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Old 06-22-2011, 10:15 PM
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Advice needed on head/cam combo please

I have just installed and broke in a freshly built 350 sbc in my latest project. Here's the thing.....I told a friend of mine who has worked at a professional engine building shop for 5 years what my goal was and told him to build me a long block to suit those needs. My goal was 450 hp/435tq. I am convinced that I am not there and need your help to determine what changes I need to "tweek" things to hit my target. Here is what I have:
- '68 - '72 seasoned sbc 350 with 4 bolt mains bored 20 over, crank polished and balanced to 8000rpm
- SpeedPro flat top pistons with moly rings 9.5 - 1 cr
- Comp Cam #12-231-2 xtreme 4x4 hyd flat tappet cam & L817 lifters
- Comp Cam single valve springs #981-16
- Comp Cam Magnum roller rockers 1.52 ratio (#1412-16)
- Sportsman II 64cc fastburn heads 200 cc intake runners (#011250)
- Edelbrock RPM air gap intake
_ Edelbrock 650cfm Thunder series carb
- MSD distributor, 6AL2 box and blaster 2 coil
- 1 5/8" Hedman long tube headers with 3" collectors
- Flowmaster 3" exhaust

I was told that the sportsman heads could support well over 400 hp but got mixed reviews on their durability and flow rates, so am not opposed to changing them. The cam chosen for me I don't believe is nearly aggressive enough and would have liked a hyd roller instead as well. Any ideas where a set up like this would have me at present as far as power/torque and changes to maximize my setup? It isn't a daily driver but wont be a regular out on the stip either.

Thanks!!

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Old 06-23-2011, 02:30 AM
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Quote:
Originally Posted by classickrazy
I have just installed and broke in a freshly built 350 sbc in my latest project. Here's the thing.....I told a friend of mine who has worked at a professional engine building shop for 5 years what my goal was and told him to build me a long block to suit those needs. My goal was 450 hp/435tq. I am convinced that I am not there and need your help to determine what changes I need to "tweek" things to hit my target. Here is what I have:
- '68 - '72 seasoned sbc 350 with 4 bolt mains bored 20 over, crank polished and balanced to 8000rpm
- SpeedPro flat top pistons with moly rings 9.5 - 1 cr
- Comp Cam #12-231-2 xtreme 4x4 hyd flat tappet cam & L817 lifters
- Comp Cam single valve springs #981-16
- Comp Cam Magnum roller rockers 1.52 ratio (#1412-16)
- Sportsman II 64cc fastburn heads 200 cc intake runners (#011250)
- Edelbrock RPM air gap intake
_ Edelbrock 650cfm Thunder series carb
- MSD distributor, 6AL2 box and blaster 2 coil
- 1 5/8" Hedman long tube headers with 3" collectors
- Flowmaster 3" exhaust

I was told that the sportsman heads could support well over 400 hp but got mixed reviews on their durability and flow rates, so am not opposed to changing them. The cam chosen for me I don't believe is nearly aggressive enough and would have liked a hyd roller instead as well. Any ideas where a set up like this would have me at present as far as power/torque and changes to maximize my setup? It isn't a daily driver but wont be a regular out on the stip either.

Thanks!!
Compression ratio is to low 10:5-12 is more likly to hit the right numbers

Cam is to small needs to be a lot bigger something like this

http://www.lunatipower.com/Product.aspx?id=1985&gid=287

and to be sure this one will make the numbers http://www.lunatipower.com/Product.aspx?id=1986&gid=287

Carb needs to be a 750cfm-850cfm vac or a double pumper

You will also need a half inch fuel line from tank to carb.

Last edited by Scandinavian; 06-23-2011 at 02:49 AM.
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Old 06-23-2011, 03:50 AM
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Comp has a dyno sheet on the similar cam #12-230-2, grind #XE250H-10 and it pulled about 417 ft/lbs @ 3700 RPM and 333 HP @ 4700 RPM. I'd expect your cam to do a bit better, but it will still be about 100 HP short of your goal.
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Old 06-23-2011, 03:41 PM
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your cam and carb aren't up to the task. I would guess you are at 300hp.

