383 sbc first dyno experience

[bob460]

I'm still shocked that your ute come's in @3650lb...........my XB sedan weigh's 3520lb....with me in it

[Tom68]

I'm still shocked that your ute come's in @3650lb...........my XB sedan weigh's 3520lb....with me in it

Holden went back to the 40's after the HK series, they added a half chassis to sedans and a full chassis to the commercials, I say that as I have my HJ 1 tonner in view.

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[Tom68]

I'm still shocked that your ute come's in @3650lb...........my XB sedan weigh's 3520lb....with me in it

I put a cage in an XA, had to run a brace down to the floor where the seat mounts to stop the floor flex. Can't find a picture of the brace.

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[steve cowan]

I'm still shocked that your ute come's in @3650lb...........my XB sedan weigh's 3520lb....with me in it

It is 3650 with me so the car is 3450.
Full body ute,drum brake rear,factory disc front.
Steel 4 Point cage,I wanted moly but did not happen.
Light weight seats.60 Lt fuel cell.
Overtime I will put glass bonnet and reverse cowl.
Upgrade brakes,aluminium diff centre. Aluminium drive shaft etc.
Up here at willowbank raceway registered streeters can go 10.50 with no tech.
I am aiming for that first.
Also I run a street series once a month.
Full exhaust, street tyre deal.
10.50 cut off so being the car that chases is an advantage in my opinion

[steve cowan]

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[skinny z]

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Is there a PipeMax calculation for the design of this exhaust?
It would be interesting to know if that entire length including the muffler would act as a collector extension of if the point of entry into the muffler would define that length.

[steve cowan]

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Is there a PipeMax calculation for the design of this exhaust?
It would be interesting to know if that entire length including the muffler would act as a collector extension of if the point of entry into the muffler would define that length.

These are 1 5/8" tri-y with a 2 1/2" collector at 19" long.
Photo is old combination from last year same cylinder heads on engine now.
Straight through sprint type muffler stainless steel, it was more about weight,they actually sound pretty good.
I spent a lot of time welding and grinding header flange to match head port.
I want to run these small headers as a test against bigger headers.
Results may surprise.

[BobbyB]

What is your theory as to why the vacuum pump cost power on the dyno. Good job, by the way.

[steve cowan]

What is your theory as to why the vacuum pump cost power on the dyno. Good job, by the way.

I an not an expert but some observations on dyno.
From initial fire up and first 15 pulls it seems engine sealed up really well,it showed no positive pressure on the crankcase vac gauge on dyno.we let the pump spin off the crank but -10 hose off rocker cover was disconnected. There was no fumes,mist at all out of rocker cover.
The main reason I chose to use a vac pump is my oil pan is tiny so my theory was the windage would be terrible and it might still be.
It could be worth moving the pick up point to the intake manifold and pull from valley area.??
So it kinda says the the pumping losses are less than what it takes to drive the vac pump.
It pulled 17" vacuum with a standard blue felpro rear main seal as well for a reference.

[BobbyB]

Did you actually pull a vacuum on the crankcase with the vacuum pump, and lose power?

[steve cowan]

First pull with vacuum at 11" was up 5hp .
Next pull with 17" vacuum was down 10hp and oil pressure was way down at top of the pull 7000rpm.
So 11" was set .
I have talked to guys who dyno alot and there are no guarantees on vacuum.
3 guys at the dyno all said 15-20 hp ,I was on the fence not having much experience.
Certainly a expensive 5hp

[BobbyB]

I have no experience… but am very curious & interested.

The guy that does my machine work has worked on race engines for decades. He says vacuum pumps work well and sees no downside.

I can see how one could rig up a deal where a tank was charged up from fast idle that would last several seconds…I think Grumpy Jenkins did something like this…

Your loss of oil pressure scares me enough to leave crankcase evac alone for a while longer.

[steve cowan]

I have no experience… but am very curious & interested.

The guy that does my machine work has worked on race engines for decades. He says vacuum pumps work well and sees no downside.

I can see how one could rig up a deal where a tank was charged up from fast idle that would last several seconds…I think Grumpy Jenkins did something like this…

Your loss of oil pressure scares me enough to leave crankcase evac alone for a while longer.

Crankcase vacuum helps keep oil leaks at bay,can keep oil cleaner depending on ring seal.
Have a look in the thread with spier racing heads about evac and pcv.
The set up with the cross over to rocker covers and pcv valve looks interesting.
Manifold vacuum pulls a crankcase vacuum and holds during a 1/4 mile pass,this is worth looking at.

[steve cowan]

The lower oil pressure readings compared to vac and no vac are normal I believe as your oil pressure gauge is a reference to atmosphere.
My engine has 50 psi hot at 7000rpm no vac.
I believe with a small oilpan 5qrt
With vacuum oil pressure lowering at high rpm is considered normal from what I know.
Of course opinions will vary.

[steve cowan]

For anyone interested, have some carb issues to sort ran car with 31 deg timing, turned tires bad on first 2 passes but ran just over 121 mph on all 3 runs.

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