[Mike H]

It will run a mid 12 with about 250 HP nitrous plate on it. I can't say how many times with cast pistons but it will do it a few times at least.

[cool rockin daddy]

Daaaaannnnnggggggg! How many times are you gonna ask us about this. You have been told time and time that your present heads suck. You can keep asking about them but they still suck. Get some Vortecs. Get some Edelbrock Performers. Get some Dart Iron Eagles. Hell, get some World S/R heads. Anything would be better than what you have. Quit beating this dead horse.

[oldbogie]

Originally Posted by jkingof9561

the pistons are the silv-o-lite flat tops (h3437) approximately 10.3:1 cr with 64 cc and a 4.000 bore...and mine has a 4.040 bore...

and the engine still not build...still thinking on what heads to put on...right now i have the (462624) heads and 2 sets of 305 heads...(081) and (601)...but am not going to be using the 305 heads cause of the cr being to high...am still looking to buy some stock gm 64cc chambers...or some better ones than the (462624)...any recomendations...??? i know vortec heads are good but dont have that special intake...maybe for my next build i will be using vortecs...but for now i just want the car to be running and want some heads that will be able to move the car good enough to hit low 13 to high 12's...

Yeah but you don't have 64 cc chambers youve got at least 12 more ccs.

Everybody will recommend Vortecs and I might add everybody thinks of the 060 Vortec when they say that which are good but won't handle you cam's lift without modifications to the upper valve guides and probably won't have springs that are compatible with your cam and on top of that won't accept your current springs without modification to the pockets. But GM has come out with super Vortecs, and while you can spend money and get or have made 060 Vortecs with the requisite modifications the cost is mighty close to just picking up a pair of better heads. These being GMPP part numbers 25534421 and 25534431. These are Vortec style heads with heavier casting thicknesses and 2.02 and 1.55 inch valves, they accept higher lifts without modification and feature a 180 cc intake for the 421 and 206 cc intake for the 431. These are complete ready to run heads, they are also available under a different P/N as machined but bare, given you already have valves, springs, locks and retainers this might be the way to go. These two heads will accept Vortec or conventional intake bolt patterns, though when they say "conventional" they mean those with the newer 70 degree angle center 4 bolts rather than the old 90 degree angle.

An aluminum version called the Fast Burn P/N 12464298 is available from GMPP with a 62cc chamber 2 inch intake, 1.55 exhaust, 210cc intake port and a 78cc exhaust port, in case anybody wants to lighten up with a big cammed 350 or a bigger inched small block like a 383-400-406. there are two versions of this head 2003 to present and an older version. The older version is considered good for a 15 HP boost when replacing the L-98 head and the 2003-up head is considered for about a 30 hp boost against the L-98. I mention that just as a yard stick for comparison. The Fast Burn aluminum head and the cast iron Vortec are comparable for power changes against the L98. Against older smog heads add about 10 more horsepower.

There are also many comparable aftermarket heads that will accept your current intake and offer other options like chamber volume, and sparkplug location and angle; so check out your favorite hot rod catalog.

Keep in mind that as ports and valves get bigger, bottom thru mid RPM torque diminishes while torque and horsepower goes up both in the RPM range and in amount.

I think you've got yourself a pretty good engine there, it just needs some tweaking to dial it in.

Bogie

[F-BIRD'88]

Use the "081" 305 heads. They are the best of what you have got. They will need larger 1.94x 1.60" valves and FULL PORTING to achieve the power levels necessary for a high 12 et.
You cr will not be excessive cause once your 081 heads are properly modified the chamber volume will be larger than now.

The 10.3:1 spec for those pistons is based on a "0 decked" block.
Unless a lot has been shaved off the block decks, those pistons will set well block the block decks at TDC resulting in less cr than 10.30:1 (64cc head.)
drill and roll pin the rocker studs and shorten the valve guide tops for aftermarket valve seals (.200" shorter)

If you do the full work up on these 081 heads, you will get the performance you're after. Your cr will be just right when you're all done.

It is not cost effective to pay some one else to do the hand porting required.
Do it yourself, then have your machinist finish with the required machining for the larger valves, seals etc.
This is what you're after.
Use the 624 heads for practice to gain hand control of the porting die grinder. Grind them to your hearts content. Then do the 081 heads.

[jkingof9561]

Originally Posted by F-BIRD'88

If you do the full work up on these 081 heads, you will get the performance you're after. Your cr will be just right when you're all done.

It is not cost effective to pay some one else to do the hand porting required.
Do it yourself, then have your machinist finish with the required machining for the larger valves, seals etc.
This is what you're after.
Use the 624 heads for practice to gain hand control of the porting die grinder. Grind them to your hearts content. Then do the 081 heads.

and what do i do or how do i do it...??? i take off all the valves and then get the grinder and just grind the inside of the hole were the valve goes...???and when do i know that its been fully worked on or what...???i would like to try it by myself...just need a little help plz...

[SSedan64]

Sounds like you better buy a head porting video and a porting kit. It's not as simple as just start grinding. You have to be careful and know a little about what you're doing.

[jkingof9561]

am thinking just to buy some aftermarket heads...anyone know how much are the cheapest aftermarket cast iron cylinder head...???i will search in ebay though...

[Blazin72]

Originally Posted by jkingof9561

am thinking just to buy some aftermarket heads...anyone know how much are the cheapest aftermarket cast iron cylinder head...???

It's a little web site called www.summitracing.com or www.jegs.com

[F-BIRD'88]

Originally Posted by jkingof9561

and what do i do or how do i do it...??? i take off all the valves and then get the grinder and just grind the inside of the hole were the valve goes...???and when do i know that its been fully worked on or what...???i would like to try it by myself...just need a little help plz...

