Thimble

iTrader: (2)

Am getting ready to start the job tomorrow.

I have the Isky cutters, 2 1/8" intake, and 1 3/4" exhaust. I had a friend ship me a stock (241) head casting to use as the guide.

Problem: The cutters stick out beyond the deck surface of the head, about 1/8". I recall reading in the past to remove the valve seats...I removed one of the intake seats, and it didn't gain me anything, the cutter dia is still larger than the seat counterbore.
The exhaust cutter fits even worse, and binds up against the chamber before even hitting the seat.

I always assumed the cutting was done at tdc, but that obviously can't happen with the cutters not fitting fully in the chambers. It would also seem, if you shimmed the head up, or, just brought the piston up until it hit the cutter, that the area cut would land in a different spot on the piston since you're cutting at an angle.

Also, on a similar thought, since the closest point of p/v clearance isn't at tdc...should the cutting be done with the piston slightly down in the bore to insure the cut matches where the valve would hit?


What's the best/easiest fix for this, and or proper way to cut the pistons if the tools can be used as-is?


Thanks for any knowledgeable answers.

N4cer

iTrader: (11)

- Why 2 1/8"? That's big. You have a bigger bore motor with big valves or something? The only good thing is that at that size, you don't need to worry about doing down the bore or not. It leaves TONS of room to play.

- My 2 1/16" fit fine at TDC with an MLS gasket and 841 casting head. Not sure why yours won't.

- Blueprint your cam with a dial indicator and a degree wheel. You'll see that despite what all the wannabe gurus say, it somehow comes closest so close to TDC that you needn't worry about the details.

- The big cutter scares me for you because that has you going deeper than you need just to get the clearance you want.

Thimble

iTrader: (2)

Hmm...I bought the cutters based on another thread I saw here several months ago...someone posted the sizes and part #s of what they used, and that's what I got.

The exhaust valve cutter is actually the one much larger than the actual valve size.

2.125" (cutter) - 2.020" (valve) = .105" larger, or .0525 clearance around the valve.

1.750" (cutter) - 1.550" (valve) = .200" bigger, or .100" clearance around the valve.


I would think with a 2.0625" cutter, you'd have to be dead nuts on with the cut, you only have about .021" clearance around the perimeter of the valve. (assuming a 2.02 oversize valve).

N4cer

iTrader: (11)

Well, I didn't see that you had 2.02" valves. Mine are 2.00". But even at that, you don't have that much deflection. And yes, you need to be right if you want it to be precise. That's why we blueprinted my setup. But I didn't notice the exhaust at all. That is big! What cam are you running that will put your exhaust side too close anyway? Mine was fine.

Thimble

iTrader: (2)

Found the thread... https://ls1tech.com/forums/generation-iii-internal-engine/637423-another-stupid-flycutting-question.html

Guess I'm not the only one to use these sizes.



I don't know about exhaust clearance. I won't know actual clearance until I check it. I bought the exhaust cutter because I figured better to have it and not need it, than to need it and not have it. As long at it took Thunder to get me the cutters, I made the right choice....I'm not leaving the car down for a month waiting for parts.


I'm running a G5X4 cam, and am now putting on 59cc (milled .025") TEA 5.3 heads with 2.02/1,55 valves, and .040" Cometics.

N4cer

iTrader: (11)

It's just a detail anyway. Personally I don't think a 2.00" valve needs that big cutter. But with your valves, you might as well. So it's cool.

Thunder took that long? Heck, I ordered directly from Isky at 5pm EST and they shipped it the next day.

Thimble

iTrader: (2)

So what do you think I should do?

Put the head/cutter on as-is and just roll the engine until the piston hits it, then cut (slightly down in the bore).....or shim the head up until it clears at tdc and cut there?

Based on the pics in the linked thread, the intake cut comes quite close to edge of the piston, and I would hate to cut with the piston down in the bore and risk nicking a cyl wall.


The third (and best or maybe only) option is to just have the seat area of the head machined out so the cutters fit fully in the chamber proper. I can get that done easy enough...but won't happen before the weekend.

Thimble

iTrader: (2)

Some pics....


