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423 SBC prediction

General engine tech -- Drag Racing to Circle Track

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prairiehotrodder
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Re: 423 SBC prediction

Post by prairiehotrodder » Mon Jul 29, 2019 2:06 pm

PRH wrote:
Mon Jul 29, 2019 12:32 pm
20+ years ago I built a high CR 406 with AFR 210’s, roller. Vic jr, Etc.

Went in a 65 Chevy II street car.
4.30’s, 9”, glide, 28” tires iirc.

Had 1-3/4x3 headers, 3” pipes into 3” flow masters coming out in front of the rear tires.
Mid-10 second car.
Remove pipes and muffs...... picked up .3 in the 1/4.
Well that makes sense because on the 383 we didn't gain much from going to the bigger heads and cam. Same exhaust system then and now.
I'm having a tough time getting my friend to give it a try with open headers.
The Word of God is quick and powerfull
www.therocketshop.blogspot.com

BigBro74
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Re: 423 SBC prediction

Post by BigBro74 » Mon Jul 29, 2019 2:24 pm

Well you can carefully explain why open exhaust may help, and then- if that doesn’t work-(provided your friend is a guy...) take the masculine approach and call
“no balls” :D
(BTW-Sarc..)
(And If your friend is female- I’ve got nothing—....)

I’m sure you will find your power- stay happy!
J

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Re: 423 SBC prediction

Post by prairiehotrodder » Mon Jul 29, 2019 7:44 pm

looked at the timeslips. All gains were in the 1/8th. Same mph as the old combo. It runs 6.62 in the 1/8 th. and 10.53 best in the 1/4 at 126 mph.
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BigBro74
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Re: 423 SBC prediction

Post by BigBro74 » Mon Jul 29, 2019 8:30 pm

prairiehotrodder wrote:
Mon Jul 29, 2019 7:44 pm
looked at the timeslips. All gains were in the 1/8th. Same mph as the old combo. It runs 6.62 in the 1/8 th. and 10.53 best in the 1/4 at 126 mph.
I guess this makes senses really if it is same cam and heads on a bigger shortblock, and the cam is 4 degrees farther advance than in the other engine. The extra compression is probably helping out otherwise so the top end didn’t drop off—— just rambling....

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Re: 423 SBC prediction

Post by econo racer » Mon Jul 29, 2019 11:05 pm

Try that 850 carb you have and see if it runs faster. What are you shifting it at? There is at least 3 more tenths there. You just got to find it. And you will :D

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Re: 423 SBC prediction

Post by GARY C » Tue Jul 30, 2019 1:02 am

prairiehotrodder wrote:
Mon Jul 29, 2019 2:06 pm
PRH wrote:
Mon Jul 29, 2019 12:32 pm
20+ years ago I built a high CR 406 with AFR 210’s, roller. Vic jr, Etc.

Went in a 65 Chevy II street car.
4.30’s, 9”, glide, 28” tires iirc.

Had 1-3/4x3 headers, 3” pipes into 3” flow masters coming out in front of the rear tires.
Mid-10 second car.
Remove pipes and muffs...... picked up .3 in the 1/4.
Well that makes sense because on the 383 we didn't gain much from going to the bigger heads and cam. Same exhaust system then and now.
I'm having a tough time getting my friend to give it a try with open headers.
That may be the Flow Masters them selves, I did a test with my nitrous 382 by adding exhaust to see if it slowed down, it never did.

1 7/8 header with 3.5 collector, straight pipe alone, added bullets, replaced with 3.5 X pipe system no mufflers, added tapered pipe from 3.5 to 3" about 2'. 6" long and Dyno Max muffler then added 3" tail pipes... no difference. The guy that bought it from me ran a 421, with and without tail pipes ran the same ET.
421 no tail pipes.
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Re: 423 SBC prediction

Post by prairiehotrodder » Tue Jul 30, 2019 11:00 am

That Nova really boogie's.

We made up some 3" collector extensions to replace the exhaust system at the next race. These will allow my friend to mount his O2 sensor and keep data-logging. We are also going to make a hold down to so he can keep the deep air cleaner base on the carb but try a run without the filter.

The funny thing about all this is that on last Saturday with the brand new engine he was runner-up in pro class and won money for the very first time. The motor was consistent and going rounds and thats why he didn't touch anything as far as trying to make it go faster.

Brian
The Word of God is quick and powerfull
www.therocketshop.blogspot.com

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67RS502
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Re: 423 SBC prediction

Post by 67RS502 » Tue Jul 30, 2019 1:33 pm

1. I think your heads are too small for the cubes, cam and comp.
2. Headers are too small. 1 7/8" is what you need. Pipemax will verify this. (my 420 picked up 1.5mph from 1 3/4" to 1 7/8")
3. Need more info on the exhaust, but flowmasters may not be the best choice especially if theyre not places in the correct place.
4. Tiny air filter is choking it, and that lid is not helping.

