Apocolipse

Hey everyone,

I am building up a 383 (4" stroke 3.905 bore) for a fun HPDE / street car.

Right now I have some stock 243 heads and a LS2/LS6 cam. I was going to just put them onto the engine and run it. The cam is lower duration and I realize it is not a max effort cam, but it would have a ton of low end power while keeping the valve train happy for countless miles.

I calculated the SCR to be about 11.8:1 and DCR around 8.9:1 depending on what method is used. Would make for quite an efficient engine that would make a lot of good and useful power and should work on good 91 with no ethanol and I will be running water injection for added protection.

My question to all of you, I was looking into buying a set of new AFR 215 heads as they seem to be the most efficient and best under the curve power heads on the market. I am not looking for a 7000+rpm screamer as rpm just costs more and more money to keep reliable (hence the reason I went stroker).

How much power am I realistically leaving on the table with the 243 vs 215 heads from say...1000-5500 rpm? I do not want to spin it much higher than that on a regular basis. I have MN6 transmission with 3.42 gears to help with the lower rpm range.

I also know there is power left with the cam. Frankly, I will likely upgrade to a custom grind but I want to compare heads first.

If I am only gaining say 20hp/tq over the whole range then I do not think IMO it is worth the extra 1500-2000 over the 243 heads.

If it is greater than that...we will have to consider it greatly as a viable option.

I did find this dyno. Went from 243 heads (apparently self ported?) to a set of 215 with a fast 90.

http://image.superchevy.com/f/57506850+q80+re0+cr1+ar0/1305-ls6-heads-cam-combination-dyno-testing-1.jpg

Does not look like much gain...it's on a 5.7 though so I wonder what difference an extra 0.6L would do to this differential.

Thank you!

StreetSpeed

Huh. Just had a 383 stroker with AFR 215 heads built for road racing. Goal was a super reliable, torquey road race motor. Block is Texas Speed aluminum with Compstar Crank and Rods. Engine was just tuned conservatively and made 400whp and 395 wtq. Power curve is pretty typical. Thus far I'm disappointed. Builder said we'd be looking for 500+tq and power band as flat as Kansas. I can only make 400whp for ST2 but the torque would have been nice. Instead I got basically I/h/e/cam LS6 power for three times the price. Of course this engine could make WAY more power than it is now, but the point was we were building a motor that could only make 400whp but take every advantage of the power curve and torque that we could, but that didn't really happen. Over the winter he's gonna swap cams and tune the power down with restrictor plates to try and get the torque and power band that was promised. PM me if you want more info, but I know little about building these things, just how to drive them and blow them up apparently.

Edit: And FWIW, my LS6 with 50,000 miles that blew up made 360whp/360wtq right after it was on the dyno at NJMP. Motor had Kooks long tubes and intake, other than that was stock. If I had a time machine I'd probably just throw a cammed LS6 in there and be done with it.

JerryTX

Did you already buy the stroker kit? I'd rather see you go LS3 for a bigger bore size and better head flow then a stroker. The only upside of a stroker is torque, everything else is detrimental to longevity.

Apocolipse

Streetspeed, did you ever get your issues figured out with your motor?

Also, yes I already picked up the parts for the stroker and had them balanced...should I reconsider? Is the cost really worth it to go with a whole other block and setup at this point?

JerryTX

Stock bore/stroke all day for a roadrace motor, do not go stroker unless your pockets are deep. Some get away with it, most do not. If your stroker parts are new/unused you can probably sell them without much loss. Get a stock LS2 or LS3 shortblock, upgrade the bolts to ARP and go with forged pistons.. that will make for the most dependable and economical roadrace setup. Save the money for the forged pistons and ARP bolts, and the dry sump!

redtopz

+1. I would sell the stroker crank and go with a stock crank. Build it for high revs, not low end torque.

Apocolipse

Hmmmm very interesting.

I have a 342 rear and was thinking torque would be king.

It's a fully forged setup. The price to get a full long block is a lot more than me building this...

SouthernSon

All things being equal (mostly), my LS6 got 440rwhp with AFR heads. I then rebuilt blown engine and get 418hp with 243 heads.

StreetSpeed

Well it runs fine, creates a ton of oil in the catch can but other than that it's good. won my first two races on it if that counts for something. So hopefully it runs forever and makes the same power for as long as I have it, but as I said there may be better ways to spend 15K than going the same route I went.
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J.R.

You have the basics of a good torquer and power engine.
Rather than spending a lot of money on heads if you just install the
appropriate camshaft, which can be done in car without pulling heads .
I would think about a Chevy hot cam (219/228 dur. at .050 with .525.525. lift at .050, on a 112 LSA). I have used this cam on LS6's (both 347 and 383) and LS3's and the torque always exceeds HP and it is not hard on valve train with .525 lift.
Another good option is a Tony Mamo grind (224/228 dur., .581/.588 lift all at .050 on a 113 or 114 LSA - idles slightly better than a 112LSA.

I do not know what head gasket you are using but I would try to use .053 stock MLS to get compression down a little. 11.8 is a little high for 91 on a
3.905 bore, especially without direct injection.

I would expect to see approx. 440WHP/460ft lbs on a conservative tune.
(approx. 12.0 AFR).

FASTFATBOY

I wouldn't recommend a stock bore 383 for a road course car, piston rock at the bottom of the bore hurts ring seal.

Sell the crank.

Send the 243 heads to Advanced Induction and have them CNC ported, have them grind a cam for your needs.

Apocolipse

My CR was incorrect. The pistons I am using actually have a slight dish to them which I forgot to calculate...huge mistake on my part.

Calculating using 243 64.5cc chambers, assuming a 0.000 deck height, 0.040 MLS, and the -6cc dish, I am at 11.0 SCR which also pulls the DCR to a more 91oct level (with this cam).

For a reasonable price I could get a valve job done on the 243, resurface a hair, smooth out the chambers and deshroud a bit, touch up the short turn radius...should get me a bit more avg flow for the cost.

Then order up a cam (the 224/228 I have heard is popular, as is the 234/238).

I am running long tubes so my exhaust flow should be really strong...and I don't want to really rev past the standard redline.

J.R.

Since this is not a race car and useable HP below the curve is more important I would try to stay with a smaller cam (duration below 235 deg. and lift below .600). This is especially true if using stock 243 heads as flow numbers max out below .600 lift.

Apocolipse

There is an AFR 224/228 cam for sale I have dibbs on...opinions?

JerryTX

If you are stuck with the stroker consider selling your LS2/LS6 stuff (heads/intake/cam) and buying stock LS3 heads and intake and a matched custom cam for your use. Untouched LS3 stuff can get you to near 500rwhp on a LS3 short block with the right cam. If you keep buying individual parts because of a low price you are going to end up with an under-performing combination for your goals.

FASTFATBOY

GM LS3 heads won't work. He will have to buy aftermarket "small bore" LS3 heads as far as I remember.

Apocolipse

That is correct due to the 3.905 bore.

JerryTX

Yup sorry missed that.

ibjamin

You are leaving a lot of power on the table using stock heads and an LS6 cam. I think that 224/228 cam would work well. Ported heads would likely get you 30-40HP over the stock ones. Don't necessarily need nice AFR's but they sure don't hurt. As long as you don't rev over 6K I think you will be fine. With all the torque you won't need to.