1957 Chevy 9" swap HP Loss?

[swampratt]

I busted the stock GM rear end in my '57 4 door car and I had a 9" Ford in the back yard that was 1" wider.
The Ford 9" is now in there and all hooked up with new axle bearings , new seals and new brakes.

A 3.5" diameter driveshaft replaced the 2.75" stock one. As it needed to be 1.25" longer to fit correctly.

I will be heading to the rear wheel dyno today to see if I lost any power from the swap.
They claim the 9" ford is a power robber.

Abel racing will dyno it (MoBoost)
https://www.facebook.com/AbelRacing/

This has been on the dyno many times testing intakes and carbs and timing curves and I think my last pass was 245 or 247 Wheel HP.
I want to hit Thunder Valley soon during test and tune to see If the ET has changed. Last pass was 14.4?
350" with flat tops and 1.84-1.50 valves in GM cast iron heads with 268H flat tappet cam on a 112 LSA TH 350 transmission
Cast iron GM Qjet intake and Cast iron Ex manifolds Qjet carb, 2 1/4" exhaust.
Nothing special.

 

[NightShade]

I helped a guy do a swap from a SB 400 to a BB 454 in a 57 when I was in my teens. He built the 400 but something wasn't right as it kept bending pushrods. We pulled the engine and trans out of a 80's suburban and dropped it in. Never got to see it run under it's own power after that though I did "drive" it while being chain towed from one place to another. Was supposed to have it completed my senior year and get to drive it to school for a week for helping out but it never happened.

The guy who owned it before the one I knew had seen some HUGE ladder traction bars and did some homebrew ones that connected to the frame near the middle of the doors (2 door version.) The one thing I know for sure is it was a HEAVY beast, we used to use a bumper jack to break the beads off the rim for tires with it.

 

[swampratt]

HA! good story..I used bumper jacks to break beads for many years..I cut the base of my jack to a round shape to better fit the base against the rim.
My 4 door weights 3570 with no driver.

Numbers are in.
Probably did not make much difference because of the Low HP of this combo.

Last Dyno with GM rear end was 228.23 HP and 13.15 Air fuel ratio.
This Dyno with 9" read end was 226.67 HP with 13.56 Air fuel ratio.

1.56 HP difference
I will call that a wash .. ambient temp and other weather factors will change it that much and more.

That is all I got for ya. A few numbers to chew on.

 

[NightShade]

The 9 inch probably has more weight in the reciprocating mass and being rebuilt and a little on the tight side could also be the difference. But I agree it is well within the margin of error ( >1%) and all kinds of other factors will also change the numbers.

If I wanted to make some more HP with a minor amount of cash I would probably swap intake and carb unless you want to keep the stock look.
I heard of what was supposed to be an old school trick for a couple HP on the chevy's was to take one of the oil flow passages on each head and drill/tap it and install a steel nipple so that the oil was forced to the other passages allowing air from the lower end free flow to the top end. The idea was that the moving parts on the bottom end sucked air in and out from the top end and having one passage on each side open would free up a couple HP as it was not fighting the oil flow and it was also allowing the oil to flow from the top end easier rather than to have it being constantly spit back up into the valve covers. It's cheap since the part is basically a piece of 50 cent threaded pipe and as long as you can pull the heads off or not get any particles into the block should be easy to do.

 

[beastep]

Interesting.

 

[swampratt]

I care less what it looks like.
This is a built to drive and hunt and fish transportation.
I tried a marine intake Qjet cast iron and then an aluminum Performer rpm intake..The RPM intake was worth 30HP
I then ported a car Qjet iron intake and it made 10HP less than the RPM intake..Great numbers in my book.

I had another cam in this engine Same lobes but ground on a 106LSA.. same intake closing point as the current grind on a 112 LSA.
It makes a lot of TQ down low for what it is.. Usable power It has 225 PSI cranking pressure,, very early closing intake lobe

This shortblock is from a 1969 station wagen was a 300HP 350.
I have had it in 3 different cars.. I have ran 601 casting heads 186 and 041 heads on this with 268H ,270H. 280H, and a herbert old solid flat tappet grind 235-245@ .050"

Oil restrictors were used in it for the solid cam .
I t had 100,000 miles on it when i got it (Freshened it ) and in 2 years in the 90s i put 75,000 miles on it .Then it sat and got freshened again and installed in my 47 dodge truck and went about 35,000 miles a year for 6 years and I busted the transmission.

I have had it in the 57 for a little over a year and about 10,000 miles on it.
Crank has never been turned and block never bored.
I was getting 18 MPG with the 3.36 gears.
Lot's of miles on this sucker.. lot's of things have been tried ..strip dominator intakes and tunnel-ram intakes.
Fastest this block has went was 176MPH in 3/4 of a mile in my 78 Nova with 3.70 gears and a TH 350 with 30" Hoosiers.
If you want the math I was cruising at 7600 rpm in high gear with those Hoosiers and the 3.70 gears. I shifted past 7800 rpm from first to second and second to third.

At 7800 I quit looking at the tachometer.. column shifter was stuck and I was trying to shift at 7600.. seen 7800 and still stuck and pulling up .. finally shifted!!
Buddy hit 8500 rpm 2 times with it and I did not let him drive it any more.
It is loose everywhere.. if it was tight it would have probably came apart.
I hit 6500 RPM in third with 29.5" tires on MoBoost dyno with 3.25 gears in my 47 dodge truck.. That was 167 MPH
He cringed and said all pulls will now be in second gear for that thing.

 

[YukonGlocker]

The argument is because of the alignment of the ring to pinion, the 9" is slightly less efficient. I've seen dyno numbers show around 1% decrease in RWH, when changing from a 12-bolt to at 9"; but without multiple passes on each, it's really hard to determine a consistent difference.

 

[swampratt]

I have felt 10HP difference on the street and the track.. but this 1.57 HP was not felt.
I hear ya on the multiple passes.
I make a minimum of 3 passes each time I dyno it.
I made 3 yesterday playing with timing. Different air temps will sometimes require a different total timing to see max HP .
as you know and jetting will need played with also.

Every time on the dyno I check HP at 35 total timing and 38 total and this time i dialed in 38 for starters then took some out and then added more than 38.

This engine has never changed more than 3 Hp with timing changes.
It is pretty happy overall.
Especially for an all iron gen 1 with a carb and around 11:1 compression.

MoBoost has a 57 2 door that beat this car by a little over a length.
His is going to swap an LS into it.. his current aluminum head 350 made 260 HP at the wheels, 4 speed stick car.
The hearsay is 400 at the wheels with the LS. and 11.50 ET
I will need to step up my game.
I have 1 turbo and some large 76cc casting 993 heads. I need to play with.