sweeet76

I would think gross horsepower would be substantially more. Net would seem to be after everything has been taken out such as a paycheck before and after the taxes are taken out.

71scgc

All speculation aside, they're still nice gains for little $$ and work. Sounds like you had a fun day, too. Ain't that what it's all about??

Taijutsu

Like many forum members, I am following this closely. My combo 350,
TFS heads, 218-224 HR, 1.6 RRs, air Gap w/650 puts out 315 rwtq @4,100
With 1 1/2 RHs the rwhp is strangled to 280 rwhp @ 5,000.
Now tell me some more hp isn't left on the table?
With that combo, I think my tq/hp should be closer. Thoughts?
I have 2.25 duals w/H pipe. I really want 300 rwhp.

R

G-Sting

jb78, thanks for posting the results. Since torque is the most significant number, you have approx. 310-325 net torque. Sweeeet.

Belgian1979vette

Anyone know what the original type pistons were on these engines ? I found some domed (+3cc) pistons in mine, with CR with composite gaskets around 10/1. When looking at the number you got, it doesn't surprise me the thing ran like a bat from hell with the victor jr and rpm above 3000 (although i must admit, the ported 292 heads probably had a lot to do with it). I suspect it still having the original cam in it as well. Due to my mishap i have to get my old iron with those pistons back together. Hopefully she will still produce good power.

jb78L-82

It really was good fun and I did learn much from John at NE Dyno!

I am really considering something along the comp cams 268 since I have to change the timing chain and get rid of the nylon cam gear-I was advised VERY strongly by NE Dyno to make that change. Word of caution to everyone who has a mid 70's to early 80's stock timing chain that the nylon cam gear can and will eventually fall apart! I am also considering the Edelbrock Performer intake BUT only if I can make it look OEM . I will keep the OEM stock 882 heads since I don't want to alter the basic engine too much-The objective is NOT ultimate HP just a little more juice!

Taijutsu- I am no engine expert and not knowing about your TFS heads, I would stil think that 300 RWHP should be relatively easy with the right combo of parts. I would think that with headers of some sort and 2.5 inch duals, not 2.25, you should may be leaving some HP on the dyno. Check the link below for food for thought!

http://www.superchevy.com/technical/...ver/index.html

jb78L-82

The other issue that I found interesting which is something I have always suspected is that the L-82 unlike the L-48 is a mid to high RPM motor since the highest torque readings are fairly high up in the RPM range and the highest HP is above 5,000 RPM and pretty much stays flat to the end of the dyno runs! The L-82 is not a bottom end motor and confirms why the engine, in my opinion, is better suited to the 4 speed than the automatic. In 78/79 the published test results confirm that the auto was slower than the 4 speed to 60 MPH.

Lastly, I was worried that the OEM cam maybe wearing with miles and the 3.70 gears, but these dyno runs seem to indicate that it is in good shape. I use Mobil 1 15W-50 Racing/High performance and have used Mobil 1 since 1986!

LancePearson

On Friday I had my 76 l48 with four speed run on a dyno at a speed shop in Richmond, Va. There is no base line from the factory so the operator whose dyno is calibrated to his drag race engine and car building business had to make some assumptions. The net effect he says of my keeping cast iron ram's horn exhaust manifolds, switching from 2-1-2 and flat pellet cat conv to true 2 1/4" duals through two wire bullet cat converters and low flow resistance mufflers and running about 13 degrees tdc on timing and nothing else was a gain of approx. 30 horsepower over what the original factory setup would have done. Since there is no baseline and each dyno is calibrated by the operator in their own way he had to use his long judgment and experience to try and relate it back to sae net numbers from GM for the 76 model. When I went I thought I'd have straight facts to work with but what I found was I had to still get interpolation to compare back to the factory. However, I know the car runs much better than when I got it and after the above changes without going into the block, changing the intake manifold, carb or anything all that much so I though the gain was pretty good for the effort.

The car ran well on the dyno with no smoke from the exhaust or glitches. He didn't tune the carb settings as we were just getting a baseline.

