350ci 470HP Peak at 6000RPM

[vortecpro]

Again the measured, observed, or in the room, HP was in the 350s.
And for a point of reference, my 327 that made 329 measured, observed, or in the room HP on the same dyno @ 6400 feet elevation ran 11.97 in my 3970 pound 1/2 long bed truck in 2000 feet DA.

[Stan Weiss]

If this was on a Super Flow dyno / software, you can not just take the uncorrected HP time the correction factor and get corrected HP. Super Flow also includes another factor using ME% which is not a constant during the pull.

Stan

[F-BIRD'88]

Here’s another example. On what appears to be an honest dyno

Not 10.5:1 cr. its 11.4:1. Not peaked @6000 rpm

[F-BIRD'88]

My question, 490hp/471tq. 150lbs of fuel, bsfc's would be .43 to .45, likely higher, any less aint happening, .43 is being generous for an old fuely head with a dual plane, is about 350 observed. Stated in thread from that build, 1.26 correction, 441-450hp corrected

Don't have the sheets anymore, or i'd post them, 355, 12.5:1, Ported Sportsman 2's, Holley Strip dominator, mild plenum work and port match, Quick fuel 850, Erson "street" roller, 258-263, .585/.550 lift, 1.6 intake rocker, made 530hp at 6600 and 45X ft lbs. around 5000. I am sure it made at least 470 by 6000, probably 500+. Kinda funny, I've built very few 350"s over the years, I usually talk then into 383's. Obviously not 10.5:1 on pump gas, but take 2-2.5 points of compression away, all else equal, it would make 470 by 6000. It's not some mystical feat, it's possible.

12.5:1 CR is not 10.50:1 CR.

530 peak HP @6600 rpm
Is not 470 peak hp @6000
keep trying.

[Monza355]

Here’s another example. On what appears to be an honest dyno

Not 10.5:1 cr. its 11.4:1. Not peaked @6000 rpm

You are correct. But I didn’t see any mention of a 10.5:1 compression ration in the original post. It also has a dual plane intake. I would say it would be stronger at 6000 rpm are with a Victor JR single plane intake. But of course we don’t know that in this case because it wasn’t tested like that. Anyways I guess 469.2 hp at 6000 rpm’s probably ain’t close enough for you

[F-BIRD'88]

Here’s another example. On what appears to be an honest dyno

Not 10.5:1 cr. its 11.4:1. Not peaked @6000 rpm

You are correct. But I didn’t see any mention of a 10.5:1 compression ration in the original post. It also has a dual plane intake. I would say it would be stronger at 6000 rpm are with a Victor JR single plane intake. But of course we don’t know that in this case because it wasn’t tested like that. Anyways I guess 469.2 hp at 6000 rpm’s probably ain’t close enough for you

Again the 11.4:1 cr is much higher than the discribed 350 sbc with 10.50:1 cr.. Again the engine peaka at a higher rpm tham 6000 rpm..

[Bigchief632]

My question, 490hp/471tq. 150lbs of fuel, bsfc's would be .43 to .45, likely higher, any less aint happening, .43 is being generous for an old fuely head with a dual plane, is about 350 observed. Stated in thread from that build, 1.26 correction, 441-450hp corrected

Don't have the sheets anymore, or i'd post them, 355, 12.5:1, Ported Sportsman 2's, Holley Strip dominator, mild plenum work and port match, Quick fuel 850, Erson "street" roller, 258-263, .585/.550 lift, 1.6 intake rocker, made 530hp at 6600 and 45X ft lbs. around 5000. I am sure it made at least 470 by 6000, probably 500+. Kinda funny, I've built very few 350"s over the years, I usually talk then into 383's. Obviously not 10.5:1 on pump gas, but take 2-2.5 points of compression away, all else equal, it would make 470 by 6000. It's not some mystical feat, it's possible.

12.5:1 CR is not 10.50:1 CR.

530 peak HP @6600 rpm
Is not 470 peak hp @6000
keep trying.

But it made 500at 6000. Take 2 points of compression away and it makes 480 there, and that's being very generous on what 2 points to compression is worth. It's NOT anymore than 20.

[Erland Cox]

If it was made to peak earlier it would probably give even more power earlier.
I built a 445 hp 350 that peaked around 6000 but it was around 12:1 cr.
L98 1.94-1.50 heads ported, ported and matched Victor JR, Crane hydraulic .480" lift 228 at .050. 106 0r 107 lobe separation.
Heads flowed 240 in don´t remember if it was at .500" or .600"
Good power up to 7000 but too weak valvesprings for higher revs.
1-5/8 headers.
This was with a 750dp, a 600 dp gave 430 hp.

