Headers and Regaining the "Detuned" 454 1971 motor
06-05-2012, 12:16 AM
#1
Drifting
Thread Starter
Headers and Regaining the "Detuned" 454 1971 motor
I'm about to buy a 1971 454ci unmodified and I'm considering some ways to boost HP and fuel economy if possible. I've always loved headers so;
How Much Horsepower Do Headers Add?
Which are a good price/deal? I'm not into the bling aspect of the header...
I read the 71 454 was a "detuned" 1970 engine. Can I get the HP back w/o a lot of work?
Suggestions?
How Much Horsepower Do Headers Add?
Which are a good price/deal? I'm not into the bling aspect of the header...
I read the 71 454 was a "detuned" 1970 engine. Can I get the HP back w/o a lot of work?
Suggestions?
06-05-2012, 12:38 AM
#2
Race Director
I'm about to buy a 1971 454ci unmodified and I'm considering some ways to boost HP and fuel economy if possible. I've always loved headers so;
How Much Horsepower Do Headers Add?
Which are a good price/deal? I'm not into the bling aspect of the header...
I read the 71 454 was a "detuned" 1970 engine. Can I get the HP back w/o a lot of work?
Suggestions?
How Much Horsepower Do Headers Add?
Which are a good price/deal? I'm not into the bling aspect of the header...
I read the 71 454 was a "detuned" 1970 engine. Can I get the HP back w/o a lot of work?
Suggestions?
06-05-2012, 12:38 AM
#3
Team Owner
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St. Jude Donor '05
Make sure you have a good curve on the distributor and tune the carb to perfection. Start doing other mods to gain power and you may lose mpg usually
06-05-2012, 02:14 AM
#4
Melting Slicks
Member Since: Jan 2003
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St. Jude Donor '08
Best way to gain HP and fuel mileage is distributor recurve, good carb tune using an A/F meter, headers, free flowing exhaust, Properly sized roller cam keeping the LSA high, better,more efficient heads. Fuel mileage is tied to volumetric efficiency. The higher VE at cruise the better mileage.
I did exactly what 63mako is saying, except using a relatively small Lunati Voodoo camshaft (the 60202), the car now has a blast 0-60 mph acceleration of only 5 seconds using a BFG street tires with almost no traction on 1st gear!, so basically yes, you can get your 454 to be transformed into a supercar HP levels without doing a major and expensice makeover.
06-05-2012, 09:57 AM
#5
Drifting
Thread Starter
Getting back the Headers... any specific suggestions or ideas on HP gain?
06-05-2012, 11:22 AM
#6
Team Owner
Do a good tune on the distributor and make sure the vacuum can is appropriate for the vacuum level your engine makes. Keep the Q-jet carb (for economy and performance), but do a rebuild on it and then adjust rods/jets, etc for best economy for cruise range of operation.
Finally, if you have a performance oriented BB engine, the only way to get any better economy is to install an overdrive transmission... whether manual or auto. For that to be effective, your rear axle needs to be at least a 3.23 or steeper ratio. OD transmissions and 'economy' rear axles don't mix very well.
Finally, if you have a performance oriented BB engine, the only way to get any better economy is to install an overdrive transmission... whether manual or auto. For that to be effective, your rear axle needs to be at least a 3.23 or steeper ratio. OD transmissions and 'economy' rear axles don't mix very well.
06-05-2012, 11:30 AM
#7
Race Director
Hooker makes headers for us too but I've heard they hang down lower and can have ground clearance issues. Whatever you get IMO the heat coating is well worth the cost because paint will burn off soon after you fire the motor. Also, I had to put a slight ding in one of the passenger side primaries because at idle it would sometimes tap the frame. I'm not even sure where it is anymore because it's small and not visible from above. That may or may not happen to you given slight tolerance variations from car to car.
Last edited by Les; 06-05-2012 at 11:34 AM.
06-05-2012, 04:16 PM
#8
Drifting
Thread Starter
I've got the Hedman headers- 2' primary tubes is the only size they make and they are definitely worth getting. I guess you could search for dyno runs with different big block combos and maybe find a "numbers gain" answer for a motor similar to yours, but the more power the engine makes the more gains the headers will give. Even on a mild big block they're worth getting because the stock exhaust manifolds just aren't that good. Back them up with a good 2 1/2" exhaust system and you'll be set for any future mods. Add heads/cam like Mako suggested and you'll be having a lot of fun but will need good tires to get the power down.
