OK, engine guys...what am I doing wrong?
Thread Starter
Drifting
Joined: Jun 2007
Posts: 1,404
Likes: 1
From: Ansonia/NYC CT
OK, engine guys...what am I doing wrong?
Maybe someone has one of those desk dynos, or something? I'm just not noticing mush difference, after a complete top end rebuild. Here's what I got...
gen 1 sbc, 2 bolt, 76' vette
vortec heads, valve job, springs, seats
GM performance aluminum vortec style intake
lunati bracket master 2 hydraulic cam and lifters, with double timing chain
# Advertised Duration (Int/Exh): 284/284
# Duration @ .050 (Int/Exh): 218/218
# Gross Valve Lift (Int/Exh): .458/.458
# LSA/ICL: 110/106
# Valve Lash (Int/Exh): Hyd/Hyd
# RPM Range: 1500-5200
sanderson block hugger headers
MSD street fire spark plug wires
accell shorty spark plugs
rebuilt Q-jet 750 cfm carb
Super T-10 reuilt less than 8,000 miles ago
3.08 rear
new wheels and tires, but over all diameter is the same
It's broken in, and I've ironed out all the kinks, runs great...and while I realize that it's the 3.08 gears that's killing me...I just sorta expected a bit more kick to the but dyno than what I'm getting. Any ideas? Tips? Suggestions? Thanks in advance, guys!
gen 1 sbc, 2 bolt, 76' vette
vortec heads, valve job, springs, seats
GM performance aluminum vortec style intake
lunati bracket master 2 hydraulic cam and lifters, with double timing chain
# Advertised Duration (Int/Exh): 284/284
# Duration @ .050 (Int/Exh): 218/218
# Gross Valve Lift (Int/Exh): .458/.458
# LSA/ICL: 110/106
# Valve Lash (Int/Exh): Hyd/Hyd
# RPM Range: 1500-5200
sanderson block hugger headers
MSD street fire spark plug wires
accell shorty spark plugs
rebuilt Q-jet 750 cfm carb
Super T-10 reuilt less than 8,000 miles ago
3.08 rear
new wheels and tires, but over all diameter is the same
It's broken in, and I've ironed out all the kinks, runs great...and while I realize that it's the 3.08 gears that's killing me...I just sorta expected a bit more kick to the but dyno than what I'm getting. Any ideas? Tips? Suggestions? Thanks in advance, guys!
Le Mans Master
Joined: Apr 2005
Posts: 6,349
Likes: 419
From: Seattle Area WA
Kevin, depending upon the head gasket used you are only in the 8.75-9.1 compression ratio range, gaining a 1/4 point in compression bu going to a thinner gasket isn't going to buy you much. You are using a tight 106 cam which should make good mid range power but without running EA I bet you are in the 275 flywheel HP range.
As mentioned above, have you recurved your distributor, it will make a big difference.
As mentioned above, have you recurved your distributor, it will make a big difference.
Le Mans Master
Joined: Dec 2006
Posts: 5,557
Likes: 9
From: Oquirrh Mountains
St. Jude Donor '09
Check your timing as suggested above. Next, check to see if the carb is opening all the way. Remove the air cleaner and have someone push the go pedal to the floor and have a look.
Le Mans Master
Joined: Sep 2004
Posts: 5,116
Likes: 5
From: Livonia MI
As mentioned, probably pull the distributor for service, as common for the mechanical advance shaft to gum up. You mentioned a Q-Jet rebuild, but is the smooth gold cadmium plating still there. Check the Q-Jets secondary metering rod power piston operation, as just a small grit lodged will hang these up. Wouldn't exactly call a cam with less than 110 LSA for a motor home, but if installed a tooth or so off, there's a problem. You mentioned very little about your intake manifold, but if single plane w/3.08 gears, your dead on the street.
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Thread Starter
Drifting
Joined: Jun 2007
Posts: 1,404
Likes: 1
From: Ansonia/NYC CT
It is a stock short block, stock pistons. The comp is 9.2 -1, could be higher, but I don't have flat top pistons. I did a comp test BEFORE the head change, and it was 8.1. The secondaries open just fine, vacuum is fine, everything runs well. Scot, honestly, 300hp was what I was shooting for, 275 is still not that bad. I feel, however, that if I did a 1/4 mile in the vette, and a 1/4 mile in my 05' civic, the civic would be a decent bit faster...and that's my honest opinion.
I got my car weighted at the local dump, and it clocked in at around 3,200lbs.
As for the intake, I don't know the part number, but it's a dual plane, high rise aluminum vortec style intake.
The main reason I went with this cam is because of the lift restrictions on the vortec heads. People have said that .470 is ok, but others say that .460 is as high as they would go. I didn't feel like this was a big cam, and still don't...but then this is all new to me. I also didn't want a cam that made top end power, as I don't plan to spin the motor much past 5 grand, ever. Well...at least not till I can afford an LS1 swap...
I got my car weighted at the local dump, and it clocked in at around 3,200lbs.As for the intake, I don't know the part number, but it's a dual plane, high rise aluminum vortec style intake.
