[mchell]

Wo….pretty darn good!

[NeighborsComplaint]

I know you have the dyno sheets prove it but I'll never understand how a low compression motor with low performance Dport heads and a smaller than stock camshaft can make the same horsepower that was claimed on a factory assembled '60s high compression motor with Ram Air heads and manifolds.

[Scott Roberts]

Originally Posted by NeighborsComplaint

I know you have the dyno sheets prove it but I'll never understand how a low compression motor with low performance Dport heads and a smaller than stock camshaft can make the same horsepower that was claimed on a factory assembled '60s high compression motor with Ram Air heads and manifolds.

I'm gonna say those 60's engines were underrated on hp.. my understanding is that was common practice..

[Steve C.]

The way we measure horsepower has changed ?


.

[Tom Vaught]

Originally Posted by Scott Roberts

I'm gonna say those 60's engines were underrated on hp.. my understanding is that was common practice..

I WOULD TOTALLY DISAGREE WITH THAT SENTENCE.

I was fortunate to have access to a Clayton Rear Wheel Dynometer at the college down the road from where I lived.
They had a Automotive program there. A/C work, Engine work, Chassis work, some welding classes, etc.

On the Calibrated Clayton Dynometer several vehicles that the Hot Rod Boys owned were tested.

1) A 375 hp advertised 396 1966 Chevelle made 285 rear wheel hp.
285 hp times 1.15 = 327 engine horsepower. the 15% adder is the typical drop from engine to tire hp loss.
The 375 HP rating was probably correct if you tested the engine without the water pump/fan drag and the accessory drag.
(Power steering). Looks Dead Nuts on the money to me.

Tom V.

[Tom Vaught]

Originally Posted by Steve C.

The way we measure horsepower has changed ?

.

Measure is the same, How it is Reported is different.

Tom V.

[Stan Weiss]

In a few cases I think they were under rated because of insurance. In most case I think the engine tested by Pontiac was select fitted parts and not a mass produced engines. Don't Royal Oak sell thinner head gaskets to get the CR up? How much farther down the bore are the pistons on a production engine from the blueprint spec?

Stan

[Tom Vaught]

Probably the only engines that could be called under rated would be the 73-74 455SD engines.

Tom V.

[Stan Weiss]

Originally Posted by Tom Vaught

Measure is the same, How it is Reported is different.

Tom V.

Tom,
Yes, most engine dynos still use the SAE J607. The car manufacture in the early '70s changed SAE J1349. I believe some chassis dynos also use SAE J1349.

Stan

[Scott Roberts]

Originally Posted by Tom Vaught

I WOULD TOTALLY DISAGREE WITH THAT SENTENCE.

I was fortunate to have access to a Clayton Rear Wheel Dynometer at the college down the road from where I lived.
They had a Automotive program there. A/C work, Engine work, Chassis work, some welding classes, etc.

On the Calibrated Clayton Dynometer several vehicles that the Hot Rod Boys owned were tested.

1) A 375 hp advertised 396 1966 Chevelle made 285 rear wheel hp.
285 hp times 1.15 = 327 engine horsepower. the 15% adder is the typical drop from engine to tire hp loss.
The 375 HP rating was probably correct if you tested the engine without the water pump/fan drag and the accessory drag.
(Power steering). Looks Dead Nuts on the money to me.

Tom V.

I dont claim to be an expert and have no problem with your disagreement... as state, I was under the understanding that was the case.... I've read ( interweb facts of course) that was the case...
I drove a bonestock 68 bird with a 400 and It sure felt like more than 330ish... seat of the pants kind of thing..

[Steve C.]

Questions and Answers – Horsepower

https://www.stevelinden.com/blog/que...ers-horsepower


,

[Tom Vaught]

Looks to me like Steve Linden matches everything I posted except for 1m FACT.
The rear wheel HP is not measured at the Axles/"Brakes" unless you take the tires and wheels off the vehicle. Tires do consume horsepower. A thing called rolling friction.
So the driveline has to include the tire contribution.

Emissions people (EPA and CARB) require on the track confirmation testing to assure the Coastdown) numbers used to dial in the dyno rolls matches the actual road measurements. I did Coastdown work for Ford and supplied the data under my name to the EPA as the "Coastdown Test Engineer".

I did the larger Trucks, F-150 thru F-350 vehicles and the Econoline vans.
Other Engineers did the Car platforms and the Small Truck and SUV type vehicles.

If the EPA/CARB was not happy with our numbers, they witnessed a reconfirmation of the track numbers. Most times it was vehicle to vehicle variability and the track numbers were the final numbers used.

So back on the HP numbers, Steve Linden is correct on 98% of his post.

Thanks Steve C for the link.

Tom V.

The AERO Contribution was confirmed at the Lockheed Wind Tunnel at Atlanta Georgia.

