Help building an L48
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Intermediate
Joined: Oct 2007
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Help building an L48
I have an L48 I picked up all rebuilt to stock specs. Heres the deal I wanna make it have some decent torque. Im lookin for low end off the line power, I do alot of autox. Id still like to have some top end but mostly down low. I dont want to get into the bottom end of the motor just do heads, cam, intake, carb. Nothin too crazy as Id like to keep it on somewhat of a budget. Im thinkin some good performance GM head or a inexpensive aftermarket head. Im not sure where to start. The car has a T5 5speed and 3.73 gears in the rear. I already have headers and 3 inch exhaust.
Matt
Matt
Last edited by camaro430sut; Oct 23, 2007 at 05:55 PM.
Advanced
Joined: Apr 2007
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My two cents:
Edelbrock Performer heads with 70cc combustion chambers. Flat-top pistons (with four valve reliefs) should give you between 9:1 and 9.5:1 compression ratio depending on your engine's particulars. (A good substitute would be Dart Iron Eagle 180's w/68cc combustion chambers)
Edelbrock Performer or even Performer RPM intake. Should be able to find a good one on ebay for a reasonable price.
Competion Cams XE268H hydraulic flat tappet camshaft.
Speed Demon 625cfm carburetor or Holley 670cfm Street Avenger. (Personally I would pick up a spread-bore pattern intake and rebuild/reuse the Quadrajet).
This engine would produce a nice power-band from 1,600 rpm to almost 6,000 rpm. Horsepower would probably end up somewhere around 350 with your headers and nice exhaust.
Edelbrock Performer heads with 70cc combustion chambers. Flat-top pistons (with four valve reliefs) should give you between 9:1 and 9.5:1 compression ratio depending on your engine's particulars. (A good substitute would be Dart Iron Eagle 180's w/68cc combustion chambers)
Edelbrock Performer or even Performer RPM intake. Should be able to find a good one on ebay for a reasonable price.
Competion Cams XE268H hydraulic flat tappet camshaft.
Speed Demon 625cfm carburetor or Holley 670cfm Street Avenger. (Personally I would pick up a spread-bore pattern intake and rebuild/reuse the Quadrajet).
This engine would produce a nice power-band from 1,600 rpm to almost 6,000 rpm. Horsepower would probably end up somewhere around 350 with your headers and nice exhaust.
Drifting
Joined: Apr 2002
Posts: 1,716
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From: New Baden Illinois
Assuming that the block has not been bored .030 over, the 70cc heads with the FP1094 head gasket (.015), you would have right around 9.6 CR with the flat top pistons. That is a good setup with those heads. However, if you go with an iron head, that is about the limit on the CR.
If you are looking for torque, don't go to big on the cam because the larger cams bleed off more compression.
If you are looking for torque, don't go to big on the cam because the larger cams bleed off more compression.
Thread Starter
Intermediate
Joined: Oct 2007
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What do you guys think about the L98 aluminum heads. I have a friend selling a set of those. Not sure if they are any good or not. I remember hearing the were similar to zz4 heads. What kind of pistons does an L48 have stock. This motor is rebuilt to stocks specs and was not bored.
Matt
Matt
Drifting
Joined: Apr 2002
Posts: 1,716
Likes: 4
From: New Baden Illinois
What do you guys think about the L98 aluminum heads. I have a friend selling a set of those. Not sure if they are any good or not. I remember hearing the were similar to zz4 heads. What kind of pistons does an L48 have stock. This motor is rebuilt to stocks specs and was not bored.
Matt
Matt
Le Mans Master
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From: Seattle WA
St. Jude Donor '14
More details on "somewhat on a budget" would help
thecorvette nailed the overall build priorities, although I might suggest other individual part choices.
* Iron heads for a budget; if you're going really low-budget the best deal on the planet for heads are the brand-new Vortecs, especially when the target is low- and mid-range power.
* A dual-plane intake for sure; the Edelbrock RPM would be a mismatch for your usage IMHO, but the Performer or Performer EPS or the Wieland Stealth would all be good choices.
* Carb size is right on and I agree with thecorvette's choices. Edelbrock Performer carb as an alternative.
* I'm not a huge fan of the XE cams for a daily driver unless power is the primary focus. They use a ramp that's similar to a hydraulic roller, and it's pretty aggressive for a flat-tappet - which means springs and noise are an issue. The 262 is about as far as I would go here for this usage.
thecorvette nailed the overall build priorities, although I might suggest other individual part choices.
* Iron heads for a budget; if you're going really low-budget the best deal on the planet for heads are the brand-new Vortecs, especially when the target is low- and mid-range power.
* A dual-plane intake for sure; the Edelbrock RPM would be a mismatch for your usage IMHO, but the Performer or Performer EPS or the Wieland Stealth would all be good choices.
* Carb size is right on and I agree with thecorvette's choices. Edelbrock Performer carb as an alternative.