If you try open headers you need header extensions, or the test is meaningless.
67 camaro
girly rollers on pumpgas:
420 - 641hp BretBauerCam, 1.39, 9.79 @ 137.5
383 - 490hp 224/224, 1.56, 10.77 @ 124.6
502 - 626hp 252/263, 049s 1.44, 10.08 @ 132.7
62 Nova cruiser
383/200-4R/12-bolt w 373s
224/224 HR cam
1.57 10.97 @ 121.2

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Re: 423 SBC prediction

Post by prairiehotrodder » Tue Jul 30, 2019 3:16 pm

The heads are the fully CNC version of the AFR 227 with the 60/40 valve spacing and offset T&D shaft rockers. They were to big for the 383 now they are to small for the 423 ???

In my experience header tube primary size hasn't made as much difference as i expected. On a 700 hp 540 i was told the 2" tubes were choking it according to pipemax so i went to a set of 2.25" lemons and gained nothing. I'm not saying you are wrong and if we don't find any other solutions that may eventually be worth a try.

We have header extensions that i think are about 14" long.
The Word of God is quick and powerfull
www.therocketshop.blogspot.com

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67RS502
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Re: 423 SBC prediction

Post by 67RS502 » Tue Jul 30, 2019 3:38 pm

I don't really care for afr heads, as they tend to have some velocity issues. I assume they are around 2.25 csa which is on the small side for a 423, especially with the cam, rpm and comp you have, and the car isn't too heavy.
I'm also not the only one who pointed this out.
Heads need to be around 2.5" csa which will end up around 240cc+/-
Header are worth 1.5mph on my deal (20+hp) shifting around 7200, if I remember right it was with a tight verter, so it may be a bit more with an 8"
Don't forget the air filter, its a cheap fix.
Good deal on the header extensions.
Whats the fuel system like in the car?
67 camaro
girly rollers on pumpgas:
420 - 641hp BretBauerCam, 1.39, 9.79 @ 137.5
383 - 490hp 224/224, 1.56, 10.77 @ 124.6
502 - 626hp 252/263, 049s 1.44, 10.08 @ 132.7
62 Nova cruiser
383/200-4R/12-bolt w 373s
224/224 HR cam
1.57 10.97 @ 121.2

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BrazilianZ28Camaro
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Re: 423 SBC prediction

Post by BrazilianZ28Camaro » Mon Aug 12, 2019 12:33 pm

If your friend have the flowmasters with the funny sound, they're costing you 50-60 RWHP.

Open headers plus extensions will wake up this combo. Keep two eyes on the plugs too.

Good luck.
'71 Z28 street strip car
Pump gas All motor SBC 427
3308 lbs-29x10.5 Hoosiers
NEW BEST ET
1.40 60' / 4.05 330' / 6.32@111.25mph

https://www.youtube.com/watch?v=99p13UK ... ture=share

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Re: 423 SBC prediction

Post by prairiehotrodder » Mon Aug 12, 2019 4:44 pm

gonna find out this week hopefully.
The Word of God is quick and powerfull
www.therocketshop.blogspot.com

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BrazilianZ28Camaro
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Re: 423 SBC prediction

Post by BrazilianZ28Camaro » Wed Aug 14, 2019 11:08 am

67RS502 wrote:
Tue Jul 30, 2019 3:38 pm
I don't really care for afr heads, as they tend to have some velocity issues. I assume they are around 2.25 csa which is on the small side for a 423, especially with the cam, rpm and comp you have, and the car isn't too heavy.
The AFR 227s are more like 2.4 CSA at the pinch, should feed this engine at 6500-6800 I believe. They always can be ported. :D
'71 Z28 street strip car
Pump gas All motor SBC 427
3308 lbs-29x10.5 Hoosiers
NEW BEST ET
1.40 60' / 4.05 330' / 6.32@111.25mph

https://www.youtube.com/watch?v=99p13UK ... ture=share

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Re: 423 SBC prediction

Post by prairiehotrodder » Wed Aug 14, 2019 12:26 pm

we made up some 16" collector extensions that have an O2 sensor in them and hopefully i can report later tonight on the progress. The owner also thinks the timing pointer is not accurate so that may be an issue. He thinks the timing is way retarded but since he doesn't know for sure he is scared to advance it with this new high CR engine. He bought a piston stop to check the pointer.
He says it starts to easy and runs to smooth for the timing to be right. We were planning to start with the timing at about 36.
Brian
The Word of God is quick and powerfull
www.therocketshop.blogspot.com

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Re: 423 SBC prediction

Post by ClassAct » Wed Aug 14, 2019 1:22 pm

prairiehotrodder wrote:
Wed Aug 14, 2019 12:26 pm
we made up some 16" collector extensions that have an O2 sensor in them and hopefully i can report later tonight on the progress. The owner also thinks the timing pointer is not accurate so that may be an issue. He thinks the timing is way retarded but since he doesn't know for sure he is scared to advance it with this new high CR engine. He bought a piston stop to check the pointer.
He says it starts to easy and runs to smooth for the timing to be right. We were planning to start with the timing at about 36.
Brian


The spark plug will tell you when the timing is correct. What the light says is what it says.

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