The main reason I went with this cam is because of the lift restrictions on the vortec heads. People have said that .470 is ok, but others say that .460 is as high as they would go. I didn't feel like this was a big cam, and still don't...but then this is all new to me. I also didn't want a cam that made top end power, as I don't plan to spin the motor much past 5 grand, ever. Well...at least not till I can afford an LS1 swap...
Thread Starter
Drifting
Joined: Jun 2007
Posts: 1,404
Likes: 1
From: Ansonia/NYC CT
Which I guess to mean is, it does not feel like 275hp. I really though I'd have a decent amount of torque, at the very least.
I will check the timing again, but I'm pretty sure I've got that all dialed in. Just for *****, though, what would you guys say my curve should be?
Also, what do you mean by not high enough comp for the cam?
I will check the timing again, but I'm pretty sure I've got that all dialed in. Just for *****, though, what would you guys say my curve should be?
Also, what do you mean by not high enough comp for the cam?
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
# Duration @ .050 (Int/Exh): 218/218
# Gross Valve Lift (Int/Exh): .458/.458
The wimpy L-82 has a 222/222 with mid 400 lift and it only put out about 225 rated hp. So you can't install a lessor cam and expect anything in the way of hp gains.
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
Skunk you are letting me down! That is a very wimpy low lift cam with 110 lobe. I don't know the head cc.
# Duration @ .050 (Int/Exh): 218/218
# Gross Valve Lift (Int/Exh): .458/.458
The wimpy L-82 has a 222/222 with mid 400 lift and it only put out about 225 rated hp. So you can't install a lessor cam and expect anything in the way of hp gains.
# Duration @ .050 (Int/Exh): 218/218
# Gross Valve Lift (Int/Exh): .458/.458
The wimpy L-82 has a 222/222 with mid 400 lift and it only put out about 225 rated hp. So you can't install a lessor cam and expect anything in the way of hp gains.
Last edited by TheSkunkWorks; Jun 19, 2011 at 08:32 PM.
Melting Slicks
Joined: Dec 2009
Posts: 3,229
Likes: 656
From: Thunder Bay
The L-82 cam (PN 3896962) is a great cam. I've run several of them over the years in a number of applications and they pull like crazy. Its a great street cam, especially with a stick. Lunati is a good manufacturer, and I can't believe 4 degrees would make that much difference. If the engine is as much of a dog as you make it sound, something is wrong. It sounds like you have all the right parts. I would look at the timing curve, and the exhaust. Block hugger headers are an improvement over cast iron manifolds, but they're not real headers, and you don't mention what you have for an exhaust system. You need a full 2 1/2" dual system. If you don't have that, that's where you need to start.
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
The L-82 cam (PN 3896962) is a great cam. I've run several of them over the years in a number of applications and they pull like crazy. Its a great street cam, especially with a stick. Lunati is a good manufacturer, and I can't believe 4 degrees would make that much difference. If the engine is as much of a dog as you make it sound, something is wrong. It sounds like you have all the right parts. I would look at the timing curve, and the exhaust. Block hugger headers are an improvement over cast iron manifolds, but they're not real headers, and you don't mention what you have for an exhaust system. You need a full 2 1/2" dual system. If you don't have that, that's where you need to start.
You have to take gkull and skunk and those guys with a grain of salt when they talk about camshaft "size". They build ridiculously powerful racing motors, and really serious street/strip machines; these little street car cams seem kinda wimpy compared to what they are used to. Kinda like spicy food. One person takes a bite of chili and says:
"Hmmmm........it's not without it's charm........suitable, perhaps, for small children and the elderly....."
The next guy takes a bite and starts screaming:
"Kill me!! Kill me now!! I can't take the pain!!!!"
gkull and the rest of you serious engine guys, please don't take this as any kind of an insult, it's just that everything is relative.
Scott
Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
As mentioned, probably pull the distributor for service, as common for the mechanical advance shaft to gum up. You mentioned a Q-Jet rebuild, but is the smooth gold cadmium plating still there. Check the Q-Jets secondary metering rod power piston operation, as just a small grit lodged will hang these up. Wouldn't exactly call a cam with less than 110 LSA for a motor home, but if installed a tooth or so off, there's a problem. You mentioned very little about your intake manifold, but if single plane w/3.08 gears, your dead on the street.
Le Mans Master
Joined: Aug 2006
Posts: 7,421
Likes: 1,558
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
You want your mechanical advance "All in" by 2500 to 3000, You can get a Excel or Mr. Gasket kit at any parts store then all you have to do is change the springs to get the curve you want.
On my stock 74 I have 12* initial plus 24* from the mechanical advance for a total of 36*, my vacuum advance ad's another 16* for a total advance of 52*.
On my stock 74 I have 12* initial plus 24* from the mechanical advance for a total of 36*, my vacuum advance ad's another 16* for a total advance of 52*.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
I fired it up expecting something great and I was disappointed! I drove it around for a year or so like that while plotting my next move
The L-82 cam has very slow ramps...... It's just GM junk intended to help the motor last 100,000 miles
Last edited by gkull; Jun 20, 2011 at 09:41 AM.