Sportsman II heads on a mild 350

[travis]

This is more of a question concerning port size, port velocity, and street rpm throttle response.

I don’t have a lot of experience with these heads, but I seem to remember back when they was the only game in town for an aftermarket head that on a mild 350, these heads were kind of soggy at lower rpms. I also seem to remember that out of the box they really don’t flow well for a 200cc head, maybe around 240 cfm or so. What I’m wondering is, with a little work and very minimal metal removal, if you picked up 30-40 cfm with a barely bigger intake port, would the higher port velocity perk up the low end and part throttle response significantly?

The engine is a very mild daily driver, but built to handle a 250 shot of nitrous. The combination currently is 9.2 compression, lightly ported 993 castings with 1.94/1.60 valves, a comp 218/230@.050 HFT nitrous HP cam on a 113 lsa, bullet proof bottom end, performer rpm intake, 750 DP Holley, 1 3/4” headers and 3” exhaust. The car currently runs 11.80’s-90’s on a 150 shot, but picks up very little on a 200 or 250 shot. He thinks it’s running out of head, but he is worried about the car not driving as nicely during the daily grind

[mag2555]

I think your too concerned with the wrong side of the heads currently being run!

If a 250 shot makes no real added power then a 150, it would seem to me that it’s running out of exh port capability that the cam being run can not further compensate for.

If your buddy would need to go out and pay for a different set of heads then spending that same money on getting his 993s ported and fitted with 2.02” valves would be a better bang for the Buck and there should also be no chance of loosing low speed response since you would have well under a 200 CC runner.

Granted the 993 castings do not have the most efficient chamber, but picking up 30 cfm with the 2.02” valve on the intake side and 50 on the exh side which is doable will wake the motor up a lot!
Also don’t forget that if your talking Apples to Apples swapping over from iron to Aluminum means the heads need need to flow 10 to 15 cfm more to make equal peak power.

[BobbyB]

I think your too concerned with the wrong side of the heads currently being run!

If a 250 shot makes no real added power then a 150, it would seem to me that it’s running out of exh port capability that the cam being run can not further compensate for.

If your buddy would need to go out and pay for a different set of heads then spending that same money on getting his 993s ported and fitted with 2.02” valves would be a better bang for the Buck and there should also be no chance of loosing low speed response since you would have well under a 200 CC runner.

Granted the 993 castings do not have the most efficient chamber, but picking up 30 cfm with the 2.02” valve on the intake side and 50 on the exh side which is doable will wake the motor up a lot!
Also don’t forget that if your talking Apples to Apples swapping over from iron to Aluminum means the heads need need to flow 10 to 15 cfm more to make equal peak power.

I never heard that aluminum heads need to flow more than iron to make equal power. Why is that?

[mag2555]

Aluminium transfers/ draws heat faster out the chamber and expanding hot air is what drives the piston.
Less average heat can be made up with greater intake flow
Or not running the coolant at low 170 degrees as many folks seen to do.

[Monza355]

This sounds like a fun combination. What’s the rest of the combo ? Weight of the car, Gearing, transmission and converter ?

With up to 250 hp shot of nitrous I would run a single plane like Victor JR. Btw. What nitrous system is he using ? I’we seen some nitrous systems advertised up to 250 hp shot but the still use the smallest “purge” size solenoids that don’t flow much more then 150 hp worth of nitous.

The sportsman heads do work well on a 350 sized engine. Especially when cleaned up. Guide bosses are huge as you may allready know. It will drive nice around town, and be much better on the strip !

[BOOT]

I had vortecs and Sportsman II's on the same engine with even the same intake, as my set of vortecs were drilled & tapped. Vortecs were a TON better low & mid. The Sportsman II advertised flow numbers are on like a huge bore and they vary in quality set to set. I made a video comparing four sets of Sportsman's https://youtu.be/O6Ovmy7iX4U I think they are a good head with work, sturdy iron heads and better than a lot of older stock heads but not vortecs for NA power.

[rebelrouser]

The few nitrous engines I have messed with on the dyno tell me that the fuel supply to the nitrous system is very important, nitrous is an oxidizer, it allows you to burn extra fuel to make more power, if there is not enough extra fuel to burn the nitrous does not make more power. Example I dynoed an engine similar to yours that was in a jet boat, we used the nitrous and his fuel systems on the dyno, at the hit the engine made good power but as the rpm's came up the power level dropped off, he did not have enough fuel to the nitrous system. used the fuel pump for the dyno, it is supposed to be capable of 1,000HP and the problem was solved.

[1980RS]

My SBC pump gas 358 ran 11.30@118mph last fall all on 91 octane. Now I do have a roller cam in it, not too big but the flat tappet cam went about as good. There is nothing wrong with the Sportsman II's on a 350 IMO. I did not run Vortec's on this engine because I run the roller cam and the Vortec's would require a ton more work to use that setup. I really want to try out my Dart 49cc chamber 200cc heads but with the price of fuel going through the roof I will leave it just as is.

[PRH]

My experience is that sportsman II’s don’t pick up 30-40cfm with minimal material removal.

That requires a fair amount of actual porting.

I’ve made over 600hp with them on a bracket race type 383.

I don’t think those heads, a modest CR 350, and a small cam are going to be the hot ticket.

