Camming a 409 sbc with small intake runner

[BowtieNut]

Just looking some opinions on a solid flat tappet can for my 10 to 1 409. It has the 062 vortex heads that I ported with 2.08/1.6 valves. They flow 304 at. 500 lift on intake and go flat beyond that. Exhaust went 227 at. 500. They flow real.strong down low .100 was 92 cfm. 200 was 187 cfm. I've had a couple different cams in it. Strongest was comps restricted application lobes. 282/256 .520 lift on intake and exhaust on a 108 Lsa. That made 513 HP at 6700 and 500 lb ft of torque at 4800. Motor ran a 6.38 at 103 mph in a 3100 lb nova. The problem I have is it goes flat anywhere from 5300 to 6000 then gets a second wind and jumps up another 20 HP up to around 6800. Anyone had a scenario such as this before. You couldn't tell at any point on the race track that it was flat. Leaves with a 1.38 60 ft and pulls hard out the big end. The cam i have in it now is a 265/236 .532 int 265/240 .562 exhaust on 112 lsa with a dual plain instead of the single plain. That combo made 488 HP at 6200 and 503 lb ft of torque at 4300 . I haven't ran that can yet at the track but I'm thinking of going back to something bigger. Car weighs 3200 5.13 gears and a Hughes 4000 stall.

[F-BIRD'88]

My baseline cam choice for this motor would be a Isky 201549 or 201547 or a Crane 111431 or 111411.
With the single plane manifold.
What is your trap rpm @103MPH?

Collector extensions may take the dip out of the power curve.

You do not state what you want from the cam change.

[zums]

dont see how your getting 304cfm out of 062s without seeing water , but i think a solid cam in the 257-263 @.05 range on a 110 would work if your keepin the 5.13s

[swatson454]

I certainly wouldn't go any wider than a 108 LSA and I also agree with F-Bird that your dip may well be found in the exhaust. Can you give us the details of it?


Shawn

[BowtieNut]

The first time on the dyno with the big cam I had to much header on it. 2 inch primary with 3.5 inch by 12 inch long collector. Reason for running those was they had the egt bungs so I could monitor that. When it was in my friends nova it had a set of hooker supercomp 1 3/4 into a 3 inch collector. Second time on the dyno with the current cam that I had cut for the street (before I came across my 81 Malibu) I had the hooker supercomps that fits the Malibu on it. With that combo it still goes flat but maybe slightly less pronounced than with the big came big header combo. I have 3 inch exhaust with one chamber race fliwmasters that I can run but I'm afraid that may hurt some power. It was going through the traps at 7000 at 103 MPH with 29 inch tires the same trans and converter combo I have for the Malibu and same gear. Only difference is I have a 28 inch tire.

[swatson454]

So no collector extension the second time on the dyno and full-length exhaust at the track?

[JWRE]

I've had good results with the cams F-bird recommended in combos very similar to yours. I've also had great results with Comps' 12-515-5 and 12-612-5, but each time the results were always better with more rocker ratio. The Comp 515 specs. are 259/266 on a 106 .550/.570 (.606/.608 w/ 1.65/1.6 rockers) Comp 612 specs. are 265/276 on a 106 .562/.557 (.619/.594 w/ 1.65/1.6 rockers). But your compression may be a little on the low side for a 106 LSA. If you can bump it up to at least 11:1 they'll work better, however if your stuck with 10:1 Comp 12-655-5 may be a better choice. It's 256/262 .558/.543 on a 108 (.610/.579 w/ 1.65/1.6 rockers). That's just my experience, others may differ. Just something to think about anyway.

[BowtieNut]

So no collector extension the second time on the dyno and full-length exhaust at the track?

No collector ext. I haven't ran it in my Malibu yet. Just saying that I have a short exhaust system with 1 chamber flowmasters that came with the car that can be put on it.

[BowtieNut]

dont see how your getting 304cfm out of 062s without seeing water , but i think a solid cam in the 257-263 @.05 range on a 110 would work if your keepin the 5.13s

It can be done. They have over 70 passes on them and probably 30 or more dyno pulls. The core shift was horrible on my set of heads so the cnc machine cut through on the push rod pinch. Had to epoxy that. The velocity is extreme in them. Probably to high on a 400. I would love to see what they would do on a 350.

[novadude]

That's a LOT of cfm @ 0.500" from a small Vortec port.

[383hoopty]

With the higher velocity in those ports , I think a106 sep will work very good also. I like those older sat night cams too. Also may want to look at a Lunati 30121106. 255/263 284/292- .581/.590 with 1.5. It is also cut on a 106.

[F-BIRD'88]

Ditch the Flow masters. Try one of the cams I suggested with 1 3/4" Malibu headers and 6 to 18" collector extensions added
...as required.
If you want to run mufflers for the street get a straight thru design. Dyno max. Magna flow, or build your own.

Any all these FT Crane-- Isky cams always dyno and run real good in engines just like yours. And run around well on the street too. A good cam design does not get old. The cam you got is working well too.

[Carnut1]

dont see how your getting 304cfm out of 062s without seeing water , but i think a solid cam in the 257-263 @.05 range on a 110 would work if your keepin the 5.13s

It can be done. They have over 70 passes on them and probably 30 or more dyno pulls. The core shift was horrible on my set of heads so the cnc machine cut through on the push rod pinch. Had to epoxy that. The velocity is extreme in them. Probably to high on a 400. I would love to see what they would do on a 350.

Bowtie, I like this project and would love to get any info on those heads. I will make a few assumptions and then give you my opinion. I will guess That the port is near 200 cc with a 2'' sq pinch point with about a 400 ft/ sec air speed through the pinch. I like this setup with a dual plane but VERY few dual planes can feed 300+ cfm. This engine is right on the ragged edge of dual plane performance. Is the intake ported? Is the head cut for a 1205 or a 1206 gasket?

[zums]

so how did the cnc machine cut through them if you ported them, high runner speed will benefit more with the 110lsa

[BowtieNut]

dont see how your getting 304cfm out of 062s without seeing water , but i think a solid cam in the 257-263 @.05 range on a 110 would work if your keepin the 5.13s

It can be done. They have over 70 passes on them and probably 30 or more dyno pulls. The core shift was horrible on my set of heads so the cnc machine cut through on the push rod pinch. Had to epoxy that. The velocity is extreme in them. Probably to high on a 400. I would love to see what they would do on a 350.

Bowtie, I like this project and would love to get any info on those heads. I will make a few assumptions and then give you my opinion. I will guess That the port is near 200 cc with a 2'' sq pinch point with about a 400 ft/ sec air speed through the pinch. I like this setup with a dual plane but VERY few dual planes can feed 300+ cfm. This engine is right on the ragged edge of dual plane performance. Is the intake ported? Is the head cut for a 1205 or a 1206 gasket?

The square area at the pinch is 2.1 inches. I use the fell pro 1255 gasket and cut them to size. I had no particular gasket dimensions in mind when I ported them. The ports are radiused a bit in the corners. Dual plain is ported. The whole package flowed 277 at. 500 lift. And yes you are spot on the runner poured like 198 CC.