L31 with LT1 bottom end

[L31MaxExpress]

So I calculated it. The Intake centerline should be 110°. The cam only has 2° built in advance being a marine cam. You have it installed 6-7° retarded. 6* based of your intake centerline measurement and 7* based off your intake close measurement. Either way just shooting yourself in the foot in terms of low-end torque and MPG.

 

[L31MaxExpress]

One other thought. If you crunch both the 395' Marine cam or the factory 264' part number Vortec cam they are both over 8:1 DCR with iron heads from GM.

The factory Vortec cam is
191/196 @ 0.050
111 LSA
106 ICL

The 395' Marine cam is
196/206@ 0.050
109 LSA
106 ICL

If you have not already chosen your head gasket, get as close to 0.040" quench as possible. On a block that has not been decked with an aluminum head this usually means using the factory GM Composition graphite vortec gaskets that are 0.028" compressed.

 

[Crazydavez28]

So I calculated it. The Intake centerline should be 110°. The cam only has 2° built in advance being a marine cam. You have it installed 6-7° retarded. 6* based of your intake centerline measurement and 7* based off your intake close measurement. Either way just shooting yourself in the foot in terms of low-end torque and MPG.

One other thought. If you crunch both the 395' Marine cam or the factory 264' part number Vortec cam they are both over 8:1 DCR with iron heads from GM.

The factory Vortec cam is
191/196 @ 0.050
111 LSA
106 ICL

The 395' Marine cam is
196/206@ 0.050
109 LSA
106 ICL

If you have not already chosen your head gasket, get as close to 0.040" quench as possible. On a block that has not been decked with an aluminum head this usually means using the factory GM Composition graphite vortec gaskets that are 0.028" compressed.

So your saying go ahead and send it. I have it measured .025" in the hole and already bought some .015" steel gaskets. Guess I can always change them later.

I was having a little trouble finding specs on the factory cam. I did find those numbers from Melling MS1320 which is supposed to be a factory grind. They had it setup at 111 ICL and 65*ABDC Intake closing.

Im gonna play with it a little more and see if my timing set lets me get to the 62* the cam card calls out That nets me a 8.39 DCR

 

[L31MaxExpress]

So your saying go ahead and send it. I have it measured .025" in the hole and already bought some .015" steel gaskets. Guess I can always change them later.

I was having a little trouble finding specs on the factory cam. I did find those numbers from Melling MS1320 which is supposed to be a factory grind. They had it setup at 111 ICL and 65*ABDC Intake closing.

Im gonna play with it a little more and see if my timing set lets me get to the 62* the cam card calls out That nets me a 8.39 DCR

Assuming you are running on the L31 PCM setup 8.39 will be more than manageable with a knock sensor.

The 1320 sounds like the B-car LT1 cam spec to me. The B-car had the same grind. Just straight up rather than the 5° advance of the Vortec.

My worry with the 0.015" gasket would be getting them to seal with an aluminum head. The factory 0.028" gasket is MLS. Has worked well for me with a non surfaced deck and aluminum heads.

 

[Schurkey]

I wanted to use steel-shim gaskets with an aluminum head. The gasket material wasn't the problem, the bore size was. The heads I selected need a gasket bore size greater than what the Mr Gasket shims provide; and the Fel-Pros are the same. Both are spec'd at 4.100 bore size.
https://www.jegs.com/i/Mr-Gasket/720/1130G/10002/-1
https://www.jegs.com/i/Fel-Pro/375/7733SH1/10002/-1

Jegs has a "store brand" steel shim gasket that lists a larger bore size--4.150. The price is right. These should be large enough for the heads I want to use.
https://www.jegs.com/i/JEGS/555/210044/10002/-1

 

[Crazydavez28]

I got out there and advanced the cam from 116 to 108 ICL

• Intake opens at 26btdc and closes 61adbc This works out to 267* @.006" 3 degrees more than advertised.
  
• DCR calculated at 8.45 Piston to Intake Valve clearance was .025" checked with plumbers putty, 1.6 rockers, and no head gasket installed.
  
• Installed springs are 120# seat pressure and 300# @.550" I will probably be happy with the setup but thinking the PTV clearance is tight. Will this make .040" with the head gasket installed?

Also, worth noting is the valves seem to be too big for the stock LT1 valve reliefs. Could a guy tastefully clearance these?

 

[L31MaxExpress]

I got out there and advanced the cam from 116 to 108 ICL

• Intake opens at 26btdc and closes 61adbc This works out to 267* @.006" 3 degrees more than advertised.
  
• DCR calculated at 8.45 Piston to Intake Valve clearance was .025" checked with plumbers putty, 1.6 rockers, and no head gasket installed.
  
• Installed springs are 120# seat pressure and 300# @.550" I will probably be happy with the setup but thinking the PTV clearance is tight. Will this make .040" with the head gasket installed?

Also, worth noting is the valves seem to be too big for the stock LT1 valve reliefs. Could a guy tastefully clearance these?

I have heard of the LT1 guys fly cutting the stock pistons to run big cams with 2.055 valves. The pockets are designed for 1.94/1.50 valves and a stock cam that only has .447/.459 lift.

 

[Crazydavez28]

These are 2.02 I 1.6 E Procomp heads that were re-worked by a local shop. Photo shows what I end up with no head gasket.

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[L31MaxExpress]

These are 2.02 I 1.6 E Procomp heads that were re-worked by a local shop. Photo shows what I end up with no head gasket.

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If it is 0.100 or more I would run it. You can run the intake valve even tighter. About 0.080".

That looks like alot more than 0.025".

 

[Crazydavez28]

If it is 0.100 or more I would run it. You can run the intake valve even tighter. About 0.080".

That looks like alot more than 0.025".

I did this again with my FelPro 1094 gasket included and it think the 0.025" measurement was the piston to deck clearance right next to the valve relief. Adding the gasket thickness increased the clearance from the valve to the side of the valve reliefs.

I still might remove an exhaust valve and scope the motion for cheap insurance. This is a low budget build with used or on-my-shelf parts...unless I wreck it then the price goes up.

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