[Shuuz]

Hello All!

I have a story, and then subsequently a question :yell:

If you read my other post in exterior, I inherited a beautiful 1984 El Camino from my father in law. He did numerous upgrades, swaps etc, however some questions are starting to arise. In approximately 1997 the motor was swapped for a GM 350 Crate Motor (LS1 was the name that everyone tell me). The transmission was replace with 700r4, and the rear end was swapped with a 10 bolt "3.73" rear end. The paperwork said that the motor should be a 350hp 350 crate motor. My father in law also stated that it was a 350/350 when he was still with us. And to verify, I asked my mother in laws brother ( a gearhead & my wifes uncle ) what kind of motor was supposed to be in it. He answers 350/350. I assume that there should be some loss of power through the transmission ( it is an automatic ).

Here is the question.

I had the car professionally tuned. I eliminated all vacuum leaks, fuel to air on computer, etc, etc. These guys really have a handle on it. They also have an all wheel dyno. The results are puzzling

On the best of 4 pulls we get this 258hp / 313tq

So I assume a 20% loss of power if it was rated at the crank. That would still give me around 280hp/ ?tq to the wheels.

I have a couple of scenarios
A) The motor is not a 350hp motor. Either salesman stuff or a exaggeration on the part of the in-law.
B) There a large performance no no somewhere (Maybe help on common issues)
C) the automatic kills the overall performance of the motor.
D) The bad brake booster is causing overall performance deterioration

While I do like HP, I am not someone who is a "racer". The point of this question is too ensure that something is not very wrong with the car that myself, an amateur, needs to know so he does not blow up/slowly destroy a family heirloom.

Thank you ECC!:You_Rock:

 

[LOCKJAW]

Does this motor have aluminum heads?
Can you offer any # stamping on block or codes?
Is it possible that the tuner made an error in setting ignition timing.

A 20% drive train loss seems pretty high. Remember that GMPP and others are offering sbc 350's in a variety of HP ratings. It could be a 330hp or 300. The numbers on the block will tell the story.

 

[El Diablo]

258 + (20% 258= 51) = 309

 

[leogexx]

is there a chance that it has the wrong torque converter needed with your combination ? and was there any dyno sheet to prove that the 350hp was an actual 350 hp or is that just a guestimate ?

 

[Shuuz]

Does this motor have aluminum heads?
Can you offer any # stamping on block or codes?
Is it possible that the tuner made an error in setting ignition timing.

A 20% drive train loss seems pretty high. Remember that GMPP and others are offering sbc 350's in a variety of HP ratings. It could be a 330hp or 300. The numbers on the block will tell the story.

Not sure on the aluminum heads. What I do know is that whatever came on the motor, cam etc has never been changed.

I can absolutely get you those codes! I just don't know where to find them. :dontknow:

We reset the timing twice. The second round the shop owner came around and did it himself. I feel confident that the timing should be right.

is there a chance that it has the wrong torque converter needed with your combination? and was there any dyno sheet to prove that the 350hp was an actual 350 hp or is that just a guestimate ?

There is certainly a chance it has the wrong torque converter. Where would I look to see if it is the wrong one. (if it is a big job to check I can always have my mechanic do it :yell

There was never a dyno sheet for the original motor that I have ever seen. :???:

 

[carlfan]

if it runs good and smooth and gets decent fuel mileage it doesn't matter.Just drive and enjoy

 

[ccc]

a tight converter wont effect total hp because it is measured well above the converters lock up rpm. the only gm crate engine with close to 350 hp has aluminium heads. look through the oil cap you should see iron or aluminium. its fairly obvious. with the age and entire drive train concidered you could be close to the 300/330 hp engine. gm didnt paint the aluminium heads. either way if it runs good and has good oil pressure with no odd noises when running,care for it well and drive it

 

[andiamo]

This is a 15 year old crate motor. What kind of mileage does the motor and tranny have on it? I'd think the HP you're getting out of it sounds pretty good. An older more worn out tranny will rob more HP from the engine is my understanding. Everything I've found on the internet says either 18% to 20% but a lot of guys are saying 20 to 25% loss with a 700r4. Most of these numbers were from carcraft articles and I usually find them to be pretty accurate. Just what I found though I'm sure there are guys with a lot more experience that will be able to tell you.

 

[fauxrs]

All crate motors are rated at Gross HP, meaning without any accessories, open exhaust, optimised fuel delivery, no alternator, fan etc....this is very different than Net which includes the exhaust installed on the vehicle and all accessories except A/C.

The change between Gross and Net SAE ratings occured in 1971 and because GM published both net and gross ratings that year we can see the marked difference.

LS6 - 425HP Gross, 325HP Net
LS5 - 365HP Gross, 270HP Net
LT1 - 330HP Gross, 275HP Net
L48 - 270HP Gross, 210HP Net

From the net rating you would then apply the 18-20% driveline loss, manuals being more efficient. Its worthwhile to note also that net ratings can vary from vehicle to vehicle depending on installed options, for example the th400 is well know to have higher parasitic losses compared to say the th350, modern transmissions are generally considered to be more efficient than earlier designs.

So frankly, I dont see any mystery whatsoever, 258 at the rear wheels isnt unrealistic for a motor rated at 350hp gross. To be honest it sounds high being only a 26% loss from the assumed 350hp gross

 

[Bobby78]

All those HP ratings are usually at very RPM's anyway. Look up GM crate engines and you'll see something like 330HP at 5500 RPM's. When will the average car/truck ever see 5500 RPM's? If yo make a habit of revving that high you'll soon have more to worry about that dyno ratings.
Just drive it and enjoy it and forget the hype!

