Standard valve drops for LS series heads?
12-23-2014, 05:52 PM
#1
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Standard valve drops for LS series heads? Ok, just wondering if anyone can confirm valve drops for standard heads?
Ive seen 0.200 for LS2 stuff, but would really like LS7 and LS3 drops
Im doing some calcs on cams and head comparisons.
Ive seen 0.200 for LS2 stuff, but would really like LS7 and LS3 drops
Im doing some calcs on cams and head comparisons.
12-24-2014, 02:58 PM
#3
LOL. I have tried to gather this data from others myself with no luck.
So, just for you I took a ride over to HPS. They had a set of virgin #317 cores on the rack. The cylinder head measured valve drop was .160" intake and .170" exhaust. If you figure in a .051" factory head gasket and subtract .006" positive deck height, you would get roughly .205" intake and .215" exhaust valve drop on an assembled engine with flat top pistons and no valve reliefs.
He did not have any square port heads, but I have been told by 2 people that the intake valve drop on those is .133". I would assume the exhaust would be the same as cathedral port, but that is an assumption. First chance, I will measure some myself.
So, just for you I took a ride over to HPS. They had a set of virgin #317 cores on the rack. The cylinder head measured valve drop was .160" intake and .170" exhaust. If you figure in a .051" factory head gasket and subtract .006" positive deck height, you would get roughly .205" intake and .215" exhaust valve drop on an assembled engine with flat top pistons and no valve reliefs.
He did not have any square port heads, but I have been told by 2 people that the intake valve drop on those is .133". I would assume the exhaust would be the same as cathedral port, but that is an assumption. First chance, I will measure some myself.
12-24-2014, 03:30 PM
#5
For an unassembled engine: Pull the valve springs, put the head on a flat surface, set up a dial indicator mic on the top of the valve stem, lift the valve firm against the seat, zero the dial, then lower the valve until it rests on the table(flat surface).
For an assembled engine, roughly the same procedure, but lower the valve from the seated position until it rests on top of the piston that is at absolute top dead center.
For the unassembled engine, the thickness of the head gasket and the deck height will have to be added for estimated actual valve drop. When doing it this way, there will be a slight margin of error due to the 15 degree valve angle, but it is only a thousandth or two.
For an assembled engine, roughly the same procedure, but lower the valve from the seated position until it rests on top of the piston that is at absolute top dead center.
For the unassembled engine, the thickness of the head gasket and the deck height will have to be added for estimated actual valve drop. When doing it this way, there will be a slight margin of error due to the 15 degree valve angle, but it is only a thousandth or two.
12-24-2014, 05:51 PM
#11
I just can't figure out how you could get over .050" more valve drop than the other guys who measured square ports. The valves are over .100" larger in diameter than a cathedral port intake valve. They would have to hit the table sooner unless they are deeper in the chamber. My PRC CNC LS6 heads had next to no margin. How much margin have you seen on stock cathedral port intake valves?
12-24-2014, 07:36 PM
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Yeah I just fished out 0.133 myself from PatG on another forum for the LS3
There is a nice excel sheet where you feed in the numbers and cam spec and it gives you a pretty close estimation so you can mess about with cam details to see what should fit.
Someone also said 232 is about the largest intake duration that will fit. Advance dependent of course.
Would be good to get a definitive list up for a sticky or some such.
There is a nice excel sheet where you feed in the numbers and cam spec and it gives you a pretty close estimation so you can mess about with cam details to see what should fit.
Someone also said 232 is about the largest intake duration that will fit. Advance dependent of course.
Would be good to get a definitive list up for a sticky or some such.
12-24-2014, 08:34 PM
#13
Yeah I just fished out 0.133 myself from PatG on another forum for the LS3
There is a nice excel sheet where you feed in the numbers and cam spec and it gives you a pretty close estimation so you can mess about with cam details to see what should fit.
Someone also said 232 is about the largest intake duration that will fit. Advance dependent of course.
Would be good to get a definitive list up for a sticky or some such.
There is a nice excel sheet where you feed in the numbers and cam spec and it gives you a pretty close estimation so you can mess about with cam details to see what should fit.
Someone also said 232 is about the largest intake duration that will fit. Advance dependent of course.
Would be good to get a definitive list up for a sticky or some such.
https://ls1tech.com/forums/carburete...ft-thread.html
If you are talking about the same spreadsheet I use, I was amazed at how accurate it was.
10-23-2019, 11:29 AM
#14
I have a thread that has that initiative already. Check out post #27:
https://ls1tech.com/forums/carburete...ft-thread.html
If you are talking about the same spreadsheet I use, I was amazed at how accurate it was.
https://ls1tech.com/forums/carburete...ft-thread.html
If you are talking about the same spreadsheet I use, I was amazed at how accurate it was.
10-23-2019, 12:46 PM
#15
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Brodix BR7 (LS7) standard 72 cc head with titanium valves the intake was about .180 and the exhaust was like a .205 drop. Flat on a table.
10-23-2019, 03:11 PM
#17
I have a spreadsheet that calculates piston to valve clearance... so I wonder if that's what speed was referring to?
But the formula you can use if you have all the motor specs is as follows:
Freedrop - piston depth - .100" + gasket thickness = total lift clearance @ TDC
(Tappet lift @ TDC lobe centerline) x (rocker ratio) = Valve lift @ TDC
If valve lift is greater than total lift clearance, you need to flycut or adjust your cam centerline.
But the formula you can use if you have all the motor specs is as follows:
Freedrop - piston depth - .100" + gasket thickness = total lift clearance @ TDC
(Tappet lift @ TDC lobe centerline) x (rocker ratio) = Valve lift @ TDC
If valve lift is greater than total lift clearance, you need to flycut or adjust your cam centerline.
10-27-2019, 03:20 PM
#18
http://www.pcmofnc.com/2013/01/10/pi...ce-calculator/
I've used this, it is pretty accurate. You have to have numbers for the cam lobes, which you can get approximately from the Comp web page that describes their lobes, using the duration and other info you know about your cam.
I've used this, it is pretty accurate. You have to have numbers for the cam lobes, which you can get approximately from the Comp web page that describes their lobes, using the duration and other info you know about your cam.
The following 2 users liked this post by patSS/00:
JakeFusion (10-27-2019), Rich2342 (03-28-2024)
10-27-2019, 08:00 PM
#19
http://www.pcmofnc.com/2013/01/10/pi...ce-calculator/
I've used this, it is pretty accurate. You have to have numbers for the cam lobes, which you can get approximately from the Comp web page that describes their lobes, using the duration and other info you know about your cam.
I've used this, it is pretty accurate. You have to have numbers for the cam lobes, which you can get approximately from the Comp web page that describes their lobes, using the duration and other info you know about your cam.
Spreadsheet seems to be broken shows Err 502 in red but cant figure out what would be error
11-04-2019, 01:31 PM
#20
Don't know what spreadsheet program you are using, but that spreadsheet only works for me if i open it in microsoft excel. Open office calc or any other prog doesn't seem to like it.