[Z Code 400]

I have ran a number of proven dyno combinations 'backwards' through Dyno 2000 program and so far, every simulation has been within 1% to 3% of the actual dyno testing, when I am able to imput all the correct engine data into the program.

I was surfing the Internet and came across this 8.96:1 455SD buildup with a claim of 419 HP and 520 lbs/ft of TQ using a .495"/.495" - 240°/240° @ .050" camshaft on a 110° lobe center.

The data sheet claims stock 'SD' cylinder heads were used and they didn't provide any flow data, so I ran the simulation with stock 6X flow values.

Based on the results of my simulations, Power was nowhere near what they claimed this engine, even when using 'E' Head flow data of 264 Intake and 175 exhaust.

My simulations, using large tube headers and mufflers, indicate horepower production of 389 @ 5000 rpm and 450 lbs/ft of Torque at 4000 rpm.

Here is the link to the specification sheet. Let me know what you think...Robert

http://www.superduty.co.uk/HPPspec.htm

"If I had better junk in my garage, I know I could go faster."

[Z Code 400]

I have ran a number of proven dyno combinations 'backwards' through Dyno 2000 program and so far, every simulation has been within 1% to 3% of the actual dyno testing, when I am able to imput all the correct engine data into the program.

I was surfing the Internet and came across this 8.96:1 455SD buildup with a claim of 419 HP and 520 lbs/ft of TQ using a .495"/.495" - 240°/240° @ .050" camshaft on a 110° lobe center.

The data sheet claims stock 'SD' cylinder heads were used and they didn't provide any flow data, so I ran the simulation with stock 6X flow values.

Based on the results of my simulations, Power was nowhere near what they claimed this engine, even when using 'E' Head flow data of 264 Intake and 175 exhaust.

My simulations, using large tube headers and mufflers, indicate horepower production of 389 @ 5000 rpm and 450 lbs/ft of Torque at 4000 rpm.

Here is the link to the specification sheet. Let me know what you think...Robert

http://www.superduty.co.uk/HPPspec.htm

"If I had better junk in my garage, I know I could go faster."

[Larry Navarro]

Robert,
did you search around for flow data on SD heads?
I can't recall but somewhere on the net, its listed.
1973 SD455 T/A
1979 SE474 T/A
http://community.webshots.com/album/16587603rOyvmFCiHs

[Jack Ferris]

Some time ago Musclecar Review did some dyno testing on stock engines to try and compare their readings to factory hp claims. Going by memory here I believe the RA4 400 with 69 Bird exhaust manifolds and mandrel bent head pipes made 400 hp. The RA3 made 370 hp. So as far as a 455 with 16 SD heads and a 240 @.050 cam is concerned, I believe those numbers to be accurate. But as Im sure you know, the hp/tq numbers are in the hands of the dyno operater and they all seem to have different numbers.

[Tom Vaught]

Quote:

455 SD heads typically flow about 225-230 at 25" H2O (238-244 at 28") on the intake and 200 at 25"
H2O (212 at 28") on the exhaust.

72 cc E-Heads will flow 275 at 25" (291 at 28")
on the intake all day long and 200 (212) on the exhaust.

The 87 cc heads ports will actually flow the same as the 72 cc heads but due to the deeper machined combusion chamber will delay the flow by about 10 cfm for each checking point.

275 at .600 on the 72 cc head will be 265 at .600
on the 87 cc head. What ever the offset is on the chamber depth is must be added to the lift on the cam to achieve the same flow number.

Tom V.

[Z Code 400]

Interesting... I have seen 9.00:1 455's with 'E' Heads (not mine) on the dyno that didn't make what the High Performance Pontiac article is claiming.

A few months ago, a local shop built a .030" 455 for a fellow with #60579 'E' Heads, 9.00:1 compression, Summit K2801 Camshaft, Edelbrock Dual Plane with 750 Edelbrock Q-Jet, Large Tube (1-7/8") Headers and 4 feet of 3" pipe exiting into a pair of #21506 Hooker Aero Chamber Mufflers.

