383 sbc first dyno experience

[HQM383]

If all your data is accurate I think I see now why so much jet had to come out of the same carb swapping fuel.

Off the dyno 0.91 lambda with MS109REG 13.36 stoich = true 12.1:1 air/fuel ratio.

Aftermarket AFR gauges work off lambda and multiply by 14.7 to display pump gas scale. Working backwards 12.5:1 display = 0.85 lambda (15% rich). Multiply that by the MS109REG stoich of 13.36 = a true air/fuel ratio of 11.3:1 (not gas scale). Something changed from dyno to in-car, or yours and the dyno oxygen sensor read different.

Changing back to higher SG pump fuel would probably made it even richer than 0.85 lambda the jetting for MS109REG had it. So you would be jetting smaller for change of SG and then a lot smaller to get to the 13.3:1 pump gas AFR (0.90 lambda).

I know I harp on about it but lambda scale is the way to go if changing fuels with different stoichiometric numbers. You would have picked up on 0.85 lambda straight away and likely trialed 0.91 lambda down the 1/4. Also, if you like 8% rich then no matter the fuel you’ll always target 0.92 lambda.

[skinny z]

Is that the same piston to head clearance in each instance? .038"?

[steve cowan]

Is that the same piston to head clearance in each instance? .038"?

Sorry Kevin,
Forget to put that in
Cast iron heads 0.030" Piston to head

[skinny z]

Is that the same piston to head clearance in each instance? .038"?

Sorry Kevin,
Forget to put that in
Cast iron heads 0.030" Piston to head

Wow! That's tight.
But it eases my mind with the .034" the iron headed 357 is sporting.
Now, if I can tame the 10.4:1 for the occasional boulevard cruise (drag racing is projected to be the primary focus) then it'll be win/win.
Thanks again Steve.

[skinny z]

Do you think the tighter quench had an effect on the burn pattern?
Increased mixture motion and all that. Although I can't say how much of a difference .008" would make in any metric.

[Elroy]

But it eases my mind with the .034" the iron headed 357 is sporting

Your 357 finally made it past the sim stage?

[skinny z]

Ha ha Elroy!
Yes it has. For a while now actually. But still coming to grips with the poor CDN dollar as there are a few bits left to get.
And the sims are still in full swing...
Thanks for asking.

[steve cowan]

Do you think the tighter quench had an effect on the burn pattern?
Increased mixture motion and all that. Although I can't say how much of a difference .008" would make in any metric.

The choice for ms109 originally was because of cast iron heads,compression, small intake lobe,the fear was it might rattle with pump gas.
My opinion is more compression for ms109,remembering fuel was put into the engine to make the power. The lambda number was not a target just a result.
My main aim at the moment is to get a basic pumpgas combo together, that's reliable so I can focus on making the rest of the car better, rear gear,tyres suspension etc.
Mark ( vortecpro) I like to follow his train of thought, he gets his stocker stuff to run pretty good.

[steve cowan]

Changed to a bigger comp roller
266 - 272 @ 0.050 "
650" lift - 1.6 RR intake
615" lift - 1.5 RR exhaust
108 LSA in at 104ICL
Bumped compression from 11.1 to 11.35.
Ran yesterday,had good conditions in the morning.

20230521_043840.jpg

20230521_043854.jpg

[steve cowan]

Been a while -
Ran most of the year on our 98 unleaded pumpgas, testing different carbs.
950 hp (750) best ET 10.46 and best 60 ft - 1.43.
850 carb with small annular boosters.
950 AED carb I modified for friend best mph to date - 126.65mph.
4150 - 1050 carb with annular boosters.
All carbs ran within a tenth and 1 to 1.5 mph of each other.
Spent more time on caltracs and fitted Calvert 9 way shocks on the rear.
Best to date -
60ft - 1.43
660 - 6.59 @ 102
1320 - 10.46 @ 126 .65 mph.
3505 pounds with me.
Car is apart at moment.
Things to try 2024
I have a new set of 28 x 9 pro radials.
Will be fitting 4.56 rear gear.
In the process of cleaning up a weiand tunnel ram intake manifold.
Upgrade from my current 1277 PSI springs to a 1.30" spring DR - 427 - RML or similar.
My aim is to get current combo to run 10.00 on pumpgas.

[steve cowan]

IMG_20230821_162705.jpg

IMG_20230723_100159.jpg

20230819_164439.jpg

20230819_172657.jpg

[steve cowan]

20230902_151148.jpg

20230902_151141.jpg

IMG_20230822_163323_01.jpg

20230810_184629.jpg

IMG_20230916_122339_01.jpg

20230916_121622.jpg

Modify a old kick out oilpan as well,crank scraper, windage tray,sharks tooth oil pump,oilpump baffle,pan rail kickout on starter motor side.
Moving vacuum pump pick up point from rocker cover to valley through base of intake manifold. I will also fit a balance pipe/ hose from oilpan to rocker cover.also going to reduce oil restrictors size to top end.i will probably dyno engine again later this year,I want to try a gasported top ring I have and see if I can resolve the vacuum pump/ more hp deal .
I am hoping my oil pan mods etc help with dropping oil pressure at the stripe but I would not be surprised if it is more a pump cavitation issue.

[408 Nova]

Very very nice setup.

Your bearings look brand new. Nice work.

Mind if I ask what your crank scraper is made out of?

[steve cowan]

Very very nice setup.

Your bearings look brand new. Nice work.

Mind if I ask what your crank scraper is made out of?

Milodon scraper,needed minimal work to fit.
I find trimming with roofing iron snips works best,the material is a bit thin but should be fine.

[steve cowan]

For anyone interested I dynoed my other tow truck engine yesterday.
880 roller block with steel caps on centre 3 mains.
Mahle pistons 1.5 , 1.5 , 3mm set oil ring at 4 pounds.
11.2 comp.
Scat 9000 crank
Scat pro comp 8740 rods.
Howards shelf solid roller
257 - 263 @ 0.050 "
427 lobes,106 LSA , 106 ICL
680" - 650" gross lift with 1.6 - 1.5 jesel sportsman rockers.
Dart SHP ported 180cc heads
2.02" - 1.5" valves
2.3" avg csa 206cc.
Ported Vic Jr, ran best with 2 " 4 hole tapered spacer.
950hp carb (770 cfm)
Also ran with vacuum pump
10.2" more vac netted no more power,tested up to 14.7"
Also tried a 1050 carb 4150 with 16 hole BLP boosters was a bit rich but cleaned up with drop base picked up a few hp and cleaned up AFR across the board.
Best for the day 12 pulls
520 ft lbs @ 5100 rpm
585 hp @ 6800 rpm.

20240103_132344.jpg

20240103_133322.jpg

The overlay is the difference with drop base ,no dropbase