SBC 408 cid, is 600 hp unreasonable N/A

General engine tech -- Drag Racing to Circle Track

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Charvelrhoads
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SBC 408 cid, is 600 hp unreasonable N/A

Postby Charvelrhoads » Wed Sep 17, 2014 9:17 pm

Hi everyone. Brand new to this forum, but I've been reading on here from time to time. Seems like a lot of knowledgeable people here. I'm hoping someone can help out here. I have a 408 sbc that I believe has more potential, but I'm at a loss. I was hoping for 600+hp. Maybe that's unreasonable. Here's what I've got.
2 bolt block filled to bottom of water pump holes, fitted with splayed 4 bolt mains
.040 SRP 4cc dome pistons, H beam 6in rods, internal balance steel crank.
Howards solid roller: in. 269 @ .050 ex. 277 @ .050 .675/.650 lift respectively
AFR 210 cnc ported cylinder heads, 2.08 in. 1.60 ex.
Edelbrock super Victor intake
Holley 950HP carb
Hedman 1 7/8 open headers

It hasn't been dynoed, but hauling 3350 lb race car in the 1/8 @ 6.90 or so only equates to 530 hp give or take.

Thanks in advance.

Kim

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Re: SBC 408 cid, is 600 hp unreasonable N/A

Postby Rizzle » Wed Sep 17, 2014 9:23 pm

Charvelrhoads wrote:It hasn't been dynoed, but hauling 3350 lb race car in the 1/8 @ 6.90 or so only equates to 530 hp give or take.

Thanks in advance.

Kim


Theres enough guys here who believe in the strip as much/more so than the dyno for power. If you put up the car specs and more info from your time slips you'll get some good info.

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Re: SBC 408 cid, is 600 hp unreasonable N/A

Postby Charvelrhoads » Wed Sep 17, 2014 9:38 pm

[quote="Charvelrhoads"]Hi everyone. Brand new to this forum, but I've been reading on here from time to time. Seems like a lot of knowledgeable people here. I'm hoping someone can help out here. I have a 408 sbc that I believe has more potential, but I'm at a loss. I was hoping for 600+hp. Maybe that's unreasonable. Here's what I've got.
2 bolt block filled to bottom of water pump holes, fitted with splayed 4 bolt mains
.040 SRP 4cc dome pistons, H beam 6in rods, internal balance steel crank.
Howards solid roller: in. 269 @ .050 ex. 277 @ .050 .675/.650 lift respectively
AFR 210 cnc ported cylinder heads, 2.08 in. 1.60 ex.
Edelbrock super Victor intake
Holley 950HP carb
Hedman 1 7/8 open headers

It hasn't been dynoed, but hauling 3350 lb race car in the 1/8 @ 6.90 or so only equates to 530 hp give or take.

Thanks in advance.

Kim

Ok, a little more info.
78 Camaro roll cage, powerglide, 1.76 planetary, 5.13 rear gears, 28 in. x 10.50 slicks, trans specialties converter. I recorded a shot of the tach as I accelerated and it stalls at 6000 rpm.
Very best time slip.
1.530 60 ft
4.405 330 ft
6.832 1/8th
101.22 mph

Most are just over 100 mph high 6.8, low 6.90 et.

Any more info I've forgotten, just say.

Thanks.

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Re: SBC 408 cid, is 600 hp unreasonable N/A

Postby vortecpro » Wed Sep 17, 2014 10:04 pm

Kim, racing cars at the drag strip requires an understanding of the data, an honestly Im really trying to help. You are showing an observed 500 HP @ the crank. Drag racing is about getting the car to leave, this is your major problem. I think a dyno test on a engine dyno would be money well spent, 600 corrected HP should be doable with that combination. Next your drive line, you need light weight drums in that trans, a real 8 inch converter that does not weigh 1 gram over 19 pounds. I would run a 30X9 radial slick with a two step off the foot brake. And keep in mind 107.2 MPH is 600 observed crankshaft HP @ 3350. So many people focus only on the engine, when in reality the car is horribly inefficient.
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Re: SBC 408 cid, is 600 hp unreasonable N/A

Postby Charvelrhoads » Wed Sep 17, 2014 10:19 pm

I appreciate your advice and input, and I know you are trying to help. Putting it on the dyno would be nice, but unfortunately not an easy task here, and not really in the budget. Converter is an 8in. but I have no idea of the weight. Glide has stock drum, turbo shaft, lightened high clutch hub. When you say getting it to leave, is that because of the 60ft time? I wrung the driveshaft out on this and had a heavy duty one built. I don't know what it weighs either, but it's constructed from .083 steel i'm told. Stock was .065 I believe.

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Re: SBC 408 cid, is 600 hp unreasonable N/A

Postby KnightEngines » Wed Sep 17, 2014 10:29 pm

If the heads are 'out the box' then there is your problem, those AFR's have turbulence issues above .550-.600" lift & the cross section through the pinch is too small for a 400+ cube engine to rev much past 5500-6000rpm.

Getting the heads ported to open up the pinch & sort out the turbulence will release a lot more HP & rpm, otherwise the combo looks pretty good.