Exhaust:






Intake:









I can't be the first one to experience this....

quick346

iTrader: (4)

how much do they charge for these things? i am a die maker and plan on makeing my own. i bet i can make them for a lot less with a stock valve with tool steel welding rod tig welded on and then cut and sharpend.

mike

quick346

iTrader: (4)

If you look at the angle of the valve to the piston. it makes no sense to cut way bigger than the valve size.

at tdc if the valve hit it would be at the highest point(towards the top of the engine) as it could ever be. at more lift or at btdc and at more lift it would be further down on the piston where the contact point would be.

so by going to a way oversized releif you will just be decreasing the static comp ratio.

not really doing anything else.

aNuBiS

iTrader: (25)

I will be doing this shortly and wondering where each piston needs to be in the bore when you cut. TDC, BDC, meet half way? lol

Any and all help would be appreciated, thanks.

brad8266

iTrader: (23)

TDC. Why would you cut it at the places where the valve isnt close to the piston ie BDC or halfway?

aNuBiS

iTrader: (25)

Half my question was sarcasm, but excellent thanks for the response.

Also, how then does he solve the problem of the cutters not fitting in the smaller head chambers in order to make these cuts..

Ericbigmac83

iTrader: (19)

It needs to be at tdc. This is where the valve is close to the piston. Since the valves are angled in comparison to the pistons, the further down the piston is -- the further away the cutter would hit the piston from where it is actually supposed to hit it

Thimble

iTrader: (2)

I ended up cutting with the piston about 1/8" down in the bore...since that's about how much the cutter extended out of the head chamber.

I set up the cutter in the head, placed the head on the block, then slowly rotated the engine until the piston just about touched the cutter, then cut. It worked out just fine. When I clayed the heads, the valve dropped slightly below, but still well within in the notch. I cut the notch .100" deep, clayed, and ended up with about .095" valve clearance (clay thickness).

I did not have to notch for the exhaust valve, had a ton of clearance there.








Finished this up Monday morning, car is running extremely well and strong with no issues. The power difference of the heads and added compression is amazing...a nigh and day difference from cam-only.

Ericbigmac83

iTrader: (19)

Looks good, whats your setup by the way?

brad8266

iTrader: (23)

In the case of the cutter not fitting you would have to let the piston drop down slightly, just enough for the cutter to fit.

aNuBiS

iTrader: (25)

Awesome pics and thanks a ton for the explanation and info's. LS1tech rocks.

Thimble

iTrader: (2)

Stock bottom end 2001 LS1 (C5 Vette).
LG G5X4 cam (24x/24x 111 lsa)
TEA 5.3l heads, stage 2 (2.02" int/1.55" exh) that have been milled .025" for a 59cc chamber.
Cometic .040" head gaskets. (resulting compression 11.5 scr / 8.6 dcr).
ARP head studs
new GM "LS7" lifters
Comp 7.375" pushrods
PRC dual valve springs/ti retainers
stock rocker arms
Powerbond 25% UD pulley
LS2 timing chain
stock LS6 oil pump
FLP LT headers, X, no cats. GHL catback
(stock) LS6 intake manifold/stock TB
38# Lucas injectors


Getting a slight bit of the sewing machine sound since the head swap. I was running 7.425" pushrods with the cam and stock heads/gasket. The milling and thinner gasket put the heads about .040" down...I figured I'd be safe in going .050" less on pushrod length. I may try a set of 7.4's to see if the noise can be calmed down, or maybe get some adjustable roller rockers.
It was dead quiet before with the cam (only)...so I know it can be made quiet, and that the steep lobe profile isn't to blame.

Irocss85

iTrader: (1)

damn, too bad I was too busy to get on here lately. but your supposed to cut the back side of the cutter down. just like if you were cutting a valve job. but with a bench grinder. you just take out the straight cut w/o reducing the diameter of the cutter face. know what Im trying to say? pretend your doin a valve job with the bench grinder. eventually, it'll fit in the empty cyl head with the seat removed, just like you did. then you'd do your cuts at TDC.

goin to be buying a set of those myself. I rented the tool from LG motorsports. should have just bought the cutters at that point. ohwell, I'll buy them later now that a friend is giving me an LS head to use. I'll see if I can find a pic of the tool I used.