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Gains porting afr195 on sbc 388

General engine tech -- Drag Racing to Circle Track

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68corvette
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Re: Gains porting afr195 on sbc 388

Post by 68corvette » Sun Feb 09, 2020 5:02 am

Here is dyno graph from 1st posts configuration:
Image

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Re: Gains porting afr195 on sbc 388

Post by PRH » Sun Feb 09, 2020 12:01 pm

Did you have an air flow sensor on the carb?
Was the airflow still rising steadily after peak hp?

Basically I’m asking if you feel the peak was occurring where it did, and fell off at the rate it did because of a lack of flow/cross section........ or might there have been some valvetrain stability issues that were contributing to where it peaked and how it fell off?
Somewhat handy with a die grinder.

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Re: Gains porting afr195 on sbc 388

Post by steve cowan » Sun Feb 09, 2020 12:17 pm

I think that is where that size engine would peak especially with airgap, it will really choke it down as in available airflow.
Looking at the reworked numbers, seems like going in the right direction, I am curious how the exhaust port sounds on the bench as I see a slight dip in the high lift numbers.
I am interested as well in your valve seat profile change you made if you are willing to expand on it :D
Overall I think the engine will gain across the board especially with a nice single plane intake
steve c

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Re: Gains porting afr195 on sbc 388

Post by Orr89rocz » Sun Feb 09, 2020 12:39 pm

I think a better intake or single plane would do better, atleast help feed past peak rpm to hang onto power longer

I had a 230/245 .603/.613 hyd roller make peak at 6250 rpm and hold to 6600. Box stock street afr 195’s. Intake was a tunnel ram style holley/weiand stealth ram efi setup

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Re: Gains porting afr195 on sbc 388

Post by 68corvette » Mon Feb 10, 2020 12:23 pm

There was not airflow meter used at dyno.
It could be also that there is hydraulic pump up, or valve bounce.
I did not measure the cam profile and valvetrain weights to calculate required spring forces, just checked that springs were within specs.
I would had expected that with this much cam the power should had been hanging there up to 6500rpm, but thought that maby intake manifold and cylinder head made it to dive.

Exhaust sounded smooth.
It was measured without pipe, so flow separated at high lift.

I have 388 with XE274H camshaft (230/236-110-.500"),RPM intake, Dart 180cc platinums and it peaks also at 6000rpm.

So definitely something is holding this beast at peaking higher :D

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Re: Gains porting afr195 on sbc 388

Post by steve cowan » Mon Feb 10, 2020 12:51 pm

68corvette wrote:
Mon Feb 10, 2020 12:23 pm
There was not airflow meter used at dyno.
It could be also that there is hydraulic pump up, or valve bounce.
I did not measure the cam profile and valvetrain weights to calculate required spring forces, just checked that springs were within specs.
I would had expected that with this much cam the power should had been hanging there up to 6500rpm, but thought that maby intake manifold and cylinder head made it to dive.

Exhaust sounded smooth.
It was measured without pipe, so flow separated at high lift.

I have 388 with XE274H camshaft (230/236-110-.500"),RPM intake, Dart 180cc platinums and it peaks also at 6000rpm.

So definitely something is holding this beast at peaking higher :D
Wondering if you would share more information on the 180 cc combination as in cylinder head average CSA etc.
I am in the process of doing a set of dart 180 for a new combination 383 sbc 4.030" bore.
I want to peak around 6500
I am working on an average CSA of 2.2" and approx 200 cc
2.02" valve I think needs duration in the 240s
Cam not purchased yet but will be Comp solid roller.
At a guess you're 180 cc combination makes around 470 hp
Pretty small cam and lift limited but would be a great street engine for sure :D
steve c

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Re: Gains porting afr195 on sbc 388

Post by 68corvette » Sat Feb 22, 2020 11:10 am

I would like to keep this topic about the AFR heads, even that my own engine would be also interesting :D

Engine got back to dyno.
It kind of was what we targeted to. New seat profiles improved the low end torque and runner shapes and increased area added more to the top.
But still the engine does not rew past 6200rpm, old peak was at 6100rpm.
I would had expected the peak to raise about 500rpm.

