Checking PTVC. Let me know if this sounds right.
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Checking PTVC. Let me know if this sounds right. So I worked on checking my PTVC today and I want to make sure I did it right. I have a 98 TA with the GMPP ASA cam in it. I had an incident when installing the cam so it forced me into doing heads as well. I bought a set of patriot performance stage 2 LS6 heads milled to 62cc. The valves are 2.02 intake and 1.57 on exhaust. I used my old head gasket and made 2 solid lifters by taking them apart and putting washers in place of the spring inside. I set the old gasket down and put the lifters in. I then put the head on and threw 3 bolts in cylinder 1. I had two bolts in the area under the valve cover and one closest to the radiator on the lower part under the header. I then adjusted my pushrods to the point they were making the test springs just start to move when I tightened up the rockers. I did not torque anything down I just snugged everything really well. I left the one lower bolt out of the cylinder cause the header was in the way. When I rotated the motor around I check incrementally from 20 degree's before and after TDC on my degree wheel. It really only got tight around 10 like I read on here. I did not get the exact amount of clearance because I used feeler guages and grabbed enough to have .100. I knew if I could slide that in I was fine. The exhaust was a hair closer then intake but I could get the .100 in on intake and exhaust.
So now that I have written this novel my questions are do I need to have the head torqued to 30ftpds or more to check this acurately? And did I set the p rod length right by having it tight when at TDC on number 1. Thanks for all your help.
So now that I have written this novel my questions are do I need to have the head torqued to 30ftpds or more to check this acurately? And did I set the p rod length right by having it tight when at TDC on number 1. Thanks for all your help.
Last edited by THE CHOP SHOP; Jan 6, 2008 at 10:26 AM.
1. degree camshaft
2. use a head gasket with the thickness ur going to be using for final assembly, if not do the math according. Run head bolts down to snug.
3. adjust the rockers to 0 lash, that means no preload on checking springs. you will turn your 8mm bolt untill you feel all the lash/slack go away in the geometry. if you go a little bit to tight(past 0 lash) you will open the valves ever so slightly. u will be able to see and feel all of this.
intake= adjust intake rocker to 0 lash when exhaust rocker just starts to open.
exhaust= adjust exhaust rocker to 0 lash when intake rocker when intake valve is 3/4" of the way closed(on the closing side of the intake stroke).
lash= with your checking springs in place and when your valves are at the closed position after you have lash them, there should be no preload on checking springs.
4. roll the motor around clockwise to when the exhaust valve begins to open and keep rotating untill exhaust valve is on the closing side. Keep rotating till the exhaust rocker arm continues to close, and stop the degree wheel at 10* BTDC, and put a dial indicator on the exhaust spring retainer, 0 dial indicator, push down slowly untill exhaust valve hits top of piston, and right down your reading. After you do that, continue to rotate engine slowly clockwise(u will see the intake rocker starting to move or already moving) and rotate the degree wheel to 10* ATDC, stop, put the dial indicator on the intake spring retainer, 0 dial indicator, push down slowly and take your reading. Hope you got atleast .065+ intake and .080+ exhaust clearance, if not you might want to think about flycutting, different thickness head gasket, or alter cam timing. hope this helps and good luck man.
Joe
2. use a head gasket with the thickness ur going to be using for final assembly, if not do the math according. Run head bolts down to snug.
3. adjust the rockers to 0 lash, that means no preload on checking springs. you will turn your 8mm bolt untill you feel all the lash/slack go away in the geometry. if you go a little bit to tight(past 0 lash) you will open the valves ever so slightly. u will be able to see and feel all of this.
intake= adjust intake rocker to 0 lash when exhaust rocker just starts to open.
exhaust= adjust exhaust rocker to 0 lash when intake rocker when intake valve is 3/4" of the way closed(on the closing side of the intake stroke).
lash= with your checking springs in place and when your valves are at the closed position after you have lash them, there should be no preload on checking springs.
4. roll the motor around clockwise to when the exhaust valve begins to open and keep rotating untill exhaust valve is on the closing side. Keep rotating till the exhaust rocker arm continues to close, and stop the degree wheel at 10* BTDC, and put a dial indicator on the exhaust spring retainer, 0 dial indicator, push down slowly untill exhaust valve hits top of piston, and right down your reading. After you do that, continue to rotate engine slowly clockwise(u will see the intake rocker starting to move or already moving) and rotate the degree wheel to 10* ATDC, stop, put the dial indicator on the intake spring retainer, 0 dial indicator, push down slowly and take your reading. Hope you got atleast .065+ intake and .080+ exhaust clearance, if not you might want to think about flycutting, different thickness head gasket, or alter cam timing. hope this helps and good luck man.
