expectations
Thread Starter
Racer
Joined: Feb 2012
Posts: 421
Likes: 27
From: Harrisburg PA
expectations
I have a ;77, with what I believe to be the original L48 motor (PO said it was rebuilt, but I cannot imagine this motor was ever out of the car--everything looks remarkable untouched);
Either way, I will be upgrading the intake and carb, going from the stock Quad and iron manifold to an Edelbrock perfomer (2101) and Holley 650 DP (4777).
I also plan to upgrade the exahust to long tube headers (1 5/8 primaries), and 2.5 true duals into Dynomax super turbos. The car currently has iron manifolds, true duals (2 inch pipes (AT BEST--might actually be smaller), and glass packs. Neither the current system, nor the planned system has cats...
What are the thoughts on performance I might pick up with the changes?
Either way, I will be upgrading the intake and carb, going from the stock Quad and iron manifold to an Edelbrock perfomer (2101) and Holley 650 DP (4777).
I also plan to upgrade the exahust to long tube headers (1 5/8 primaries), and 2.5 true duals into Dynomax super turbos. The car currently has iron manifolds, true duals (2 inch pipes (AT BEST--might actually be smaller), and glass packs. Neither the current system, nor the planned system has cats...
What are the thoughts on performance I might pick up with the changes?
Drifting
Joined: Oct 2012
Posts: 1,524
Likes: 61
From: Medina Ohio
The intake and carb will be negligible. The headers and exhaust will help, you should notice a bit, but it will not be anything dramatic.
(often times the increased exhaust sound will make it feel like a larger improvement then it is)
Still a good start and win-win.
(often times the increased exhaust sound will make it feel like a larger improvement then it is)
Still a good start and win-win.
Last edited by Ibanez540r; Jun 8, 2015 at 05:02 AM.
Melting Slicks
Joined: Apr 2009
Posts: 2,632
Likes: 112
From: Great Plains Iowa
NEVER put a mechanical secondary carburetor on a street engine. Mechanical secondary carburetors are made specifically for track racing or drag racing where 4000+ rpm is constant. Only use carburetors that have either air valve secondaries (AVS) or vacuum secondaries that prevent the secondaries from opening before they're needed. People are thrilled over the term "double pumper" when in fact they don't know what double pumpers are made for.
If you want a good Holley for street use I suggest buying a #80458SA that is a 600 cfm with vacuum secondaries and an electric choke.
If you want a good Holley for street use I suggest buying a #80458SA that is a 600 cfm with vacuum secondaries and an electric choke.
Pro
Joined: Oct 2009
Posts: 664
Likes: 89
From: Marysville Ohio
I have a ;77, with what I believe to be the original L48 motor (PO said it was rebuilt, but I cannot imagine this motor was ever out of the car--everything looks remarkable untouched);
Either way, I will be upgrading the intake and carb, going from the stock Quad and iron manifold to an Edelbrock perfomer (2101) and Holley 650 DP (4777).
I also plan to upgrade the exahust to long tube headers (1 5/8 primaries), and 2.5 true duals into Dynomax super turbos. The car currently has iron manifolds, true duals (2 inch pipes (AT BEST--might actually be smaller), and glass packs. Neither the current system, nor the planned system has cats...
What are the thoughts on performance I might pick up with the changes?
Either way, I will be upgrading the intake and carb, going from the stock Quad and iron manifold to an Edelbrock perfomer (2101) and Holley 650 DP (4777).
I also plan to upgrade the exahust to long tube headers (1 5/8 primaries), and 2.5 true duals into Dynomax super turbos. The car currently has iron manifolds, true duals (2 inch pipes (AT BEST--might actually be smaller), and glass packs. Neither the current system, nor the planned system has cats...
What are the thoughts on performance I might pick up with the changes?
My .02cents - A good distributor tune up and recurcve for performance will also help on top of the exhaust. If you go this route, you will almost certainly need to rejet the carb for the increased air the engine will need.
I would keep the Qjet if you have access to someone who KNOWS how to set one up or rebuild it -usually much cheaper and it can work very well for you.
The ignition tune can get you the most noticable seat of the pants feel for very little cash - on a stock engine, about the cost of a set of springs (like $8-$10). Lots of posts on the forum on how to curve your distributor - search Lars timing curve, you will find great info.
Melting Slicks
Joined: Apr 2009
Posts: 2,632
Likes: 112
From: Great Plains Iowa
I have a ;77, with what I believe to be the original L48 motor (PO said it was rebuilt, but I cannot imagine this motor was ever out of the car--everything looks remarkable untouched);
Either way, I will be upgrading the intake and carb, going from the stock Quad and iron manifold to an Edelbrock perfomer (2101) and Holley 650 DP (4777).
