beneficial intake/head setup on lm7
09-29-2013, 07:52 PM
#11
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First, your 862 heads have cathedral ports and have 61.15cc combustion chambers (not 58cc like someone posted). The 243 heads are 64.45cc and definitely outflow the 862 heads. If the compression ratio is kept the same they should gain you at least 20 hp. To keep the compression ratio about the same, you would need to mill the 243 heads at least .020". If you mill .030" that would give you about 59.XXcc which would raise the CR a little. Performance cams like higher CR and higher CR gives you a little more power. It will need to use premium gas with higher compression, but you will get the best performance by running about 10:1 with the cams you are considering.
lol alright well looks like the general concensous is running a tbss intake with milled 243 heads and a 220/224 cam at 10.1 cr? do you guys suggest having them ported and polished and a valve job done while they are at the shop or just have the milling job done?
09-29-2013, 08:35 PM
#12
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If the heads have low mileage and in good condition you probably don't need a valve job. If they have quite a few miles on them or if you don't know their history, then it would be good insurance to have a multi-angle valve job done.
Who's doing the machine work? I've heard Burlington Performance in Raytown is pretty decent.
Who's doing the machine work? I've heard Burlington Performance in Raytown is pretty decent.
09-29-2013, 09:16 PM
#13
Honestly I would keep the 216/220 cam.
Do the 243 head swap and bump compression.
220/224 cam will move the power out till 3500 I bet
Smaller cam more power n torque sooner.
I wouldn't focus on peak power of the bigger cam. Power and toque under the curve is key.
Do the 243 head swap and bump compression.
220/224 cam will move the power out till 3500 I bet
Smaller cam more power n torque sooner.
I wouldn't focus on peak power of the bigger cam. Power and toque under the curve is key.
09-30-2013, 07:17 AM
#14
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If the heads have low mileage and in good condition you probably don't need a valve job. If they have quite a few miles on them or if you don't know their history, then it would be good insurance to have a multi-angle valve job done.
Who's doing the machine work? I've heard Burlington Performance in Raytown is pretty decent.
Who's doing the machine work? I've heard Burlington Performance in Raytown is pretty decent.
i figured a lil bit bigger cam with better heads/intake and a stall will move it a lil more. with the 216/220 and the set up now it seems like my power is all up top, i dont really like that, i want it more midrange. but ill prolly get everything first and see how it runs with the 216/220 before i decide to go bigger or stay the same.
09-30-2013, 05:49 PM
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Prices vary from shop to shop. A straight valve job might cost about $150 where as a performance multi-angle valve job and mill might go for $300. I'd pick a machine shop that has a good reputation doing the LS performance heads and plan on paying a premium price. No sense skimping on heads, that's where you make or break a lot of power.
10-02-2013, 09:49 AM
#16
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I did some looking online and found some 243 (well, they said thats what they are) for like 100-125 bucks each. they are selling them so low cuz one of the header bolt holes is stripped and need to be re threaded or helicoiled. true 243 heads have yellow valve springs correct? these do not have the yellow valve springs but i believe in the pic the casting number is 243. would it be wise to purchase these since they are so low and then rethread the stripped out header bolt hole or spend some more and get some 243 heads that just need to be cleaned/milled?
10-02-2013, 06:00 PM
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Not all 243 heads have yellow valve springs. Besides, you don't want to use old worn springs anyway. Casting number is the real key. Whether to get those heads or not is your call. One bolt hole is a fairly easy fix, but might be an indicator of other abuse or problems.
10-03-2013, 07:37 AM
#19
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i wasnt gonna use the old springs, id use the ones i have now which are good for up to .600 lift. i just was making sure so that i didnt buy some heads that werent 243 that someone put yellow springs on trying to pass them off as 243.
