Rocker Arm Help

[foureyefox347]

Ok so I build a 347 and I put ported gt40p heads on and I have a tfs stage 1 cam. now I want to put 1.7 ratio roller rockers so if I gave out the specs of the pistions and the heads is there anyway for me to check or calculate if the valves will hit the piston with out taking that heads back off

 

[84Ttop]

This is something that has to be checked. How would you know if you had .001 or .100 of clearance without checking? The deck height on every block is different among other things. Check to know or cross your fingers and go, up to you

 

[liljoe07]

X2

Not to mention the various other things that can be off as well. There are lots of tolerances that can swing either way and stack up against you, or for you. That being said, you can do it with the heads on if you have the right tools.

 

[mikestang63]

Better to check now that risk major damage later. As mentioned, every block and heads are different and things like
Block deck height
Head deck thickness
Head gasket thickness
Rocker arm ratio
Cam grind tolerances
Cam timing
Cam bore alignment
Main bore alignment
Crankshaft throw tolerances
Crank journal tolerances
Piston wrist pin tolerances
Connecting rod tolerances
Valve spring height
Bearing clearances
Push rod length

.... well you get the idea.... all impact PTV clearance

Method with head off- preferred

http://www.enginelabs.com/engine-tech/engine-blueprinting-how-to-check-piston-to-valve-clearance/

Method with head on

http://www.cranecams.com/faqview.php?s_id=24

 

[foureyefox347]

well it looks like the heads are comin off again

 

[tpstang]

I have the same situation now, because I just bought a set of heads and want to run trick flow cam. ptv was the biggest question I was dealing with but gave in to pulling the engine down because it just isn't worth the risk.

 

[Dave2000GT]

I'd just let it ride, should be fine.

 

[84Ttop]

I'd just let it ride, should be fine.

You buying his valves or something? This is terrible advice!!!!

 

[mikestang63]

I'd just let it ride, should be fine.

Just wow. I would say that makes the top 10 for 2013 of bad advice.

tfs1 cam that has the following specs

Duration @ .050" (degrees) - 221 intake/225 exhaust
Cam Lift (intake/exhaust) - .312"/.319"
Lift w/ 1.6 rocker (intake/exhaust) - .499"/.510"
Lobe seperation (degrees) - 112°

vs. the stock cam with the following specs
Duration @ .050 210intake /210 exhaust
Lift with 1.6 rockers 444/.444
Lobe seperation 115 degrees

So take the new lift with the 1.7 RR is
Intake (.499/1.6) x 1.7 =.530 lift
Exhaust (.510/1.6) x 1.7 = .542 lift

Although peak lift has nothing to do with PTV, the increased overlap of the cam and the RR will. With a longer duration and shorter lobe seperation . General rule of thumb is .080" on the intake side, and .100" on the exhaust side. I'd also be making sure his springs are good enough for this lift.

 

[84Ttop]

Just wow. I would say that makes the top 10 for 2013 of bad advice.

tfs1 cam that has the following specs

Duration @ .050" (degrees) - 221 intake/225 exhaust
Cam Lift (intake/exhaust) - .312"/.319"
Lift w/ 1.6 rocker (intake/exhaust) - .499"/.510"
Lobe seperation (degrees) - 112°

vs. the stock cam with the following specs
Duration @ .050 210intake /210 exhaust
Lift with 1.6 rockers 444/.444
Lobe seperation 115 degrees

So take the new lift with the 1.7 RR is
Intake (.499/1.6) x 1.7 =.530 lift
Exhaust (.510/1.6) x 1.7 = .542 lift

Although peak lift has nothing to do with PTV, the increased overlap of the cam and the RR will. With a longer duration and shorter lobe seperation . General rule of thumb is .080" on the intake side, and .100" on the exhaust side. I'd also be making sure his springs are good enough for this lift.

So with the year coming to an end do we make an official Bad advice of 2013 thread? Just curious..

 

[mikestang63]

@Noobz347 .. top 10 worst advice of 2013 thread? maybe a sticky? lol

 

[Noobz347]

Just wow.

This ^^^

Please don't run the motor until the clearance check is performed. It seems like a pain in the ass if you've never done it before, but it's really a fairly simple procedure.



Unless... You're into pain and just wanna see what happens when things wrong.

 

[Dave2000GT]

You buying his valves or something? This is terrible advice!!!!

They make new pistons every day, so why worry?

 

[mikestang63]

They make new pistons every day, so why worry?

View attachment 122138

 

[A5literMan]

:stick2::roast:

 

[liljoe07]

Hehe..... All of the above!

 

[foureyefox347]

Just wow. I would say that makes the top 10 for 2013 of bad advice.

tfs1 cam that has the following specs

Duration @ .050" (degrees) - 221 intake/225 exhaust
Cam Lift (intake/exhaust) - .312"/.319"
Lift w/ 1.6 rocker (intake/exhaust) - .499"/.510"
Lobe seperation (degrees) - 112°

vs. the stock cam with the following specs
Duration @ .050 210intake /210 exhaust
Lift with 1.6 rockers 444/.444
Lobe seperation 115 degrees

So take the new lift with the 1.7 RR is
Intake (.499/1.6) x 1.7 =.530 lift
Exhaust (.510/1.6) x 1.7 = .542 lift

Although peak lift has nothing to do with PTV, the increased overlap of the cam and the RR will. With a longer duration and shorter lobe seperation . General rule of thumb is .080" on the intake side, and .100" on the exhaust side. I'd also be making sure his springs are good enough for this lift.

yea im pretty sure my springs are rated for that lift and duration i got the alexs parts gt40p springs they say good for .560 lift

 

[Grabbin' Asphalt]

Lmaobad advice thread would be Great!!!