I was present for the run-in and test period. Peak output was 359 horsepower @ 5000 rpm and 491 lbs/ft of torque @ 3000.

When I plug all the specifications 'backwards' into my Dyno 2000 program, the simulation reports power output of 368 @ 5000 rpm and 495 lbs/ft @ 3000 rpm.

However, the specifications given in the HPP article do not match up when plotted into Dyno 2000.

In my opinion, 240° @ .050" is not the best choice for 8.96:1 compression and would be better suited to a 9.50:1 to 10.00:1 motor...Robert

"If I had better junk in my garage, I know I could go faster."

[Larry Navarro]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>In my opinion, 240° @ .050" is not the best choice for 8.96:1 compression and would be better suited to a 9.50:1 to 10.00:1 motor<HR></BLOCKQUOTE>
Hey Rob, just a quick note...at one time I had a stock SD455 motor in an old '73 t/a, 3800lbs.
The motor was a standard bore, 8.4:1(as factory)compression with a SD Q-jet and iron intake, tri-y headers and full exhaust. Best 1/4 mile performance 108MPH, high 12's.
Now, this was a STOCK SD motor...the only "trick" piece that was in it was a H-O Racing hydraulic camshaft with 242/252@.050, 113LSA, .501" lift with 1.5 ratio.
I don't know if you can "back-in" those track figures to the desktop but it would be interesting to find out what horsepower the motor was capable of.

1973 SD455 T/A
1979 SE474 T/A
http://community.webshots.com/album/16587603rOyvmFCiHs

[b-man]

Robert,

Here are some specs on my mild 455 bracket engine. Perhaps you could run them through your desktop dyno to see how much power it makes.

455 std. bore, zero-deck, all stock cast pistons/rings/rods/bolts/crank/bearings/balance.

1971 #197 455 HO heads, pocket ported with a slight port clean-up (not enough to remove but half of the 'as cast' look inside the ports). No flow figures, but a good guess would be 240 intake and 210 exhaust @ 28", about equal to a stock 455 SD head I suppose. Exhaust crossover blocked with an aluminum plate on the intake side, not filled. Milled .025", my guess is the stock 111cc chamber is now 105cc. Compression ratio calculates (guestimates?) to 8.6:1 with a .040" crushed head gasket.

HO Racing HC-03 hydraulic cam and lifters (244/252@.050, 113 intake/120 exhaust LCA .550/.554" lift w/1.65 Erson SST rollers). HO Racing VS-12 springs (1.71" installed, spring seats cut) and stock retainers. Installed 4 degrees advanced using a Cloyes Tru-Roller 3-keyway timing set.

Box-stock 650 Holley DP carb, only mod is a 50cc pump on the secondary side. Torker II intake with exhaust crossover removed and water crossover seperated, no port matching or internal mods. Carb sits on a 1" open phenolic spacer. Stock '74 aircleaner with a 2nd snorkel added, both are plumbed into the cowl for cool air.

HO Racing round-port Tri-Y headers (1-3/4" primary/2" secondary/2-1/2" collectors) dumping into a 3" home-made exhaust with 3-1/2" Flowmaster 2-chamber race mufflers, 3" tailpipes over the axle.

I used a formula that was published in a HPP magazine 'shoot out' to determine the horsepower from actual track runs. After I see your dyno results I will post the actual track ET/MPH and race weight as well as the horsepower figures.

------------------------------
My wife says I never listen to her, at least that's what I think she said.

[Steve C.]

Jack's point is well taken. Engine dynos are like flow benches, they can vary from bench to bench and from operator to operator. I can take my actual dyno sheets and the exact engine parameters and input them into my Performance Trends EA v3.0 program and its off, especially in the peak rpm.

[Z Code 400]

B-Man,

Please stand by. We are processing your request...Robert

"If I had better junk in my garage, I know I could go faster."

