Rangersltw

iTrader: (11)

I have a TRex cam 242/248 .610/.615 110LSA. I am pulling my 241s and replacing them with 243 heads.



edit: I am thinking I will be getting them milled .036 to achieve a 11.1:1 CR How much should I fly cut to maintain proper PTV clearance?

TransAmcoupe98

iTrader: (10)

I dont think you will have clearance if you mill them without flycutting your pistons. Out of curioisty, what gear are you running with this cam?

Rangersltw

iTrader: (11)

I know I wont. That is why I said I was fly cutting them. My question is how much should I fly cut them. I am running 4.30 gears w/ a 9in.

TransAmcoupe98

iTrader: (10)

Oh I apologize, I didn't see that part. I have some info I'll post in a few. Those gears will do nicely with that cam.

Rangersltw

iTrader: (11)

Thanks! I currently have 4.10s with my 10bolt now. Its just not enough. Im still waiting on my MWC 9in. It should be done soon.

TransAmcoupe98

iTrader: (10)

I want to say that .1'' is about as deep you should go safely. I couldnt find specifics on the t-rex, but I don't think you would need to go that deep.

Rangersltw

iTrader: (11)

I have the cam specs posted in the OP.

TransAmcoupe98

iTrader: (10)

I meant about how much is the norm people are flycutting using the t-rex. Give thunder racing a call, they have pretty good CS.

Rangersltw

iTrader: (11)

I just had a thought. If I am not having clearance issues now and then get the heads milled .036. If I fly cut at least .036 Wouldn't that be the same clearance I currently have?

TransAmcoupe98

iTrader: (10)

Not necessarily. I dont know how much clearance you would have with that cam on unported heads. If you had any, wouldn't be much at all, not safe enough in case of an over rev.

PREDATOR-Z

Even in stock setups the margins are below recommended operation. Will the Trex clear milled heads? NO
You should flycut .080 or 2cc

01ssreda4

iTrader: (96)

I find out the max that's safe to cut a stock piston and cut it that much.

EDIT: or just listen to predator's suggestion.

mark21742

Bolt them on and clay them.....take what you find and subtract .040" and that will tell you how much you need to cut the pistons to be safe.

Since your bumping up your compression go with a .40" gasket too...stock pistons come .005-+" up out of the hole, so this will give you your optimum quench area and help keep knock down if you get a bad tank of gas

2000whitevert

iTrader: (1)

Lift is not the only thing that should be used to determine ptv clearance. Cam timing events are a big part of this. I agree with claying your set up to be certain. As with any engine modification checking clearances is the only insurance to avoid a problem.

Rangersltw

iTrader: (11)

I already have a stock GM gasket for replacement. What is OEM thickness? Will having the .40 gasket make that much difference? I will be claying. I'll cut them to .080 and check ptv.

mark21742

Stockish .051". Since you already have them, run them...but if you end up pulling your heads again later and needing more gaskets, pick up the .040"

BuckaroooZ28

iTrader: (1)

T Rex hit my stock 241 valves.....self clearance lol

PREDATOR-Z

When does max lift occur???? Contact is probable from 10* BTDC to 10* ATDC. So lift (at the range we use) have little to do with PTV clearance. Do not confuse with tappet lift.

95ONE

iTrader: (1)

If you're going to cut that much off the deck, don't forget to get the shorter Push Rods while you're in there. My new pushrods needed to be shorter by the exact amount I milled the heads also subtracting the .01 for the thinner headgasket from stock thickness.(Not exactly shocking) - in your case, .050 shorter. ( .036 milling + .010 thinner gasket = .046) I suggest starting there.

.080 on Intake. .10 on exhaust. - Exhaust expands more with more heat is the reason. I bet you're already too close to the pistons and just haven't hit yet. If you're heads are going to be off. Don't be lazy. Clay the pistons and KNOW what you need to do.

or just slap those puppies on there and GO! There's always a choice.

Rangersltw

iTrader: (11)

My overall goal with decking the heads is to be around 11:1 CR. How can I figure out how much I will lose with fly cutting? I will be claying the pistons to check for PTV.