cam/head swap and keeping stock like driveability..
10-07-2012, 02:16 PM
#1
cam/head swap and keeping stock like driveability.. How big can you go with a cam using a bump in compression to help keep the stock characteristics. I realize their are always tradeoffs, not looking to keep the same curve, but where/how would dynamic compression come into play on a stock ls1 for say a 228 or a street sweeper HT? What would be favorable specs concerning opening and closing points or LSA? Just wondering what exactly you can get away with before you actually have more of a race car that needs some gearing or a converter. Thinking of a 5.3 head swap and bigger cam. Want to eventually get gears but looking at a max of 3.73-3.90 for highway driving @ 65-70.
specs: 62,000 miles 6spd, 3.42, ram air, most free mods, SLP lt/LM1 exhaust, no intake and not tuned so far.
specs: 62,000 miles 6spd, 3.42, ram air, most free mods, SLP lt/LM1 exhaust, no intake and not tuned so far.
10-07-2012, 02:25 PM
#2
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Well for reference (mods in sig) I have great drivability down to around 1500 rpm. The heads and cam make for a slight finesse coming off idle, but nothing big at all. I have about 11 to 1 compression as well. The drivability is not much different than my buddy's bolt ons only LS1.
10-07-2012, 02:57 PM
#3
Thanks for the experience, and build info. Thinking maybe the SSHT would work well for what I want and its a little smaller. By cahnce do you know the specs for your cam, was it on a 114/112/111? Do you think a taller gear would hurt it much?
10-07-2012, 03:10 PM
#4
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Specs are 595/598 lift, 232/234 duration, and a 112 LSA + 2
Personally, I think a taller gear is what you want. I wouldn't change my 4.10's for anything. It has great drivability and power
Personally, I think a taller gear is what you want. I wouldn't change my 4.10's for anything. It has great drivability and power
10-07-2012, 05:16 PM
#5
A bump in compression will give you more usable TRQ and HP in the lower rpms with DD duty, but the tune is the major key to driveability. A 228/228 with a wider 114lsa will have a wider smoother power band and would work good with a bump in compression to give it back DCR it loses to a tighter 111 or 112lsa 228/228 cam, but with nicer street manners.
Also shorter gearing like a 3.90 or 4.11 should help, not hurt driveability, for one thing 6th gear will become more useable. Still I wouldn't go any larger than a 232/234 for a DD.
Also shorter gearing like a 3.90 or 4.11 should help, not hurt driveability, for one thing 6th gear will become more useable. Still I wouldn't go any larger than a 232/234 for a DD.
10-07-2012, 08:32 PM
#6
A bump in compression will give you more usable TRQ and HP in the lower rpms with DD duty, but the tune is the major key to driveability. A 228/228 with a wider 114lsa will have a wider smoother power band and would work good with a bump in compression to give it back DCR it loses to a tighter 111 or 112lsa 228/228 cam, but with nicer street manners.
Also shorter gearing like a 3.90 or 4.11 should help, not hurt driveability, for one thing 6th gear will become more useable. Still I wouldn't go any larger than a 232/234 for a DD.
Also shorter gearing like a 3.90 or 4.11 should help, not hurt driveability, for one thing 6th gear will become more useable. Still I wouldn't go any larger than a 232/234 for a DD.
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10-07-2012, 10:58 PM
#8
Yes, that's always a good idea.
Okay, hopefully this will make more sense to you.
With a 228/232 114lsa +4 with the heads milled down to a 64cc chamber size, or if you go with a .040" head gaskets, this will give stock DCR and have 2* of overlap. The IVC is 44 and EVO is 54.
Example:
With stock compression you would need run a 111lsa +4 to get it to stock DCR, but you would have 8* of overlap, The IVC is 41 and the EVO is 51.
Okay, hopefully this will make more sense to you.
With a 228/232 114lsa +4 with the heads milled down to a 64cc chamber size, or if you go with a .040" head gaskets, this will give stock DCR and have 2* of overlap. The IVC is 44 and EVO is 54.
Example:
With stock compression you would need run a 111lsa +4 to get it to stock DCR, but you would have 8* of overlap, The IVC is 41 and the EVO is 51.
10-08-2012, 09:37 AM
#10
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10-08-2012, 09:56 AM
#11
You can technically do low duration cam on a wide LSA and not loose driveability and I am sure there are shops that would gladly sell you but you wont gain a whole lot either, do the gears first. If you are really worried about it do the 3.90s.
The gears make 6th a lot more useable and then open up your cam possibilities.
The gears make 6th a lot more useable and then open up your cam possibilities.
10-08-2012, 10:58 AM
#12
Ths gears dont worry me, I have to get a tune for inspection. I would like to just do a cam and the tune to go with it. It won't be a race car, and I wont mind some low speed torque loss, as gears will happen probably the 3.73, have been researching turbo build, and have searched the TU1 and how it is a a dd
In NA usage till the turbo gets put on. Not much info for that cam in that scenario. So I have kind of decided to vo as big as I can within reason ans swap out when that time comes. when its not a dd...
In NA usage till the turbo gets put on. Not much info for that cam in that scenario. So I have kind of decided to vo as big as I can within reason ans swap out when that time comes. when its not a dd...
10-08-2012, 12:56 PM
#14
No, if I went with the TU1, I would probably mill the 317's I have .010 and use a .040 gasket, and live with that till the turbo build. Just not sure how long till that will be, so was thinking PRC 5.3 and reasonably big cam for the money and just see how good that is, maybe enough for me? If not,
when the time comes just sell stuff and swap parts when I can do the turbo.
when the time comes just sell stuff and swap parts when I can do the turbo.
10-08-2012, 04:00 PM
#15
Im sorry i dont mean to jack your thread, but im curios as to the mpg you get with your mods???? im thinking about doing a full engine build H/C/I and im thinking of going with the EPS 236/248 .615"/.615" but i dont want to lose too much mpg and street manners.
10-08-2012, 05:40 PM
#16
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OP look at my sig. It is a 224R w/ PRC stg2.5 5.3 heads milled to 61cc with OEM thickness head gaskets. It runs 11.1 CR I get 21mpg with 80% city 20% hwy. I won't say it drives like stock because it doesn't, but it is as streetable as ANY H/C LS1 you'll ever see. I have 3.90 gear ratio and at 60mph it pulls 1500rpm.
The car surges very little say, driving through a parking lot at idle, but it is barely noticeable. Just incase you are wondering here is a cold start idle vid. This vid is my personal car.
The car surges very little say, driving through a parking lot at idle, but it is barely noticeable. Just incase you are wondering here is a cold start idle vid. This vid is my personal car.
