4.8 to ls1

Hey guys, I just bought an ls1 from HPE a couple of weeks back. Im going to ditch the 4.8 and put the ls1 in its place. I also got a deal on some 243s that will be going on it, along with my headers. Ill be pulling the cam outta my 4.8 (222/224 .568/.571 113) and putting it in the ls1 also. Were going to dyno it with the 4.8 and then again after the swap so it should be interesting. Hopefully i can get into the 13s with it. What kind of power do you guys think this thing will make?

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Originally Posted by casey.shoemake

Hey guys, I just bought an ls1 from HPE a couple of weeks back. Im going to ditch the 4.8 and put the ls1 in its place. I also got a deal on some 243s that will be going on it, along with my headers. Ill be pulling the cam outta my 4.8 (222/224 .568/.571 113) and putting it in the ls1 also. Were going to dyno it with the 4.8 and then again after the swap so it should be interesting. Hopefully i can get into the 13s with it. What kind of power do you guys think this thing will make?

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4.8 will make about 290-315whp. LS1 will make 390-415whp. Biggest difference will be the lower rpms, and torque though. My cammed 4.8 made as much as my stock Ls1 does. edit Another option for you is to get your 4.8 heads ported and polished. Some places do that for around $500. Out flow the 243's and have a smaller CC chamber.

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Originally Posted by ff_jeff

4.8 will make about 290-315whp. LS1 will make 390-415whp. Biggest difference will be the lower rpms, and torque though. My cammed 4.8 made as much as my stock Ls1 does. edit Another option for you is to get your 4.8 heads ported and polished. Some places do that for around $500. Out flow the 243's and have a smaller CC chamber.

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Were talking about pp the 862s rite? Wow, always thought the 799/243 were the next best thing to l92 heads. I wonder what the compression would be like with the smaller chambers of the 862s?

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Originally Posted by casey.shoemake

Were talking about pp the 862s rite? Wow, always thought the 799/243 were the next best thing to l92 heads. I wonder what the compression would be like with the smaller chambers of the 862s?

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here LS1 Info and Specifications - SMOKEmUP.com
the stock 243 heads are nice. But many people use the 5.3/4.8 heads and port them. If you have a set, and jus pay for machine work, you dont have to buy the $500 243 heads, then machine them. at 61cc stock, you can even mill a little more off. 243 heads are 64.4 cc.
a ported 243 should out flow a ported 5.3, but you will pay for it. Check out prc heads, tx speed heads ect. They all sell ported 5.3 heads. I think their 5.3 flow like 300 at .600 lift.
with 61 cc heads, and a stock head gasket thickness (.051) you should be at around 10.75 CR. or so. With a .041 gasket right at 11.0cr.

Thanks. Good info, so stock for stock the 5.3 head would be better? Talked to my cousin and he picked up the 243s for me, for free. So as of rite now which ones will yield the most power in stock form? Saw your thread on ls1tech also, they were talking about putting the ls1 valves in the 5.3?

Im just running P&P'd 862's on my iron 5.7 should run fine either way you go

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Originally Posted by casey.shoemake

Thanks. Good info, so stock for stock the 5.3 head would be better? Talked to my cousin and he picked up the 243s for me, for free. So as of rite now which ones will yield the most power in stock form? Saw your thread on ls1tech also, they were talking about putting the ls1 valves in the 5.3?

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I would not run the stock 5.3 heads on the LS1. If the 243's are free, IMO I would either put them on, or Sell them for $500 and use the money to port the 5.3 heads.

Ive been doing some thinking and now im wondering how my current cam will be in the ls1? Ive searched and find tons of stuff for cars, not heavy trucks. If i could put 360 to the wheels id be happy.