Stage 2 heads on production block

[Nick Micale]

Some would have to a back to back comparison between heads on a stock block. But based on tuning my friends car running mid 9s@15 psi boost with a 274 motor, I don't think you can do that with production style heads or can you? His injector duty cycle is double mine with same injectors and turbo and same boost can someone explain that?

The flaw in your data here is the OP is wanting to do this on a production 3.8 block, NOT a big bore 274 cu.in. block. Also, no other info on turbo, conditions, build and other items are not given, so what is to explain?

Bison already stated runner volume is going to kill port velocity which means at normal RPM it most likely will not be very responsive.

Another big issue is the small bore may not clear the open valves, and even if the block is chamfered for clearance, the mixture flow will be greatly disturbed and screw up the combustion process.

Like Ken said, this is a waste of time, effort, parts and $$$$ to do this, so what we have here is an "internet fantasy" discussion with no real chance of it ever being done!

 

[norbs]

What if you used a non stage 4.1 engine to do the test?

 

[forzfed]

Some would have to a back to back comparison between heads on a stock block. But based on tuning my friends car running mid 9s@15 psi boost with a 274 motor, I don't think you can do that with production style heads or can you? His injector duty cycle is double mine with same injectors and turbo and same boost can someone explain that?

My buddy ran 9.7@145mph with his Stage II, full weight GN and 15psi on a old T-76. What turbo is your buddy using?

 

[norbs]

gt4202 which is about 75mm with a t4 1.28 AR His stage 2 heads use 2.19 , 1.7 exh valve

 

[Paul Lohr]

Thanks everyone for helping me with my questions about 3800 series II heads on a production 3.8 block.

norbs, yes this could be tested on a production 4.1 block. For purposes of increasing low end torque, it makes sense to use a larger bore. As far as the valves possibly contacting the bore of the production 3.8 block...I think the bore sizes of the 3800 and 3.8 production block are the same, correct? I am probably missing something here. Thank you for helping with this, norbs.

 

[forzfed]

What Norbs meant was, depending on the size of valve in the Stage II head you might hit the bore on the 3.8. Like he mentioned above his friends intake valve was a 2.19. That is a good bit bigger than stock. I believe his exhaust valve is the size of a stock intake valve.

 

[norbs]

If you could get a junkyard 4.1 and keep the boost down and slap on some stage 2 heads for a cheap price , you could create a monster for low buck!

 

[Mike Licht]

It is no "internet fantasy" or fairy tale. I did it and the motor is done. In my case it was very cost effective too. I bought a set of cast iron small valve stage two heads and put them on a 109 stroker shortblock with a solid roller cam. It was esy for me to convert a 4 BBL intake to EFI and I had a set of stage 2 twin headers which can also be built very inexpensly if you wish to DYI. I have less that $1k in the completely done heads with rockers and valve covers. The is not after market head that can compete with that. This project is not for everyone, you must be will to make lots of things, it is not a "bolt on" deal by any means. I jusl love to do things a little different but that is how we learn. Shane has the motor and the car it was going in now he bought it before I could put it together. The car was Travis Beckendorff's old Spooky 1 car. To be honest I am very sorry I sold it all, it would have been fun to finish and run for a while.
Mike

 

[norbs]

So your saying the valves did not hit the piston bore? What size valves were in the heads?

 

[Mike E]

I think the problem you'll run into if your buying used stage 2 heads is that most of them have the chambers opened up for bigger than a 4" bore. I'm not production block expert, but I doubt many of the 4.1 blocks will go any bigger than 4.000". If you find a good set of heads that will work and can build headers and other small fab work, the conversion isn't that tough. I do efi conversions for a reasonable price. You will no doubt have less out of pocket expenses than gn1 or TA heads, but you'll have a lot of sweat equity in it.

I've been keeping track of my stage 2 motor build costs and so far I'm about $2K less than I would have spent on a max effort champion or TA headed 109 block motor. All of the savings are in the top end of the motor. My stage motor has more potential and has somewhat better parts.

 

[Mike E]

So your saying the valves did not hit the piston bore? What size valves were in the heads?

I've got a set of heads with a 2.08,1.6 valves that should clear a 3.800" bore. As long as you don't go crazy on lift, they should clear the bore. But the chambers are 4.090" wide at the widest point.

 

[norbs]

I've got a set of heads with a 2.08,1.6 valves that should clear a 3.800" bore. As long as you don't go crazy on lift, they should clear the bore. But the chambers are 4.090" wide at the widest point.

WIth the chambers begin so wide, would this cause a head gasket leak between the bores?

 

[Mike E]

Potentially yes. Obviously the more material you have between the bores, the more strength you'll have. But your only real options for larger bore off the shelf headgaskets that I've found are 4.02 and 4.09 bore. A head that is ported to 4.03 or 4.04 chamber isn't going to add any extra strength to a 4.09" bore gasket. In my opinion even a 4.09 bore head is still going to be able to make power power than a production block can handle.

You have to understand that there is some risk to reliabiltity running old used stage 2 parts. If you want something that you can pour the power to and never have any issues, you better buy new TA heads. If your fine with old used stuff having the occasional issue, then you get a good trade off in cost.

 

[jpwalt1987]

Thanks everyone for helping me with my questions about 3800 series II heads on a production 3.8 block.

.

I have a feeling that the Series II 3800 heads are being confused with ACTUAL Stage 2 heads based on this statement above.

 

[Mike Licht]

The cast Iron heads have 2.02 intakes and a 1.6 exhaust, they were ment for stage 2 3.8 blocks. I got mine for around $750 or so and they flow more air than a max ported TA or Chanpion head.
Mike

 

[Paul Lohr]

Sorry for crossing up the Stage 2 heads with the 3800 Series 2 heads.

Thank you everyone for helping with the questions. I have definitely learned from the discussion.

Paul Lohr