The basics

More info

still more

and

More specific to 305 heads

[oldbogie]

Originally Posted by jkingof9561

am thinking just to buy some aftermarket heads...anyone know how much are the cheapest aftermarket cast iron cylinder head...???i will search in ebay though...

Ya know life just isn't fair, when I was in high school and dinosaurs ruled the earth, you leaned about poting by starting with an electric drill with a rotary bit and began carving on a set of heads (OK actually with the block on flat heads). Some worked, some didn't and you leaned which was which from your paper route money.

Now a lot of thoughtful guys have written books with words, pictures and graphs on the subject, so you can skip the leaning what does or doesn't work phase and get to the results.

One of these guys is David Vizard, he has a ton of books out there both as engineering texts and in popular print the latter being a lot cheaper and whole lot easier to understand. Here's a URL to speed you on you way; http://www.bestwebbuys.com/How_to_Bu...?isrc=b-search

So far as tools go I personally recommend the hobbyist engine builder buy an electric die grinder. Most books and contributors recommend an inexpensive air driven die grinder, the problem with air driven die grinders is that they need to be connected to a pretty good compressor for best results which will be expensive. Something a lot more capable than a Craftsman 5 horsepower oil-less compressor and that starts talking some serious money.

But the problem with older heads versus the Vortec style head is more about subtle shape changes of the combustion chamber than about port flow. A tight chamber provides several benefits

- Better control of the incoming mixture flow. It develops a strong swirl around and down the cylinder that does a better job of mixing the fuel and air together for a better more efficient burn while also providing a better (more dense) filling of the cylinder. Open chamber heads as a comparison are lazy, the mixture rapidly expands upon passing the valve, stalling its speed which reduces mixing of fuel and air while the loss of momentum results in a less dense charge filling the cylinder.

- The spark plug of a Vortec style combustion chamber is moved toward the center of the chamber, this reduces the burn time since the distance to the extreme edges is close to the same in all directions. This allows less spark lead to be used which allows a smoother pressure and temperature increase to maximum values which reduces the tendency to detonate and decreases the formation of NOx. It also reduces forces on the piston that want to drive it backwards against normal direction which frees up a bit of power.

- The close proximity of the combustion chamber wall from the spark plug past the exhaust valve (for the SBC's heads) redirects the exhaust passing the valve on that side in such a way that the flow stays more attached to the short side turn such that it doesn't interfere with the major flow entering from the inner portions of the valve. This feature is not required on the new LS series engines because the valves are stood up which improves exhaust short side flow without having to play games with combustion chamber shapes. But you can't achieve this configuration on an SBC and have it be effective.

- The beak that protrudes between the intake and exhaust valves helps keep the two functions separated during cam overlap. It helps keep exhaust from creeping into the intake and redirects early intake flow away from the still open exhaust.

--- These are features that the open chamber smog heads don't have and can't be duplicated on them. The old heads that predate the smoggers have a touch of these features by being a tighter shape to the valves and have the plug located closer the the cylinder centerline in a semi-quench pad on that side of the chamber. The L98 head is the start of a return to these features but is lacking in details of plug location and plug side quench plus no beak, so these are a compromise like the much older heads but are a lot better than the open chamber smoggers.

The Vortec head also raises the intake port giving the mixture flow a straighter shot at the valve, this improves mid thru top end power quite a bit but does reduce power below 2500 RPM a small amount 2-3 lb ft and HP typically. The relocated port dictates a unique intake manifold, it so happens they also changed the bolt pattern, but a conventional intake won't seal the ports even if it could bolt up.

While the Vortec head is known to develop often considerable more peak power than previous heads, perhaps more importantly that power doesn't flop over past the point of peak out put, while is does begin to diminish, the Vortec carries its power output at a high level for another 500-600 RPM before flopping.

Bogie

[jkingof9561]

well for me getting the vortec heads isnt a problem...theres too many junkyards locally and some of the owners know my dad pretty well...but i just need to get money to buy that special intake for the heads...but i just need to wait untill they're finish working with the block and pistons,i am building 2 engines at the same time...and i already have all of the parts for the other engine so am going to leave this one last so i can finish one first then start looking for the heads and intake...

[jkingof9561]

which heads will be better... (3947041) or this ones...(3917291)...???

[Holder350]

Heres the info that I have on theses 2 castings.......


"041" – 3947041, also 3947041X. A good performance head. They were found on 1969-1970 302 and 350 engines. They had either 1.94/1.50" or 2.02/1.60" valves, 64CC combustion chambers, DO have accessory holes, I don't have port volume data for the regular 041, the 041X intake port should be 165CC's, the 041X exhaust port should be 65CC's. These heads have a single somewhat triangular shaped casting mark (slope on the upper left).


"291" – Could be 3912291, or 3917291. This is another good performance casting. They were found on 1967-1968 302, 327, or 350 engines. They could have either 1.94/1.50" or 2.02/1.60" valves, 64CC combustion chambers, DO NOT have accessory holes, intake port volume should be 161CC's, exhaust port volume should be 65CC's. These heads have double hump casting marks.


IMOH I would go with the 041 heads......just for the fact that they have the acc holes.

Other than that.....go with the big valves...if neither have the big valves then see about getting them machined for them.

[jkingof9561]

are these heads any good...??? (14102183) or i dont know it might be 193 the last 3 numbers...all i know they are 1.94/1.5 valves...

any information about them...???and specs...???flow numbers ect...???

[Mustangsaly]

Originally Posted by jkingof9561

are these heads any good...??? (14102183) or i dont know it might be 193 the last 3 numbers...all i know they are 1.94/1.5 valves...

any information about them...???and specs...???flow numbers ect...???

www.mortec.com