I'm so used to looking at small block flow numbers that those numbers look huge to me. I'd bet there's probably a 50hp+ difference between the 'as cast" and the CNC ported heads.

 

Yea, and just imagine that most of the 540 guys think these are actually a bit small :lol:

Desktop Dyno says the CNC heads are good for 51 hp, and I'm starting to believe it.

 

Heads are the key. If you have restrictive heads you have to go to very aggressive valve timing to make any power, and all that duration and overlap kills low end torque.

Free flowing heads and conservative valve timing will make the best torque bandwidth, which is what you need for the street. There's a limit to how big you can go with a head on a carbureted engine because of mixture distribution and fuel evaporization problems, but with a modern EFI engine these problems are overcome with precisely matched injectors and the pressure atomizes the fuel very well.

The current LS6 engine has very conservative valve timing (overlap is bad for emissions and idle stability), but they get a lot of area under the curve because of the very high lift. Combine this with heads that flow substantially better than any vintage small block head and you have and engine with more low end torque than a mildly tuned vintage 350 and big block top end power.

The way to build a street high performance engine today is free flowing heads, conservative valve timing, and EFI.

Duke

 

Hi Jay, your buildup sounds pretty similar to the 434 that I just purchased from another forum member. The specs and pics are on my page http://cemu.org/car/434 This is the funny thing about this motor. It was built on a GM 509 casting two bolt block. The guy who originally built the motor ended up investing some $1700+ into the block. It has splayed billet main caps, billet front cap, and it was fully sleeved with steel. I'm not sure why he didn't invest in an aftermarket block, I think it may have been one of those things where he kept building it up incrementally. Because of the unique setup I have no idea what RPM and power ranges I can trust on this motor. I think 600 hp and 7000 rpm would not be a problem, but how much more it can take (for future expandability), I have no clue.

It has a 240/246 Crane hyd roller with .595/.595 duration with 1.6s. AFR 210 Race Ready heads, port matched Victor Jr. and a Race Demon 750 carb. On paper (Engine Analyzer) this motor makes 600 hp with 1 3/4" headers. I have no idea what to expect in reality, hopefully around 550 or a little better. I'd be quite curious to hear Monty's prediction. As you can see everything was chosen pretty conservatively. The 240 cam on a 434 is pretty moderate, as are 210 cc heads and Victor "Jr.". Fortunately it does have a two piece timing chain cover, so it won't be hard to upgrade the camshaft in the future. I'm also toying with the idea of bringing the heads into Fast Times before I install the engine to see if I can get 300 cfm out of them. Either way, this motor should be a lot of fun from idle to 6500 or so, and propel my car deep into the 11s on Radial T/As.

I'm going EFI soon, and depending on how the job situation works out I'd like to do a meager 8-900 hp 6500 rpm twin turbo setup, but that will probably mean going to an aftermarket block. I might just keep my eye on one of those Bill Mitchell 427 short blocks for $4000. Have you considered one of those? As far as people talking about the 434 buildups costing a lot of money - they are right. This setup is a moderate one and it came with receipts showing a total right up at $10k. That did include a McLeod starter, MSD distrib and a nice carb though.

Rob





[Modified by robzr, 11:03 AM 5/13/2002]

 

Rob,

I ran your setup through DD200, and assuming 10.5 CR, it predicted 533hp@5500rpm and 547tq@4500rpm. It also predicted 500+ ft lbs from 3000-5600 rpm! If you really want to get 600 hp, you'll need to get the airflow up above 300 cfm, and run a little more cam - although I think that 240/246 cam is a pretty good grind. I'm actually looking at those exact duration numbers for a turbo cam, but on a 114 LSA and around .650" lift.

If you're really interested in doing a turbo setup, let me know. I want to build some more headers and I'd be willing to help you do it. I've bought all the equipment (TIG welder, chop saw, band saw, and sanders) that's needed, we'd just need to order the flanges and u-bends. 304 stainless would probably cost around $1000, and 321 stainless around $1500.


