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Newbie here so I apologize if this question has been asked. I can’t imagine it hasn’t.
I am a proud third owner of a stock 40k mile 1973 L82 Stingray w/o AC. I love the car.
However, I would like to tap into the hidden HP.
The car is bone stock with the exception of a Edelbrock Performer Manifold. (I have the original).
I have just changed ALL the fluids, valve cover gaskets, belts, control arms, ball joints, front springs, swapped a Borgeson power unit, new brake lines, master cylinder, calipers, pads, rotors, tires and battery. So it starts, stops, and is safe.
Question; Without changing the stock appearance of the L82 what performance upgrades can I do to tastefully make changes that will push 425/450 hp ? (planning to also add a vintage AC so, I want to consider that in the build)
Also, I have a belt squeal at about 3200 RPMs
even with the new belt. Any ideas?
Thanks!! Stock motor.
Last edited by bobwardjr; Nov 30, 2020 at 07:35 AM.
You need to desmog it if that works for your area. Original catalytic converter is very restrictive. EGR can be blocked and the ignition can be recurved. Carb will need to be recalibrated once the EGR is disabled.
Dual exhaust will help. Long tube headers are a decision but you can still keep the manifolds if you prefer.
Now comes the real power - The engine can be stroked to a 383. This is the way for you to get the torque you want. Bores could still be viable with the low miles so the engine could end up slightly smaller than a 383 if it does not need a rebore. You will need a trustworthy machine shop close by for this.
The heads will need to be upgraded. I would advise you to purchase a pair of quality heads that have the right size chambers for your target compression ratio. This is critical.
I think these two links would be a good starting point for you. Both are running on the forum now. Then you can decide how much money you want to spend, Where you want the power to be (low RPM or high), and how much of the original look you are willing to sacrifice.
You need to desmog it if that works for your area. Original catalytic converter is very restrictive. EGR can be blocked and the ignition can be recurved. Carb will need to be recalibrated once the EGR is disabled.
Dual exhaust will help. Long tube headers are a decision but you can still keep the manifolds if you prefer.
Now comes the real power - The engine can be stroked to a 383. This is the way for you to get the torque you want. Bores could still be viable with the low miles so the engine could end up slightly smaller than a 383 if it does not need a rebore. You will need a trustworthy machine shop close by for this.
The heads will need to be upgraded. I would advise you to purchase a pair of quality heads that have the right size chambers for your target compression ratio. This is critical.
Thats the direction I would go.
By looking at the photo above this car has already been de-smogged. There aren't any original smog items remaining that I can see. Probabaly no EGR either since it has the edlebrock intake. Interested to know if it still has the original Qjet with that intake. Might still have it since the original air cleaner is present. Also no catalytic converter on the 73's they are still true dual exhaust Corvettes. Cats started in 75. From this photo I can't really tell if there are plugs in the exhaust manifold where the smog tubes(trees) would have been attached. Maybe the exhaust manifolds were changed out as well? I also see that there isn't any EVAP hoses coming off the PCV valve so that tells me the EVAP system is also non functional. The previous owners must have already been try to get minimal HP gain. That being said, still a nice looking engine. Glad to see you decided on a 73. Good luck with your future projects..
Tooch
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
Belt squeal. Your belt width looks too narrow on the water pump pulley. If its not a 1/2" wide, buy one that is. Make sure there is proper belt tension. Is the mounting bracket tight on the cylinder head? Worn alternator bearings? Are the pulleys misaligned?
By looking at the photo above this car has already been de-smogged. There aren't any original smog items remaining that I can see. Probabaly no EGR either since it has the edlebrock intake. Interested to know if it still has the original Qjet with that intake. Might still have it since the original air cleaner is present. Also no catalytic converter on the 73's they are still true dual exhaust Corvettes. Cats started in 75. From this photo I can't really tell if there are plugs in the exhaust manifold where the smog tubes(trees) would have been attached. Maybe the exhaust manifolds were changed out as well? I also see that there isn't any EVAP hoses coming off the PCV valve so that tells me the EVAP system is also non functional. The previous owners must have already been try to get minimal HP gain. That being said, still a nice looking engine. Glad to see you decided on a 73. Good luck with your future projects..