[Z Code 400]

Larry,

That is interesting. That is a lot of cam for 8.4:1 compression, especially on a 113° LSA.

I would have to say the added displacement of the 455 (and its stroke) allow it to gobble-up the 240° of duration.

However, I would almost wager the engine would make nearly equal amounts of power and torque with a more conservative profile and improve driveability in the lower rpm ranges.

I do know that 240° @ .050" in a 8.5:1 400 is a disaster. I have witnessed this personally on a car at a local shop...Robert

"If I had better junk in my garage, I know I could go faster."

[Z Code 400]

B-Man,

a stock bore and stroke 455 with stock pistons, zero-deck clearance and .040" gasket would have 8.92:1 compression calculating 7.0cc's volume for the valve reliefs.

Also, the lobe separation information doesn't quite check out. Cand you send me the valve events at .050" lift???

I would like to confirm all the numbers before running the simulation.

Thanks...Robert

"If I had better junk in my garage, I know I could go faster."

[firechicken]

Robert,
I had the HPP magazine that the SD 455 was tested in and followed the build up they did on it. They did give head flow #'s at one point in the series. The heads were bowl blended and gasket matched and flowed in the 250+ cfm range @ .500 Although most of my issues of HPP were destroyed by an accident I remember this article quite well. The cam was a TFX solid 240/240 @ .050 and was run with the stock SD intake. A set of long tube headers was worth like 40 hp over the stock SD exhaust manifolds

[Tom Vaught]

I remember the article now too.

The engine was built by Taylor on the east coast and the cam he used was one of his own grinds.

TFX stands for Taylor Family Experimental.

The engine should run a lot better with a 240 cam when a 250 head at 28" h20 is used.

Tom V.

[Tom McQueen]

The SD motor (464ci, 9.7:1) currently in the GTO has had mild port work done on the heads (260 cfm @ 28"). Also using an ancient Chet Herbert RAIV solid roller grind (.600"/244@.050"/110CL with 1.65 rockers) and an equally ancient Doug Nash intake with a 1.25" spacer and 825 Demon. Havent driven the car much yet, but will by months end. Im curious as to how well its gonna run using all those 'Classic" parts.

[Lloyd-TX]

do you recall my engine combo?

4.200 bore 455 (467"), 9.98:1 compression, 276/176 flow @ .500-.600 lift @ 28" 7F6 heads, 232/235 @ .050 .540"/.555" net lift solid flat-tappet cam ground on a 108 LSA & intake lobe centerline @ 105 ATDC, stock '72 HO intake, SD Q-Jet, 2.45" outlet SD exhaust manifolds, etc. Best engine dyno pulls were @ 33 degrees ignition lead: 530 CBTQ @ 3,000 and 430 CBHP @ 5100 RPM on 93 octane pump fuel.

Dunno if my combo is too far from this one to help???

Later,
"455HO" Lloyd

1972 Formula 455HO; Lucerne Blue; 12.96 @ 104 MPH @ the '03 PSN's
1970 GTO 455HO; Palomino Copper
1972 GTO 455HO; Sundance Orange

[GONZO]

Robert I should have never "lent" you my desktop dyno stuff.

RAIV Don't leave home without it.
www.musclecarrace.com

[Z Code 400]

Gonzo,

I appreciate the use of the file. I lost mine during a reformat and can't remember who I loaned my disc too.

Thank goodness I was able to save all the engine files!!!

I can't seem to stop!!!!...Robert

"If I had better junk in my garage, I know I could go faster."

[Z Code 400]

A bit off-topic, but I need stock or Stage 1 flow data for a 455 Buick I am building. Any information would be appreciated. Thanks...Robert

"If I had better junk in my garage, I know I could go faster."

[Skip Fix]

I know my buddies ported Stage 1s would flow in the 270 range @ 28". Some fast A bodies! Easy to get 10.90s with them.