How much power can you make with a set of fully ported stage1 se heads?

Im going to be doing a 494 aluminium rod stroker engine.I have a set of fully ported stage1 se heads.I was wondering how much power it would be capable of making.

 

Do you have the flow numbers?
What will the compression ratio be?
What intake manifold will you be using?

Paul

 

The heads flow 374 intake at 600. lift and 238.9 at 600. lift.They do have2.260 and 1.755 valves.The comperssion will be around 13 to 1.Im going to use a ported sp1 intake.

 

Enough power to blow a girdled factory 455 block into junk.....

 

Nice.One of the reasons im running aluminum rods is less stress on everthing.Im going to keep the rpm down also.

 

....let me guess...you're going to talk him into running a 350?? Until some of you 350 guys have some of these motors actually in cars, making 700 to 800 horses...we won't know how they will hold up either.

My uneducated guess would be around 750-800 range. Just a guess though. Those are some pretty good intake flow #'s

 

with a big cam and carb around 700-740

 

Jay what cam? Custom?

 

The intake flow is really good but this would be a lot easier if the exhaust flow was closer to 250 cfm or more. That's where the Stage 2 heads come into play.
The cam will have to focus on the exhaust with a 10 degree spread AND more lift than the intake.
I'm thinking something along the lines of the TA 408S
To get the peak horsepower the engine will have to run past 6500 rpm.
If you run a vacuum pump or a dry sump system with a multi stage pump that will pull a vacuum, you could gain some extra power.

So I'm with Standup 69 (Post#7) where he posted 700 - 740 depending on the rpm you are willing to run this to.

Paul

 

Wow alot of responses and info.I have a 308s cam but if something will work better i have no problem getting it.I want to keep the rpm around 6500.I have a set of stage2te heads but i want to use the stage1se just to see how much power i can get out of them.I would be happy to make 700 to 750.Thanks.

 

Jay

If you look at the head flow, the exhaust is only 64% of the intake flow.
On the Stage 1 heads it is better to have closer to 70% or in this case between 250 and 260 cfm on the exhaust.
But the name of this game is to see how much power this particular set of heads can make as is. Right?
So if you are trying to maximize power using this head, the exhaust is going to need a lot of help.

The 308 cam only has a 6 degree spread between intake and exhaust duration and it has less exhaust lift than intake lift
which doen't help the situation.

The 408 has a 14 degree spread and it has more lift on the exhaust than the intake which is what is needed.
The only problem is, if the intake manifold is ported to match the intake flow and the right size carburator is used,
the peak horsepower should be above 6500. But you won't know until you try it.

Paul

 

Jay I may have the cam for you I will look at the spec today. I had it done for a customer and he went with a hyd, I will bring it tomorrow.

 

Thanks for the info Paul.

---------- Post added at 06:47 PM ---------- Previous post was at 06:45 PM ----------

Thanks Engie.

 

Jay

374 cfm on the intake seems a lot for a Stage 1 SE head. Some of the best raised port heads are around that flow.
Forgive me for asking, just doing a double check. Are you positive that is the correct figure for your heads?
Can you give some background info on these heads?
Thanks

Paul

 

Thats what i thought also.I bought the heads off a friend and fellow board member that has a bunch of hi performance parts.He had TA do the heads.It took TA a really long time to get them done so long infact that my friend used another set of heads.Mike from TA called my friend and said he had them done and at the time they flowed more then any other set of stage1 heads that hes done.So my friend paid for them and put them on the shelf.I bought all my 494 parts off him and the heads.He said each port was flow tested.Some people say that TA flow numbers are not true but i figuerd that i will take a chance and see what happens.I also have another engine that has stage1se heads and a 608 hyd cam 38 over with 13to1 that went 9.82 in a 3100 pound regal.

 

This isn't relative to the OP, but I just have to ask now that I see this here.
When you refer to the spread, 6 or 14 degrees, what exactly is this and how does it affect things?
I'm always trying to learn.

 

Jon
There are 2 parts to the exhaust cycle. First is the time from when the exhaust valve opens to BDC during the power stroke.
The second is as the piston moves from BDC towards TDC pushing out the exhaust.
(I'm leaving out scavenging from the exhaust system)

When the exhaust valve first opens, the exhaust under high pressure blows out into the exhaust manifold or header pipe as the piston moves down at the end of the power stroke.
As the piston moves upward, any pressure left in the cylinder works against the piston and becomes a power loss.
At low rpm, no problem but as the rpm increases there is less time to get rid of the pressure before BDC.
Opening the exhaust valve earlier will give more time to evacuate the exhaust at higher rpm and obviously how well the exhaust port flows is one of the other factors in high rpm exhaust evacuation.

This next part is a generalization that Im going to use to discuss the relationship between duration and port flow in order to help me answer your question.
At sea level for a N/A engine, if the exhaust port flows near 80% of the intake port, the exhaust valve duration and lift can be the same as the intake duration and lift to maximize the high rpm performance of the combination.
As the exhaust flow percentage decreases from that point, the exhaust valve duration needs to increase over the intake duration to compensate.
So now there is a difference or Spread between the exhaust and intake durations. The same can be done with valve lift as long as the port flow increases with the higher lift.

So as the difference between intake port flow and exhaust port flow increases for various heads, you must compensate with increased exhaust duration or lift or both if you want to focus on high rpm performance.
If you only care about low end and midrange power then it is not important if there is a Spread in duration.

As you go higher in elevation there is less exhaust to evacuate so the spread can be less.
When a power adder is used there is more exhaust to evacuate, so more help is needed on the exhaust side.

Again this is a simplification in order to give a short answer. There are volumes written on the subject.

I hope this was helpful.
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Paul

 

do you know what the .400 lift flow number is? this with also be a big factor in power output on a 494

 

Awesome!
thanks Paul, that helps clear up the discussion and makes sense to me. Now I just have to convince this 49 year old mind to store that info. ou:

Jon

 

True.
Back in Feb 2006 I posted my ST1 SE head flow numbers as recieved from TA Perf and met some abrasive opposition.
We again flowed the heads locally and verifyed very similar numbers at 0.600" lift.

Combustion Chambers at 69 cc's
Intake At 263cc's
Exhaust at 179cc's

Closed 145# @ 1.850
Open 340# @ 1.250
Coil bind @ 1.070
Seal to retainer 0.850

Valve Intake Exhaust
0.050 38.70 30.10
0.100 50.20 57.20
0.200 149.40 121.90
0.300 213.60 167.50
0.400 276.00 196.80
0.450 303.00 212.60
0.500 329.50 226.10
0.550 349.30 233.70
0.575 356.50 236.20
0.600 361.60 237.50