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before/after 383 dyno results

General engine tech -- Drag Racing to Circle Track

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randy331
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before/after 383 dyno results

Post by randy331 » Sat Mar 02, 2019 11:44 am

Thought a few may be interested in this project.
Had a guy bring me a 383 SBC out of his Vega drag car, wanting more power and lower et.

Engine is,
1.58" venturi x 1.75" throttle bore Holley carb with anular boosters (tried 2 on the dyno)
Brodix HV1000 intake with a little port match
Brodix track 1 heads un ported other than cnc Brodix did at intake flange
2.08 x 1.6 valves with 45* radius seats (valve job may be by previous engine builder)
Comp cams 263/270 105 lsa cam with 1.52 Comp rockers TK intake lobe / RZ ex lobe Net lift is .625-.630 at the valve
SRP 7cc dome piston with 1/16-1/16-3/16 rings 13-1 comp
6 inch rods
Stock oil pump W/milodon pan
He has 2" custom headers
I think it has a Brodix top end kit on it. Has Brodix part number on the valves, Brodix cast valve covers etc

We already took it to the dyno just as it was ran in the car, 2" headers and all.
So,... a few guesses what power it made and at what RPM before I post the results ?

The car is a light car. 2250 race weight is what he told me, but I didn't weigh it.
It's ran a few 5.90s 1/8 mile at 114

Most of the changes are already decided or done, but I'd like to hear what others would do to an engine like this ?
He's spending a little money so keep that in mind. (Jesel shaft/Jesel belt drive)

I told him he may be better off just starting over with a Dart or Bowtie block and build 400+ inches, but I guess something was said to him by the previous owner of the car that,... 5.90s is all he'll ever get out of that engine,..so we're staying with the 383 for now.

I'll go over what I'm doing after a few guesses on power and changes they'd make.
We'll take it back to the dyno when it's back together.

Other questions just ask.

Randy

1972ho
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Re: before/after 383 dyno results

Post by 1972ho » Sat Mar 02, 2019 12:29 pm

I would guess it made about 500-550 hp not sure on torque as there is no .60ft time to compare.

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Re: before/after 383 dyno results

Post by Ericnova » Sat Mar 02, 2019 12:44 pm

532 hp on the initial set-up.

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Re: before/after 383 dyno results

Post by Carnut1 » Sat Mar 02, 2019 12:48 pm

565hp to start. Randy, vj, Randy porting, Randy special cam durations. Real block, fix that intake. Add 100hp at least. Nice project.
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Re: before/after 383 dyno results

Post by 77cruiser » Sat Mar 02, 2019 1:13 pm

519 @ 6400
Jim

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Re: before/after 383 dyno results

Post by PRH » Sat Mar 02, 2019 2:36 pm

I’ll assume things were measured to verify the 13:1cr.

Big heads, big headers, aggressive intake lobe.........assuming no issues with valve or ring sealing........ had I dynoed it here, I would have been thinking it would be in the 575-585hp range.
If the primary tubes are rather short, along with the collectors, I’d be expecting the tq peak to be pretty soft....... maybe 470-480ish tq.
A little more length on both, 480-500ish tq.

As always, trying to guesstimate numbers from an unfamiliar dyno is always sketchy.
Somewhat handy with a die grinder.

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Re: before/after 383 dyno results

Post by randy331 » Sat Mar 02, 2019 2:49 pm

Best was 515 TQ @ 5100 rpm and 560 HP @ 6200 rpm.

It was pulling enough fuel through it to make 600 or so, but the BSFC #s tanked up top.
It had ex residue up 3- inches into the intake manifold.
Timing requirements sure indicate contaminated charge mix.
When we started it on the dyno I checked timing and it showed 48*, I figured it must have been bumped from the way it was in the car, so.. I put it back at 36*. More where I'd expect this chamber/compression/stroke to need.

We tried to make a pull at 36* but it wouldn't hardly run. Made 471 HP I think. Sounded bad. We put it back to 48* and it ran much better, Later backed it to 45* and it ran just about as good. Figured the timing tab was off, so I checked it when I got back home with it, but it was right, so.... be one interesting thing to look at when it goes back to the dyno, to see if the changes reduce the best power timing.

The current cam was in @ 103* ICL.
What valve events need to be different?

Randy

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Re: before/after 383 dyno results

Post by zums » Sat Mar 02, 2019 3:58 pm

randy331 wrote:
Sat Mar 02, 2019 2:49 pm
Best was 515 TQ @ 5100 rpm and 560 HP @ 6200 rpm.

It was pulling enough fuel through it to make 600 or so, but the BSFC #s tanked up top.
It had ex residue up 3- inches into the intake manifold.
Timing requirements sure indicate contaminated charge mix.
When we started it on the dyno I checked timing and it showed 48*, I figured it must have been bumped from the way it was in the car, so.. I put it back at 36*. More where I'd expect this chamber/compression/stroke to need.

We tried to make a pull at 36* but it wouldn't hardly run. Made 471 HP I think. Sounded bad. We put it back to 48* and it ran much better, Later backed it to 45* and it ran just about as good. Figured the timing tab was off, so I checked it when I got back home with it, but it was right, so.... be one interesting thing to look at when it goes back to the dyno, to see if the changes reduce the best power timing.

The current cam was in @ 103* ICL.
What valve events need to be different?