Bowl blended and using 10.5-11:1, nice solid cam, nice single plane, good carb, decent headers....... they’ll get you into the 450hp range.

I built a 355 like that ages ago, went in a 69 Camaro street car, 10” converter, 4.10’s...... went high 11’s.

[F-BIRD'88]

With either of the heads.. Do not "lightly port" them
This means a minimal port flow increase because you barely touched them.. Get in there and get serious.
Open them up to get port FLOW. The stock heads need to minimal cross sectional area spot OPENED UP. that is deep in the port.
Same on the Sportsman heads . These heads were INTENDED TO BE FULLY PORTED. Great castibgs for that.
Get in there and make em flow..
Ditch the "Nitrous Cam". It is your cork.
Get a cam that lets it in and out sether N/A or on spray.
EG Lunati/UDHarold 401A6Lun #30120516 in on 104.
If hyd use Comp XE284H-10 12-250-3 again in on 104 (move it)

The Vic Jr and Perf RPM will both work great.
(throttle respose) This is mostly a myth.
But once you ditch the "nitrous cam"
For either of these, installed correctly it will have plenty throttle response.
With these you can simply lock out the diz mech advance cureve. Keep the vac adv. Run the locked timing at 35-36 N/A and 27 to 32 on the juice.
Converter should be 3000+++++. More is better on nitrous.. The high stall avoids shocking the connecting rods at low rpm on a big shot.. A race converter is not too much..
It will GLH.

You can make either of these heads work well.
The details of the nitrous kit matter.
What is the jetting and fuel pressure etc..
What was the difference in MPH?

[F-BIRD'88]

On ALL the stock sbc smogger heads like yours you want to block the twined center exhaust port heat riser passages to stop the center exhaust ports from cross talking. Improves the Exhaust scaveging.

I have used old melted down stock pistons to fill these nastey twinned EGR heat risers and just jamming them full of big thick aluminum foil works great too. (Catering grade HD aluminum roasting pans)
Do this after you serious, generous port them.
Get some airflow going on... (178/182cc intake port volume)

[nxtruck]

FBird,
I’m pretty sure the 993 castings don’t have the twin heat riser passages. I have a pair of 993s on the 355 in my shop truck and they did not have the twin passages. I did have a pair of 882s on a 383 in a square body Suburban several years ago that did have the twin heat riser passages and one of them ended up cracking after a few years worth of driving and towing. I’m thinking that the older, heavier-casted smog heads (441, 993, 487, etc.) did not have the twin passages.

[steve cowan]

This is more of a question concerning port size, port velocity, and street rpm throttle response.

I don’t have a lot of experience with these heads, but I seem to remember back when they was the only game in town for an aftermarket head that on a mild 350, these heads were kind of soggy at lower rpms. I also seem to remember that out of the box they really don’t flow well for a 200cc head, maybe around 240 cfm or so. What I’m wondering is, with a little work and very minimal metal removal, if you picked up 30-40 cfm with a barely bigger intake port, would the higher port velocity perk up the low end and part throttle response significantly?

The engine is a very mild daily driver, but built to handle a 250 shot of nitrous. The combination currently is 9.2 compression, lightly ported 993 castings with 1.94/1.60 valves, a comp 218/230@.050 HFT nitrous HP cam on a 113 lsa, bullet proof bottom end, performer rpm intake, 750 DP Holley, 1 3/4” headers and 3” exhaust. The car currently runs 11.80’s-90’s on a 150 shot, but picks up very little on a 200 or 250 shot. He thinks it’s running out of head, but he is worried about the car not driving as nicely during the daily grind

Being a daily driver making the induction tract and cam bigger will obviously change driveabily, everyone has a different interpretation of that.
As said SP 2 can be made to work well but they need more than fluff and buff.
On my set I filled floor and raised roof and kept total cc at 204 .they flow 280 cfm at 700".
The exhaust need a lot of time / effort to get to work .

[travis]

The car is a 1981 Monte Carlo, no idea what it weighs but guessing around 3600 w/driver. TH350 with a Dynamic 10" convertor that flashes around 3800-4000 on the bottle. NX system supposed to be a 50-300 hp shot and a progressive controller. 9" Ford rear currently with 3.50 gears and 26x10.5 ET Streets...he said it is quicker and launches cleaner than the 4.10's he had in it before. The car looks and drives like any tame 13-15 second street car (which it really is off the bottle), it is quiet and barely has any cam sound at all. It's the smoothest launching and driving 11 second car I've ever experienced.
He said he had tried a Holley strip dominator and it is about a tenth quicker, but the RPM drives better in low speed traffic.
I'm guessing it could use more cam too, but we both suspected that the heads are holding it up at this point. The car only picks up .1-.15 going from a 150 shot to a 200, and another about .1 going from 200 to 250. But, the mph is only up about 3mph going from a 150 to the 250 shot. A/f's are low 12's across the stripe, and it runs smoothly start to finish, no cutting out or signs of any issues on the plugs or anything weird. It's clearly launching harder with the bigger shots, just not pulling like we think it should up top.

[PRH]

If you guys feel that putting bigger heads on it is the right path forward.......go for it.
Whatever the outcome....... you’ll learn something.

I have very limited exposure to NOS....... but I can see the bigger heads helping with a bigger shot......... at the expense of the NA performance.
I think the bigger head approach would like more cam as well, while spraying.