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Author Topic: Who runs a Pontiac SD-4 4V (Cosworth head) Engine?  (Read 6175 times)
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michaelmount
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« on: September 25, 2016, 07:58:45 PM »

I heard at least one car (truck?) at Speedweek is running the 4V Pontiac SD-4.  I'll be on the salt next year with one of these rare engines and I'd like to contact these folks to share experiences.  Can anyone help me identify/contact them?
Thanks!
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gkabbt
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« Reply #1 on: September 26, 2016, 05:30:19 AM »

Michael, I think this is what you are looking for.

This:

I LOVE this sport because of the incredible ingenuity of some of the builders.
Case in point, my last five pics are of Jack Iliff's (jacksoni on here) 3522 G/GC Nissan 240SX.
Block, crank, etc. is a Pontiac SD 4 cyl and the head is from an Infinity IRL engine.     WOW  shocked  shocked  shocked

Gregg

Is from this thread:
http://www.landracing.com/forum/index.php/topic,15812.0.html

He logs on here regularly but you can always shoot him a PM!
Google maps shows that you're only about 45 minutes from him!

HTH,
Gregg




« Last Edit: September 26, 2016, 05:33:20 AM by gkabbt » Logged
Jack Gifford
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« Reply #2 on: September 28, 2016, 12:15:41 AM »

Well, at least from the front, our Pontiac DOHC engines look similar. grin But mine is based on stuff that predates SD-4 stuff by two decades- M/T hemi head, M/T aluminum block, etc. However, I just finished my DOHC design this year.


* hemi_four_asm55.jpg (110.07 KB, 800x600 - viewed 195 times.)
« Last Edit: September 28, 2016, 12:20:02 AM by Jack Gifford » Logged

M/T Pontiac hemi guru
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« Reply #3 on: September 28, 2016, 11:58:04 AM »

That is some nice lookin stuff there young man! cheers
  Sid.
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MRK
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« Reply #4 on: October 14, 2016, 12:21:29 PM »

I believe Dick Martin runs that type of engine.
He runs a Fiero in F/GT. He's gonna stop driving and his daughter is going to run the car at El Mirage in November. At least that's the story he gave me last time we spoke.
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SteveM
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« Reply #5 on: October 21, 2016, 04:01:44 PM »

Amazing stuff!  Those SD Pontiac engines have always fascinated me.

Who is willing to make a horsepower guesstimate on the G/GC engine with the Infinity IRL head?

400HP???

Steve.
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wobblywalrus
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« Reply #6 on: October 21, 2016, 07:10:17 PM »

My Triumph has a Cosworth head.  All of my experience before this was with hemi heads.  They are very different to tune.  A big obstacle to success was the old habits and instincts I had to unlearn.  A good engine simulation software package will help in a big way.
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Jack Gifford
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« Reply #7 on: October 21, 2016, 11:11:41 PM »

... A good engine simulation software package will help in a big way...
Agreed. For any engine design.
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M/T Pontiac hemi guru
jacksoni
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« Reply #8 on: October 22, 2016, 08:17:25 AM »

Amazing stuff!  Those SD Pontiac engines have always fascinated me.

Who is willing to make a horsepower guesstimate on the G/GC engine with the Infinity IRL head?

400HP???

Steve.

Steve- remember that G/ is a 2 liter class. The best numbers I have seen reported for world class 2 liter are in the 315-325 range NA. There may be others that do better but F2 Hart engines and similar Cosworths which one must consider to be well developed are in that range. World class engine builder I am not... cheers  Want to revise your estimate on the HP?  cool rolleyes
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Jack Iliff
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wobblywalrus
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« Reply #9 on: October 22, 2016, 09:14:47 AM »

My engine is a 995 cc twin so its half the size you are discussing.  The engine in my build diary is making between 80 and 90 hp at the flywheel with a 6000 + foot elevation using mild cams.  There is another build going on unseen in the background using some proprietary and factory race parts that folks are sensitive about describing on the I-net.  Power is a bit more on that rascal.  These are virtual builds using engine simulation software that appears to be accurate based on comparison with real-world results during the last ten years.

A well done two valve head engine probably can be made to make more peak power with a reasonable redline like 8,500 or 9,000 rpm.  The valve gear will be pretty highly stressed due to the lift and duration needed to do this.  It will be the limiting factor for operating rpm.