[Modified by Monty, 3:31 PM 5/13/2002]

 

Hey Monty - I really hope it does better than 530 hp! BTW the 434 is 10.8:1, you were close. Car Craft just squeezed 540 hp out of a 383 (10.5:1, AFR 195 Race Ready, 248/248 .525 294S solid flat tappet, Victor Jr., 750 cfm HP). Regardless, if I have to change the cam and get those heads worked, I shall see my 600 hp and maybe even a little more. One of my hotrodding "goals" is to keep my car truly "streetable" which to me means I can take it on road trips, keep the RPMs at 6500 ish to ensure long cylinder/valve spring life, run hyd rollers for low maintainence, and seeing 15 mpg would be nice as well. I can put 10k miles on the vette in a year if it would just keep running for a year.

As far as the turbo setup goes, it's going to happen - just a matter of time and money. It looks like I may soon get hired as a w2 consultant, so that should help me out in the next few months. After rebuilding my 700r4, I'm going to convert the Victor Jr. to a FAST setup, and then begin the serious planning of the twin turbos. I will definately take you up on your offer to help when it comes building time, as well as picking your brain during the planning. I also recently bought a metal band saw, a Miller MIG setup (with a argon tank and soon a co2/argon tank), and a milling machine (for brackets, flanges, etc). I think your TIG setup would be far better for the headers though. I do need to figure out if I can use my current block for 6500 rpm 900 hp 15 psi. That basically means the difference between a $1000 piston swap/freshening and a $3500-4000 aftermarket block upgrade.

Rob

 

Monty/Robz, I was talking to our welder at work regarding welding up a stainless exhaust system, and he mentioned when tig welding stainless or stainless alloy tubing (inconel, hasteloy,etc.), to have shielding gas in the inside of the tubing. He tig welds stainless frequently on aero-derivative gas turbines, and said any weld procedure he has seen for stainless involves shielding gas in the pipe when doing butt welds. Not following this procedure will cause contamination (oxydation??) of the inside of the weld and weaken it.

He says he usually just uses masking tape over the ends of the pipe, pokes a small hole in each end, and purges it with an inert gas.

I realize that car exhaust systems are not the same as high pressure from the compressor of a jet, but it would be well worth doing for the price of the inert gas. You may already know of this, but I am offering this for a heads up if you haven't. :cheers:

 

Yes, all of the stainless steel tubing was back-purged while it was welded. I have a spare 80 cf tank and regulator solely for this purpose. I did it the exact same way you described, tape each end up, insert the hose in one end and poke a small hole in the other. Thanks for the "heads-up" anyway, I didn't know about it either until I started this project. Due to the increased heat involved, as well as the cost, I wanted to ensure it was done right.

 

http://cgi.ebay.com/ebaymotors/ws/eb...077973&r=0&t=0

Rob

 

It's pretty nice, but the compression would be way up there. And, it doesn't state who makes the crank. I think I would just rathere pay the $1800 for everything ready to go.

After doing some more reading and talking to some engine gurus, I've been thinking of just stroking my 350. I could do it fairly cheap, and I was thinking of modeling it after Car Craft's new buildup of a 540 horse 383. The motor Car Craft built had out-of-the-box AFR 195's. They used stock rods (ARP bolts), new cast crank, crappy forged pistons, and a flat tappet solid cam. It made 542 hp @ 6300 and 517 tq @4600.

I was thinking of just doing this because I will never have enough airflow to get these numbers out of a 427 (after I paid for the expensive rotating assembly).

I could build a stronger bottom-end than theirs, but just use a Scat cast crank, Eagle I-beams and either JE or SRP forged pistons. With the money I'm saving on the rotating assembly, I could get my heads worked on and bring the flow over 300 cfm (while maintaining excellent low-lift numbers). I could run a solid roller cam with a little more duration than theirs. They ran a 294S, they even stated it could possibly use more cam. I could go to the 306S.

What do you guys think. Once again, I really need advice. I'm getting ready to start something. I ran my car last night and it was a bid disappointment.
It ran the same 12.6s as before. I'm hoping it had something to do with the 10-15mph head wind, the nasty bod off the line, or my inadequate fuel system(high RPM pop at the end of the track). I was really hoping to get in the low 12's, but I guess there's always next time. I don't think I'll be able to run it for a while, though, because I graduate tonight and leave for senior trip next week.

