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Discussion Starter · #1 ·
I have a question regarding factory small block heads, I am trying to make 400hp out of a 350(2 bolt main) and am wondering if factory open chamber heads will support this based on flow. The is a low buck engine for a street strip car not a daily driver. I have tried to find flow numbers for the open chamber heads and have found some info particularly on the 882s this http://racingfeed.com/downloads/chevy_flow_data.pdf has numbers that include the 882 and my dd dyno program also has some numbers which suggest they will support 400 hp is this believable? I have three sets of open chamber heads, early 882s(1.94/1.5), 993s(1.94/1.5), and 493s(1.94/1.6) and am trying to decide which to use. I know the best answer is to go with vortecs but I already have an intake vortecs seem to go for $400 used and I heard they are limited on lift(machining cost) and I already have the others(all of which would need rebuilt). So my question is will the factory open chamber heads support 400 hp and which ones of the three I have would be the best choice?
 

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Or use Vortecs and flat tops. As cast they are more than capable of 400 hp. For the money you'd spend on all that F-bird recommends you could have three sets of vortecs. That saves a lot of money for the intake of your choice.

Heck for that matter, the amount of money you'd spend modifying older heads to get that much power, you could probably buy a complete 350-hp vortec engine from Ebay.

Vortecs flow over 230 cfm as-cast. Why spend crazy money modifying old-school heads? No offense, but you can buy vortecs, higher-lift springs and retainers, and the intake to go with it for LOTS cheaper than you can make a set of 305 heads flow like that.
 

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F-BIRD'88 said:
I do the 305 head hop up with new valves, springs, seals shims and all machine work nesssessaryfor hi perf use and a quick flow test for $440 (Can) all tax inc. .
Hey, that's cheap. You should charge more for that. That's pretty easily $1000US worth of work and parts. I take back what I said :)
 

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Discussion Starter · #4 ·
I do like the idea of using the 305 heads but I want to go over what I would need to do in a little more depth so I get it done and can accurately price it out in our area. I need to port the heads how extensively the picture you show is great is that it or do the runners need modified is epoxy used? At what lift are you getting 230cfm? Studs need pinned (I can do this) along with deshrouding the valves, machine shop increases the valve size for both valves and does a valve job(three angle?) exhaust valve edge taken off? Is this all the machine shop needs to do assuming the guides are ok? Ill look for that casting this week to see whats available. I will compare the costs with the vortecs the vortec prices Ive seen for stock vortecs is around $400 and require machining for lifts exceeding 470 is this correct?
 

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F-BIRD'88 said:
I do the 305 head hop up with new valves, springs, seals shims and all machine work nesssessaryfor hi perf use and a quick flow test for $440 (Can) all tax inc.
I port them, deshroud the chambers for large valves and modify the rocker studs at home.
I clean and assemble them myself at home after machining.
Done it many times. I have vortec heads Have done more than 1 set of these also. I know how much it costs to buy and get them ready to use.
they do work well. The ported large valve 305 head route is cheaper by far. They work very well also. My ported 305 heads flow more than stock vortec heads do out of the box.
You can do it too.
Note: stock vortec heads flow 228cfm in and 153ex
have flow tested more than 1 set.

What are you using for equipment at your HOME to do this type of work??

We have done quite a few engines using the Vortec heads with a good valve job a 79 degree bowl hawg and cut for 59CC's and have seen 432 horse and 468 on the torque and its only a 355.

On our SBC circle track engines 11:01 Ford flat tappet cam and HP 600 we have seen nubers up to 515 and 488 on the torque.

The 305 head does not have a fast burn chamber or raised intake and exhaust ports.

And if the 305 heads were that good ALL the shops i deal with would be using them. HMMMMMMMMMMMM

I really doubt you have the proper equipment at home for doing seat and guide work and cutting the decks. Maybe a die grinder at best!!!
 

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Discussion Starter · #6 ·
What Vortec head is the one to have are there differences, what is a decent price for the vortecs. What needs to be done to them to run .500 lift are the stock rockers sufficient for 400 hp is the stock valve size sufficient? I guess in short I am asking what would need to be done to them to support 400 hp in a 355 pump gas engine?
 

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They'll do it in stock form. They're good for about .470" lift as-is, but its tough to find aftermarket cams under .470" and its tougher to make 400 hp with a .470" cam.

