|07-28-2012 02:54 AM|
0.080" on the intake and 0.100" on the exhaust is considered by many to be a good safe clearance. You will probably find the closest near-miss at the exhaust valve on overlap, when the piston is chasing the exhaust valve back onto its seat.
|07-28-2012 02:40 AM|
Thats great info. That is a good plan. Is it super critical to use a solid lifter for mock up?? I guess I can probaly just buy a couple of solids instead of a hole set. Also what is minimum VTP clearance?
Is there a cam manufacture in particular that sells a "street" solid roller and lifters??
|07-27-2012 10:29 PM|
If you were willing to mock up the motor w the heads, using the cam you got now (with solid lifters)
degree the cam in accuratly and then make some very precise valve to piston clearance and valve open at TDC measurements, you can interpolate what the new cams VTP clearance will be.
VTP clearance is usually closest at around 10deg BTDC and 10deg after TDC.
The exhaust side is the critical spec as the piston and valve chase each other.
May people have notched the piston valve relief deeper and larger radius by hand using a die grinder and 3M discs on a assembled motor with some creative house keeping and masking.
Its not that hard to do.
Any amount of hand releiving needed to get good VTP clearance will be small.
Again the exhaust is the critical factor. You can move the new cam around a bit too to gain clearance.
You need not sweat over this.
When looking at cams this big (duration) you should strongly consider running a mechanical street roller cam.
More power, easy lash setting maintenance. More rpm. These street roller cams are low noise and easy to keep set.
and always out perform a hyd roller.
|07-27-2012 09:26 PM|
|hpete||That seems like a lot of cam for a stock bottom end.|
|07-27-2012 07:44 AM|
Agreed, can't really tell anything without mocking it up. Too many variables.
However, it's not THAT big a "deal" to have the valve reliefs "fly-cut" (type of cutter used for the operation). Any automotive machine shop that has a "piston vise" and a mill can do it. This is the procedure to be used when cams and pistons not "stock" are used. Common practice.
|07-27-2012 05:32 AM|
Here is a page on things to check.
Stock piston valve reliefs need to be checked and clearanced if needed w/2.02" intakes. Aftermarket pistons tend to have more generous reliefs.
|07-27-2012 02:29 AM|
safer is better
when i doubt go to a place like howards cams or elgin or something and buy a cheap solid cam with close to the same numbers...may be impossible when comparing to a roller but its worth a try. most solid lifter stuff is 90 bucks from them. Or as an alternative. check with some local dirt track guys and see if they have a comparable one laying around you could use to test. Us dirt guys never get rid of anything.
|07-27-2012 12:12 AM|
Either should fit.
The larger XR294r-10 cam I would definatly mock up with the heads and Check VTP clearance.
All part of the joys of building Hi performance motors.
|07-27-2012 12:01 AM|
|prostcelica||I'm going to use either AFR 180 street or patriot freedom series 185. I was hoping to use a comp XE288 or XE 294 hydraulic roller. I would attach the link on the cams but I'm posting from my phone so I hope that helps. The only cam I have is a flat tappet magum 270. its 224 at .50|
|07-26-2012 11:05 PM|
Do you hav another similar cam to mock up with?
Similar duration @.050" and LSA. The lift has little to do with VTP clearance
as the piston is way down the bore when the valves are at full lift.
The duration and overlap has more to do with it.
valve opening at near TDC.
You don't give any info on the heads Non stock valve location etc.
|07-26-2012 10:39 PM|
|prostcelica||Hmmmm. I was planning on checking clearances but I'm worried about buying a $300 cam and not being able to use it.|
|07-26-2012 09:16 PM|
There's no way to know and nobody can tell you rather or not your going to have clearance issues you have to check it and there's no way around it.
A cheap method we use is play dough with talcum powder to prevent the valve from sticking.
|07-26-2012 08:58 PM|
|vinniekq2||That cam though not high lift,likely wont fit.depends also on duration and lobe angle.always check clearances|
|07-26-2012 07:54 PM|
I have a stock SBC 350 bottom end. I am going to be putting some aluminum heads, roller cam, intake etc.
My question is how much valve lift can I get away with before running into valve to piston issues??
Stock flat tops with with 4 eyebrow valve relief, .025 deck heigth, .015 head gasket.
I heard you can run into issues with the eyebrows being to small to accomodate 2.02 valves??
Any input would be great. Thanks in advance.
PS: cam I wont to use has following lift......int .54 / exh .562