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Old 11-08-2009, 03:17 PM
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Why doesn't this combo make more power?

I have a 350 Chevy bored 030 over.
TRW forged flat tops 5.7 rods
Approximately 9.7 compression ratio
Sportsman II cylinder heads
Weiand Action Plus Intake
650 Mighty Demon Carb
Comp Cams Solid flat tappet cam
246@.050 .489 lift 110 lobe seperation
1.6 ratio roller rockers
Mallory unilite Dist.
MSD 6AL ingnition box
The car this engine is in has a B/W Super T10 4-Speed & a 4.56 gear.
On the Chasis Dyno this engine made 266HP & 295lb of torque.
Is this what can be expected with this combo & what improvements would you suggest.

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Last edited by hvy barrel; 11-12-2009 at 08:28 AM.
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Old 11-08-2009, 03:27 PM
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Quote:
Originally Posted by hvy barrel
I have a 350 Chevy bored 030 over.
TRW forged flat tops 5.7 rods
Approximately 9.7 compression ratio
Sportsman II cylinder heads
Weiand Action Plus Intake
650 Mighty Demon Carb
Comp Cams Solid flat tappet cam
246@.050 .489 lift 110 lobe seperation
1.6 ratio roller rockers
Mallory unilite Dist.
MSD 6AL ingnition box
The car this engine is in has a B/W Super T10 4-Speed & a 4.56 gear.
On the Chasis Dyno this engine made 266HP & 295lb of torque.
Is this what can be expecting with this combo & what improvements would you suggest.

Have you had it tuned? spark curve, fuel/air ratio, etc?
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Old 11-08-2009, 03:42 PM
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Yes, I spent alot of time elinimating vacuum leaks, tuning the carb & setting up the distributor.
The A/f ratio was a just a little on the lean side, not too much. about 15:1.
The ignition curve is set to 34 degrees total all in by 3000.
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Old 11-08-2009, 04:31 PM
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Change the cam to a Isky #201549 installed 6 to 7deg advanced (99deg in c/L)
Change the intake to a Professional Products Hurricane. Port match the Hurricane intake to the Sportsman II heads. (1206 gasket)) Fully port the Sportsman II heads.
The out of the box as cast Sportsman II heads have a huge fat valve guide boss sticking right in the middle of the flow in both the intake and exhaust ports. Needs generous streamlining.
Typical stock as cast air flow is around 224cfm.
A good ported Sportsman head will flow 260 to 290/300cfm. Big difference.

When used on a 350 the Sportsman II head likes to rev and needs a big cam with lots of duration and lift.
These heads are just getting busy at .550" valve lift. Need lots of lift.
The valve job and short side port radius contour is critical on these heads.

Mill them down or angle mill to get the cr up where it needs to be (10.5:1)
If your flat top pistons are below the deck of the block like .045" below deck at TDC your cr is much lower than you think.
Tear it down and deck the block properly.

A 355 with CC'd 64cc heads and -5cc flat top pistons and a true O deck clearance with .040" gasket will have a true 10.33:1 cr
Yours is probabily 9.3:1 Could be as low as 8.55:1 with a 72cc Sportsman head. Don't assume your chambers are as advertized.

(with this isky cam)
Lock the distributor mefchanical advance timing out and time at 36deg BTDC fixed.
(you can still emply vacuum advance for street driving if you want.)

When done right this true 10.5:1 cr 350 combo with Warmed up Sportsmans II heads and the Isky cam makes verified 500hp on pump gas on a engine dyno.
Needs a 750 to 920 cfm HP carb and 1-3/4" headers for best results.

You have the basics of the combo. Make these changes and it will perform for you. No guess work required, but the details matter.

Last edited by F-BIRD'88; 11-08-2009 at 04:44 PM.
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Old 11-08-2009, 05:05 PM
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What F-Bird describes is the same basic combination I run. I don't run the
sportsman heads, like he said they will work if ported. Will run high tens
@ 3200# with good chassis preparation.
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Old 11-08-2009, 05:07 PM
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thank F-bird, I have felt that the compression was too low.
How much can you advance a cam over the manufacturer's recommended installation?
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Old 11-08-2009, 05:16 PM
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Quote:
Originally Posted by hvy barrel
thank F-bird, I have felt that the compression was too low.
How much can you advance a cam over the manufacturer's recommended installation?
Till the intake valve smacks the piston.

The Sportsman heads do not like a small cam or a small intake or small headers.
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Old 11-08-2009, 05:45 PM
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Thanks Guys
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Old 11-08-2009, 06:14 PM
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Toss the Weiand, low rise, stock replacement, 180* intake. It's hurting your mid to top end.
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Old 11-08-2009, 07:08 PM
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Quote:
Originally Posted by hvy barrel
Yes, I spent alot of time elinimating vacuum leaks, tuning the carb & setting up the distributor.
The A/f ratio was a just a little on the lean side, not too much. about 15:1.
The ignition curve is set to 34 degrees total all in by 3000.
15:1 AFR .. lol.... lucky you didn't hurt it IMO...
shoot for 12.5:1

and try a little more timing AFTER you fix the A/F ratio
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Old 11-08-2009, 08:21 PM
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Quote:
Originally Posted by NXS
15:1 AFR .. lol.... lucky you didn't hurt it IMO...
shoot for 12.5:1

and try a little more timing AFTER you fix the A/F ratio
That was according to the dyno. The plugs look good & I don't hear any pinging while the engine is running or under a load. I do plan on changing the jets though. Funny thing is that is any of my buddies are driving behind me they tell me the that it smells very rich.
How much timing are you talking about?
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Old 11-08-2009, 08:25 PM
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Quote:
Originally Posted by sqzbox
Toss the Weiand, low rise, stock replacement, 180* intake. It's hurting your mid to top end.
I already have an Edelbrock Performer RPM that I was running & plan to reinstall. I changed it to eliminate it as an oil comsumption problem I was having.
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Old 11-08-2009, 10:04 PM
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As stated 15 to 1 is far to lean.
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Old 11-09-2009, 06:27 AM
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Funny as it sounds a lean mixture can smell rich due to lean miss fire not rich enough to burn properly and the unburnt fuel goes out the exhaust.
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Old 11-09-2009, 07:20 AM
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Performer RPM is a good choice over the weiand. I was going to suggest the
Edelbrock RPM air gap. Put a 4 hole 1" spacer under the performer and gain a little velocity if you have room under the hood. That should raise those dyno number's to over 300 on the torque and closer to 300 on the HP.
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