* I'm not a huge fan of the XE cams for a daily driver unless power is the primary focus. They use a ramp that's similar to a hydraulic roller, and it's pretty aggressive for a flat-tappet - which means springs and noise are an issue. The 262 is about as far as I would go here for this usage.
Last edited by billla; Oct 25, 2007 at 06:52 PM.
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Thread Starter
Intermediate
Joined: Oct 2007
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By on a budget Im thinkin about 2000 to get heads, cam, intake, etc.. and get it in the car. The bottom end is all fresh, brand new thats why Id rather not mess with it. What size chambers should I look for. Im going to need a vortec intake to go with the heads right?
Matt
Matt
Burning Brakes
Joined: Oct 2004
Posts: 829
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From: Scottdale Pa
* Iron heads for a budget; if you're going really low-budget the best deal on the planet for heads are the brand-new Vortecs, especially when the target is low- and mid-range power.
* I'm not a huge fan of the XE cams for a daily driver unless power is the primary focus. They use a ramp that's similar to a hydraulic roller, and it's pretty aggressive for a flat-tappet - which means springs and noise are an issue. The 262 is about as far as I would go here for this usage.
Vortec heads are great bang for the buck 
The XE line of cams absolutly suck,
very very noisey
The 262 cam will rock with those gears vs. the 268
I just installed these this summer on my L48 . These are 64cc Very happy so far......
http://www.sdparts.com/product/SD806...RPMAirGap.aspx
Last edited by Crab; Oct 25, 2007 at 08:32 PM.
Le Mans Master
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From: Seattle WA
St. Jude Donor '14
I think you can get by for way less than $2K if the short block is complete. GMPP Vortecs, CompCams roller-tip rockers, pushrods, CompCams cam (around .450 lift) and lifters along with a new Edelbrock Performer intake and you're in pretty good shape.
Someone check me on this, but the L-48 had 8.5 CR with 75cc heads - so a drop to a 64cc chamber with the Vortecs should take you right to 9.5 or so (10cc = 1 pt CR). I would definitely verify the CR with the short block before buying heads.
I'd expect around 310 HP at the flywheel with this combo with headers and a good exhaust. HP peak would be around 5000, with a fat torque curve from 2000 - 4500 or so.
Someone check me on this, but the L-48 had 8.5 CR with 75cc heads - so a drop to a 64cc chamber with the Vortecs should take you right to 9.5 or so (10cc = 1 pt CR). I would definitely verify the CR with the short block before buying heads.
I'd expect around 310 HP at the flywheel with this combo with headers and a good exhaust. HP peak would be around 5000, with a fat torque curve from 2000 - 4500 or so.
Drifting
Joined: Apr 2002
Posts: 1,716
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From: New Baden Illinois
Yep, Vortecs are a good bang for the buck. I would think that you should be able to get more than 310 flywheel hp, though. With headers and a decent intake, you should probalby be closer to 330-340.
Thread Starter
Intermediate
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Well that sounds awesome. Is there any head casting I should look for inparticular or is there only one 64cc vortec head? Also can you recommend me a cam youd use as im not to familiar with what all the cam specs mean.
Matt
Matt
Le Mans Master
Joined: Jun 2004
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From: Seattle WA
St. Jude Donor '14
I spent some decent DD Advanced time here and was right in that 310 ballpark.
Only a chassis dyno will tell us for sure
Le Mans Master
Joined: Jun 2004
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From: Seattle WA
St. Jude Donor '14
SDPC (www.sdpc2000.com) sells complete top-end kits (http://www.sdparts.com/product/SD806...merIntake.aspx) that may save you a few bucks
but I prefer roller-tip rockers if you can afford them (CompCams P/N 249-1417-16) Self-aligning rockers are required for the Vortecs.You'll get a boatload of feedback on cams, but my recommendation for a strong street engine would be the CompCams High Energy 260H (mild idle, good low- and mid-range), High Energy 268H (more power for a bit rougher idle) or the Extreme Energy 262H if you don't mind a little valvetrain noise and want maximum power for the street. There are certainly other good choices, and I encourage you to call CompCams and Crane with your specs and get their professional opinion. Key question is the gear ratio. Remember that you are lift-limited to .475 max and that you need vacuum to run stuff
A big cam (high lift, long duration) is not the right match with these heads.
Melting Slicks
Joined: Sep 2002
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From: Engineers do it better.
Since your bottom end is already done, I'd say leave it alone and concentrate on top end. Get the 64cc Performer heads to drop the compression a bit. With my combo (Performer Heads, Magnum 270H cam, Holley SA 670, Performer Intake, Hooker Ceramic Header, MAD Chambered exhaust, Crane XR1 conversion) the car makes 250+ rwhp. With your 5 speed, you'll probably be very close to 300 rwhp.
Good Luck.
Good Luck.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
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From: Seattle WA
St. Jude Donor '14