Randy
Got a real hog on your hands, lots of room for improvement, if your keeping duration specs of said cam i would start by spreading the LC 5*, 13.1 should be able to handle 61-62 abc no problem with 3.75 stroke and 6" rod. 1 3/4 headers, 52-55*seats, those changes alone should help clean up the runner, what other parts are you keeping , are the heads 220cc, avr csa, throat csa, never had a chance to map the brodix intake, do you have all that info, gains will be a good bit i predict when you get done straitening out all the original problems. Also, what style pan, got questions about the carb too
Tom

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Re: before/after 383 dyno results

Post by PRH » Sat Mar 02, 2019 4:08 pm

My general overview.......

Really fast intake lobe, pretty slow ex lobe, tight lsa, headers too big...... all of that contributes to the sooted up intake.
The radius valve job is likely as delivered from Brodix.
That’s how the Dirt Spec heads come.
The unported ex port isn’t great, and you have an ex lobe that has less high lift area than the intake lobe, and a valve job that probably flows pretty well at low lifts...... in both directions.
Tight lsa, fast opening intake valve with reversion-eze valve seat, long lazy ex lobe leaving the valve open to long after the intake starts to open, headers too big for effective scavanging in the rpm range the motor is being run.

I would use a slightly slower intake lobe, and a noticeably quicker ex lobe, spread the lsa out a bit, reconfigure the valve seats to be less effective at the lifts seen in the overlap area.
I gather it’s mostly an 1/8th mile ride, in which case I wouldn’t add too much duration.

Would have seen interesting to just put in a different cam to see what happened.
Same with trying some smaller headers....... like 1-3/4 to 1-7/8 stepped, then try a 3” and 3.5” collector.
Last edited by PRH on Sat Mar 02, 2019 4:49 pm, edited 3 times in total.
Somewhat handy with a die grinder.

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Re: before/after 383 dyno results

Post by ClassAct » Sat Mar 02, 2019 4:16 pm

The valve job is highly suspect. A good valve job will change cam timing requirements.

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Re: before/after 383 dyno results

Post by ClassAct » Sat Mar 02, 2019 4:17 pm

ClassAct wrote:
Sat Mar 02, 2019 4:16 pm
The valve job is highly suspect. A good valve job will change cam timing requirements.

EDIT: I did not see that right above me PRH just flat NAILED it. His explanation is much better than mine.

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Re: before/after 383 dyno results

Post by PRH » Sat Mar 02, 2019 4:27 pm

It was pulling enough fuel through it to make 600 or so, but the BSFC #s tanked up top.
Of course, if the pan sucks or it has too much oil in it you’ll get the same kind of results regarding bsfc.
Somewhat handy with a die grinder.

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Re: before/after 383 dyno results

Post by randy331 » Sat Mar 02, 2019 5:07 pm

Well, sounds like you guys are suggesting the same type of things I been working on or planning to do.

I've welded up the pushrod area and widened it and raised the port roof.
It's getting a Jesel 1.7 intake 1.6 ex shaft with offset pushrod and new offset lifters to allow the wider pushrod area.
It now has a 50* intake valve job (not radius) and a 50* radius ex valve job.
Ports were 216-218 cc and now are 228-230 cc. The throat is still a little small 1.78" diameter on intake.
New cam is 267 rx intake lobe and 280 nsc ex lobe on 110* lsa.
The piston to head was .060" and is now .040
Porting the intake also.
it has a couple pin bushings spun a little in small end of the rods, so it's getting a new set of 6" Callies compstar rods.
He's getting new headers too. We tried the 1 3/4 x 1 7/8 dyno headers Joe has at the shop and it picked up some power with those. Think it made 570 with those headers, but could have maybe been better with some tuning with those headers but we called it a day.
Getting a vacuum pump.
Getting a Jesel belt drive so we'll be able to move the cam on the dyno.
Think a new pan in gonna happen too. Not sure what pan.
Not sure his springs were up to the task, so it's getting a new set Of Manley Nextec springs with tool steel retainers.
It had 5/16 .080 wall pushrods and I have room for 3/8 so that's what it's getting.

An interesting side note,.. I brought my new carb I bought for our pulling truck and made a pull with it. I did it just to see how it would run on something it's too big on. My new carb is a Whitener 4500 series 1.92 venturi x 2.25" throttle bore and we had to run it through one of the adapters down to the 4150 intake. It ran fine. Nice 13-1 afr all through the pull with the middle jets of the 5 Mark sent for non oxy fuel. it was pulled down to under 4000 rpm. Guess it won't flame out on our 421 that makes 200 more HP?? LOL

Randy

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Re: before/after 383 dyno results

Post by PRH » Sat Mar 02, 2019 5:16 pm

Should make enough to kill the stock block easy enough.

I realize many don’t feel there is any value in ex flow numbers, but I still like to see them.
Any before/after ex flow numbers you can share?

Even if it’s just the .400 and up data.
Last edited by PRH on Sat Mar 02, 2019 5:29 pm, edited 1 time in total.
Somewhat handy with a die grinder.

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Re: before/after 383 dyno results

Post by randy331 » Sat Mar 02, 2019 5:27 pm

PRH wrote:
Sat Mar 02, 2019 5:16 pm
Should make enough to kill the stock block easy enough.
Well, lets hope not, but there's always a chance that could happen.
I've seen stock 350 blocks live at the 650 HP level.
My son has a stock 350 block making 630 HP he ran in his pulling truck all one summer and it was all a bunch of used stuff he put together.
Then he loaned it to friend of half the next season.

Randy

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