Erland

[F-BIRD'88]

Hard to run these 12:1 CR examples on pump gas.

"peaked around 6000"
Means it peaked at a higher rpm.

I built a very similar 12.5:1 cr 350 with ported 305 heads sane valve size. similar flow.. It really liked to rev up.
Its the nature of built 350's.
The whole o point is if you limit rpm to 6200 you leave much of the power to accelerate the #3600 car unused.
You need to gear these 350 engines up to make use of the engine power available. Otherwise the #3600 car is not going to be very fast in ¼ mi.

[Tom68]

If it was made to peak earlier it would probably give even more power earlier.
I built a 445 hp 350 that peaked around 6000 but it was around 12:1 cr.
L98 1.94-1.50 heads ported, ported and matched Victor JR, Crane hydraulic .480" lift 228 at .050. 106 0r 107 lobe separation.
Heads flowed 240 in don´t remember if it was at .500" or .600"
Good power up to 7000 but too weak valvesprings for higher revs.
1-5/8 headers.
This was with a 750dp, a 600 dp gave 430 hp.

Erland

So a bit under cammed for a single plane will peak at 6000. If you upped the cam to get 470hp most likely it would occur higher than 6000.

[F-BIRD'88]

If it was made to peak earlier it would probably give even more power earlier.
I built a 445 hp 350 that peaked around 6000 but it was around 12:1 cr.
L98 1.94-1.50 heads ported, ported and matched Victor JR, Crane hydraulic .480" lift 228 at .050. 106 0r 107 lobe separation.
Heads flowed 240 in don´t remember if it was at .500" or .600"
Good power up to 7000 but too weak valvesprings for higher revs.
1-5/8 headers.
This was with a 750dp, a 600 dp gave 430 hp.

Erland

So a bit under cammed for a single plane will peak at 6000. If you upped the cam to get 470hp most likely it would occur higher than 6000.

You're catchin on.

[Tom68]

Hiya Tom,
I noticed you have been a member here for less than a year. There is a wealth of information on this site. Quite a few have quit sharing information.

Of course runner length matters and whether wet flow or dry flow and wherever the wet flow is introduced. Bring apples to apples questions, not apples to oranges.

If you have a desired rpm band to maximize, tune the runner length/size/taper to comply, also exhaust. IR is a whole different world(as you know) than carb dual plane or single plane manifolds, tunnel rams too. EFI dual plane and single plane is a different world too.

If you were building for maximum possible hp at 6000 rpm intake runner length would have to be the first thing optimised, a single plane in current lengths won't be the winner. A dual plane will do alright with losses for it's terrible wetflow properties. So I guess a long runner tunnel ram with something like two 660s would be the best carb'd option to acheive it.

As you say IR and injection whole different deal but easy to get necessary lengths.

[Tom68]

You're catchin on.

350 470 6000. First thought is that's every other SBC. Reality's a bit different.
It was probably true for every other LS 20 years ago.

[Erland Cox]

If it was made to peak earlier it would probably give even more power earlier.
I built a 445 hp 350 that peaked around 6000 but it was around 12:1 cr.
L98 1.94-1.50 heads ported, ported and matched Victor JR, Crane hydraulic .480" lift 228 at .050. 106 0r 107 lobe separation.
Heads flowed 240 in don´t remember if it was at .500" or .600"
Good power up to 7000 but too weak valvesprings for higher revs.
1-5/8 headers.
This was with a 750dp, a 600 dp gave 430 hp.

Erland

So a bit under cammed for a single plane will peak at 6000. If you upped the cam to get 470hp most likely it would occur higher than 6000.

The engine was in an old class racer Camaro gen 3, Swedish Camaro cup. It originally had a 305 with that speced cam so when I built a 350 I reused it.
The reason for not using more cam was both the 1-5/8 headers and the Super T10 gear box.
I have a 4th generation Camaro cup car too and it has a modified zz4 engine.
Longer rods with flat tops and really high thin rings.
Same L98 heads but unported and the ZZ4 GM intake. 1.3/4 Hooker headers.
GM hot cam with 1.6 rockers.
It makes 395 hp and 550 Nm:s. They are said to make 420.



The red curve is with a bad distribotor cap, the center teminal was missing.
Both of them run on Swedish pump gas 98 but we only use the high rating so it is lower rated in the US.

Erland

[KnightEngines]

Screenshot_20221123-085737_Gallery.jpg

Set the limiter at 6100.
Job done.

The only reason I can't show you one that peaks at 500hp & 6000rpm is because I rarely feel the need to cap anything at 6000, it'd be stupid.