The good news is, if you're using an aftermarket cam you'll probably be needing upgraded springs anyway. There is a VERY common package available from multiple sources that allows for .550" lift without any machine work.

Flat top pistons should give you between 10 and 10.5:1 depending on your valve reliefs and compression height. That's fine for pump gas with the fast burning vortec chambers. A cam that is about 224/234 on a 110 LSA should put you squarely at 400+ hp at about 5500 rpm and 450-ish tq at 3500 rpm. Small tube headers, air gap intake, 600 cfm carb, and that will be one heck of a runner.
 

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Oh.. forgot the other question...

Pretty much any casting is as good as the next. Some say that the "hecho in Mexico" heads aren't as good, but I've yet to see definitive proof of that. One of the reasons vortecs flow so well is an extra 30-degree back cut at the valves and other rumors are floating around that the 906 casting lacks that back cut. Others report that they simply have different exhaust valve seats that aren't cut the same and they hurt flow. I have two sets of 906s that have the extra back cut, but they have both been rebuilt so who knows how they were originally configured. At any rate, they all flow better than any old-style heads and they're only different by a few cfm. For a 400-hp engine, any will do just fine.

Some good tech here: http://www.chevymania.com/tech/vortec.htm
 

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curtis73 said:
Hey, that's cheap. You should charge more for that. That's pretty easily $1000US worth of work and parts. I take back what I said :)
Talk and pretty pictures are cheap. So is some people's labor. It's the price of finding out that one guy's great deal is someone else's reality check that is priceless.. Anybody doing THAT much work to a set of highly shrouded, small port heads and claiming THAT much power out of them lives in a very optimistic world. As was stated by one who should know, if those heads were capable of that kind of modification with reasonable expense (for the machinist as well as the end user), there would be a lot more performance shops turning them out like hotcakes.

But they aren't........


:rolleyes:

tom
 

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machine shop tom said:
Talk and pretty pictures are cheap. So is some people's labor. It's the price of finding out that one guy's great deal is someone else's reality check that is priceless.. Anybody doing THAT much work to a set of highly shrouded, small port heads and claiming THAT much power out of them lives in a very optimistic world. As was stated by one who should know, if those heads were capable of that kind of modification with reasonable expense (for the machinist as well as the end user), there would be a lot more performance shops turning them out like hotcakes.

But they aren't........


:rolleyes:

tom
Tom

I see you read right through this guy at least I try to post factual info here and not try to mislead every body,
 

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F-BIRD'88 said:
I do the 305 head hop up with new valves, springs, seals shims and all machine work nesssessaryfor hi perf use and a quick flow test for $440 (Can) all tax inc.
I port them, deshroud the chambers for large valves and modify the rocker studs at home.
I clean and assemble them myself at home after machining.
Done it many times. I have vortec heads Have done more than 1 set of these also. I know how much it costs to buy and get them ready to use.
they do work well. The ported large valve 305 head route is cheaper by far. They work very well also. My ported 305 heads flow more than stock vortec heads do out of the box.
You can do it too.
Note: stock vortec heads flow 228cfm in and 153ex
have flow tested more than 1 set.
F-BIRD'88

If your going to blow smoke up my ***** you better build a bigger fire then that. LOL
 

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Seems to me that taking a stock pair of Vortecs and adding the beehive springs will give you the lift capacity you want at a fraction of the price of porting out 305 heads. 400 HP easy. If manifold is a concern, pick up some used Dart SS heads.
 

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The only time you should use a stock type 305 head is if class rules require them. There are some 305 classes out there, and if that's what was required, that is what I would run.

I've done a bunch of these things, and to make them decent heads takes an incredible amount of work. A set of stock vortec heads will blow them away.

Hand porting old iron heads is not something you want to do for a living if you want to live very long. It's too easy to get good stuff, out of the box. Been there, done that, bought the T-shirt, gave it away.


