Cheap L82 Performance Hacks?
Safety Car
Joined: Jan 2009
Posts: 3,736
Likes: 56
From: anchorage ak
If you had very little moneY lots of time and could afford the pats, but the best low budget mods are exhaust including headers which can be done cheaply if you shop and do the work your self, headers, again you'd need to find a used pair plus the curve kit.1.6 rockers on a stick cam would probably tip on the nose with stick springs
Drifting
Joined: Jun 2015
Posts: 1,266
Likes: 156
Since you're willing to change head gaskets then you're close to some other worthy mods. If the heads are in good shape, an afternoon with grinding stones can do a lot for heads of that vintage. I followed basic porting articles written in the seventies and went from a trap speed of 105 to almost 109 with my mildly hopped up '69 L-46. I did not try to enlarge the ports just cleaned things up. I also deburred the chambers which ended my run on issues. The thin head gaskets will also give you a reasonable quench for better octane tolerance.
Pro
Joined: Oct 2009
Posts: 664
Likes: 89
From: Marysville Ohio
And set ignition timing for performance - search for posts on ignition timing and you will see a ton of info that can improve how the car feels and responds to the butt dyno.
Working with the timing curve is the cheapest "hack" you are likely to find. It's nearly free (except for the cost of advance springs maybe?)
Le Mans Master
Joined: Oct 2010
Posts: 6,929
Likes: 842
From: melbourne florida
2023 C3 of the Year Finalist - Modified
Correct they do have valve reliefs and the advertised compression is 9 to 1 ,that may be optimistic maybe not. A set of 64 cc heads will get you knocking on the door of 10 to 1 and there is a fair amount of power to be had in that. People like to quote 3% per point of compression as a rule of thumb but I don't know what fool came up with that.the are too many variables in an engine to make a call like that.
That cam was built for an 11 to 1 compression ratio so the closer you can get to that figure the better chance the cam has.
That cam was built for an 11 to 1 compression ratio so the closer you can get to that figure the better chance the cam has.
Thread Starter
Melting Slicks
Joined: Jun 2016
Posts: 2,979
Likes: 332
From: Woodinville WA
And on the 1.6:1 ratio rockers/ roller rockers. Why one vs. the other?
Can the stock heads and springs and rod length support just swapping for 1.6:1 ratio roller rockers without issue?
Adam
Can the stock heads and springs and rod length support just swapping for 1.6:1 ratio roller rockers without issue?
Adam
Racer
Joined: Apr 2011
Posts: 367
Likes: 7
From: Congupna Victoria
This is an excellent question.
One I'm curious as well.
And if possible, what performance increase you can expect, assuming nothing else changes.
I did a "True Dual" exhaust change, but kept the std manifolds. No headers - a true "bolt on" mod.
I dyno-ed the car the day before, then dyno-ed it again immediately after - there were NO other changes.
Power was 170Hp @ wheels, went up to 195Hp @ wheels
Pretty happy with that - can definitely feel it! More fun to drive
Thread Starter
Melting Slicks
Joined: Jun 2016
Posts: 2,979
Likes: 332
From: Woodinville WA
Alan,
This is an excellent question.
One I'm curious as well.
And if possible, what performance increase you can expect, assuming nothing else changes.
I did a "True Dual" exhaust change, but kept the std manifolds. No headers - a true "bolt on" mod.
I dyno-ed the car the day before, then dyno-ed it again immediately after - there were NO other changes.
Power was 170Hp @ wheels, went up to 195Hp @ wheels
Pretty happy with that - can definitely feel it! More fun to drive
This is an excellent question.
One I'm curious as well.
And if possible, what performance increase you can expect, assuming nothing else changes.
I did a "True Dual" exhaust change, but kept the std manifolds. No headers - a true "bolt on" mod.
I dyno-ed the car the day before, then dyno-ed it again immediately after - there were NO other changes.
Power was 170Hp @ wheels, went up to 195Hp @ wheels
Pretty happy with that - can definitely feel it! More fun to drive
I don't know who this Alan guy is, but I did find an article that speaks pretty well to the benefits of roller rockers vs. stamped; I just always wonder in the back of my mind about the impartiality of paid-for magazines. (And paid-for internet forums, for that matter...)
http://www.hotrod.com/how-to/engine/...l-block-chevy/
P.S. 25+ HP just for exhaust has GOT to make you feel good! It's insane how exhaust limited these poor cars are.
Adam
Last edited by NewbVetteGuy; Jul 18, 2016 at 11:13 PM.