The four valve head gives the advantage at very high rpm where its lighter valve gear is the only practical option, like 10,000 rpm or more.  Piston life becomes the limiting factor.  Then, the Cosworth style has the advantage.

The numbers Jack is saying are realistic.   

 
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Stainless1
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Robert W. P. "Stainless" Steele Wichita, Kansas



« Reply #10 on: October 22, 2016, 09:26:50 AM »

Well developed DOHC bike engines in the 100ci range make about 2.5+ HP per ci, smaller make more, 3+, harder to keep that level as the size grows.  
So 300 would not be out of the question.... how much are you putting on the ground?
Approximately....  cheers
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Stainless
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MSA Bockscar Lakester #1000 my fastest mile 245 and change, 84 ci turbobusa motor... but Corey's 233 MPH H/BFL record is still 3MPH faster than mine.
jacksoni
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« Reply #11 on: October 22, 2016, 10:45:57 AM »

My opinion, because of engine parameters, rpms available to bikes (say 13K and such) make them somewhat different animals and yes they make amazing numbers. My previous engine made 235 at wheels on best run. I am pretty sure this one makes more but haven't had it on chassis dyno. Engine dyno said 293 at 9500 or so  making therefore hair under 2.5/ci. It still needs some work. Have not tried adjusting cam timing at all and we didn't get a good run when I shortened the intake stacks. Longer ones made essentially same power at 9000. The ports were designed for methanol and are a bit too big really. Only other difference to the Infinity IRL otherwise is bigger bore, smaller stroke and longer rod. Lots of difference in other words. Displacement the same.

With respect to simulations, my very good (EngMod4T) software says about 310. Considerably more optimistic Engine Analyzer Pro says 350+. Haven't run Dynomation recently (have lost my key at least temporarily) but it was also somewhat optimistic in one mode, wildly optimistic in another with my previous engine ( 2 valve head) and pretty useless therefore. There is always the GIGO problem of course.
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Jack Iliff
 G/BGS-250.235 1987
 G/GC- 169.741  2009
 G/GMS-178.835 2010
joea
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« Reply #12 on: October 22, 2016, 10:57:38 AM »

stainless speaks the truth with regard to bike engines....

one route is that Wobbly has taken...with that particular design...he has developed his twin with a lot of work to garner 80-90 hp from that 1 liter...pretty neat project...

other modern engines in 1 liter capacity...have over twice that hp from
a STOCK engine...for example the bmw 1000 RR makes about over 185 hp

and without changing pistons has made 216 hp example Carpenter racing
website (realiable)....

but what Jack and others do with very durable auto engines in larger displacement is phenomenal....!!!
« Last Edit: October 22, 2016, 11:53:55 AM by joea » Logged
fordboy628
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« Reply #13 on: October 23, 2016, 07:34:05 AM »

For normally aspirated engines, in simple terms, torque (a WORK measurement) is going to be dependent on displacement (PLAN) * efficiency, so for a given BMEP value, the torque value is the resultant.

Since any power calculation is a function of work performed over a time period, rpm utilized affects the calculation.

IE:

1/    X torque @   5,252 rpm =  X bhp
2/    X torque @ 10,504 rpm = 2X bhp
3/    X torque @ 15,756 rpm = 3X bhp

etc . . . . . .

This is why F1 engines were running 20,000 rpm several years ago . . . . . . . .

AND, why NASCAR now has "the gear rule" . . . . . . .


If three differing engine types are all the same displacement, and achieve the same BMEP, then:

A/    a pushrod, 2 valve NCF, "bathtub" chamber, making peak power @ 5,252 rpm = X bhp
B/    a 4 valve, DOHC, pentroof CF, (Cosworth) making peak power @ 10,504 rpm = 2X bhp
C/    a 5 valve, multi-cam, roller brg crank, CF bike, making peak power @ 15,756 rpm =3X bhp

You get the idea.

For accuracy, peak bhp rpm must be figured into the equation when comparing bhp/liter or bhp/cubic inch.

 cheers
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« Reply #14 on: October 23, 2016, 12:01:58 PM »

For normally aspirated engines, in simple terms, torque (a WORK measurement) . . .

Torque is not a measure of work.  Torque x revolutions is a measure of work.
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