L31 with LT1 241 cam?

[Supercharged111]

No lope, my 93 Z28 sounds like a truck. It has stock manifolds, dual 2.5" to 3" y pipe, and a bullet muffler dumped at the axle. It does idle around 800 RPM though, probably sound a bit different down in the 500-600 range. Too wide an LSA though for any lope, the stock cam sits on a 111 LSA. LT1 used 2 different cams. The information is getting harder to find, I believe the LT4 website that seems to no longer exist broke the cams down by year. Looks like a 241 cam is the early cam for the splined opti. The later vented optis were driven by a longer pin on the cam. The difference in lift and duration is negligible, but the LSA and ICL changed too and I'm having trouble getting good repeatable numbers on that. Late LT1s were rated 10hp higher but also had dual cats, so who knows where the extra hp came from. IMO you're splitting hairs trying to decide which stock LT1 cam you have, as long as you have ~.450" of lift it's not a B body cam and you will see a difference.

https://www.enginebuildermag.com/1999/09/rebuilding-the-chevrolet-lt1-engine-2/

 

[trx125]

Almost ready.

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[Supercharged111]

What's the installed height on those valve springs?

 

[trx125]

1.75" and drilled the push rod holes to 1/2" just for sheets and giggles. I have to install the lifters, push rods and rockers, then do a final check for coil bind.

 

[Supercharged111]

Those valve springs are meant to go in at 1.80" BTW. So now they're good to .500" lift vs. .550" with much higher seat pressures. Did you measure to see what your pressures are?

 

[trx125]

I have not checked pressures. The machine shop set the height. I just went out and checked a few of the springs and measure 1.755 to 1.76 best I can tell. The lt1 241 cam with 1.6 rockers is good for 480/490 lift. I'll have to see if I can borrow a scale and measure the seat pressures.

 

[L31MaxExpress]

Those valve springs are meant to go in at 1.80" BTW. So now they're good to .500" lift vs. .550" with much higher seat pressures. Did you measure to see what your pressures are?

You are a little off on those numbers. At a 1.8 installed height the LS6 springs are good to 0.570" lift, coil bind 0.640. At a 1.75 install height they are good to 0.520" lift and do not coil bind until 0.590" lift. Reverse calculating the spring pressure from the change in height gives you about 17# higher spring pressure. So 107# rather than 90# closed. Will also hit 290 open at .500" and about 298 @ .520". LS6 springs are 345 lb/in rate. 90# @ 1.8 and 290 @ 1.25

 

[trx125]

Well, I got it finished and install installed in the Tahoe.

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[1BigCarrot]

Looks good mate, nice and clean

 

[Supercharged111]

Looks good mate, nice and clean

Give it time.