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Will I need to flycut pistons?

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Old 04-08-2008, 05:38 PM
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Default Will I need to flycut pistons?

Just wondering if I will need to flycut my pistons with this setup:

Ported LS1 stage 2 heads - UNMILLED
Stock thickness head gasket
TSP 228R cam (.588/.588 - 228/228 -114)
1.8 roller rockers


Just wanted to make sure that this will work no problem. With the 1.8 rockers it will bring the lift of the cam up to .623, so I just want to be safe.

ALSO,

Can I get some recommendations for the 1.8 rocker arms? Harlands?

Thanks.
Old 04-08-2008, 08:19 PM
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With 1.7's id say youd probably clear just fine, but with the 1.8 theres just not enough anecdotal evidence out there to say one way or the other. Measure using a checker spring from 15* BTDC to 15* ATDC checking with a dial indicator every 2* or so. Thatll give you a good idea on how close you come.
Old 04-11-2008, 12:39 AM
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anyone else?

WTF is a checker spring?

Not familiar with this flycutting/clearance thing at all.
Old 04-11-2008, 06:43 AM
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Here is a link to assist in the flycutting learning curve.

https://ls1tech.com/forums/generation-iii-internal-engine/709183-how-flycut-pistons.html

R/

Frat
Old 04-11-2008, 10:11 AM
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Why do you want to go to 1.8 rockers? I would stick with the 1.7 IMO.

Bill
Old 04-11-2008, 03:11 PM
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Originally Posted by Bill Bowling
Why do you want to go to 1.8 rockers? I would stick with the 1.7 IMO.

Bill
I went with the 228R - .588 lift so that it would run very well with stock heads. I don't want to change the cam again when I install the cylinder heads, so to get some more lift/power out of the cam I want to go with 1.8's. 1.8's will give me .622 lift with this cam.

Why would you NOT go with 1.8's?
Old 04-11-2008, 03:46 PM
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You should not have any piston to valve clearance issues with that setup!

Here's a short lesson on valve timing and its relation to piston to valve clearance for anyone curious



That's a diagram of a random cam I found online. The basics of the valve events are the same though! People wonder why I tell them that amx lift is not the most important thing to consider when wondering about piston to valve clearance. Here's why! You see at the peak of the red curves (when the cam is at max lift), the piston about half way up/down the cylinder. That's not where you have piston to valve clearance issues, since your valves are only open ~.600" (of course that varies on the cam and rockers). You have clearance issues when the intake valve is chasing the piston after TDC (see the red line ramp up right before TDC?). So if your cam has a nasty aggressive lobe on it and gets off the seat with fast ramps and big low lift numbers, you're more likely to kiss pistons. The opposite goes for the exhaust. That piston is chasing the exhaust valve as its closing.

So....if you've got those real aggressive lobes and big duration, you're more likely to kiss pistons and valves together. That's where valve reliefs come in to play.

Again, that's the abbreviated version. Don't nit-pick
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Old 04-11-2008, 04:19 PM
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Originally Posted by Matt@Texas-Speed
You should not have any piston to valve clearance issues with that setup!

Here's a short lesson on valve timing and its relation to piston to valve clearance for anyone curious



That's a diagram of a random cam I found online. The basics of the valve events are the same though! People wonder why I tell them that amx lift is not the most important thing to consider when wondering about piston to valve clearance. Here's why! You see at the peak of the red curves (when the cam is at max lift), the piston about half way up/down the cylinder. That's not where you have piston to valve clearance issues, since your valves are only open ~.600" (of course that varies on the cam and rockers). You have clearance issues when the intake valve is chasing the piston after TDC (see the red line ramp up right before TDC?). So if your cam has a nasty aggressive lobe on it and gets off the seat with fast ramps and big low lift numbers, you're more likely to kiss pistons. The opposite goes for the exhaust. That piston is chasing the exhaust valve as its closing.

So....if you've got those real aggressive lobes and big duration, you're more likely to kiss pistons and valves together. That's where valve reliefs come in to play.

Again, that's the abbreviated version. Don't nit-pick
Thanks a bunch for the info Matt. I'll probably be giving you a call to order the rockers and whatever else I need for the head swap soon.

PS the cam runs really strong and with the spray the car feels like it was built to run on the juice.

I strongly recommend this cam fro NO apps. I am sure that you guys make a NO app cam, but this one suited my fancy so I ordered it on a 114 centerline and here we go.

I should see a bit more power when I install my Magnaflow, electric cutout, and bottle heater, so I'll let everyone know how that goes. Then I'll swap the heads and re-tune. Hoping for 550+ rwhp on the spray!
Old 04-11-2008, 04:48 PM
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Originally Posted by SPDEMON
Why would you NOT go with 1.8's?
I heard they were more stressful on the valve train but I am not an expert.

Bill

Old 04-12-2008, 10:57 PM
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Where did you hear that from?

On LS1 Tech? Friend?

Any info woud help/ be appreciated.
Old 04-21-2008, 05:27 PM
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Can I get a little more input on 1.8 rockers possibly being harsh on the valvetrain?

I'd really appreciate it.
Old 04-21-2008, 06:49 PM
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Originally Posted by SPDEMON
Can I get a little more input on 1.8 rockers possibly being harsh on the valvetrain?

I'd really appreciate it.
I just heard it on another site before I replaced my rockers. I do not rem the source. It could have been way off.

Bill
Old 04-21-2008, 07:44 PM
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Originally Posted by Bill Bowling
I just heard it on another site before I replaced my rockers. I do not rem the source. It could have been way off.

Bill
ive heard you should try to get all your lift out of your cam and not your valve train, its making the valve train do more than it needs to. thats just what i "heard" im no expert either.
Old 04-21-2008, 09:09 PM
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Originally Posted by Bill Bowling
I heard they were more stressful on the valve train but I am not an expert.

Bill


I'm no expert either but have always heard the same thing also; if your running agressive profiles, it's best to stick with 1.7's. If you look at TR's websight they say not to run 1.8's with most of their cams due to the agressive ramp rates. I think it has to do with valvetrain geometry, the mass of the moving parts, and the required spring pressures. Not to say that some poeple don't get away with it.



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