Hooker makes headers for us too but I've heard they hang down lower and can have ground clearance issues. Whatever you get IMO the heat coating is well worth the cost because paint will burn off soon after you fire the motor. Also, I had to put a slight ding in one of the passenger side primaries because at idle it would sometimes tap the frame. I'm not even sure where it is anymore because it's small and not visible from above. That may or may not happen to you given slight tolerance variations from car to car.
Hooker makes headers for us too but I've heard they hang down lower and can have ground clearance issues. Whatever you get IMO the heat coating is well worth the cost because paint will burn off soon after you fire the motor. Also, I had to put a slight ding in one of the passenger side primaries because at idle it would sometimes tap the frame. I'm not even sure where it is anymore because it's small and not visible from above. That may or may not happen to you given slight tolerance variations from car to car.
06-05-2012, 05:34 PM
#9
Race Director
That opens up a whole new can of worms. There are a number of really good choices out there. It ultimately depends on how much power you want, how much you're willing to spend, and how you want to use the car. You'll want to select your heads to match your cam choice along with the rest of your components such as intake manifold, rear gears, transmission, etc. I personally like what I've read about the Brodix Race-Rite Oval Port heads. They make great power for a potent big block street engine with a true performance street cam and they have the exhaust ports at the stock height so header clearance isn't a problem. I chose Edelbrocks because I needed closed chamber heads and they were the only good aluminum head with a closed chamber. If not for that, Brodix would be my choice for my goals. AFRs would be a great choice if you're planning on a serious build and max power is your goal.
Bottom line, if you're considering heads you need to take inventory of your current equipment and decide what your goals are. There are some really knowledgeable guys here in terms of big block builds and I'm sure they'll be glad to help if you can define your goals.
Bottom line, if you're considering heads you need to take inventory of your current equipment and decide what your goals are. There are some really knowledgeable guys here in terms of big block builds and I'm sure they'll be glad to help if you can define your goals.
06-06-2012, 09:37 AM
#10
Melting Slicks
Member Since: Aug 2008
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You can certainly boost horsepower in either of these old school engines...a high rise intake manifold in place of the low slung OEM manifold needed for Corvette hood clearance is a good place to start.
Headers, and the corresponding big tube dual exhaust system, will gain more horsepower from a hi-po engine like the LS-6 than from the boat anchor LS-5. I would expect no more than ~50 hp gain at the most for a docile, street-driven rat motor.
Doing so while also trying to get increased gas mileage is nigh onto impossible. Perhaps you should focus your efforts towards a modern computer-controlled, fuel injected engine.
06-06-2012, 10:07 AM
#11
Drifting
Thread Starter
Since this is a CORVETTE forum, should we presume that the 454 you intend to buy is either the 8.5:1 compression LS-5, 365 hp hydraulic cam engine or the solid lifter 9.0:1, 425 hp LS6? Or did yours get pulled from the engine bay of a 1971 truck?
You can certainly boost horsepower in either of these old school engines...a high rise intake manifold in place of the low slung OEM manifold needed for Corvette hood clearance is a good place to start.
Headers, and the corresponding big tube dual exhaust system, will gain more horsepower from a hi-po engine like the LS-6 than from the boat anchor LS-5. I would expect no more than ~50 hp gain at the most for a docile, street-driven rat motor.
Doing so while also trying to get increased gas mileage is nigh onto impossible. Perhaps you should focus your efforts towards a modern computer-controlled, fuel injected engine.
You can certainly boost horsepower in either of these old school engines...a high rise intake manifold in place of the low slung OEM manifold needed for Corvette hood clearance is a good place to start.
Headers, and the corresponding big tube dual exhaust system, will gain more horsepower from a hi-po engine like the LS-6 than from the boat anchor LS-5. I would expect no more than ~50 hp gain at the most for a docile, street-driven rat motor.
Doing so while also trying to get increased gas mileage is nigh onto impossible. Perhaps you should focus your efforts towards a modern computer-controlled, fuel injected engine.
(I'm assuming) It's a stock LS-5 matching numbers motor to the 1971. I might be best till I actually get the car and make sure the PO hasn't done any mods I don't know of... I should be getting it tomorrow...
06-06-2012, 11:07 AM
#13
Race Director
That's a pretty Vette. 
