Checking Pushrods Geometry — 1970 LT-1 Clone - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**mattfranklin** · 05-05-2018, 09:33 PM

I’m finally putting together my vintage 1970 LT-1 clone.
I’m inclined to go with stock parts, but adjustable pushrod checking with a dry erase marker shows 0.050 shorter might be slightly better. Tough call because I have stamped steel and non-roller rockers, so the contact is wider and more smudged. I'm looking at the right hand valve stem, intake for #1. This one is with the checker set for stock dimensions.

EDIT:
Procedure...
Clean surfaces with brake cleaner.
Set adjustable pushrod to desired length.
Insert pushrod.
Mark top of stem with dry-erase marker.
Turn engine to TDC compression stroke.
Tighten rocker nut to ~zero lash.
Spin the engine over for two cycles (4 revs).
Loosen rocker nut and see how it wears.

**mattfranklin** · 05-05-2018, 09:40 PM

Previous pic was stock. This one is 0.050 shorter.

I’m leaning towards stock, because, well, stock. And I think as it wears the pattern will work its way closer to the middle anyway.
Also, with stamped steel there isn’t a super sharp line.

**truckdude239** · 05-06-2018, 01:51 PM

If your using a stock cam and valve componations id just stay stock

crazy longhorn · 05-07-2018, 05:45 PM

Get the "strike line", as close to the middle of the valve tip, as you can! longhorn

**mattfranklin** · 05-08-2018, 12:40 AM

Thanks for the comments. I fiddled with it a little more this evening. I set the adjustable for half a turn in from stock. And I think it pretty well nailed the strike line / witness mark / whatchamacallit. Right in the center. I measured with my new caliper (Neiko 8" digital for $25 on Amazon) and got 7.792". Pretty dang close to what Comp Cams says is “stock.”

71cadc10 · 05-12-2018, 12:45 PM

just wanted to note, you aren't getting to full lift unless you have a solid lifter in there? the lifter cup is compressing down as you turn it over. You probably will get about 1/2 cam lift.

**mattfranklin** · 05-12-2018, 03:09 PM

I'm going to use a set of Crane 11621-16 pushrods, stock length. Chrome-moly. Quality I trust.

**mattfranklin** · 05-12-2018, 03:10 PM

Quote:

Originally Posted by 71cadc10

just wanted to note, you aren't getting to full lift unless you have a solid lifter in there? the lifter cup is compressing down as you turn it over. You probably will get about 1/2 cam lift.

Good comment. I'm running a solid lifter cam, so I'm good. If I were using a hydraulic cam I'd use my checker springs.

05-05-2018, 09:40 PM	#2
mattfranklin Senior Member Join Date: Dec 2011 Location: Moraga, CA Posts: 801	Re: Checking Pushrods Geometry — 1970 LT-1 Clone Previous pic was stock. This one is 0.050 shorter. I’m leaning towards stock, because, well, stock. And I think as it wears the pattern will work its way closer to the middle anyway. Also, with stamped steel there isn’t a super sharp line. Attached Images __________________ (Very) Slow-Going Build Thread: Stock 1970 Short Step with Stock 1970 LT-1 http://67-72chevytrucks.com/vboard/s...d.php?t=567340 Last edited by mattfranklin; 05-06-2018 at 01:02 AM.

05-06-2018, 01:51 PM	#3
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,217	Re: Checking Pushrods Geometry — 1970 LT-1 Clone If your using a stock cam and valve componations id just stay stock __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube

05-07-2018, 05:45 PM	#4
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,403	Re: Checking Pushrods Geometry — 1970 LT-1 Clone Get the "strike line", as close to the middle of the valve tip, as you can! longhorn __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

05-08-2018, 12:40 AM	#5
mattfranklin Senior Member Join Date: Dec 2011 Location: Moraga, CA Posts: 801	Re: Checking Pushrods Geometry — 1970 LT-1 Clone Thanks for the comments. I fiddled with it a little more this evening. I set the adjustable for half a turn in from stock. And I think it pretty well nailed the strike line / witness mark / whatchamacallit. Right in the center. I measured with my new caliper (Neiko 8" digital for $25 on Amazon) and got 7.792". Pretty dang close to what Comp Cams says is “stock.” Attached Images __________________ (Very) Slow-Going Build Thread: Stock 1970 Short Step with Stock 1970 LT-1 http://67-72chevytrucks.com/vboard/s...d.php?t=567340 Last edited by mattfranklin; 05-08-2018 at 10:06 AM.

05-12-2018, 12:45 PM	#6
71cadc10 Registered User Join Date: Apr 2004 Location: Boiling Springs, PA Posts: 435	Re: Checking Pushrods Geometry — 1970 LT-1 Clone just wanted to note, you aren't getting to full lift unless you have a solid lifter in there? the lifter cup is compressing down as you turn it over. You probably will get about 1/2 cam lift. __________________ 71 C10 long bed, 2003 6.0L, 06GTO E40, T56, 12bolt 4.10 rear

05-05-2018, 09:33 PM	#1
mattfranklin Senior Member Join Date: Dec 2011 Location: Moraga, CA Posts: 801	Checking Pushrods Geometry — 1970 LT-1 Clone I’m finally putting together my vintage 1970 LT-1 clone. I’m inclined to go with stock parts, but adjustable pushrod checking with a dry erase marker shows 0.050 shorter might be slightly better. Tough call because I have stamped steel and non-roller rockers, so the contact is wider and more smudged. I'm looking at the right hand valve stem, intake for #1. This one is with the checker set for stock dimensions. EDIT: Procedure... Clean surfaces with brake cleaner. Set adjustable pushrod to desired length. Insert pushrod. Mark top of stem with dry-erase marker. Turn engine to TDC compression stroke. Tighten rocker nut to ~zero lash. Spin the engine over for two cycles (4 revs). Loosen rocker nut and see how it wears. Attached Images __________________ (Very) Slow-Going Build Thread: Stock 1970 Short Step with Stock 1970 LT-1 http://67-72chevytrucks.com/vboard/s...d.php?t=567340 Last edited by mattfranklin; 05-05-2018 at 10:26 PM.

05-12-2018, 03:09 PM	#7
mattfranklin Senior Member Join Date: Dec 2011 Location: Moraga, CA Posts: 801	Re: Checking Pushrods Geometry — 1970 LT-1 Clone I'm going to use a set of Crane 11621-16 pushrods, stock length. Chrome-moly. Quality I trust. __________________ (Very) Slow-Going Build Thread: Stock 1970 Short Step with Stock 1970 LT-1 http://67-72chevytrucks.com/vboard/s...d.php?t=567340



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.