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Discussion Starter #1
My Current set up:
406 10:1 compression
Hyd Roller cam 231/239 @ .050" dur, 535/550 lift
AFR 195 Eliminators
Air Gap RPM
750 Holley with a few Braswell parts
1 5/8" headers
~3200 PTC nitrous converter

The above combo has awesome low end torque and power and is a blast to drive around town. However, it seems to run out of steam on the top end and stop pulling up top. Everyone who rides in it has said the same. I have had it on the dyno and it peaks early around 4K RPM

Couple things I've thought about that would cause this;
1. heads are too small
2. headers are too small
3. valve springs are weak

So I've considered swapping out the entire top end for larger runner heads, larger headers, and a port matched single plane.

Thoughts and opinions?
 

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Let the Clutch Out
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My friend has a 421 SBC with AFR 210's and make peak power @ 6000 and some change but it still runns 10.20's in his 56 Chevy. he has 1 3/4 headers , Victor Jr., Solid Roller .630 Lift 274 @ .50 on a 108 and a 850 Holley .Oh and its 10.5 to 1
1.36 Sixty
10.20 1/4
126 mph
 

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Wait a sec'... the power peaks at 4000rpm or the torque does? That cam should see max power at 5800-6000, I would think. How's the fuel system, including routing? What about ignition and supporting components? Your engine hard parts seem fine, look elsewhere, and no, it is NOT the headers that are "choking" the engine. Subscribing.....


---==Temio Williams
Yuba City, CA
 

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Not a big fan of the dual plan intake I had way back 355 with cast camel hump heads almost the same cam with less comp was running 12.3/12.4 e.t and tried a airgap and slowed to 12.7s ..seem to pull real good down low ..bit fall off up top ..just saying

Maybe worth trying a open plenum victor Jr
 

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imo dual plane just suck every car (race or street) i've seen with one picked up 2-3 tenths from any dual to a victor jr or equivelent, a little dur. wouldn't hurt either but the intake is probably cheaper to start with.
 

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Discussion Starter #9
Was that cam degreed in or just lined up with the timing gear dots?

That's another thing. The dots were lined up and it was installed straight.

Wait a sec'... the power peaks at 4000rpm or the torque does? That cam should see max power at 5800-6000, I would think. How's the fuel system, including routing? What about ignition and supporting components? Your engine hard parts seem fine, look elsewhere, and no, it is NOT the headers that are "choking" the engine.
-HP was peaking early in the rpm range and falling off.
-The ignition is a HEI with an Accel module and coil.
-Fuel system is stock hard lines to an Edelbrock mechanical fuel pump and braided line to fuel log. Inline filter between pump/log.
-I get mixed reviews reference the header sizing.
 

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Headers are small, but not to the degree of shutting down power above 4k. My 400 with 195's, 1-5/8", vic jr. peaked at 6400. I'd investigate (read "throw away") that accel module.
 

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i had a accel bluebrinted hei dist in a 406 shifted it 6k evry pass for years but did have to change cap and rotor every 6 months would start spittin at higher rpm that was 9-1 and smaller cam and heads but single plane intake
 

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EFI/N2O JUNKIE
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My first 406 was 11:1 with a small hyd roller cam, ran it with 1 5/8" headers, Accel Super Ram intake (EFI) which dies-off much quicker than a dual-plane. Had no problem going to 6500 at all. Cam was around 224/230 @ .050, about .550 lift, ported Corvette aluminum heads, no where near your AFR 195's.
 

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Bracket racer
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What's the valve spring pressure? Also, how much timing? Fuel pressure?
 

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Discussion Starter #14
What's the valve spring pressure? Also, how much timing? Fuel pressure?

-Valve springs are the AFR originals.
-Timing is ~37-38* all in around 2400. This is without the vac adv can hooked up of course.
 

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Bracket racer
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What kinda fuel pump do you have? As far as the heads go, my dad has a 400 with a set of vortec heads on it (170 cc runner) and it pulls hard to 6000, so I don't think the heads are the problem.
 

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every thing is just alittle to small thats why it has killer torque at low rpm, cam i think is the biggist restiction, you have to get the fuel ,air in before you get it out
 

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check the plugs the combo sounds ok but if it's badly rich or lean it will lay over like that i had that problem while doing some track testing, what jets are in the carb. we jetted my buds s10 up 6-7 front and back picked up 1/2 sec but still wasn't poppin just labored the topend
 

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My Current set up:
406 10:1 compression
Hyd Roller cam 231/239 @ .050" dur, 535/550 lift
AFR 195 Eliminators
Air Gap RPM
750 Holley with a few Braswell parts
1 5/8" headers
~3200 PTC nitrous converter
Looks like a decent street/strip combination that should be fun to drive and have wonderful street manners.

If you get it running right, with that cam chosen, I would estimate you should be able to make in that 480-500 HP area with a HP peak right around the 5700 rpm area..... with shifts coming in a little over 6k several hundred rpm before valve float should be coming into play. The torque peak should be right around 4000 rpm. Your car should be a deep 11 second ride if you're in that low to mid 3000lbs area.

I agree with the others.... you have issues either with spark, fuel or valve-train. Up to you to find which one is the guilty party.
 
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