2 relief flat tops with 64cc heads with a -0.015" deck height should yeild 10:1 cr.

I would buy a 3310 holley 750 vacuum secondary carb and a compcam 292H. This will get you 425 to 450hp at 6800 rpms.

this cam needs a 3000 to 3500 stall and a 4.11 gear.
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Old 06-23-2011, 04:59 PM
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Sounds like everyone agrees my cam in much to small.....what about the heads? With a bigger cam will those heads support it?
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Old 06-23-2011, 06:33 PM
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200cc sportsman should be enough.
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Old 06-23-2011, 06:37 PM
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I would think that for a 450HP 350 you are going to at least need a HYD roller.
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Old 06-23-2011, 08:26 PM
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Quote:
Originally Posted by classickrazy
I have just installed and broke in a freshly built 350 sbc in my latest project. Here's the thing.....I told a friend of mine who has worked at a professional engine building shop for 5 years what my goal was and told him to build me a long block to suit those needs. My goal was 450 hp/435tq. I am convinced that I am not there and need your help to determine what changes I need to "tweek" things to hit my target. Here is what I have:
- '68 - '72 seasoned sbc 350 with 4 bolt mains bored 20 over, crank polished and balanced to 8000rpm
- SpeedPro flat top pistons with moly rings 9.5 - 1 cr
- Comp Cam #12-231-2 xtreme 4x4 hyd flat tappet cam & L817 lifters
- Comp Cam single valve springs #981-16
- Comp Cam Magnum roller rockers 1.52 ratio (#1412-16)
- Sportsman II 64cc fastburn heads 200 cc intake runners (#011250)
- Edelbrock RPM air gap intake
_ Edelbrock 650cfm Thunder series carb
- MSD distributor, 6AL2 box and blaster 2 coil
- 1 5/8" Hedman long tube headers with 3" collectors
- Flowmaster 3" exhaust

I was told that the sportsman heads could support well over 400 hp but got mixed reviews on their durability and flow rates, so am not opposed to changing them. The cam chosen for me I don't believe is nearly aggressive enough and would have liked a hyd roller instead as well. Any ideas where a set up like this would have me at present as far as power/torque and changes to maximize my setup? It isn't a daily driver but wont be a regular out on the stip either.

Thanks!!
Not there! This combination will not produce 450 horses. I was going to go off and design an engine for you that would, but there are so many mismatches of parts and I don't know what transmission, final gearing and tire size, and what this is going to be used for are important questions. The answer to which may shed more light on what your friend is thinking about with this combination.

While my hip shot says the headers are too small as is the cam and with it the rocker ratio, the ports are too big and the compression too low. I'm not a fan of the Carter carb unless you're strictly looking to drive on the street but the CFM isn't enough for 450 hp. Knowing what you think is a rev limit would be good info as well.

The Sportsman head is a nice head but it's essentially a large port and valve version of the Vortec head and is smog legal so it's aimed more as a street replacement performance head than it is a race part. I don't think it's output is as good as the Vortec, the chambers aren't quite as good, they probably even out at high RPMs but putting around they seem to not deal with wet flow as well as the GM heads.

Bogie
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Old 06-23-2011, 11:33 PM
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I would agree and have been considering AFR 195 Eliminators along with a roller cam. This project is one that I want to do right and the engine is a huge part of it, so your suggestions are all valued. It will see some 1/4 mile runs and weekend challenges. As you probably already know, so much of a 68 Camaro is run by vaccuum but there are ways to maintain that and still have an aggressive cam. Torque is a sticker for me though too. I also want a set up that enables me to drive and enjoy rather than be wrenching and tuning constantly. I think the bottom end will support what I am trying to do, but combinations that work together is what I want up top. Does that help?
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Old 06-23-2011, 11:39 PM
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Sorry...forgot to include some info asked for. I have a TH350 with a stage 2 kit in it for a trans and final gears are 3.42's. 15" tires on it. Rev limit 6800.
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