L-82 Top End Change
Thread Starter
Le Mans Master
Joined: Oct 2007
Posts: 7,446
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From: Tennessee/Rhode Island
L-82 Top End Change
Ok Guys, I have been doing some research and I am now considering a top end change for the L-82 even though it only has 65,000 miles on it since I figure that I can keep the 882 smog heads, the cam (if someone wants it if the car is sold) and intake. Just read an article in Super Chevy magazine where they dynoed a bone stock L-82 at 313 Gross HP at 5,500 RPM and 355 torque @3,800 which are right on the money in terms of RPM for a stock motor and about 250 HP Net. With the changes only described below the new numbers were 414 HP @5,900 RPM and 415 torque @ 4,100 RPM-Gross again. Here are the 3 changes:
RHS 64 CC 200 CC runners-aluminum heads-$650 per side=$1,300
Pro Comp Dual Plane manifold-$125
Comp Cams XE274H-$350
I would reuse my Holley 4175 650 CFM spreadbore and my comp cams 1.52 roller tipped rockers. I figure about $2,000 for the heads, intake, new valve covers, gaskets, 274 complete kit with Timing chain, springs etc.
Good deal? Recommendations if the combo is better than above for the same money.
RHS 64 CC 200 CC runners-aluminum heads-$650 per side=$1,300
Pro Comp Dual Plane manifold-$125
Comp Cams XE274H-$350
I would reuse my Holley 4175 650 CFM spreadbore and my comp cams 1.52 roller tipped rockers. I figure about $2,000 for the heads, intake, new valve covers, gaskets, 274 complete kit with Timing chain, springs etc.
Good deal? Recommendations if the combo is better than above for the same money.
Le Mans Master
Joined: Apr 2005
Posts: 6,350
Likes: 423
From: Seattle Area WA
I would look at a set of Brodix IK 180s to keep your port velocity a little higher than the 200cc heads. Definately stick with 64cc chambers. Instead of that intake I would go with a Holley Street Dominator (copy of LT1/Z28intake) or Weiand Stealth but those are not spread bore intakes. IMHO that XE274 is a bit on the long duration side unless you are just after higher RPM driving. I would consider the XE268 and have it ground on a 112LSA at a minimum. The old 270 isn't a bad cam either. IMHO, the problem with some of these comp cams is the 110LSA and their peaky power band vs your L46 cam or the LT1 cam.
Another cam to look at is Cranes 113531.
The usual problem with magazine builds is that they shoot for top end power without any consideration for a wide power bandwidth. For a sports car ideally you want a 80% or better bandwidth power, note that most magazine dyno pulls start at something like 2,500/3,000 RPMs and not off idle to max RPMs.
Another cam to look at is Cranes 113531.
The usual problem with magazine builds is that they shoot for top end power without any consideration for a wide power bandwidth. For a sports car ideally you want a 80% or better bandwidth power, note that most magazine dyno pulls start at something like 2,500/3,000 RPMs and not off idle to max RPMs.
Last edited by Scott Marzahl; Jan 18, 2011 at 04:09 PM.
Racer
Joined: Mar 2008
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From: KY
Le Mans Master
Joined: Apr 2007
Posts: 7,353
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From: Graceland in a Not Correctly Restored Stingray
274* advertised intake duration should actually be right on target for an L82 w/smaller 64cc chambers, but agree I'd have it ground at 112* LSA (and 108* ICL). As far as the intake ports, I'd be looking at 180-195cc ones (don't forget AFR's) for better bottom-mid range port velocity than the 200's for this level of build.
The 650 might prove smallish on top end, so if you get into the market for a carb I'd consider some more cfm. FWIW, I'd shop Edelbrock, Holley or Weiand for the intake. In any event, the L82 is an excellent foundation. Yes, the mags and TV shows often ignore other important factors while in search of big numbers. My $.02
The 650 might prove smallish on top end, so if you get into the market for a carb I'd consider some more cfm. FWIW, I'd shop Edelbrock, Holley or Weiand for the intake. In any event, the L82 is an excellent foundation. Yes, the mags and TV shows often ignore other important factors while in search of big numbers. My $.02
Last edited by TheSkunkWorks; Jan 18, 2011 at 05:32 PM.
Thread Starter
Le Mans Master
Joined: Oct 2007
Posts: 7,446
Likes: 972
From: Tennessee/Rhode Island
Thanx for all the replies. So it sounds like 185CC runners are better for low to mid range torque with 64cc chambers. These will fit with an appropriate dual plane manifold under the hood of my 78? Also, I prefer a spreadbore manifold since I have the carb that I am going to use right now, a Holley 4175 650 CFM-a little small but should work fine. As for manifolds, an edelbrock Performer (RPM?) will fit under the hood with a stock air cleaner?
Since I am not a cam/head expert by any means, I doubt that I would have a custom grind cam so I am inclined to go with the comp cams either the XE274H or XE268H as they come, but want good idle quality, vacuum and decent bottom end. However, I do have a 4 speed with 3.70 gears so most of the time the engine is above 2,000 RPM and cruises at 70 MPH at 3,500 RPM-4,000 RPM (80 MPH). Which cam-268 or the 274 with this setup for what I am looking for? I would only occassionally rev it to 6,000 RPM. Most of my operating range would be between 2,000-5,000 RPM's with the 3.70 gears and close ratio 4 speed. Thanx again.