Tooch
- Headers.
- Recurve distributor. 36 degrees mechanical all in by 2500 rpm. Additional 14 degrees of vacuum advance. Hooked to manifold, not ported vacuum.
- New heads. AFR if you can afford it. Edelbrock RPM are also good.
- L-82 cam is pretty god but old tech. Hydraulic roller retrofit with same .050" specs would give more lift and wake up engine a bit without hurting idle quality.
- Rejet distributor (if needed). Recommend using a wideband AFR to tune.
- Electric fans
That should be an easy 400 hp at the crank without too much trouble.
Just be aware that when most guys are quoting crank HP, they are talking gross, without accessories. Your 250 HP Net is probably close to 300/320 gross already. The big drop for GM was 1971/1972 when compression dropped. Get the compression back up to 10:1 or so with aluminum heads and have some fun.
Last edited by SteveG75; Nov 30, 2020 at 10:24 AM.
Unfortunately, the OP is trying for 425+hp and original look. The most bang for the buck is the heads and headers, but the most visible changes to the original look are heads and headers. Not sure which the OP is more willing to give up. Seems like concessions are needed. Not sure whether a 430 hp crate at $4700 and putting his 40,000 mile NOM engine on the shelf isn't a nice compromise.
This below...my OEM 78 L-82 rebuilt/upgraded to 425+ Gross HP in 2014...Pretty much looks like an L-82, idles better than a stock L-82 and goes like stink with BIG Mid Range Torque. You have everything in your motor to make top street usable power and torque (I would not stroke an OEM L-82 350), using the L-82 components, and you can make it look like a stock L-82. I did this exact transformation!
I bored my engine (I had to .030). Reconditioned and reused the L-82 forged crank/rods. Ported the aluminum L-82 aluminum intake. OEM L-82 valve covers. L-82 dual snorkel cold air intake system. Painted chevy blue (1978 color).
I did not paint the AFR heads but if I did you would be hard pressed to think it was not stock. Even now most people do not know that the engine has about 150 more Net HP than an OEM L-82.
Howards Roller cam (.525/.525 lift, duration 219/225, LSA110, operating range 1,500-5,600 RPM). I rarely rev the motor to 6,000 RPM and it has BIG TQ for a SBC Gen 1, a match to just about any SBC V8 displacement, sub 400 CI. My 10C6Z06 427 LS7 7.0 liter has BIGGER TQ but for a C3, the motor has very streetable power. This engine also has 1 7/8 inch LTH and is more than a handful for the C3 chassis and suspension for the street. The L-82 355 runs on 89 octane with 10.2:1 compression mostly due to the cam and AFR aluminum heads.
Only 2 minor changes I would make now is slightly more compression to 10.5:1 (not a big deal at all though at 10.2:1, currently, and, a roller cam with .550 or .560 lift to maximize the full flow potential of the AFR heads, at the same duration (don't go too high duration for a street motor, for max mid range power). For a street motor, the lower duration of 219/225 was prefect for max torque between 2,500-4,500 RPM which is where the engine lives 99% of the time...it came out almost perfect, for me!
Last edited by jb78L-82; Nov 30, 2020 at 03:19 PM.
You will not get the power increases you envision without doing significant changes to the engine, such as jb78L-82 has described. That is about the only way to get what you want with a nearly-stock appearing engine.
- Headers.
- Recurve distributor. 36 degrees mechanical all in by 2500 rpm. Additional 14 degrees of vacuum advance. Hooked to manifold, not ported vacuum.
- New heads. AFR if you can afford it. Edelbrock RPM are also good.