I was happy with the results though his particular method of calibration is slightly different than some of the other dyno results I've seen here on the forum.

Here's a youtube of the car on the dyno running up into the rpms to get the graphs. He did five pulls I think it was and this was one of them.

http://www.youtube.com/watch?v=56CMNpa7LkU

Lance P.

BKarol

I had never gone to a dyno to even watch so I decided last year to get some pulls in and had a great time with 10 other cars. Jeff and I went this past Saturday and spent about 2 hours there talking engine stuff. John was willing to talk too

This chart shows one of my runs last august 2010. (003 blue lines). and also 2 runs from last month. Last year 194rwhp was about 220hp which the car was rated at in 1978. I wasnt that disappointed but learned a few things from John. I have an Edlebrock intake, diff cam,and about 100,000 on the original engine.

In the spring I put on true dual exhausts with magnaflows, with my regular manifolds and put less tension on the air valve. I was totally shocked to see such an increase and still can believe the numbers for the $ and the ease getting the exhaust out is important for hp. And you have to decide how far you want to go. This is it for me. I have enough hp to get to a car show or cruise, or occasional trip to the dragstrip.

I copied this before the smoothing.

LancePearson

J....what is the source of the mechanical drive train losses you quote? "(18% drive train loss-number varies from 15-20% depending on year of car and transmission)" It is always an interesting set of numbers. I pretty much assume the drive train losses are not a % but more or less fixed for any given car's actual drive train....if you have a mid 70's low horsepower epa motor then the % will be higher and if you had a bigger block engine in it then the % would be lower but the mechanical losses still the same.

Not questioning your number but what do you think the losses are in terms of the rated net sae horsepower or rwhp? How did you figure that number as it's a big factor in getting power actually to the rear wheels. Wonder what effect different rear end ratios have on this as well as vibration in the drive train.

I have been unable to find facts though I'm sure that GM knows both rwhp and sae net on virtually every engine drive train combo they sell...just not in their interest to publish the lower rear wheel hp numbers. In the 1970's they didn't always report accurate numbers even when they had them so it all gets to be problematical anyway...why I'm curious.

Any facts we can all learn from.

jb78L-82

Those numbers come from NE Dyno and I have also seen them quoted elsewhere from various sources over the years. I would assume that the drive train losses come from the type of transmission, frictional losses from the transmisson through the driveshaft, through the diff, through the half shafts to the wheel-all along the route HP and torque are lost. Modern cars are much more efficient along this route so there are less losses until the HP actually gets to the wheels.

Well known fact, for example, that the Turbo 400 eats tons of HP due to its design before the HP actually reached the drive wheels. My 2010 Z06 from various sources losses about 10% to the rear wheels-Net HP 505, RWHP-450.

jb78L-82

What were your RWHP and RWT numbers?

7t9l82

we used. to get good results advancing the stock cam 4 degrees. it helped both e.t and m.p.h. it would be nice to verify on the dyno. retarding the cam was a cheap way for the car companies to meet emissions. i know on the Ford 460 setting the cam straight up was worth about 35 h.p.

billla

Nice numbers I have no trouble seeing 50+ HP from intake, cam and exhaust - engines are a system, and matching components will produce the best overall power at a given build/modification level

jb78L-82

My original intent when changing the timing chain was to just advance the cam 4 degrees (I already have the comp cams adjustable timing chain) but after talking to John at NE Dyno this past Saturday and doing some of my own research, many people are telling me that it will help but will not do much for HP. I must say that I am dubious about "not doing much" since logically it makes sense if the engine is able to make power more efficiently it would make more HP but I am no expert. Others say, it just moves the HP/Torque curves down 500 RPM which may expalin the better Et's you observed. Any thoughts about HP gains advancing the cam 4 degrees? If someone has documentation to a HP increase, I would prefer to go that route and then in the Spring I would go back to the Dyno after the change,

jb78L-82

The only problem is that he got the 50 HP with the exhaust only! The cam and intake were already on the car for the baseline run (192 RWHP) and the recent Dyno run (248 RWHP) was with the exhaust change only plus the carb adjustment-no other mods. I don't think that you can say that Karol got 53 HP with a cam, intake, and exhaust! If he had done the baseline run with the OEM intake, L-82 cam, and the OEM 2-1-2 exhaust and then switched out the Cam, put on the Edlebrock intake, and the magnaflow 2.5 true duals, then I could see the combo worth +53 HP but that was NOT the scenario. See where I am going and why I made the statement originally about the 50 HP increase with exhaust only?