Joe
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Thanks Joe. I did pretty mush everything you listed. My only changes were I did not degree the cam because my numers kept changing on me. I could spend a little more time with it but figured I would jump into the PTVC and if it was way out one way or the other I would know it was off. From what you described I had things snugged down and the rockers were at zero lash. My only other change was using feeler guages instead of my dial indicator in between the tip of the valve and the rocker. I was told by a friend this works just as well and I felt it would be more acccurate since my magnetic base is what was giving me a hard time on the degreeing.
Thanks Joe. I did pretty mush everything you listed. My only changes were I did not degree the cam because my numers kept changing on me. I could spend a little more time with it but figured I would jump into the PTVC and if it was way out one way or the other I would know it was off. From what you described I had things snugged down and the rockers were at zero lash. My only other change was using feeler guages instead of my dial indicator in between the tip of the valve and the rocker. I was told by a friend this works just as well and I felt it would be more acccurate since my magnetic base is what was giving me a hard time on the degreeing.
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So I took another crack at it today because the last time I checked I had the piston at TDC when I set the rockers to zero lash. This time I had the cam on the base circle (when I did not see the pushrod move up for a while) and tightened it to zero lash on both intake and exhaust. When I do it that way things are a little tight. I think I am in the 60's on intake and 80's on exhaust. I am using a solid lifter that is full of washers to make the lifter act like it is fully pumped up. Are my measurements today more accurate then before or am I still not understanding this right. The one thing that concerned me a little is it seemed like it kept getting tight past 10 up to 0. I have the front cover off to make sure the degree wheel has not moved and it seems to still be dot to dot when the wheel is on 0.
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Thanks Joe I tried doing it that way and it was tough to figure out exactly when the intake was 3/4 closed. I read another post saying saying to put it on base circle. I will go out now and give it another shot the way you described. When the intake is at that point do you know roughly where it would be on the degree wheel? Thank you for your guidance.
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Verdad Gallardo Thanks Joe I tried doing it that way and it was tough to figure out exactly when the intake was 3/4 closed. I read another post saying saying to put it on base circle. I will go out now and give it another shot the way you described. When the intake is at that point do you know roughly where it would be on the degree wheel? Thank you for your guidance.
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Well I set zero lash the way you said and it seems like it is the same. I am pretty shocked that it is so tight. It looks like the intake is aroud .050 and exhaust around .070. What makes me wonder is that my stock heads were 67cc since they were 853's on my 98 block. I went to 62cc so It should be around .030 that was milled. With as tight as I am I would think I could not even run stock 243's and be super safe. I did go with a 2.02 valve but I dont see that tightening things up that much. My only guess is with the new valve and the way the seat is cut I may have lost some clearance there. Just to make sure there is nothing I need to add on to the reading cause the lifter is solid right? I am pretty sure there is not but it is worth a shot.
Since these are Patriot heads, you may want to contact Gunnar and ask him if the valves sit lower in the chamber than stock. Also, you may want to check the cam intake center (degree it) than re-check the PTV.
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I checked from 20 BTDC to 20 ATDC. It got tight in different areas and seemed like it would be ok in the 10 range but when I set the degree wheel on I just put it dot to dot and put the pointer on zero. I figured since I did not put the dial indicator on the piston before I zero'd it if I check around those area's I would be ok. When it was at ten it did not seem so tight. Is 10 all I need to worry about and 5 or 20 nothing to worry about if it is tight?
I would check it every 2 degrees from 20 before to 20 after and then take the lowest value. Also, have you cleaned up the top of the pistons so you aren't hitting carbon?
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Pistons are clean and I did check incrementally even at TDC. I thought that was ideal but if I only need to check at 10 After and Before then I think I am in better shape.
Usually you do 20 before to 20 after to develop a curve of clearance from which you can determine the minimum. Since you have been through it a few times and know where you minimum is located, you can probably just check that unless you change the cam timing (degree it to a different position).
I checked from 20 BTDC to 20 ATDC. It got tight in different areas and seemed like it would be ok in the 10 range but when I set the degree wheel on I just put it dot to dot and put the pointer on zero. I figured since I did not put the dial indicator on the piston before I zero'd it if I check around those area's I would be ok. When it was at ten it did not seem so tight. Is 10 all I need to worry about and 5 or 20 nothing to worry about if it is tight?
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I am using my balancer install tool so that I have enough room to have the wheel spin and not bang into anything. What I did was crank pretty hard on the nut that is into the crank for a few revolutions before I put it on 0 (that way it would not move on me). I kept the front cover off when I rotated it and checked when I was at 0 if I looked like I was dot to dot and it was. On the end of the balancer tool I just used my 24 socket on my socket.