- L-82 cam is pretty god but old tech. Hydraulic roller retrofit with same .050" specs would give more lift and wake up engine a bit without hurting idle quality.
- Rejet distributor (if needed). Recommend using a wideband AFR to tune.
- Electric fans
That should be an easy 400 hp at the crank without too much trouble.
Just be aware that when most guys are quoting crank HP, they are talking gross, without accessories. Your 250 HP Net is probably close to 300/320 gross already. The big drop for GM was 1971/1972 when compression dropped. Get the compression back up to 10:1 or so with aluminum heads and have some fun.
Correct! Contrary to others you don't need to build a stroker to make 420 or even 450 h.p I think a set of heads and headers would amaze you.
Correct! Contrary to others you don't need to build a stroker to make 420 or even 450 h.p I think a set of heads and headers would amaze you.
Correct/agree^^^, and I stated the same previously, that I would NOT stroke an OEM L-82, not needed to produce street 425-450 Gross HP, since modern engine parts will easily produce that power and appropriate TQ.
Unless you are looking for 475-500+ Gross HP from a SBC Gen 1, most people should skip stroking the block, since a 355 will easily make strong mid 400 Gross HP with concentrated strong mid range TQ, if cammed, correctly, using top notch modern engine parts.
But i can unterstand if you want to keep your shortblock. But then Heads/Cam/Intake/Carb/Headers/Exhaust are to reevaluate regarding output potential as well as effect on final combination
Last edited by Harris Roc Malouda; Dec 1, 2020 at 07:04 AM.
Appreciate all the advice guys.
I would prefer to not stroke the motor, I like this approach.
Please re Read my post #9 and PM me with questions. Those parts from my build will give you approximately 440-450 Gross HP.
As stated previously as well, slightly more lift from the howards rollers cam (,550/.560) , if you can find it from howards, with the same duration of around 219/225, LSA 110, would give you slightly more mid range power from the AFR heads for the street......with no loss of driveability: Idle, low end power, and certainly more top end.
Please re Read my post #9 and PM me with questions. Those parts from my build will give you approximately 440-450 Gross HP.
As stated previously as well, slightly more lift from the howards rollers cam (,550/.560) , if you can find it from howards, with the same duration of around 219/225, LSA 110, would give you slightly more mid range power from the AFR heads for the street......with no loss of driveability: Idle, low end power, and certainly more top end.
Can I ask you how much money you have into it and how much of the work you did yourself? The reason I am asking is I have about $7500 into parts, machining, balancing and head work in my BB. I did most of the work myself under the direction of my engine builder /friend. If I had it to do over, I probably rebuild it again since I learned a lot and got the exact engine I wanted. However, I realized it cost me as much or more than an equivalent (in power and performance) new engine.
Can I ask you how much money you have into it and how much of the work you did yourself? The reason I am asking is I have about $7500 into parts, machining, balancing and head work in my BB. I did most of the work myself under the direction of my engine builder /friend. If I had it to do over, I probably rebuild it again since I learned a lot and got the exact engine I wanted. However, I realized it cost me as much or more than an equivalent (in power and performance) new engine.
I bought the AFR heads and Howard retro roller kit in 2013 for the 2014 build. Prices are now 6/7 years old.
I had the bottom end professionally rebuilt by a local expert reconditioning the Forged L-82 crank, L-82 rods, etc. Builder installed JE Forged racing pistons and rings. New Oil pump, new freeze plgs, hot tanked the block, .030 bore. no decking the block. Reused the L-82 OEM oil pan.
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
Originally Posted by jb78L-82
All in back in 2013/2014 for parts, builder's part, and my free labor Approximately $5,500. Steal and a deal.
Similar cost here but I needed to add 33% more for the difference in the Cdn $. However, I enjoyed doing the build myself, no assistance from anyone except forum members here and I knew exactly what parts went into my engine.
Last edited by resdoggie; Dec 1, 2020 at 02:34 PM.
1973 L82 HP increase
