X64v Posted December 18, 2007 Share Posted December 18, 2007 I've finally grown tired of beating my L24 to hell with a turbo (it was fun, but I really don't need to sink any ring lands in my daily driver during my first year of college), so while I build a proper L28et, I thought I'd at least throw a cam in the E31 I have laying around to get a little pep back. My question: With comparably dressed L24/28s (same headers, induction, SCRs), how do cams sized for an L28 with it's bigger valves perform on an L24 with it's smaller valves? I would guess that with the valves being smaller along with the decrease in displacement, a cam would feel about the same in both motors, but I want to double check here. Bottom line: Would the same cam feel 'bigger' on a small valve L24 than a big (normal) valve L28, or would it feel about the same? I'm not really looking for a cam recommendation for my particular set up, just the relation as asked. Quote Link to comment Share on other sites More sharing options...
johnc Posted December 18, 2007 Share Posted December 18, 2007 I don't think there's much of a difference (if any) in cam design and specs between the L24 and L28 engines. I've never heard of a L28 specific cam or a L24 specific cam. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted December 18, 2007 Share Posted December 18, 2007 The stock L24/L26/L28 cams are damn near identical, and all very small. You'll occasionally see people talking about their "C" cam and how badass it is. BS. The C cam is a 260 cam and has a very minutely longer duration but an equally tiny amount of reduced lift. ANY of the stock cams is tiny, and I'd be shocked if any of them produced a hp difference that was beyond the margin of error on a dyno test. They are all very very close in terms of lift and duration. If you want a cam, go buy an aftermarket cam. With your turbo setup you just want to make sure that you get something designed for a turbo that doesn't have too much overlap. Search the words turbo, cam, overlap, and you should find plenty of info to help you make a good decision on a cam. I like regrinds because they're cheap and I've had good success with them. Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted December 18, 2007 Administrators Share Posted December 18, 2007 The stock L24/L26/L28 cams are damn near identical, and all very small. You'll occasionally see people talking about their "C" cam and how badass it is. BS. The C cam is a 260 cam and has a very minutely longer duration but an equally tiny amount of reduced lift. ANY of the stock cams is tiny, and I'd be shocked if any of them produced a hp difference that was beyond the margin of error on a dyno test. They are all very very close in terms of lift and duration. If you want a cam, go buy an aftermarket cam. With your turbo setup you just want to make sure that you get something designed for a turbo that doesn't have too much overlap. Search the words turbo, cam, overlap, and you should find plenty of info to help you make a good decision on a cam. I like regrinds because they're cheap and I've had good success with them. I second everything jmortensen stated above. Quote Link to comment Share on other sites More sharing options...
X64v Posted December 18, 2007 Author Share Posted December 18, 2007 Thank you guys, that answers my question. jmortensen - Yes, I agree that the stock cams are puny. I'm looking at a regrind (specifically a .495"/290°), but could only find info on how it would perform on an L28 with regards to drive-ability, useful powerband, etc. Since this is going on an N/A L24, I wanted to make sure that a .495/290 on an L24 would act the same as a .495/290 on an L28 (come in at the same rpm and all that). Quote Link to comment Share on other sites More sharing options...
JMortensen Posted December 18, 2007 Share Posted December 18, 2007 Thank you guys, that answers my question. jmortensen - Yes, I agree that the stock cams are puny. I'm looking at a regrind (specifically a .495"/290°), but could only find info on how it would perform on an L28 with regards to drive-ability, useful powerband, etc. Since this is going on an N/A L24, I wanted to make sure that a .495/290 on an L24 would act the same as a .495/290 on an L28 (come in at the same rpm and all that). Yes, they will act the same. What might make a difference is that a stock L28 has a lower compression ratio than a stock L24. I had a stock (at least compression ratio wise) L28 and I ran a .490/280 and it worked fine, but I noticed a big increase in bottom end power when I upped the compression ratio from ~8.3:1 to ~11:1. Quote Link to comment Share on other sites More sharing options...
X64v Posted December 18, 2007 Author Share Posted December 18, 2007 Yes, they will act the same. What might make a difference is that a stock L28 has a lower compression ratio than a stock L24. I had a stock (at least compression ratio wise) L28 and I ran a .490/280 and it worked fine, but I noticed a big increase in bottom end power when I upped the compression ratio from ~8.3:1 to ~11:1. Ah, I didn't know that about the SCR relating to bottom end performance, thanks! I'll be at about 9.2:1 Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted December 18, 2007 Share Posted December 18, 2007 I think you will have a good combo there. In my L26 I swapped from the "C" cam to a Maxima cam and I think I lost a *little* top end but gained *little* power earlier on. Didn't do squat to reduce power but gave a *little* more bottom end grunt. Maybe I lost under 5hp? Less of a power loss than when my SU's have their occasional female day. Basically stock cams are the same...LOL I'm at 9.2:1 SCR and it's LOTS of fun to drive around town. Good luck!! OTM Quote Link to comment Share on other sites More sharing options...
johnc Posted December 18, 2007 Share Posted December 18, 2007 There are stock cams and then there are "stock" cams. Getting a SCCA legal ITS/BSP "stock" cam from Sunbelt, Rebello, or some of the other L6 engine builders will be a suprise as to how much power can be made with stock lift and duration. Had one from Javier at JG Engine Dynamics in a BSP legal L28 running SUs and it made 191 horsepower. Funny how good a "stock" cam can be. Quote Link to comment Share on other sites More sharing options...
X64v Posted December 19, 2007 Author Share Posted December 19, 2007 I think you will have a good combo there. Hopefully enough to keep me semi-satisfied after being bit by the turbo bug, until I can build a proper turbo engine. Less of a power loss than when my SU's have their occasional female day. :lmao: There are stock cams and then there are "stock" cams. Getting a SCCA legal ITS/BSP "stock" cam from Sunbelt, Rebello, or some of the other L6 engine builders will be a suprise as to how much power can be made with stock lift and duration. Had one from Javier at JG Engine Dynamics in a BSP legal L28 running SUs and it made 191 horsepower. Funny how good a "stock" cam can be. What did they do to them? Change ramp rates? Quote Link to comment Share on other sites More sharing options...
CamH Posted December 19, 2007 Share Posted December 19, 2007 holy crap! my room mate posted that when i let him use my computer. sorry guys. Quote Link to comment Share on other sites More sharing options...
carusoracer Posted February 20, 2008 Share Posted February 20, 2008 Great thread! So which shop has been able to produce the best grind for a good street ie TQ cam and or AutoX Cam for a L28 with 9:2 Compression? Quote Link to comment Share on other sites More sharing options...
ozconnection Posted February 21, 2008 Share Posted February 21, 2008 Years ago I ran a JDM L20ET engine (without the turbo on it) in my car whilst my L28 was being rebuilt. It's a long story but what I eventually ended up trying was the turbo cam in my L28 engine built for normally aspirated use. When that cam was in my L20, the thing would rev out easily to 7.5K but when the L28 used the same cam, it was really torqey but ran out of puff at 5k. Same cam in two different engines!! Very different result about how they "felt" on the road. I couldn't believe it was the same cam in both engines. Yes, there is a whole bunch of difference between the two, especially noted items are comp. ratio, rod ratios and port/valve sizes. Less noted is ignition timing ie advance rate and static timing. To put it another way, there is more to changing the character of your engine than slotting in a cam. Its everything else around it that also influences its feel on the road. Cheers, Mark Quote Link to comment Share on other sites More sharing options...
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