capn smokey

iTrader: (1)

I have heads that flow 270+cfm and 11.5:1 cr but im still running a tiny 230ish cam and I would like to know my ptv. I need to be running a huge 244-252 range cam to make the most power out of my setup but i think my valves might hit the pistons with anything more than what i have now. I have a zz4 with 50cc rhs heads btw. ANy help would be awesome.
Thanks-Jeremy

9000th01ss

iTrader: (10)

Yea, you can do it with nothing special.
All you really need is a solid lifter or one made solid, if you're installing a solid cam you'll already have one.

I do it like this.
Start by mocking it up.
Make sure you have proper valvetrain geometry, and cam timing.
Remove an intake and exhaust valve spring and let the seal hold the valve, or use tape.
Adjust valve lash to zero.
Rotate the engine slow by hand.
If theres no bind put a stack of feeler gauges between the valve tip and rocker(.080 for the intake and .100 ex or whatever you think it should be), let it open the valve--keep it at zero lash.
Rotate it very slow, if it stops you have valve contact.
Remove feeler gauges until it'll turn again. The thickness of those feeler gauges will tell you how much clearance you have.
If the valves hit and you need to cut, use more precise tools.
This works if you have a good understanding of what you're doing and you pay attention.
If you're the type that screws things up easy, has weak mechanical ability this might not be the best way for you to check.

capn smokey

iTrader: (1)

Thanks bro, never thought of that. Also i am not one of low mechanical ability, Ive built a few cars in my day but Ive always just checked ptv with clay and the heads off. At this point Im way too lazy to tear my motor apart, thanks for the info. Btw, this method will tell me how much more lift I could take at a sustained rate but how might I know how much more duration i could have. My current cam is .550 lift and I dont need much more than that but I do need more duration.

Irocss85

iTrader: (1)

yeah that ways could work, but you'll need to use extreme caution and patience to make sure its accurate. best way is to use a cam degree kit. it'll come with checking springs (very lightweight springs you can compress by hand to install inplace of valve springs). this will take out any slop YOU could induce by not being careful enough. anyways, put the degree wheel and find tdc just like you would degreeing a cam in. back up about 15degrees to btdc. then put a dial ind. on the valve spring (the flat portion) using the mag. pedastal stand. use your finger to push the valve open until the valve touch's the piston, right down every 5 degrees. so it'll look like this

15btdc = .120"
10btdc = .097"
5btdc = .093"
0tdc = .090"
5atdc = .080"
10atdc = .092"
15atdc = .113"

the point where its the tightest is usually just after tdc. not at tdc like you'd think. (or was it just before? I think its after). but every cam/deck height, valve thickness, head gasket thickness will be different. thats why its ALWAYS a good idea to check after you put in a new cam. esp. in your case, where your heads are prolly milled down quite a bit to get that small of a chamber? this was is far superior to the clay method. which is pretty much equal to how most people test bearing clearance's with those strips. (forget the name). its just a rough check. but not the best way. if you do it like above, you can have full confidence, and know exactly what the clearance is, and where its the tighetest. what pistons do you have? if you need more ptv, the piston deck's are prolly thick enough (at the eyebrow) to go a little deeper. you also might need to widen the eye brow, as milling the heads, thinner head gaskets, decking the block all move the center of the valve in towards the center of the eng. (towards the cam). and the arch wont be at the best poss. angle cause theyre made for stock deck heights and such.

anyways, I'll bet you'll need to cut the pistons a little due to your setup if your wanting a high lift cam, AND longer duration then what you got.

look in the gen III intern. eng. I wrote a sticky about cutting ptv clearance w/o pulling the pistons out of the engine. its not hard but does take some time and care. I got lots of good pics in there that will prety much explain everything IF you need to do it.

chris

capn smokey

iTrader: (1)

awesome bro, they are unmilled heads btw. I bought the heads with a 50cc chamber because zz4s come with dish pistons and are down in the hole a lil bit. I wish i could just put my specs in a formula or program and come up with a rough number that way. I just want about .030-.050 more lift and about 14-18degrees more duration, I think a .600ish cam with 244/248@.50 would make my motor scream. It already lays down 400whp through a t-56 but I think have the right combo of parts to do 440-460whp with a different cam. Thanks for the input guys.

JPH

iTrader: (2)

soft spring method all the way.