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Re: SBC 408 cid, is 600 hp unreasonable N/A

Postby Strange Magic » Wed Sep 17, 2014 10:32 pm

I have a 408 sbc that I believe has more potential, but I'm at a loss. I was hoping for 600+hp. Maybe that's unreasonable. Here's what I've got.
2 bolt block filled to bottom of water pump holes, fitted with splayed 4 bolt mains
.040 SRP 4cc dome pistons, H beam 6in rods, internal balance steel crank.
Howards solid roller: in. 269 @ .050 ex. 277 @ .050 .675/.650 lift respectively
AFR 210 cnc ported cylinder heads, 2.08 in. 1.60 ex.
Edelbrock super Victor intake
Holley 950HP carb
Hedman 1 7/8 open headers


Your intuition is correct, unless your parts listed are fairly trick, although they are nothing more than off the shelf stuff, and that's ok. Your looking for answers as to why as well as validation as to your hunch. Your hunch is correct, you are not making 600. Cubic inch and compression is king when it comes to making power. A simple switch to a nice custom piston, ring package and a vacuum pump will get you everything you need and then some. 2.0 inch primary race headers will also enhance the power as well.

Putting it on the dyno would be nice,


don't waste your time, it won't tell you anything you don't already know, in your case.
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Re: SBC 408 cid, is 600 hp unreasonable N/A

Postby Charvelrhoads » Wed Sep 17, 2014 10:54 pm

[
Strange Magic wrote: A simple switch to a nice custom piston, ring package and a vacuum pump will get you everything you need and then some.


What would you recommend for pistons and rings? I should be in the neighborhood of 13:1 compression now. What should I be looking for? I've seen some vacuum pumps lately, what exactly do they do to enhance hp? thanks.

KnightEngines wrote: AFR's have turbulence issues above .550-.600" lift & the cross section through the pinch is too small for a 400+ cube engine to rev much past 5500-6000rpm.


There is no one local I would trust to port my heads. AFR's post some good flow numbers, that's why I went with them in the first place. Can you recommend a better head, or someone somewhere that does good quality port work? Thanks.

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Re: SBC 408 cid, is 600 hp unreasonable N/A

Postby KnightEngines » Wed Sep 17, 2014 11:12 pm

The heads can be sorted, just post your location & I bet the guys on here know someone close that'll be able to sort them.
Cost to port them properly will be a lot less than the cost of another set of heads, they can do what you're after with the right work, exhaust ports need very little work & the intakes only need opening up at the pinch & the turn reworked to get them stable.

AFR tells fibs a little.

A fellow engine builder recently build a nice 383 chev with AFR210's - heads were out the box, motor was 11:1 comp, good sized solid roller, super vic intake & QF850 carb etc - by all rights it should have been a high 500'sHP engine.
It struggled to a wheezing 510odd HP.
Those heads out the box just do not make HP despite what AFR claim.

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Re: SBC 408 cid, is 600 hp unreasonable N/A

Postby MaxFlow » Thu Sep 18, 2014 1:05 am

I agree the afr 210 head on the 406 isn't enough stalling at 6000. 500hp is about it without work.

These guys here know a ton more about drag racing combinations than I so I'd listen to them.
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Re: SBC 408 cid, is 600 hp unreasonable N/A

Postby cgarb » Thu Sep 18, 2014 1:51 am

Are you racing at high elevation? If you were racing in Denver thats not bad numbers really. Somewhere around sea level and it seems more in need of help.

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Re: SBC 408 cid, is 600 hp unreasonable N/A

Postby Charvelrhoads » Thu Sep 18, 2014 6:16 am

MaxFlow wrote:I agree the afr 210 head on the 406 isn't enough stalling at 6000. 500hp is about it without work.
These guys here know a ton more about drag racing combinations than I so I'd listen to them.


I know these guys know a ton, that's why I'm here, and I appreciate everyone's input as they've all had different experiences, and experience is what I need I think.
I get the feeling that my heads may be some of the issue. Not sure if I should port them, or replace. More ideas and opinions needed from racers that have been there.

cgarb wrote:Are you racing at high elevation?


About 1620ft elevation. Minot ND.

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Re: SBC 408 cid, is 600 hp unreasonable N/A

Postby englertracing » Thu Sep 18, 2014 6:52 am

the vac pumps helps ring seal, allows low tension thin modern rings, and reduces windage in the crank case.
you can do it with a vac pump or the right dry sump pump

if you were going with custom pistons id also do lateral gas ports.

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Re: SBC 408 cid, is 600 hp unreasonable N/A

Postby mag2555 » Thu Sep 18, 2014 7:48 am

A intake airflow level of 300cfm@28" should get you 600 HP with ease, the problem as was stated with those heads as they do have the needed air flow ,is the excessive port velocity due to the too small of a pinch point for your amount of CID!

The cure is 25 minutes worth of rework time spent in each a Intake runner!
Getting your port velocity down to 375 to 350 fps at .650" lift with the manifold bolted on will do just fine!

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Re: SBC 408 cid, is 600 hp unreasonable N/A

Postby Walter R. Malik » Thu Sep 18, 2014 8:14 am

600 horsepower is certainly a realistic goal with that combination.
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