs in the tops of the pistons.

The flycutting of the pistons can do three bad things....

1. weakens the piston because the design of the piston wasn't made to have valve reliefs cut into them.

2. if the reliefs are not radiused the sharp edges of the cuts can cause knock due to hot spots.

3. the other bad thing about the reliefs is that they cause the compression ratio to drop since they add volume. Now most times you have a milled cylinder head that has a lower volume in the chamber anyways to cause this so when everything is all teamed up the compression ratio will be higher.

Flycutting does not change the piston velocity, that is all due to RPM, rod length and stroke. It usually does lower the mass of the piston some, that will lower the forces the pin, rod and crank see at the same R and piston g's. (F=ma) Either way it's not going to be a lot and if you really wanted to improve that getting rid of that king kong stock piston pin would help more.

Bret

[sleepyalero]

Thanks!

[02GT_SkyHigh]

I wasnt super stoked that I didnt have the proper clearance..
First we put a bit of clay on top of the pistons to check clearance, the after the first full revolution seen it was touching.
We replace the valve springs with very light duty regular everyday springs and measured clearance between the top of the valve and the rocker.
It was super cpmplicated....

We used my old 3400 heads as a angle guide and used old valves that are 0.010" wider than the 3500 valves. Used a drill and measured depth with a feeler gauge for 0.060"..

Got my dremmel and did as much cleaning up as i could (No sharp edges, Polished, no grooves in recess like in pics)

What a Bitch.
S&S headers wont clear a 4t65 right?
So spensive for this project... the tranny will be worth more than the car and the engine jeeeeesussss

[AaronGTR]

That's why I don't recommend going with a 4T65 over a built 4T45. It was easy for GM to do on their concept cars. They have lots of money/resources, and easy ability to tune the PCM for it. Little more difficult for the average person. For what it costs to do a 4T65, I'd just do a manual swap.

[HOYS]

Originally Posted by 02GT_SkyHigh

I wasnt super stoked that I didnt have the proper clearance..
First we put a bit of clay on top of the pistons to check clearance, the after the first full revolution seen it was touching.
We replace the valve springs with very light duty regular everyday springs and measured clearance between the top of the valve and the rocker.
It was super cpmplicated....

We used my old 3400 heads as a angle guide and used old valves that are 0.010" wider than the 3500 valves. Used a drill and measured depth with a feeler gauge for 0.060"..

Got my dremmel and did as much cleaning up as i could (No sharp edges, Polished, no grooves in recess like in pics)

What a Bitch.
S&S headers wont clear a 4t65 right?
So spensive for this project... the tranny will be worth more than the car and the engine jeeeeesussss

S&S won't clear a 4T65.

Its pretty possible to do a 4T65 swap without too much headache if you get axles made and don't try to do some janky axle things.

What is your compression now with those valve reliefs as that increases the dish volume of the piston considerably. Did you check to see how much material is left after doing those cuts?

Originally Posted by AaronGTR

That's why I don't recommend going with a 4T65 over a built 4T45. It was easy for GM to do on their concept cars. They have lots of money/resources, and easy ability to tune the PCM for it. Little more difficult for the average person. For what it costs to do a 4T65, I'd just do a manual swap.

GM had issues with it in some concept cars. I can't find it but a GM built Sunfire with a 4T65 swap actually used a standalone trans controller. This can always be an option with these cars. There has been pretty good success with the logic switching for the transmission control in the PCM. Its a value that HPT or DHP won't let you modify but it seems to change the logic in which the trans shifts. The 4T65 logic is backwards from the 45 which will be your main issue. Everything else comes down to how the solenoids are actuated...which most of the time the solenoids interchange if you know what you are looking at. With some fancy spoofing and number changing you can have a 65 running pretty easily. I know of one swap that has been DD'd for about two years now.

For the money I would also do a manual swap...but for big power builds a 4T65 will always be better as if you have the cash you can make it hold juuuust about anything with OTS parts.

[Nick-G]

Originally Posted by HOYS

There has been pretty good success with the logic switching for the transmission control in the PCM. Its a value that HPT or DHP won't let you modify but it seems to change the logic in which the trans shifts. The 4T65 logic is backwards from the 45 which will be your main issue.

Tiny Tuner is able to change the shift logic.

[young gun]

Originally Posted by Nick-G

Tiny Tuner is able to change the shift logic.

He is alive!

[MAC the KNIFE]

computers and tuning are what's keeping me from doing a manual swap in the GAGT. i can make the pieces fit, but i'm not geek enough to tackle ecm/tcm stuff.....yet

[HOYS]

Originally Posted by Nick-G

Tiny Tuner is able to change the shift logic.

Oh I know

[sleepyalero]

Originally Posted by MAC the KNIFE

computers and tuning are what's keeping me from doing a manual swap in the GAGT. i can make the pieces fit, but i'm not geek enough to tackle ecm/tcm stuff.....yet

Thats why you get a custom PCM from MMS or wottech.

[MAC the KNIFE]

Originally Posted by sleepyalero

Thats why you get a custom PCM from MMS or wottech.

nobody makes a pcm for the build i'm wanting to do tho

[sleepyalero]

Uhh.... you tell them what you have done and boom they tune it to what is needed. Thats why its a "custom" pcm brother.

[Vegeta]

If you put a lot of time and money into your engine, you will want your car tuned. Not mail order anything. Using computer feedback and ideally wideband as well, a tune for your car will net the best results. Mail order is best for the basic mods, where people generally don't care about the absolute best results. Better than stock is good enough. A long distance tune with feedback and sending files to be flashed locally is as mail order as you can get for a custom tune.

[sleepyalero]

I had a guy in canada fine tune my car. We got her up to 242 ft lbs of tq to the flywheel

[02GT_SkyHigh]

Tranny should be done in 10 days.
The motor is assembled minus the oil pan.
I think this is all gonna come together soon!
Ill keep you updated

[sleepyalero]

Cool