[steve25]

25 seconds with a needle nose plier on those early FB 330 hp motors and you did then have more than that amount of HP!
Removing the limiter they had got you the 350 hp motor.

[TCSGTO]

Either the RAIV was under rated or the RAIII was overrated sine there is no way only 4 HP separated the two.
I remember an old Roger Huntington article where he had the factory dyno curves for some 60's hipo engines. If they wanted to rate conservatively they pull the HP from below peak. For instance the 426 HEMI was rated at 425Hp @ 5000 rpm when it actually peaked closer to 6000 and 470HP.
Factory advertised ratings were just that, advertised.

[Scott Roberts]

Originally Posted by TCSGTO

Either the RAIV was under rated or the RAIII was overrated sine there is no way only 4 HP separated the two.
I remember an old Roger Huntington article where he had the factory dyno curves for some 60's hipo engines. If they wanted to rate conservatively they pull the HP from below peak. For instance the 426 HEMI was rated at 425Hp @ 5000 rpm when it actually peaked closer to 6000 and 470HP.
Factory advertised ratings were just that, advertised.

Same stuff I read... so who's right, Tom or the internet... the internet if full of underrated stories but Tom says thats false... in all caps. I'm going with motor city tom...what could those other guys possibly know.

[unruhjonny]

Originally Posted by TCSGTO

Either the RAIV was under rated or the RAIII was overrated sine there is no way only 4 HP separated the two. ...

I seem to recall an article from several years ago where these engines were dyno'd and came out nearly nuts on their respective ratings.

I digress, I wanted to comment about something else entirely;
I noticed this:

Originally Posted by SD455DJ

... W72 400. He rebuilt the original numbers matching engine with .040" over Icon forged pistons w/4.5 cc valve reliefs that are .005" out of the hole and with .045" x 4.328" Felpro head gaskets to provide .040" quench depth. The 6X-4 heads were minimally cut for trueness and measured 92.45 cc's average for an final static compression ration of 8.75 to 1. ...

now, before I say much else, could you tell me if this isn't a PSMCD eligible motor?
Because unless there has been another rule change, the rods alone should disqualify this motor...
Also iirc this engine should have had an advertised compression of 7.6:1, and if I am correct this would be a bump of more than a full point - which should again make it disqualify.

I have not read of any builds here that have the piston out of the hole, most are (if my memory serves me) about 0.020" down so that was interesting for me to read.
I normally read that with the piston down and the thicker fel-pro gasket, that engines like this often yield a marginal drop in compression;
granted the overbore helps kick it back up;
And in this example the reduced cc valve reliefs would help too - I cannot off hand recall the size of the cc valve reliefs in pistons from this period - can someone post this to help me out?

This is pretty cool to see the honest to goodness power that can be made from a very stock appearing motor.

You guys sure do some interesting engine builds!

[Scott Roberts]

This is pretty cool to see the honest to goodness power that can be made from a very stock appearing motor.

[/QUOTE]

There is a lot more power to be had in the F.A.S.T class.. stock appearing engines that make big power...

[steve25]

Folks consider this tid bit.
A 426 Hemi tipped the scales at 843 pounds!!
It needed every spec and more of that 425 hp rating to really beat up on a well tuned RA4 engine!

[Stan Weiss]

Originally Posted by Tom Vaught

Looks to me like Steve Linden matches everything I posted except for 1m FACT.
The rear wheel HP is not measured at the Axles/"Brakes" unless you take the tires and wheels off the vehicle. Tires do consume horsepower. A thing called rolling friction.
So the driveline has to include the tire contribution.

Emissions people (EPA and CARB) require on the track confirmation testing to assure the Coastdown) numbers used to dial in the dyno rolls matches the actual road measurements. I did Coastdown work for Ford and supplied the data under my name to the EPA as the "Coastdown Test Engineer".

I did the larger Trucks, F-150 thru F-350 vehicles and the Econoline vans.
Other Engineers did the Car platforms and the Small Truck and SUV type vehicles.

If the EPA/CARB was not happy with our numbers, they witnessed a reconfirmation of the track numbers. Most times it was vehicle to vehicle variability and the track numbers were the final numbers used.

So back on the HP numbers, Steve Linden is correct on 98% of his post.

Thanks Steve C for the link.

Tom V.

The AERO Contribution was confirmed at the Lockheed Wind Tunnel at Atlanta Georgia.

Tom,
This is exactly what they been doing for sometime on high HP cars. They use a hub dyno. It eliminates the tire slippage and give much better results

Stan

[Scott Roberts]

Originally Posted by Stan Weiss

Tom,
This is exactly what they been doing for sometime on high HP cars. They use a hub dyno. It eliminates the tire slippage and give much better results

Stan

Define "some time"