Vt stage 2 cams

TNstanggurl · Oct 7, 2004

Just wondering if we will have ptv contact if we get the VT stage 2 cams. We have the comp 270's right now and have pretty much came to the conclusion that we are have ptv at high rpm's. I called comp and they said that the lifters are pumping up and that is what is causing it. So I just wanted to make sure that if we get the stage 2 we will not have ptv contact.

GinoGT · Oct 7, 2004

I haven't heard of any PTV issues for VT's cams. Stupid SHM puts that 5* advance into their cams.

TNstanggurl · Oct 7, 2004

vt's

ttt

jbrown · Oct 7, 2004

heres a stupid question what is PTV?

GinoGT · Oct 7, 2004

jbrown said:
heres a stupid question what is PTV?

Piston to Valve contact, usually caused by the cams not being timed right, or having too much lift.

Yes, it is as bad as it sounds. Very effective way of trashing engine components.

maddogg545 · Oct 7, 2004

When you engine has PTV does it make a wierd sound? If so, what does it sound like?

YellowJacketGT · Oct 7, 2004

TNstanggurl said:
Just wondering if we will have ptv contact if we get the VT stage 2 cams. We have the comp 270's right now and have pretty much came to the conclusion that we are have ptv at high rpm's. I called comp and they said that the lifters are pumping up and that is what is causing it. So I just wanted to make sure that if we get the stage 2 we will not have ptv contact.

VT stage 2 port with Comp 268 cams CP 17cc pistons..
Had to fly cut for valve clearance..

Great sound.... Not too aggresive

kboy262 · Oct 8, 2004

I to second the 268H. Grant it they are on my NPI head car, they are great mod. Not too aggressive but helps out a lot in the higher end of the powerband. No problems so far after 6,000 miles.

Avenger · Oct 8, 2004

Dyno results

I know it hasn't been asked but I think this is the right thread to present some dyno numbers

VT Stage 2 cams on stock 00 GT

nickthegenius · Oct 8, 2004

maddogg545 said:
When you engine has PTV does it make a wierd sound? If so, what does it sound like?

In the worst cases, it sounds like the clicking of your injectors x 100 and can hear it over your exhaust and everything. Less severe cases you may just hear a light metallic clicking/tapping at higher RPMs. Either way, it is bad for the engine and can trash you pistons, valves, and possibly the head depending on how the piston hits the valve and what it pushes it into.

prsrizdgt · Oct 8, 2004

YellowJacketGT said:
VT stage 2 port with Comp 268 cams CP 17cc pistons..
Had to fly cut for valve clearance..

Great sound.... Not too aggresive

I am a little coonfused now. The forged piston is dished 17cc's right? And the comp cam only has .550 lift. Why cut the pistons for valve relief?

kboy262 · Oct 8, 2004

prsrizdgt said:
I am a little coonfused now. The forged piston is dished 17cc's right? And the comp cam only has .550 lift. Why cut the pistons for valve relief?

Actually I think he says his are the 268H (NPI cams) not 268AH. The 268H have only .500" lift.

YellowJacketGT · Oct 8, 2004

prsrizdgt said:
I am a little coonfused now. The forged piston is dished 17cc's right? And the comp cam only has .550 lift. Why cut the pistons for valve relief?

These are ported heads. They were milled a bit to clean them.

The reason they need to be cut is they were hitting the edge. The shop did an on engine manual test. The disk is in the middle of the piston. The outer edges are still high...

Actually I made a mistake the Comp cams are XE270AH. .550 lift Duration @.050 Intake 234 Exhaust 238..

These cams significantly opened up my top end. HP stays flat up top rather than fall off.. 5500 - 6400 stayed at 500rwh..

nickthegenius · Oct 8, 2004

Don't forget that the lift isn't the only thing that can cause PTV. Another thing with the Comps is the extra 5* advance that is ground into them. Add that to a cam that already has a decent amount of duration and you end up with the valves open long enough that the piston meets it at the top of the bore and *bam*.

prsrizdgt · Oct 9, 2004

YellowJacketGT said:
These are ported heads. They were milled a bit to clean them.

The reason they need to be cut is they were hitting the edge. The shop did an on engine manual test. The disk is in the middle of the piston. The outer edges are still high...

Actually I made a mistake the Comp cams are XE270AH. .550 lift Duration @.050 Intake 234 Exhaust 238..

These cams significantly opened up my top end. HP stays flat up top rather than fall off.. 5500 - 6400 stayed at 500rwh..

YellowJacket, did you go with forged rods also? What brand of parts did you choose?

Vt stage 2 cams

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