I also plan to upgrade the exahust to long tube headers (1 5/8 primaries), and 2.5 true duals into Dynomax super turbos. The car currently has iron manifolds, true duals (2 inch pipes (AT BEST--might actually be smaller), and glass packs. Neither the current system, nor the planned system has cats...
What are the thoughts on performance I might pick up with the changes?
Either way, I will be upgrading the intake and carb, going from the stock Quad and iron manifold to an Edelbrock perfomer (2101) and Holley 650 DP (4777).
I also plan to upgrade the exahust to long tube headers (1 5/8 primaries), and 2.5 true duals into Dynomax super turbos. The car currently has iron manifolds, true duals (2 inch pipes (AT BEST--might actually be smaller), and glass packs. Neither the current system, nor the planned system has cats...
What are the thoughts on performance I might pick up with the changes?
People have gotten the idea "double pumpers" (mechanical secondaries) are great carburetors because they read (or hear) about them all the time. What they don't know is double pumper carburetors are designed specifically for drag or track racing where revs are kept above 4000 rpm and the engine can tolerate having the secondaries open. For street engines NEVER use a double pumper/mechanical secondary carburetor because your engine can only swallow a limited amount of air at lower rpm's. To use a double pumper/mechanical secondary carburetor on a street engine is inviting horrendous bogging problems.
Le Mans Master
Joined: Oct 2010
Posts: 6,937
Likes: 848
From: melbourne florida
2023 C3 of the Year Finalist - Modified
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Thread Starter
Racer
Joined: Feb 2012
Posts: 421
Likes: 27
From: Harrisburg PA
On the bright side, from a cost perspective, I already have the intake and the carb (Holley) on the shelf...
As for NEVER running a DP on the street, I had one on my mild 350 build (as a dailt driver) in my '67 Camaro for years, and it suited me very well...properly tuned, mild build, with street rear gears, the thing got me 15-18 mpg on the highway (like I said mild (300hp) 350 build...
I tend to like the holleys because they are infinitely easier to tune than the Q-Jet (or perhaps its just because that's what I grew up with...
I suppose I will look at the exhaust side before messing with the induction.
Ill also play with the timing curve a bit--that had not occurred to me originally, as the motor is plainly stock...
As for NEVER running a DP on the street, I had one on my mild 350 build (as a dailt driver) in my '67 Camaro for years, and it suited me very well...properly tuned, mild build, with street rear gears, the thing got me 15-18 mpg on the highway (like I said mild (300hp) 350 build...
I tend to like the holleys because they are infinitely easier to tune than the Q-Jet (or perhaps its just because that's what I grew up with...
I suppose I will look at the exhaust side before messing with the induction.
Ill also play with the timing curve a bit--that had not occurred to me originally, as the motor is plainly stock...
Drifting
Joined: Sep 2007
Posts: 1,572
Likes: 51
From: Wichita Kansas
On the bright side, from a cost perspective, I already have the intake and the carb (Holley) on the shelf...
As for NEVER running a DP on the street, I had one on my mild 350 build (as a dailt driver) in my '67 Camaro for years, and it suited me very well...properly tuned, mild build, with street rear gears, the thing got me 15-18 mpg on the highway (like I said mild (300hp) 350 build...
I tend to like the holleys because they are infinitely easier to tune than the Q-Jet (or perhaps its just because that's what I grew up with...
I suppose I will look at the exhaust side before messing with the induction.
Ill also play with the timing curve a bit--that had not occurred to me originally, as the motor is plainly stock...
As for NEVER running a DP on the street, I had one on my mild 350 build (as a dailt driver) in my '67 Camaro for years, and it suited me very well...properly tuned, mild build, with street rear gears, the thing got me 15-18 mpg on the highway (like I said mild (300hp) 350 build...
I tend to like the holleys because they are infinitely easier to tune than the Q-Jet (or perhaps its just because that's what I grew up with...
I suppose I will look at the exhaust side before messing with the induction.
Ill also play with the timing curve a bit--that had not occurred to me originally, as the motor is plainly stock...
I know heads can be costly but well worth the money. Nothing wrong with some of the lower cost cost heads out there for street use.
Thread Starter
Racer
Joined: Feb 2012
Posts: 421
Likes: 27
From: Harrisburg PA
Eventually, I will build a mild 355...I have a pair of 461 heads (64cc chamber) that I plan to use (they are just sitting on the shelf)...
Was just wondering what might get me the best "bolt on result" in the interim...next couple of years or so...
Was just wondering what might get me the best "bolt on result" in the interim...next couple of years or so...