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Racer
Joined: Apr 2011
Posts: 367
Likes: 7
From: Congupna Victoria
Pizzagulley, I don't know who this Alan guy is, but I did find an article that speaks pretty well to the benefits of roller rockers vs. stamped; I just always wonder in the back of my mind about the impartiality of paid-for magazines. (And paid-for internet forums, for that matter...)
Adam
Adam
my apologies.... got your name incorrect due to a combination of poor memory and laziness...
Do you have a link to the article?
Thread Starter
Melting Slicks
Joined: Jun 2016
Posts: 2,979
Likes: 332
From: Woodinville WA
Newb Question: Can anyone tell me whether our L82s have 3/8th studs or 7/16th studs??
When I started looking at roller rockers, that was an immediate piece of information that they wanted me to provide and I'm clueless...
Also what's considered the top 3 or so roller rockers these days? I've heard high praise for Hardland Sharp, but they're aluminum and I heard that aluminum ones don't last as long as steel.
The steel ones are supposedly heavy so a downer there and then you've got things like Comp Cams Ultra Pro Magnum that are super durable steel but then lighter than normal steel ones, right?
Are there any Ultra Pro Magnum competitors out there?
Adam
When I started looking at roller rockers, that was an immediate piece of information that they wanted me to provide and I'm clueless...
Also what's considered the top 3 or so roller rockers these days? I've heard high praise for Hardland Sharp, but they're aluminum and I heard that aluminum ones don't last as long as steel.
The steel ones are supposedly heavy so a downer there and then you've got things like Comp Cams Ultra Pro Magnum that are super durable steel but then lighter than normal steel ones, right?
Are there any Ultra Pro Magnum competitors out there?
Adam
Racer
Joined: Apr 2011
Posts: 367
Likes: 7
From: Congupna Victoria
Got this off Hotrodders.com
From the factory the 350 uses a 1.5 to 1 ratio rocker, the LT4 excepted at 1.6 to 1. There is power to gained switching from a 1.5 to a 1.6 whether or not the change includes roller bearing or not. The 6+ percent in rocker ratio changes the peaks for torque and horsepower by about 6 percent and moves those peaks about 6% higher in the RPM band. Imagine that. But one for one on ratio the power difference between a ball and socket rocker and a roller isn't outside the range of the variance you see in an engine from one dyno run to the next with the same setup, a couple,,,three horses one way or the other.
Where the difference between identical ratios but roller versus ball/socket does show up is reliability over 6000 RPM. When the revs get up here you just can't get enough lubrication onto the ball and socket to control the heat. The more aggressive the lift against duration and the stronger the valve spring pressure when combined with high RPMs the sooner this hits the wall. So the top end power and the time you can keep the engine there will be limited by the inevitable heat failure of these parts. A rocker with a roller trunnion gets simply, though not cheaply, around this problem.
Many rockers come with roller tip, including those intended for lower RPM operation by virtue of the ball and socket pivot. This is intended to trade the non roller's scraping action on the valve stem tip for a rolling action. This should reduce stem and guide wear by reducing the side to side pull and push of the sliding motion between rocker and tip for a rolling contact. This is more critical with lots of lift and high pressure springs. My own rules are roller tips get used when the lift gets above .47 inch. The other advantage I see is that it's easier to set them up where the motion on the stem tip can be kept as close as possible about the centerline of the stem such that off center loads that will result in stem and guide wear can be minimized. The rollers not generating anything like the heat of the ball and socket design allows the upper end lubrication to be used to cool the valve springs. Many race only engines reduce the push rod oil feed since the roller doesn't need much and they install a spray bar on the valve springs for cooling them.
Another advantage is many brands of roller rockers are serviceable with new bearings and trunnions which is certainly more cost advantageous than having to scrap entire rockers when replacement of these parts becomes necessary.
The biggest downside of roller rockers is that a failure puts shrapnel into the oily side of the motor. This possibility drives us to screens at the return drains and strong magnets positioned in the heads and valley to stop the migration of failed roller bearing parts into the oil sump. For this reason it's smart to purchase quality rockers.
So in the end on a one for one ratio trade, rollers don't make any power. When going from a 1.5 to a 1.6, there is about a 6 percent overall power gain and that will also be about 6 percent further up the RPM band and it tends to broaden the top power a bit which is to say the engine will hang onto the power peak longer. Wear in the stem to guide interface is reduced when using high lifts. But if these things come apart they make one hell of a mess if the wreckage isn't contained.