billla

I was hoping not to get back into it

To say that the intake and "unknonwn" cam had NO IMPACT on power and the exhaust added ALL THE GAIN SEEN just makes no sense. The exhaust enabled the other modifications to reach their full potential...this is the way engines - as basically an air pump - work. As noted - the engine is a system and the components work together.

As an example, let's say someone bolts on 220cc heads and a big cam on a stock L-82 and makes 300 FWHP (badly ). They then put on a high-rise single-plane intake and long-tube headers and make 400 FWHP. Your contention would be that the heads and cam had no impact...and all the gain was due to the intake/headers? So another guy bolts a high-rise, single-plane intake and long tube headers to a stock L-82...and wonders why they aren't making 400 FWHP

This is why so many "what will I get if I bolt on this single part" spawns such discussion - a single part may not add much...but a balanced combination of the right parts adds quite a bit!

We're not going to agree here, which is hopefully OK for both of us

jb78L-82

Oh I agree that the exhaust helped the whole package BUT in Karol's case having the cam and intake for baseline weakens your contention somewhat. What makes all this interesting is that Karol does not know anything about the cam and from the numbers versus my stock internals the cam seems to be awefully close to the L-82 cam. Why do I say that? The PO may have put it a "replacement" L-82 cam with very little difference in the specs. Karol's dyno charts look very similiar to mine with his cam and intake.

How else can we explain that his L-82 with unknown cam, edelbrock Performer intake with open air cleaner, 2.5 magnaflow exhaust with no headers makes 15 RWHP more then my L-82 with the OEM cam and intake, 2.5 duals/McJacks headers (many people say shorties do nothing-I certainly don't buy that argument one bit). I find it hard to believe that a cam and intake are worth only 15 RWHP over my setup!

How would you explain that John at NE DYNO who is an expert told Karol and me on Saturday that a cam ONLY using the OEM intake is good for 25-30 HP on my engine? If I change my cam this winter and do a dyno run next Spring and the RWHP is 263 with a cam only, stock heads, and OEM intake, what are people going to say then-I don't believe the numbers? I am also wondering what your thoughts would be if I advanced the stock L-82 cam by 4 degrees and pick up X number of HP when some say that advancing the cam has no effect on HP, it just moves the HP/Torque curves?

I understand your logic and theoretically agree but the numbers on this post from my L-82 versus Karol's L-82 weaken your arguement which is the beauty of having Dyno numbers and why this discussion is intriguing.

billla

I can't really debate how you interpret these results or the "weakening" of my argument, as we'll just go around and around We can guess about all kinds of stuff, but in the end I don't see a "stock, exhaust-only" situation here in either case, and I just don't see your arguments...just as you don't see mine . It's not a matter of not believing the numbers - dynos can be run to produce anything, but that's not my point - my point is that you're looking at a complex, interrelated system and only talking about the component parts and then drawing a lot of conclusions and interpretations that I don't believe from my experience are realistic.

jb78L-82

Ok I respect your point of view although I don't completely agree.

I think though you would have to concede on my L-82 that 233 RWHP with my mods is substantially more than 220 Net HP rating from the factory. How much more is debateable since I don't have baseline numbers on my engine but whether it is 35, 40, 45 or even 50 RWHP from a stock internals engine, you have to agree, I hope, that it is very substantial? Maybe someone out there who has seen comments about duals will help but don't expect much more HP will finally cease. The documentation is out there and I am not the first or the last word on this subject but the dyno numbers are very interesting and not surprising to me after all these years with the car.