Make sure you get all the paperwork he has on the car, including mod receipts. You could have a mystery cam or other parts in there that aren't original and now's the time to get that info if he has it. It's also possible, since the car is over 40 years old, that the motor has been gone through and the compression is higher than stock. The more info you have, the better decisions you can make about what changes you want to make- if any.
Make sure you get all the paperwork he has on the car, including mod receipts. You could have a mystery cam or other parts in there that aren't original and now's the time to get that info if he has it. It's also possible, since the car is over 40 years old, that the motor has been gone through and the compression is higher than stock. The more info you have, the better decisions you can make about what changes you want to make- if any.
06-06-2012, 11:32 AM
#14
Race Director
That's a pretty Vette. Make sure you get all the paperwork he has on the car, including mod receipts. You could have a mystery cam or other parts in there that aren't original and now's the time to get that info if he has it. It's also possible, since the car is over 40 years old, that the motor has been gone through and the compression is higher than stock. The more info you have, the better decisions you can make about what changes you want to make- if any.
Make sure you get all the paperwork he has on the car, including mod receipts. You could have a mystery cam or other parts in there that aren't original and now's the time to get that info if he has it. It's also possible, since the car is over 40 years old, that the motor has been gone through and the compression is higher than stock. The more info you have, the better decisions you can make about what changes you want to make- if any. They are only original once and the value is the highest stock. Think long and hard before you tear it apart. A compression check, tune up, distributor recurve, dyno tune on the carb and a factory air cleaner is the direction I would go if the engine is stock and numbers matching. This will get you a lot more performance than you would think it would.
06-07-2012, 12:28 AM
#15
Drifting
Thread Starter
That's a pretty Vette. Make sure you get all the paperwork he has on the car, including mod receipts. You could have a mystery cam or other parts in there that aren't original and now's the time to get that info if he has it. It's also possible, since the car is over 40 years old, that the motor has been gone through and the compression is higher than stock. The more info you have, the better decisions you can make about what changes you want to make- if any.
Make sure you get all the paperwork he has on the car, including mod receipts. You could have a mystery cam or other parts in there that aren't original and now's the time to get that info if he has it. It's also possible, since the car is over 40 years old, that the motor has been gone through and the compression is higher than stock. The more info you have, the better decisions you can make about what changes you want to make- if any.
06-07-2012, 12:29 AM
#16
Drifting
Thread Starter
They are only original once and the value is the highest stock. Think long and hard before you tear it apart. A compression check, tune up, distributor recurve, dyno tune on the carb and a factory air cleaner is the direction I would go if the engine is stock and numbers matching. This will get you a lot more performance than you would think it would.
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06-07-2012, 12:41 AM
#17
Race Director
Here is some reading for you. A performance distributor recurve can add 30 HP and torque, much better throttle response. run cooler and improve fuel mileage. Cost: about $10. $30 if you need a vacuum can.
http://www.lbfun.com/warehouse/tech_...t%20Timing.pdf
http://www.lbfun.com/warehouse/tech_...%20ADVANCE.pdf
http://www.lbfun.com/warehouse/tech_...ance_Specs.pdf
http://www.lbfun.com/warehouse/tech_...ng%20Paper.pdf
http://www.lbfun.com/warehouse/tech_...t%20Timing.pdf
http://www.lbfun.com/warehouse/tech_...%20ADVANCE.pdf
http://www.lbfun.com/warehouse/tech_...ance_Specs.pdf
http://www.lbfun.com/warehouse/tech_...ng%20Paper.pdf
06-07-2012, 09:47 AM
#18
Instructor
After you get the car figure out what has been done and what you're willing to do. Low compression 454's will still perform great with a cam, intake and headers. Recurving the distributor will turn it into a whole new animal.
06-08-2012, 12:49 AM
#19
Drifting
Thread Starter
Ok, I got the car and here's what CAM was replaced. I don't know what I'm looking at here. Can someone tell me how this will work with the 454? (I have a whole rebuild list I need to scan and post which shows what was done during the rebuild...)
06-08-2012, 12:58 AM
#20
Race Director
Well, that's a mild cam. It might be just fine, depending on what level of performance you're looking for. Definitely post the rest of the info you have. How long ago was the rebuild done and how many miles are on the motor since then? Have you had a chance to drive it yet? If so, are you happy with how it runs? By the way, congrats on your purchase. It looks very clean from what I've seen.