Bogie
In summary - reliability is improved as is "revability"...and a claim of 6% improvement - I'd take that as an "up to 6%" improvement.
Not sure the cost would warrant that change??
The 6% improvement doesn't seem to have been verified - just an estimate based on an additional 6% lift, from 1.5 to 1.6 - not exactly robust science!!!
From the factory the 350 uses a 1.5 to 1 ratio rocker, the LT4 excepted at 1.6 to 1. There is power to gained switching from a 1.5 to a 1.6 whether or not the change includes roller bearing or not. The 6+ percent in rocker ratio changes the peaks for torque and horsepower by about 6 percent and moves those peaks about 6% higher in the RPM band. Imagine that. But one for one on ratio the power difference between a ball and socket rocker and a roller isn't outside the range of the variance you see in an engine from one dyno run to the next with the same setup, a couple,,,three horses one way or the other.
Where the difference between identical ratios but roller versus ball/socket does show up is reliability over 6000 RPM. When the revs get up here you just can't get enough lubrication onto the ball and socket to control the heat. The more aggressive the lift against duration and the stronger the valve spring pressure when combined with high RPMs the sooner this hits the wall. So the top end power and the time you can keep the engine there will be limited by the inevitable heat failure of these parts. A rocker with a roller trunnion gets simply, though not cheaply, around this problem.
Many rockers come with roller tip, including those intended for lower RPM operation by virtue of the ball and socket pivot. This is intended to trade the non roller's scraping action on the valve stem tip for a rolling action. This should reduce stem and guide wear by reducing the side to side pull and push of the sliding motion between rocker and tip for a rolling contact. This is more critical with lots of lift and high pressure springs. My own rules are roller tips get used when the lift gets above .47 inch. The other advantage I see is that it's easier to set them up where the motion on the stem tip can be kept as close as possible about the centerline of the stem such that off center loads that will result in stem and guide wear can be minimized. The rollers not generating anything like the heat of the ball and socket design allows the upper end lubrication to be used to cool the valve springs. Many race only engines reduce the push rod oil feed since the roller doesn't need much and they install a spray bar on the valve springs for cooling them.
Another advantage is many brands of roller rockers are serviceable with new bearings and trunnions which is certainly more cost advantageous than having to scrap entire rockers when replacement of these parts becomes necessary.
The biggest downside of roller rockers is that a failure puts shrapnel into the oily side of the motor. This possibility drives us to screens at the return drains and strong magnets positioned in the heads and valley to stop the migration of failed roller bearing parts into the oil sump. For this reason it's smart to purchase quality rockers.
So in the end on a one for one ratio trade, rollers don't make any power. When going from a 1.5 to a 1.6, there is about a 6 percent overall power gain and that will also be about 6 percent further up the RPM band and it tends to broaden the top power a bit which is to say the engine will hang onto the power peak longer. Wear in the stem to guide interface is reduced when using high lifts. But if these things come apart they make one hell of a mess if the wreckage isn't contained.
Bogie
In summary - reliability is improved as is "revability"...and a claim of 6% improvement - I'd take that as an "up to 6%" improvement.
Not sure the cost would warrant that change??
The 6% improvement doesn't seem to have been verified - just an estimate based on an additional 6% lift, from 1.5 to 1.6 - not exactly robust science!!!
Last edited by puzzigully; Jul 19, 2016 at 02:00 AM.
Safety Car
Joined: Jan 2009
Posts: 3,736
Likes: 56
From: anchorage ak
Alan,
This is an excellent question.
One I'm curious as well.
And if possible, what performance increase you can expect, assuming nothing else changes.
I did a "True Dual" exhaust change, but kept the std manifolds. No headers - a true "bolt on" mod.
I dyno-ed the car the day before, then dyno-ed it again immediately after - there were NO other changes.
Power was 170Hp @ wheels, went up to 195Hp @ wheels
Pretty happy with that - can definitely feel it! More fun to drive
This is an excellent question.
One I'm curious as well.
And if possible, what performance increase you can expect, assuming nothing else changes.
I did a "True Dual" exhaust change, but kept the std manifolds. No headers - a true "bolt on" mod.
I dyno-ed the car the day before, then dyno-ed it again immediately after - there were NO other changes.
Power was 170Hp @ wheels, went up to 195Hp @ wheels
Pretty happy with that - can definitely feel it! More fun to drive
I think that some of the new LS engines use 1.6 and 1.7 ratio rockers, i might be mistaken as I do suffer from C.R.S...