 

[steelybill]

Seems like listing a production engine at a specific HP is a ball park figure. The engine built before this one may have put out 10 hp more, or even 10 HP less, for example.
I don't believe crate engines are dyno'ed before they are crated & shipped, so numbers may not be all that precise. So why not one engine at 355 HP , and the next one 348 etc...??
Production tolerances are likely a factor here too...

 

[fauxrs]

Seems like listing a production engine at a specific HP is a ball park figure. The engine built before this one may have put out 10 hp more, or even 10 HP less, for example.
I don't believe crate engines are dyno'ed before they are crated & shipped, so numbers may not be all that precise. So why not one engine at 355 HP , and the next one 348 etc...??
Production tolerances are likely a factor here too...

For the most part this is true, the manufacturer clearly doesnt test each and every motor that comes off the line, the test is usually one engine off the line is selected, base model options are attached and the test run, that determines the advertised HP for that model, higher performance motors are tested with their options and their HP are thus derived.

For crate motors its similar but no accessories are attached.

To be sure there are probably very minor differences from motor to motor but these differences should really be inconsequential, hell in the past GM made up HP numbers from whole cloth to avoid insurance penalties to future owners.

All those HP ratings are usually at very RPM's anyway. Look up GM crate engines and you'll see something like 330HP at 5500 RPM's. When will the average car/truck ever see 5500 RPM's? If yo make a habit of revving that high you'll soon have more to worry about that dyno ratings.
Just drive it and enjoy it and forget the hype!

Quite true, what is often more important than peak HP is how much torque rests under the curve, torque is what we feel when we drive the cars, in fact HP is just mathematically derived from a torque measurement.

 

[LOCKJAW]

Sounds like you have a nice ride. Whatever power you do have is far beyond what was original. I asked you to see if the heads are aluminum because that would indicate that it is a "performance" motor with between 330 and 355 hp. Aluminum heads are unpainted and easy to identify.
Drive what you got. Others would "kill" to own it.

 

[Jack_K]

258 + (20% 258= 51) = 309

Actually, you would figure it this way:

We want to find out what HP that 258 is 80% of.
258 = .8x (.8 is 80%)
Solving for x, yields x = 258/.8

258 divided by .8 = 322.5 HP

It's probably a 300 or 330 HP crate engine.

However, if the loss is only 10%, 258 / .9 = 286.66 HP (290 HP crate)

Let's also try 15% loss, 258 / .85 = 303.5 HP (300 HP crate)

What's a reasonable loss from flywheel to wheels?

Jack

 

[fauxrs]

Actually, you would figure it this way:

We want to find out what HP that 258 is 80% of.
258 = .8x (.8 is 80%)
Solving for x, yields x = 258/.8

258 divided by .8 = 322.5 HP

It's probably a 300 or 330 HP crate engine.

However, if the loss is only 10%, 258 / .9 = 286.66 HP (290 HP crate)

Let's also try 15% loss, 258 / .85 = 303.5 HP (300 HP crate)

What's a reasonable loss from flywheel to wheels?

Jack

18 to 20% from SAE NET is the rule of thumb I've always heard, a calculation from gross is difficult, because net varies with accessories not included in gross.

 

[Shuuz]

Wow! Thank you for all the responses! You guys are great.

I fully realize, and am very appreciative of what the motor is. I certainly will never make any modifications to it performance wise. I see myself as the caretaker / curator! My goal is to make sure that something is not going horribly awry!

I did some work here when I got home and got you all the pictures that you were looking for. These were the only numbers that made sense to take pictures of. :???:

http://imgur.com/a/B0YYx#2

I also included pictures of the inside of the oil cap / valve cover area if that helps any.
The motor certainly has a mean growl to it, and it has only gotten better since I have had everything tuned.

This is a 15 year old crate motor. What kind of mileage does the motor and tranny have on it? I'd think the HP you're getting out of it sounds pretty good. An older more worn out tranny will rob more HP from the engine is my understanding. Everything I've found on the internet says either 18% to 20% but a lot of guys are saying 20 to 25% loss with a 700r4. Most of these numbers were from carcraft articles and I usually find them to be pretty accurate. Just what I found though I'm sure there are guys with a lot more experience that will be able to tell you.

The mileage of the motor and transmission is approximately 50,000 miles.

I hope that maybe this answers some questions!

-Thank you again,
Martin:You_Rock:

 

[CANTED]

Martin wrote that this was a LS1 from what he was told. The LS1, which is all aluminum, was first introduced in 1997 in the Corvette and rated at 345 hp. The next year it was used in the F body's and rated at 305-325 hp. If the swap was was done around 97' I'm assuming that a crate version became available around then as well. As most of you know this would be a very involved swap but definitely doable and I've never heard of any regrets with a LS1 swap. If that is indeed what you have Martin, you have a great engine in there. If you have been given bad info, the next logical choice would be that it is a LT1, which is quite different. I recently read an article in Chevy High that gave dyno numbers and their estimate was 22 percent loss with a 700r4. Post up a picture of the engine Martin, I'm curious now.
OK I just noticed the pictures. Looks like a LT1.

 

[CANTED]

LT1's are all aluminum headed and hp ratings go from 300 down to 260.

 

[Keyser Sose]

I saw gilby lurking around there late at night a few times. I think he took your missing horsepower

:secret:

 

[oldtinsmith]

LT1's are all aluminum headed and hp ratings go from 300 down to 260.

IIRC, Corvettes and F-bodies came with aluminum heads and the Caprice and Caddys came with cast iron heads.

Doug