Custom grind cam questions, help?
Custom grind cam questions, help? Putting back together my LQ4 with PRC 2.5 243 heads with GM valves. Stock LQ4 dished pistons and using a stock MLS gasket for a 6.0.
Put a degree wheel on the EPS cam today and found out that it was 107.25 where the ICL on the card is 108. I'm assuming where I have it now is as best as it will get?
Second question, with the cam the way it is, I measured PTV clearance with a couple different pushrod lengths. I was suggested to get 7.425 pushrods, so that was my first test. PTV ended up being extremely small. So I then used the old 7.4 pushrods and it was much better (this is indeed using modified lifters to convert to solid roller). With the 7.4's it looked to be in spec, the exhaust definately was, the intake was probably somewhere around .090-0.100. Does this sound right?
Cam specs 231/234 .617/.612 112+4
Third question. After seeing the way pushrod length affected the PTV so much, I decided to re-measure pushrod length. I used the Comp tool and came up with 10 turns, which comes to 7.3, and then adding preload puts the pushrods around 7.35. I used regular LS7 lifters seeing as it shouldn't matter if they are hydraulic or solid considering I'm going for 0 lash and not compressing the lifter at all.
For those that don't want to read.
Will PTV be an issue, what pushrod length should I use, and is 107.25 close enough to the cams 108 ICL spec.
Sorry for the silly questions this is my first custom grind cam install.
Put a degree wheel on the EPS cam today and found out that it was 107.25 where the ICL on the card is 108. I'm assuming where I have it now is as best as it will get?
Second question, with the cam the way it is, I measured PTV clearance with a couple different pushrod lengths. I was suggested to get 7.425 pushrods, so that was my first test. PTV ended up being extremely small. So I then used the old 7.4 pushrods and it was much better (this is indeed using modified lifters to convert to solid roller). With the 7.4's it looked to be in spec, the exhaust definately was, the intake was probably somewhere around .090-0.100. Does this sound right?
Cam specs 231/234 .617/.612 112+4
Third question. After seeing the way pushrod length affected the PTV so much, I decided to re-measure pushrod length. I used the Comp tool and came up with 10 turns, which comes to 7.3, and then adding preload puts the pushrods around 7.35. I used regular LS7 lifters seeing as it shouldn't matter if they are hydraulic or solid considering I'm going for 0 lash and not compressing the lifter at all.
For those that don't want to read.
Will PTV be an issue, what pushrod length should I use, and is 107.25 close enough to the cams 108 ICL spec.
Sorry for the silly questions this is my first custom grind cam install.
With it in there at 107.25, you are a little advanced from the card. I'd leave it. Unless you have an adj. timing set.
For the PTV. You need to set pushrod length to 0 lash with your solid lifter when doing the test. And best to have checking springs on cyl 1.
Ron
For the PTV. You need to set pushrod length to 0 lash with your solid lifter when doing the test. And best to have checking springs on cyl 1.
Ron
TECH Addict
Joined: Sep 2009
Posts: 2,481
Likes: 5
From: PA/MD
Yup, exactly what Ron said, it sounds like you have plenty of ptv, but when checking you were actually cranking the valve opened when it should have been closed....measure for 0 lash, then add whatever preload you want to the measurement.
I do infact have an adjustable cam gear with the offset bushings. I had a comp cams kit but without the crank socket and centered the wheel on the bolt. I'm thinking that could have thrown my measurem
ents off.
Now with checking the ptv can I turn the engine over using the checker as my pushrod without hurting the tool? And do I really need to use the checker springs if ive already got solids to measure? I don't have a problem doing it, its just one more tool ill need to buy and now funds are low. Id like to get this done so I can stop worrying about it
Thanks for the help guys.
ents off.
Now with checking the ptv can I turn the engine over using the checker as my pushrod without hurting the tool? And do I really need to use the checker springs if ive already got solids to measure? I don't have a problem doing it, its just one more tool ill need to buy and now funds are low. Id like to get this done so I can stop worrying about it
Thanks for the help guys.
I doubt your checking pushrod will survive full spring load. They will bend. Do you have some checking springs? You could just use the inners I think. You have it apart far enough.
Ron
Ron
Thanks Ron for the help. Yeah I figured the tool would bend or shear off the threads under full spring load. I will try and remove the outer spring and check. I do have checking springs that came with the kit.