Hope ya'll can steer me in the right direction,
Jay

 

Hi Jay,

I think that 383 recipe is pretty cool, but it's still a 383. To get much more power out of it not only will it have to breath better, but it'd have to spin higher, and that would be at the cost of streetability. And if you do want to spin that bottom end much higher and make more power, and/or spray it or anything like that, you are approaching the limitations of it. I recommend that you focus more on your bottom end, because that is your foundation, and is not easily changable. Make your bottom end strong enough so as it does not limit your future upgradability. Use your current heads on it, and just be happy with your 500-550 hp :) When you've raised a little more cash a few months down the road, it's just a few hours to pull the heads, and bring them in. Use a two piece timing chain cover (and maybe some pop up lifters) to make swapping the cam easier as well. It might be better to upgrade your power in slightly smaller steps anyways, that way you get used to driving the car and you don't just jump into a real fast, dangerous ride not really knowing what to expect or how to handle it in unique situations. It sucks getting suprised going around a corner when the trans shifts and it's wet out...

Another thing to keep in mind is that if you pull your 350 and get it built up, then the leftover components from the 350 are pretty much worthless. If you base your buildup on a new block, you can sell your old short block and recover some of the costs of your new build up. Work out the numbers both ways, see in which way you come out ahead.

I highly recommend you at least do a 400 small block based buildup. Those extra cubes are very cheap considering the cost and availability of 406 cranks and pistons (they are more numerous than 383 components). For a bit extra you can do the 434 short block. You also may want to consider that assembled Bill Mitchell 427 short block for a hair over $4000. It's based on an aftermarket block, and you couldn't build one that nice for that money.

You could also save a little money by running a flat tappet cam with your current valve springs, and then upgrading the springs and upgrading to a roller cam when you get your heads worked in the future.

My personal philosophy is that these hot rods are really fun, so I dump a lot of my money into it and sacrifice other parts in life where my money would go (and does for most other people). But that's what I like, so it makes me happy, and that's what life is about. Everyone else in my life thinks I'm nuts and maybe even irresponsible for doing that. Who knows, maybe they are right, but regardless I have my fun hobby and toy, and that makes me happy :) Also I do know my limitations and I do not neglect other important areas of my life. I think a lot of guys on this forum are in that same situation.

Rob



[Modified by robzr, 10:35 AM 5/17/2002]

 

I agree with Robs suggestions (and philosophy ;) ). BTW, those Dart 215's you've got are darned good heads. With a little work they can be great heads, as good if not better than any other 23* head. A set of them on the 427 shortblock Rob suggested would easily make the power and torque you're wnating and could be done for less than $5000 using alot of your existing parts.

 

Hey guys, I just got back from senior trip. I'm really wanting to start building. I was going to tear my 400 down today and get it cleaned, but I just don't know if that's what I want.

I mean, if Car Craft got 540hp out of a 383 with a wimpy flat tappet, it sure seems like I could get 560+hp out of it with a slightly larger roller cam. It would be much cheaper, and the horsepower would be greater. Also the rings are lower on the pistons, so it could handle a decent shot of nitrous. I wouildn't want to put too much on a Scat cast crank, but I would have 4340 rods with ARP bolts and very good pistons. Regardless, 560hp should be goot for LOW 11's in my street Vette.

I definately understand what all of you are saying about building a good short-block and porting my heads when I get the money, but I'm going to be starting college soon and I won't have money to do anything. I would really like to get it right the first time.

As always, inpuyt is appreciated.
Jay

 

Alright guys, I've had over 200 views since I posted my last reply. I could really use some more input. Monty and others have always helped me out before, so I' hope they still can.
Jay

 

IMO if your block is all good to go with .040 over. Just get a 3.875 stroker 4340 crank and you would end up with something like 398 CI. The amount of block pan rail grinding is determined by your rod/rod bolt combo. Last year i did a 383 and a 393 . Neither required lower block epoxy filling. 4 inch stroker cranks in a SBC i would consider it a must do.

Without much work Your heads can be made to flow @300 cfm at .600 and 230ish exhaust.

The best thing you could do is 3.875 stroke and use thermal coatings for your pistons, chambers (after a polish), exhaust ports after short side P&P, & the exhaust valves and build it at @ 11.0 C/R Then as you have money move up to a solid roller cam.