I have a 350 chevy with a solid bottom end, flat-top pistons, comp cams with 236 int 244 exh duration @ 0.05" and 0.490" int and 0.485" exh lift 108 degree LSA.  Also, a performer RPM intake and 700 cfm double pumper are being run with 1 5/8" headers.  I have the old style camel hump heads (2.02/1.60) right now but was pondering a set of aluminum AFR's.  This cam makes power to 6500 rpm and is in a street car.  Worth the money or not?  How much will HP increase?

Thanks

Casey

IMO, the biggest question is regarding your existing heads.  Are the intake valves 2.02" or 1.94"?  Camel hump heads were offered in both configurations. 

Based on your pistons and cam, if they're 2.02s I think you'll experience a negligible difference with the aftermarket heads.  If they're 1.94s, the aftermarket heads may be worth the expense if your budget allows.  Either way, if you operate below 5,000rpm - I don't think you'd notice a bit of difference.

* Certainly today's aftermarket heads are superior to the old-style 2.02 camel hump heads.  But the fact is that those heads were pretty darn good from the factory.  

A couple of other questions should be asked first:

1) what type of use do you intend your car for, is it to be street, strip or a combination of the two?  Aluminum heads are nicel for getting rid of unwanted heat and helping your combination to run cooler.  Couple this with the improved flow and performance is the first benefit.

2) Define worth the money?  sounds stupid but everyone has different ideas of what is too much money. 

On a stock rod 350 with flat top pistons you are not realistically pushing enough compression to require better than premium pump gas. Another option would be a set of Pro Action iron lightning heads. we run them on our street/strip 67 chevelle (383 stroker, 10.5:1 true, 0.613 lift solid roller) and have actually found them to be just slightly more than we need on motor alone.  Add the nitrous oxide and it's a different story though. 

As to power gains any head that breathes better and helps you get rid of combustion chamber heat will add horsepower.  Rellistically your benefit will depend on the tune up after the head swap.  Also be aware that too big an intake runner will kill your intake charge velocity and hurt power.  That's why our gains are best on the spray. 

Dude, by editing your original post with add'l info after myself and others have replied causes confusion.

Anyways... your present set-up you won't see measurable gains with the aftermarket heads you refer to.  Consider spending some $$ to have the double-hump 2.02 heads (w/ 64cc chambers) cleaned up a little.  IMO, there are few things cooler than a small-block sporting good flowing OEM heads painted Chevy orange.

* If you were packing more compression or had a wilder bumpstick, you might be better off with aftermarket heads.  Just one man's opinion.

Would a good set of valve springs help high rpm operation?  Also, I am running a 3.23 posi.  Would it be adviseable regearing to a 3.90 or 4.10 ratio?

Thanks

well i would of that thought that you would of had a good set of valve springs on the engine already!

if your factory heads are unported you are giving up quite a bit, but i believe that ported those heads arent very bad, but if you want to turn this thing into more of a drag car the aftermarket heads will give more power at the top end

of course this is a completely different engine but CHP's Impersonator II was really a eye-opener for me and kinda works into what might happen with aftermarket heads on your motor. Un-ported vortec castings were used on a mild cammed 406 SBC and in the second installment AFR 180 cc heads were bolted on. The AFR heads gave up torque all the way to 4000 RPM's of course they showed gains of almost 70 HP on the very top end but it made much more of a top end orientated engine, it moved peak torque from 3500 to 4200 and peak HP from 5000 to 5500, and it made me think that if the car it was in was set up to be a street car with a low RPM converter and tall gears (of course it would go a lot faster with lower gears and more stall but thats not how street cars are setup!) actually how much faster it would go with the addition of AFR heads and especially for their horrible price

And this was the smallest cylinder head in their lineup! and it was on a big engine like a 406! the larger heads also required 1.6 rockers to show larger gains, thus in a street accelerating valve guide wear and lowering mileage. to look at trends a AFR head will show even more pronounced lower RPM losses on a 350 than a 406 and it showed some 22+ ft lbs losses at many RPM points, so hopefully armed with some more information you can make a choice

Are you sure the lift figures you gave on your cam are right? You had a lot of duration bet not a lot of lift?Aluminum from what I have read does not make any more power then cast iron that has the same chambers ,runners ,and so on CHP did dyno test some time ago.It does not make sense  but that was the reasults.  

everything else being perfectly equal a iron head makes less HP than a aluminum head because it holds in more heat and thus uses more heat on the power stroke, but not many aftermarket companies make high perf iron heads because big time drag racers are looking to get the weight off of their front end thinking that, that will offset the lose of heat plus more and get them quicker times

i agree, the cam seemed very soft!

