so got wondering how much the sidepipes/headers with the edelbrock q-jet performer helped the L48, it made 197hp and 255tq, it was done breathing around 4200rpm, not too bad for an engine that was built in 1977. ill post after i put the L82 heads on and a small cam to see this tired 350 wake up!

 

Does your car have a standard or automatic Th350?

I had a very similar set up as my base line dyno on this link http://forums.corvetteforum.com/c3-t...mp-xe268h.html My results were 19 rwhp less than you though and I wonder if it is the parasitic drain from the TH400?

 

I think that is good. Changing the heads and cam will be interesting seeing how
much you gain. Good luck.

 

You'll basically be turning it into an L82 with "L82 heads and a small cam".

The L82 heads are not very good at all. They're the same as the L48 heads with larger valves. If you really want to wake the motor up, go with a new head. Vortecs are LEAPS AND BOUNDS better than the 333822s or 462624s. You will need to run a new intake but you should see a huge performance jump.

If that's RWHP, that is actually phenomenal for a stock L48. You've already likely beaten a stock L82's output.

 

Mine is a th350 tranny with 3.08 gears

 

The L-82 actually has a few advantages over the L-48: the 882 heads on the L-82 as noted have bigger valves and actually flow pretty decently for an engine back then with the major drawback being the heads had a tendency to crack due to thin castings and very high operating temperatures. Are they as good as more modern heads such as the vortecs or AFR's, NO? The L-82 has a 9:1 compression versus the 8.5:1 of the L-48 along with a slightly bigger exhaust Y pipe 2.5 versus 2.25 and slightly better mufflers. The L-82 cam is MUCH better than the L-48 which is a standard passenger car cam versus the L-82's higher lift and longer duration. The L-82 intake in 78 is aluminum and better than the L-48 cast iron passenger intake on the L-48.

Last October 2011, I put my 66,000 mile internally stock L-82 on the dyno (see below for the actual video) to see what it would do with Stock heads, cam, intake, crank, and pistons with the only modifications being McJacks shorty headers, 2.5 inch duals, Monza turbo Mufflers, comp cams 1.5, not 1.6, roller tipped rockers and a 4175 650 CFM Holley Q-Jet replacement breathing through the stock dual snorkel OEM air filter housing:

http://forums.corvetteforum.com/c3-t...-the-dyno.html

Results 233 RWHP/269 Torque!

Just so happens that I will be updating the above post this Saturday: Back to the dyno since I changed the slightly stretched OEM timing chain with nylon gears to a comp cams double roller timing chain with an adjustable key so that I could advance the cam 4 degrees which I did. Want to see if the 4 degree cam advance did anything for HP since the cams in the 70's were ground retarded from the factory due to emissions. The cam advance really seems to have awoken the motor. Stay tuned!

 

So this is a 35 year old L48, original everything except for carb and exhaust system, originally rated at 180 hp at the flywheel. Now its doing 197 hp, at the rear wheels, through an automatic trans. Plus, it didn't have to rev past 4,200 rpm to do it. You must be a hell of a tuner.

 

jb78-L82: Yes, I've read your post and replied to it. (http://forums.corvetteforum.com/1578935701-post53.html)

I neglected to mention that the L-82's only major difference will be pistons when the OP is done. I forgot about intakes... perhaps I just assumed they've all been replaced with alum setups by now but that's certainly not true.

The OP has already changed exhaust which undoubtedly helped quite a bit.

Like Ganey(and me afterwards) has been saying for years, exhaust is a MAJOR benefit for these cars.

While your car posts very respectable numbers, I don't think I'd go through the effort of installing a "big-valve" 882 on an L-48.

I also look forward to the new report. From what I hear adjusting cam timing should bump low end torque. If possible an overlay would be awesome.

 

Thanx for your comments and thoughts. I will be posting the new Dyno run on the previous post as a continuation of the saga.

BTW-The conventional Wisdom is that advancing the cam 4 degrees on a cam installed straight up will just move the torque curve about 500RPM down the RPM band. However, based on many comments from others on the forum and a personal recommendation from a close friend who built engines in the 70's/80's, advancing a retarded installed cam by 4 degrees will result in substantial HP increase in the engine, not just moving the torque curve-we will see on Saturday!

 

The ratings changed in 72 to SAE ratings, 180 was supposed to be hp as installed in the vehicle with all accessories installed and running, so after headers, sede pipes and an edelbrock intake i picked up 17hp, which i dont think is bad

 

I think there's some confusion. The 197hp you mentioned - was that on a chassis dyno or an engine dyno?

FWIW, SAE HP is rated on an engine dyno. All accessories are installed but it's measured at the crank, not the tire of an installed vehicle.

 

Chassie dynojet

 

Happy dyno = happy customer

 

Better than when the tuners use a sad dyno for the before tune and a happy dyno for the after tune.

 

good thread...

 

"How much HP did I make?"

"How much did you WANT to make?"

"500 HP"

<punching buttons> "Well, will you look at that: 501 HP! That'll be $350."

 

Perhaps you can enlighten the OP, myself, and others how the dyno guy does this.

I went to a dyno day with 10 other NCRS people who were told up front that the results will probably be lower than expected. Some were corvette restorers, engine builder, and one guy with a month old Mustang.

I have the print out of hp,torq,af,day,time,humidity, etc. Where can I look to see if he faked the numbers. Apparently you deal with these unscrupulous dyno shops, so please shed some light on this. You can be sure if he did something wrong his reputation will be shot.

Thanks.

 

I would like to hear this explanation as well!!!

 

My brother took his '97 'vette with a cam 'n' heads upgrade to a chassis dyno near where I live, (Oxford, MA) expecting to see 400-420 horsepower at the rear wheels. No matter how they tweaked it, the best he saw was 392 Horsepower. Nothing to sneeze at, and the car is fast enough to be scary, but he was a little upset that he didn't hit that "magic" 400 horsepower mark, and he let the dyno operator know it. The dyno operator said "We don't run a "happy dyno" here, it is what it is." PM me if you live in my area, (southern New England) and I'll tell you the name of the shop.

(I don't know what's so "new" about New England, it's almost 400 years old!)

That being said, I used to work in the IT field, so I know a little something about computers, and if you know what you're doing, it's pretty easy to tweak almost any program's data output. I believe billla works in the IT field, also, so he probably knows what he's talking about, besides, he has a pretty well desrved reputation on this forum for not slinging the bull****. Read this article on how dyno operators can cheat results:

http://www.pencilgeek.org/2009/09/ex...s-how-the.html


Keep the shiny side up!
Scott

 

I know who you are talking about! John is the operator who did my pull last October 2011 with my L-82 (pretty stock except the exhaust-2.5 inch duals, Monza Turbos, Mcjacks shorty headers) and the engine did 233 RWHP, stock NET was 220 HP, not RWHP). I am going THIS saturday for another round of pulls with my new timing chain and the OEM L-82 cam advanced 4 degrees to see if there is any difference. Be on the look out for the followup posts on this issue on Saturday:

http://forums.corvetteforum.com/c3-t...-the-dyno.html