Dyno doesn’t lie
Racer
Joined: Sep 2011
Posts: 381
Likes: 90
From: Portland, the original!
Not for nothing but with a 6,500 redline I'd guess max HP is likely a few 100 RPM higher.
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,240
Likes: 9,385
From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
we all need to remember when talking 1970s horsepower that if you made one horsepower per cuber you were a king and 400 hp to 500hp was only for the rich and famous
Team Owner
Joined: Jan 2007
Posts: 53,648
Likes: 878
From: Southern Cal Ca
St. Jude Donor '22
reminds me of a tv show episode.
basically they had a 73? ford mustang.
stated a factory hp, 220 I think.
ran the car on dyno and measured 185@
did some work, a little modding and got
238.
I could help wondering where they got the
base hp at the wheels when cars were not measured or reported that way.
anyway I would expect more at the wheels
on a lt1.
basically they had a 73? ford mustang.
stated a factory hp, 220 I think.
ran the car on dyno and measured 185@
did some work, a little modding and got
238.
I could help wondering where they got the
base hp at the wheels when cars were not measured or reported that way.
anyway I would expect more at the wheels
on a lt1.
Thread Starter
Burning Brakes
Joined: Dec 2021
Posts: 805
Likes: 260
Sounds like the engine in your friends car needs some looking at (it is 50 years old after all),
I would start with a good old fashioned tune up - first off - shoot a can or two of carb cleaner spray through the carb - then put in new points, plugs, wires, cap and rotor. Then verify both the static ignition timing and verify that the centrifugal advance in the distributor is coming in at the right time, and that all the timing is in by say 3,700 RPM. (I say to do the carb cleaner before changing plugs because some of the deposits that the carb cleaner removes can end up on the plugs.)
Does the car now feel faster ?? If not - it's probably worthwhile to do a compression test and see what the internal condition of the engine is. A carb rebuild may be in order, and I would also check valve clearance.
That engine SHOULD make at least 300 HP on a chassis dyno.
I would start with a good old fashioned tune up - first off - shoot a can or two of carb cleaner spray through the carb - then put in new points, plugs, wires, cap and rotor. Then verify both the static ignition timing and verify that the centrifugal advance in the distributor is coming in at the right time, and that all the timing is in by say 3,700 RPM. (I say to do the carb cleaner before changing plugs because some of the deposits that the carb cleaner removes can end up on the plugs.)
Does the car now feel faster ?? If not - it's probably worthwhile to do a compression test and see what the internal condition of the engine is. A carb rebuild may be in order, and I would also check valve clearance.
That engine SHOULD make at least 300 HP on a chassis dyno.
Race Director
Joined: Mar 2017
Posts: 11,960
Likes: 4,518
From: Virginia
Perhaps repeat the test after replacing the transmission and diff fluid with synthetic.
Pro
Joined: Mar 2022
Posts: 564
Likes: 185
That would be rear wheel HP which would be about 60hp less than with the engine reading at the crank out of the car on a dyno stand. Gotta remember there is parasitic drag between the crank and rear wheels. So adding that back to the number gives you about 250 hp. That from a small block might be about right but the LT1 was rated at 330hp at 5,600rpm (crank). I suspect the engine is somewhat tired.
Melting Slicks
Joined: Jul 2005
Posts: 2,649
Likes: 863
The OP didn't indicate if the car was a stick or an auto. From what I've seen ..Most of the LT1 C3's were stick shift cars ...
A 15% drivetrain loss is petty typical for a manual trans car. 330 Crank HP - 15% drivetrain loss = 285 Rear Wheel HP.
There seem to be about 90 HP "missing"... Your friend may have been an excellent mechanic - and the car may be very reliable - but if it were my car - I'd be trying to find those missing ponies.
A 15% drivetrain loss is petty typical for a manual trans car. 330 Crank HP - 15% drivetrain loss = 285 Rear Wheel HP.
There seem to be about 90 HP "missing"... Your friend may have been an excellent mechanic - and the car may be very reliable - but if it were my car - I'd be trying to find those missing ponies.
Race Director
Joined: Nov 2003
Posts: 10,696
Likes: 3,094
From: Cottonwood AZ
C1 of Year Finalist (performance mods) 2019
The OP didn't indicate if the car was a stick or an auto. From what I've seen ..Most of the LT1 C3's were stick shift cars ...
A 15% drivetrain loss is petty typical for a manual trans car. 330 Crank HP - 15% drivetrain loss = 285 Rear Wheel HP.