The cam is a circle track cam.  The whole motor is set up for a dirt track street stock minus the 4 barrel intake system and headers.  It was a freebie from a friend that owed me some $$$.  All I know is that it pulls real hard after 4k and I thought some better heads might help it on the top end.  

Some dirt classes only allow a 2 barrel and manifolds.If he was serious he should have a 500 cfm carb on it .This could be a restriction.I am not saying to put a 800 cfm double pumper on it.It should have the old style ram horn manifolds on it. allthough they are the best stock manifolds they may be a restriction an higher rpm.I am sure the article showed reasults that the iron heads and aluminum had no more then 5 h.p difference.I know the discipation of heat would favor the aluminum and I was shocked at the reasults but it was done at CHP>What heads are on it now? The valve springs may be shot they may be replaced often when run at the track.Ever seen the amount of time they are run between 3500 and like 6500 rpm? I give much credit to the bottom end on thoes engines.  

There's Camel Humps and there's Camel Humps, some are better than others, so what's the casting or part number?

At a theoretical level it's considered that cast iron heads will produce more power than aluminum heads because the cast iron transferrs heat slower, therefore, the belief is that more heat stays in the cylinder longer and pushes harded on the piston because more heat yields more hot gas expansion. This like all other engineering things must be balanced with a number of other constraints.

These days one of the biggest constraints is 92/93 octane fuel and its relationship to thermodynamics in the engine. What we see when combustion chamber design and fuel octane and other factors are held constant is that aluminum allows the use of more compression before detonation is encountered. Under these conditions, which are pretty real life, it turns out that the additional point of compression that aluminum allows, because of its faster heat transfer, is worth more power than the higher retained heat of a cast iron head that has to run a point of compression lower to keep the excess heat, resulting from its slower heat transfer, from causing detionation.

Contemporary porting and combustion chamber design such as that found in the GMPP Fastburn and similar aftermarket heads is worth 30-40 horsepower out of the box compared to older head designs of the 70's, 80's and the 90's Swirl Ports that have not been ported. Against a stock Camel Hump the gain is probably more like 15 to 20 ponies or less. While many of these aluminum heads show a worthwhile top end gain, it usually comes at the expense of mid range torque; so your gearing and where this engine "cruises" will be important considerations, as you don't want cruise rpms to be under the fat part of the torque curve.

Aluminum will also reduce front end weight by 50 pounds, this does help handling, weight transfer and distribution, and power to weight ratio. But overall aluminum heads will probably be more like gains from fine tuning rather than gross gains from major competition parts since where your starting from is already pretty good.

Bogie

Maybe I should just go with a roller cam set-up and trash the current cam.

I still think you should try new springs .Unless they were just changed I bet it does not take that many races at that constant rpm to kill em.Springs would not be a huge investment but you do need aftermarkets.Edelbrok makes some called sure seat.You need to check the lift of the cam to what the spring is made for. Just go with a little over too much preasure will wipe the cam out.Ask the racer what rpm they run it at.Or are you not on good terms with him.I think something small has ben over looked.Was the cam installed advanced or stright up?We need a little more info.  

Sorry i got it mixed up .Pulls hard AFTER 4 grand. I think the lift figures may not be maxing out the flow limits of the heads yet.Are you sure the bottom end will take 6500 which is where I think u r talking.You could change the gears to keep it in its powerband.323s dont soumd right with the duration figures of the cam.  

Hey man, I was wondering... what ratio rockers are you running?? with that cam and your rear end gear ratio ur running now...the aluminum head swap will not help much. I would port and do some bowl work unshroud the area around the valves in the double hump heads, especially if you have 2.02/ 1.60 valves(dont forget to polish the exhaust ports also)mabe if u run 1.5 ratio rockers, switch to 1.6 (and screw-in studs) then mabe a 3.73 gear which is a great street / strip gear. And you still have a couple nichols to jingle for entry fees. You can get a lot of power out of oem heads if you massage them just right. I built a 406 with O E heads and got great results. decked the block, left the flat tops 5 thousands in the hole, used a lunati cam (300 advertised duration and 515 lift) 1.5 roller rockers,750 holley dble pumper, holley street dominator intake and a lot of hand work on the heads. My 1970 short bed pick-up ran the 1/8 mile 8.0's with mickey thompsons, 3.73 gear, and a 3000 rpm stall.

Good luck.......