L46 Engine Specs
Dr. Detroit
Joined: Mar 2012
Posts: 10,095
Likes: 4,022
From: New Braunfels Texas
On a fairly stock build I like to use the Elgin "Z-28" flat tappet spring.......get it in the kit with new locks and retainers. Add some umbrella valve seals or have the heads machined for positive Viton seals.
https://www.ebay.com/itm/Small-Block...S!-1:rk:1:pf:0
You cannot beat this kit up to .500 lift.......it just works. It is a high quality spring and will work perfect with a L-46 or similar cam.
Spring Specs :
- Intake & Exhaust
- Single with Damper
- Seat Pressure 118 @ 1.700
- Open Pressure 318 @ 1.210
- Coil Bind 1.160
- I.D 0.876"
- O.D 1.260"
- Wire Diameter .162"
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
according to sealed power that GM pn 3911068 crosses with pn VS-677
But I find it incredible how a CONVENTIONAL NOT BEEHIVE spring with seat pressure around 76 pounds could be ideal for L46 cam; much less LT1 cam.
specs for VS-677
closed 76, open 194, rate 262
https://fme-cat.com/overlays/part-de...ing&brandId=SP
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Functional equivalent of a "Z-28 spring" is sealed power (or melling) pn VS-739R; IMO that looks like a good match for either L46 or LT1 cams.
specs for SP VS-739R
closed 104, open 277, rate 365
https://fme-cat.com/overlays/part-de...ing&brandId=SD
But I find it incredible how a CONVENTIONAL NOT BEEHIVE spring with seat pressure around 76 pounds could be ideal for L46 cam; much less LT1 cam.
specs for VS-677
closed 76, open 194, rate 262
https://fme-cat.com/overlays/part-de...ing&brandId=SP
----------------------------------------------------------------------------------------------------------------------------------------------------
Functional equivalent of a "Z-28 spring" is sealed power (or melling) pn VS-739R; IMO that looks like a good match for either L46 or LT1 cams.
specs for SP VS-739R
closed 104, open 277, rate 365
https://fme-cat.com/overlays/part-de...ing&brandId=SD
Race Director
Joined: May 2006
Posts: 18,668
Likes: 2,564
from the GM Heritage Center for 1970 Corvette. PDF page 96 shows the spring specifications and they line up with what jackson shows for the Sealed Power spring
https://www.gmheritagecenter.com/doc...t-Corvette.pdf
https://www.gmheritagecenter.com/doc...t-Corvette.pdf
Thread Starter
Advanced
Joined: Dec 2017
Posts: 72
Likes: 7
Wow, that's a great link. It even has torque curves for all three 350's. Good reinforcement for going with the L46 cam. I like that torque curve. Looks like it does much better at low rpm than the LT1 build that I was considering, and I've got power brakes and air conditioning, so want that. As far as the springs, I'll put my trust in the Chevy engineers. I've heard several times that they liked to make their cam grinds valve train friendly (who know ....maybe to save money on manufacturing variables). I'm actually going with about 10:1 compression, but the L46 and L82 used the same cam, and the L82 compression ratio was even lower than that, so I assume 10:1 will work fine, and of course that will probably rob a little torque from an exact L46.
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,062
From: altered state
St. Jude Donor '05
If youre open to it an Isky 270 mega cam would make an awesome replacement, the torque comes on hard, sounds good too. No need for steep gears, can work power brakes, etc
https://www.jegs.com/i/Isky-Racing-C...SABEgLzAfD_BwE
https://www.jegs.com/i/Isky-Racing-C...SABEgLzAfD_BwE
Last edited by cv67; Jan 29, 2019 at 01:30 PM.
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Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
from the GM Heritage Center for 1970 Corvette. PDF page 96 shows the spring specifications and they line up with what jackson shows for the Sealed Power spring
https://www.gmheritagecenter.com/doc...t-Corvette.pdf
https://www.gmheritagecenter.com/doc...t-Corvette.pdf
Its specs do line up with the VS-677 spring.
But they don't line up with my opinion.
Guess I'm gonna have rush out & stick Chevette springs in everything.
Le Mans Master
Joined: Mar 2004
Posts: 7,458
Likes: 1,484
From: Little Rock AR
True - over the years....All the factory SBC springs were the same... Including the mighty LT-1. The only "special" springs were made shorter for valve rotator applications.
The -142 so-called "Z/28 spring" was never factory installed in a production engine. It was an over the counter piece designed for the GM -140 "off-road" cam.
The -142 so-called "Z/28 spring" was never factory installed in a production engine. It was an over the counter piece designed for the GM -140 "off-road" cam.
Last edited by stingr69; Jan 29, 2019 at 02:36 PM.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,444
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Valve float is very destructive. I would not put my name on a H-flat cammed motor with old junk in it. I actually use larger diameter h-roller type springs on the few h-flat cammed motors that I built. Large diameter runs cooler and last longer. I also start out with 120- 140# closed rates. They have done dyno testing on motors with low spring rates and then switched in high spring rates and the power levels changes were insignificant.
I haven't worn out my vette motors cams running 230 seat and 640# open
Last edited by gkull; Jan 31, 2019 at 06:39 AM.