There seem to be about 90 HP "missing"... Your friend may have been an excellent mechanic - and the car may be very reliable - but if it were my car - I'd be trying to find those missing ponies.
A 15% drivetrain loss is petty typical for a manual trans car. 330 Crank HP - 15% drivetrain loss = 285 Rear Wheel HP.
There seem to be about 90 HP "missing"... Your friend may have been an excellent mechanic - and the car may be very reliable - but if it were my car - I'd be trying to find those missing ponies.
You people have missed the point of my previous post about the test rpms. As I stated the 1970 LT1 was rated at 6000 rpms but had a factory redline of 6500 these were the days of high horsepower penalties for too much h.p. by the insurance companies. The manufacturers got around this by simply rating engines at lower rpms which reduced the h.p. SO, if the car would have been tested at 6500 rpms the results would have been better. The 70-71 LT1 were the same engine except for the compression ratio for unleaded gas use. They used the same cam. This test left a lot of h"p. on the table with the low rpm test.
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Melting Slicks
Joined: Jul 2005
Posts: 2,649
Likes: 863
You people have missed the point of my previous post about the test rpms. As I stated the 1970 LT1 was rated at 6000 rpms but had a factory redline of 6500 these were the days of high horsepower penalties for too much h.p. by the insurance companies. The manufacturers got around this by simply rating engines at lower rpms which reduced the h.p. SO, if the car would have been tested at 6500 rpms the results would have been better. The 70-71 LT1 were the same engine except for the compression ratio for unleaded gas use. They used the same cam. This test left a lot of h"p. on the table with the low rpm test.
We would need to see the dyno printout to be sure - but most of the time the dyno operator will keep running the engine speed up until they see one of three things:
1. The HP numbers starting to fall off.
2. Evidence that the valves are starting to "float".
3. The customer specified an upper RPM limit.
Without seeing the data from the dyno run - can't say for sure. The C3 LT1 should make around 300 HP on a chassis dyno - the 190 HP at just over 5,000 RPM is not indicative that the motor would make 300 HP if spun to 6.500 RPM ... for that to happen - the torque curve would have to still be assending at 5,000 RPM (and pretty aggressively at that).
Intermediate
Joined: Jun 2013
Posts: 32
Likes: 7
From: CT
This is a good thread so I will throw in my own experience, the best money you can spend on a engine build is to have your motor Dino when you are done!
My last motor build was a Buick 464 for my Buick GS 455, first Pull on the Dino 412 hp. Last pull about one hour later was 474 hp! Just from fine-tuning the timing and change jetting in the carburetor I gained 62 hp. And this was a common engine build nothing special. so unless you are building an exact copy of a know motor you really don’t know the horsepower until it’s properly tuned.....
My last motor build was a Buick 464 for my Buick GS 455, first Pull on the Dino 412 hp. Last pull about one hour later was 474 hp! Just from fine-tuning the timing and change jetting in the carburetor I gained 62 hp. And this was a common engine build nothing special. so unless you are building an exact copy of a know motor you really don’t know the horsepower until it’s properly tuned.....
Last edited by Advanced24; Dec 11, 2022 at 10:44 PM.
Drifting
Joined: Apr 2022
Posts: 1,396
Likes: 1,323
From: Melbourne Florida’s Barrier Islands
People like chrome bumper cars because they represent the last of the swinging 60s. I like all C3s because they truly are ridiculous vehicles that look like cartoons. I’ve had my 70 LS5 (turbo 400] for over 30 years and while it hasn’t been dynoed, it can do rolling burnouts below 40 mph. Just from that, I’d say the power is adequate. It took some time in the MSD software to get to this point, might have a bit more in it, but I’m satisfied.
my 2 cents on the torque converter, it’s probably not needed to go to a higher stall with that cam, when I put comp cam 280 in my car and I remember thinking anything smaller I wouldn’t need one.
my 2 cents on the torque converter, it’s probably not needed to go to a higher stall with that cam, when I put comp cam 280 in my car and I remember thinking anything smaller I wouldn’t need one.
Burning Brakes
Joined: Jul 2018
Posts: 979
Likes: 258
From: Maryland
It's all about personal preference. Let's face it: the C3 design is beautiful, but if it has a fault it is a very long nose. Some like the additional length that rubber bumper C3s provide, some do not. I like both cars, but if forced to choose I prefer the chrome bumper years. The extra $ they command is just a fact of supply and demand. You could make the same case for the C2 v C3 design. The C3 design has better handling and is probably a more refined car. But the preference seems to be, at least for now, to the C2 design. Of course, as the car collectors age maybe some of this changes?