Since I am not a cam/head expert by any means, I doubt that I would have a custom grind cam so I am inclined to go with the comp cams either the XE274H or XE268H as they come, but want good idle quality, vacuum and decent bottom end. However, I do have a 4 speed with 3.70 gears so most of the time the engine is above 2,000 RPM and cruises at 70 MPH at 3,500 RPM-4,000 RPM (80 MPH). Which cam-268 or the 274 with this setup for what I am looking for? I would only occassionally rev it to 6,000 RPM. Most of my operating range would be between 2,000-5,000 RPM's with the 3.70 gears and close ratio 4 speed. Thanx again.
Last edited by jb78L-82; Jan 18, 2011 at 06:06 PM.
Le Mans Master
Joined: Apr 2005
Posts: 6,350
Likes: 423
From: Seattle Area WA
With those parameters I would tend to go with the XE268 for better manners but your call. For the widder LSA for a smoother idle all you need to do is call comp and ask for it. Yes I would stick with 180-190cc runners for your heads. I don't think that you won't fit a RPM under the hood with a stock aircleaner, a Lt1 drop base yes. Take some clay and do a clearance check of what you have now and add in the extra height for the new intake. I had to remove the insulation blanket when I had a '78 to fit the Holley intake on my 383 but I also had a nitrous plate under the carb.
Last edited by Scott Marzahl; Jan 18, 2011 at 06:21 PM.
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Thread Starter
Le Mans Master
Joined: Oct 2007
Posts: 7,446
Likes: 972
From: Tennessee/Rhode Island
OK-closing in on this. 64cc heads with 180-190 cc runners-good. XE268 with a custom grind for a LSA of 112 for smooother idle. What spreadbore intake will fit under the hood with the OEM air cleaner? What about porting the OEM aluminum L-82 intake? Does an aftermarket one add much power with the new heads? Thanx, again.
Le Mans Master
Joined: Apr 2005
Posts: 6,350
Likes: 423
From: Seattle Area WA
Ideally you want the intake ports to match the heads. At least the Brodix IKs use a medium intake gasket @ 1.34"x2.20" compared to a stock gasket @ 1.23"x1.99". If you are trying to keep the intake portion looking stock then maybe pick up another intake off Ebay for cheap and port match it or maybe port match a Weiand 8004/8125.
Le Mans Master
Joined: Apr 2007
Posts: 7,353
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From: Graceland in a Not Correctly Restored Stingray
With 64cc chambers if you go with the 268 you might consider installing it at 108* ICL whether you have it ground with the 112* LSA or not, just to give yourself a tad more margin in case you get some less than premium gas. Yes, CompCams will be more than happy to grind to your specs, so don't be afraid to ask, but I suggest dealing with them directly whenever you go off of the main menu.
Le Mans Master
Joined: Apr 2005
Posts: 6,350
Likes: 423
From: Seattle Area WA
Any particular reason you are stock on using a factory air cleaner I don't recall them being open element or twin snorkel, but rather the closed type with a lot of restriction. A 750 Holley on a Street Dominator would be a much better intake combo. You could step up to a 750 annular discharge carb.
Last edited by Scott Marzahl; Jan 19, 2011 at 11:11 AM.
Pro
Joined: Dec 2004
Posts: 534
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From: Connecticut
OK-closing in on this. 64cc heads with 180-190 cc runners-good. XE268 with a custom grind for a LSA of 112 for smooother idle. What spreadbore intake will fit under the hood with the OEM air cleaner? What about porting the OEM aluminum L-82 intake? Does an aftermarket one add much power with the new heads? Thanx, again.
Thread Starter
Le Mans Master
Joined: Oct 2007
Posts: 7,446
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From: Tennessee/Rhode Island
Thanx for the edelbrock 2101 feedback. The 78 OEM L-82 air filter housing is actually a dual snorkel one with a cold air intake connections to the area right above the top of the radiator sourcing cold air from in front of the radiator/comdenser-It is actually a really good system! I run the stock filter housing with a K&N OEM filter and prefer that setup to open element filters that ingest the hot air under the hood.
Safety Car
Joined: Jan 2009
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From: anchorage ak
Id run Afr 180cc eliminators 64 cc chambers, with th xe268hr retrofit roller, 1 5/8" headers if your going to use the stock cleaner about the only after market intake you can use is the wieand action plus, but its not spread bore, your stock aluminum should work fairly well, with this set up youll need around a 2400 rpm stall, should be fun driving.
Thread Starter
Le Mans Master
Joined: Oct 2007
Posts: 7,446
Likes: 972
From: Tennessee/Rhode Island
Id run Afr 180cc eliminators 64 cc chambers, with th xe268hr retrofit roller, 1 5/8" headers if your going to use the stock cleaner about the only after market intake you can use is the wieand action plus, but its not spread bore, your stock aluminum should work fairly well, with this set up youll need around a 2400 rpm stall, should be fun driving.
The only problem is that the AFR heads are expensive for the amount of time I drive the car-about 500 miles per year. Same with a roller cam. I think that if i go this route I would use the RHS 64cc 180 heads (about $650 per head/aluminum) with a comp cams XE268H complete kit and the oem aluminum intake on the L-82. I think that I can use my 1 5/8 inch shorty headers and the Holley 4175 650 CFM spreadbore. I can do the whole deal for about $1,800 with a new timing chain and gears. Thanx.
Melting Slicks
Joined: May 2006
Posts: 2,590
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From: Nashville TN
St. Jude Donor '09
Flow numbers are pretty good for the money. Great value!!!
Safety Car
Joined: Jan 2009
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From: anchorage ak
even if you only drive 500 miles a year i'd still go with the afr's, cnc-motor sports has them for 1465.00 and when compare flow numbers the afrs out flow rhs and brodix. but rhs & brodix out flow the stock 882 smog heads, even with the flat tappet cam you will still want to run 2000 to 2400 rpm stall.