Here are the 2017 vs 2020 dyno measurements on the same graph.
Image

Here are the manifold pressures

Code: Select all

3,000	-0.5
3,100	-0.3
3,200	-0.3
3,300	-0.3
3,400	-0.3
3,500	-0.1
3,600	-0.1
3,700	-0.3
3,800	-0.4
3,900	-0.6
4,000	-0.6
4,100	-1
4,200	-1.4
4,300	-1.5
4,400	-1.3
4,500	-0.9
4,600	-0.8
4,700	-0.8
4,800	-1
4,900	-1.1
5,000	-1.2
5,100	-1.2
5,200	-1.2
5,300	-1.1
5,400	-1.1
5,500	-1.2
5,600	-1.1
5,700	-0.9
5,800	-0.9
5,900	-1.2
6,000	-1.5
6,100	-1.4
6,200	-1.2
6,300	-1.2
6,400	-1.4
6,500	-1.4
Picture of the hacked runners:
Image

Air sensor was not available at dyno.
There would be room to shim springs to add 28lbs / 20% to seat and that would be easy and cheap test.
We also discussed about testing with solid followers, but that would need follower and pushrod investment.
Also intake manifold would be easy test to verify if the problem is there.
But the cas is a street car and owner would prefer dual plane for good driveability.

Overall we are happy with the porting results, but I was personally a bit disapointed as I was expecting more HP to the top end, having about 550hp at 6500rpm.

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Re: Gains porting afr195 on sbc 388

Post by PRH » Sat Feb 22, 2020 11:44 am

If you had access to a pretty good single plane to test, I’d do it.

I think looking for a peak at 6500rpm from that combo with a dual plane is a stretch.

If it peaks at the same point with a decent single plane...... then shim the springs.

Those are pretty good gains...... same everything except the head work?
Somewhat handy with a die grinder.

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Re: Gains porting afr195 on sbc 388

Post by RevTheory » Sat Feb 22, 2020 11:52 am

What have you tried for carb spacers?

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Re: Gains porting afr195 on sbc 388

Post by 68corvette » Sat Feb 22, 2020 12:21 pm

PRH wrote:
Sat Feb 22, 2020 11:44 am
If you had access to a pretty good single plane to test, I’d do it.

I think looking for a peak at 6500rpm from that combo with a dual plane is a stretch.

If it peaks at the same point with a decent single plane...... then shim the springs.

Those are pretty good gains...... same everything except the head work?
That sounds like a good plan.
There should be Super Victors for a loan, so test would be free except the dyno time.
Though we could do G-tech or GPS based acceleration measurement to run the baseline HP graph.
That should be enough to see how power curve shape changes, that would be free.
Or wheel dyno, which are not expensive, but would need two visits.

There was an intake manifold change from "crosswind", which is chinese rip off of the RPM air cap.
Fuel distribution was better with crosswind and dyno operator had said that it might had made better hp based on previous experiences.
I doubt there is many ponies difference to either direction.

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Re: Gains porting afr195 on sbc 388

Post by 68corvette » Sat Feb 22, 2020 12:23 pm

RevTheory wrote:
Sat Feb 22, 2020 11:52 am
What have you tried for carb spacers?
I do not know if spacer was tested.
Car is an C3 Corvette, so it could be that I need to surface some off from the carb bad before it fits under the hood.

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Re: Gains porting afr195 on sbc 388

Post by RevTheory » Sat Feb 22, 2020 12:41 pm

68corvette wrote:
Sat Feb 22, 2020 12:23 pm
RevTheory wrote:
Sat Feb 22, 2020 11:52 am
What have you tried for carb spacers?
I do not know if spacer was tested.
Car is an C3 Corvette, so it could be that I need to surface some off from the carb bad before it fits under the hood.
I was thinking a 1.5" tapered spacer but there's no way that's going to work under a C3 hood.

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Re: Gains porting afr195 on sbc 388

Post by cv67 » Sat Feb 22, 2020 3:22 pm

77cruiser wrote:
Sat Feb 08, 2020 6:59 pm
Thought i read one of his posts that said he always touched them a bit.
He did, the lobes were super aggressive also

Did a set of 195 st heads..they carried to .650-7 rather than stalling early. Exh picked up nice which was probably not necessary but was spraying it a lot. Intake didnt pick up a ton up top but modest gains everywhere, slight cam change with Jones and some grinding picked up a super ram by close to 30 to the ground.
193 finished size

TO the guy that did the comp ports didnt know there was room some heads get thin in places made that mistake.
No sonic checker though

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