Just got back inside, went out and measured pushrod length again and came up with 9-3/4 to 10 turns on two different cylinders, according to the common census of LS7 preload measurement that should put me right at 7.375. Huge releif knowing I needed shorter pushrods the way I was getting PTV readings before
Just got back inside, went out and measured pushrod length again and came up with 9-3/4 to 10 turns on two different cylinders, according to the common census of LS7 preload measurement that should put me right at 7.375. Huge releif knowing I needed shorter pushrods the way I was getting PTV readings before
Trending Topics
Your push rod length has nothing to do with your ptv clearance. If you are losing ptv with a longer push rod, it is too long and your opening the valve. Since you have the solid lifters, you need to find 0 lash, count the turns and add your pre load. That is your push rod length...then you can measure ptv clearance.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo Yes that's where I'm at now. I ordered the Comp LS socket for the degree wheel. I had it centered on the crank bolt but I still think it was off. I'm releived I at least have the pushrod length done.
Thanks for the help everyone
Thanks for the help everyone
I do infact have an adjustable cam gear with the offset bushings. I had a comp cams kit but without the crank socket and centered the wheel on the bolt. I'm thinking that could have thrown my measurem
ents off.
Now with checking the ptv can I turn the engine over using the checker as my pushrod without hurting the tool? And do I really need to use the checker springs if ive already got solids to measure? I don't have a problem doing it, its just one more tool ill need to buy and now funds are low. Id like to get this done so I can stop worrying about it
Thanks for the help guys.
ents off.
Now with checking the ptv can I turn the engine over using the checker as my pushrod without hurting the tool? And do I really need to use the checker springs if ive already got solids to measure? I don't have a problem doing it, its just one more tool ill need to buy and now funds are low. Id like to get this done so I can stop worrying about it
Thanks for the help guys.
The process I use is to set the piston to TDC by hand. You can feel the piston pause at TDC. Then install the degree wheel and tighten it real well. Re-do the TDC feel method. Next fashion a pointer that you can move around and line it up with 0. This just gets you close.
Next you need a positive stop. I used a flat piece of 1/2" alum bolted across the cylinder. It works because the pistons stick out a bit. Rotate the engine back about 20 degrees, bolt on the stop, then rotate until the piston just hits the stop. Note how far BTDC is it. Then rotate the other way until it hits again. Note the reading. Exactly half way inbetween is true TDC. Remove the stop across the cyl. Rotate until the pointer hits that number, then move the pointer to 0.
Well everyone I finally figured it all out. There's alot of confusion with this and now I can see why. I bought the LS socket from Comp and it was $50 well spent indeed. Makes everything so much easier. Ended up with 107.75 ICL, which the smallest bushing sent it to 106/109. So the cam was ground right and there are no offset bushings required, which is a huge plus.
I did get the pushrod length correct and verified it again today, ended up being 7.375 even though I was recommended 7.425.
Checking the PTV clearance, I was just being an idiot. First I was using the solid lifter with the right pushrods, and the checking springs and torquing the rockers to 22lb ft. The valve knicked the piston, leaving a little indentation in the piston but the valve was good. I couldn't figure out what the hell I was doing wrong. The clay kept sticking, it was just really pissing me off. Came back inside and searched, and it ended up being my dumbass torqueing the rockers down, instead of tightening to 0 lash on the base circle that was throwing my readings way the hell off.
Checked with 0 lash on cylinder #1, ended up being over .115 on both intake and exhaust.
Someone should really do a good write up with pictures to help us dumbasses out haha.
I did get the pushrod length correct and verified it again today, ended up being 7.375 even though I was recommended 7.425.
Checking the PTV clearance, I was just being an idiot. First I was using the solid lifter with the right pushrods, and the checking springs and torquing the rockers to 22lb ft. The valve knicked the piston, leaving a little indentation in the piston but the valve was good. I couldn't figure out what the hell I was doing wrong. The clay kept sticking, it was just really pissing me off. Came back inside and searched, and it ended up being my dumbass torqueing the rockers down, instead of tightening to 0 lash on the base circle that was throwing my readings way the hell off.
Checked with 0 lash on cylinder #1, ended up being over .115 on both intake and exhaust.
Someone should really do a good write up with pictures to help us dumbasses out haha.