Nairb
 

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I have a question regarding factory small block heads, I am trying to make 400hp out of a 350(2 bolt main) and am wondering if factory open chamber heads will support this based on flow. The is a low buck engine for a street strip car not a daily driver. I have tried to find flow numbers for the open chamber heads and have found some info particularly on the 882s this http://racingfeed.com/downloads/chevy_flow_data.pdf has numbers that include the 882 and my dd dyno program also has some numbers which suggest they will support 400 hp is this believable? I have three sets of open chamber heads, early 882s(1.94/1.5), 993s(1.94/1.5), and 493s(1.94/1.6) and am trying to decide which to use. I know the best answer is to go with vortecs but I already have an intake vortecs seem to go for $400 used and I heard they are limited on lift(machining cost) and I already have the others(all of which would need rebuilt). So my question is will the factory open chamber heads support 400 hp and which ones of the three I have would be the best choice?
You could get close to 400 ponies with a good set of open chamber heads. The early, big port heads like the 441's or 487 heads flow enough air, but their big, slow burning combustion chamber will lose 20 ponies over a good compact chamber like the early double hump heads had. A good set of early double hump heads would be better, but they are getting scarce and usually need too much work to justify using them. With matching components, enough cam, and compression ratio, I would think 375 horsepower on 441s or 487s would be very doable.
 

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Discussion Starter · #15 ·
Ive done a bit more research on the open chamber heads originally my flow data came from dd dyno and I believed it was supported by a car craft article where the numbers were nearly the same(same source?) Ive read the Lingerfelter book where he stated the 993 heads flow better then the 882s I read the Vizard book on head porting he supplied actual flow data on the stock 993s using Vizard numbers with my pump gas combo the best HP I get through dd dyno is 335, I believe the Car Craft data is flawed or they tested a really good stock 882 head. With Vizards porting the 993 flow is dramatically increased and according to dd dyno will support 400 hp. After reading the book I dont believe he likes the open chamber heads.. So combined with some of the feedback the open chamber heads are going back on the shelf. My choices now are either going to be the vortecs or the 305 head. Comparing the two with machining cost in my area I cannot do the 305 heads for $450 it would be more like $650+ so even with the purchase of a vortec manifold the costs would be close and I would not have to spend all the time porting. I think the vortecs are the way to go for me. If anyone has a good set of vortecs they want to sell pm me. Thank to all for the info the search begins :) .
 

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Discussion Starter · #16 ·
I think the costing is going to depend on what I can get a set of Vortecs for and yes the machining cost I agree the beehives are nice but expensive. I do like the idea of the 305 heads but I have to consider time a bit also since the track opens up April first and I need to have this engine done to test out the car a bit. We built a 406 with the iron eagle platinum 230cc heads forged everything 600hp engine but I want to be sure everythinkg on the car is functioning properly prior to using it.
 

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KGRIFF said:
I think the costing is going to depend on what I can get a set of Vortecs for .
Ebay. I got some for $300, stock rebuilt - and I got some for just over $400 pocket ported with Manley SS valves already modded for .550" lift. Bargain if you ask me.
 

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Hey! Try to stay in your shoes there F-bird. You can find somebody parting out trucks all the time and get vortecs for 200 bucks a pair and then add the beehives. Can YOU add THAT up?! You have had two respected engine builders check in and say YOUR solution is not the way to go for most people. It worked for you, great! I am sure everybody on the board would love to see actual flow bench results of your 305 heads instead of you merely SAYING that they flow more. Prove it, son.
 

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F-BIRD'88 said:
Just remember. The time it takes to properly port your own heads at home is just time you would have wasted typing on the internet anyways. If you had the money for new aftermarket heads you would not be asking how you can achieve your goals using a stock head.
You can hit the flow nesssessary for 400BHP using the open chamber heads. But the chamber is too big. What will break the bank is haveing to mill the heads down to get compression. Thats why you want to start with a #416 casting. It will cost you less all said and done.
The port flow will be the same with either head.

others will sit and tell you you cannot do this and that and ..... But what do they offer?
I do these heads. I port other heads too. I don't do this for a living. I won't do your heads for you, but I can tell you how its done. I don't bull**** you. I don;t need to brag and try to impress you.
We get this and wee get that with this yada yada yada. Who is "We"? We is someone else.

I've shown other people how to do this. They got the results they were looking for. And for less $$$ than the speed shops.
Once had a friendly contest with a Speed Shop owner. He ported and flowed his Camel back heads (041) with 2.02's. Did it his way. Then he flowed my 305 heads with 1.94" valves. Back to back.
My heads flowed more air. Even after checking to find the "leak in the flow bench" LOL . Then he later copied what I did in other 305 heads. Same result.
I really think your blowing smoke again.

PLEASE STEP AWAY FROM THE BOOKS AND MAGAZINES.
 
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