Okay guys, this thread is for open discussion. Whats going on is I have some parts that I have put together over the years and I am thinking I have something here that might be good, but I was looking for some advise for the finishing touches.

So I will start with the parts:

2 Bolt main 400 block, .030 over. Blueprinted, 9.025 deck height. Stock crankshaft not ground. Eagle SIR 5.7" 5140 capscrew rods. Speedpro hyper-u flat top pistons w/ 6cc worth of valve relief. Balanced. Machine shop said it was going to be okay for a 6,200 redline.

ZZ4 cylinder heads, untouched.

http://www.summitracing.com/parts/LUN-60104/ this camshaft with matched springs and lifters.

Exhaust system is being finished tomorrow. Hooker 2460 shorties into 3" pipe with H. Into Dynomax Bullets and then turn downs before the axle.

SLP runners.

Holley 58mm Throttle body (my stock one is hashed a little)

2800 stall, just installed in the car still waiting to see if it works!

Then I have all the regular L98 pieces minus the original heads.


Now with all this, I figure I can build something worthwhile! I mean I can use the 406 with the TPI and 3" dual exhaust. The only hang up is my ZZ4 heads. Now I know I need 67cc combustion chambers to hit 10.5/1 CR. But the ZZ4s will put me up well into the 11.6/1 area. So that wont work. anyone have info that discredits the 58cc combustion chamber? Or can I polish the cambers up to 62cc's which would give me a usable 11/1? I already plan on porting the heads if they ever come off the car again So it really wouldn't be a big deal.

You guys see what I have, what would you do? 406TPI?

P.S. The car is used for road racing and drag racing. And I am keeping it automatic.

 

nobody?

 

Have you taken a look at this thread? Have you bought the cam linked in your post?
https://www.thirdgen.org/forums/tpi/...culations.html

You can adjust excel sheet to match your intake system of stock manifold (I'm assuming) and SLP runners. This will give you a ballpark of where your peak torque RPM will be and what cam intake duration to match up with it.

Build will definitely be a beast. I would look into beefing up the rear end to handle the torque. Hyper pistons are fine but won't like nitrous if your timing is off any.

I can't recall exactly but I thought polishing exhaust port wasn't worth it on heads, I think working intake side is fine. Benefit of 400 block are its 4.125 in diameter cylinder bores. 4in bore heads like ZZ4 will work fine but heads with 4.125 in bore will help unshroud valves for better performance. If you're keeping ZZ4's, I wouldn't worry about too much. Just focus on getting heads to flow right amount of air for your horsepower goal.

Sounds like you are almost there getting everything together. You will have to keep us updated!

 

Just gonna chime in here...
IMO you have some mismatched parts there.

First off I love the 406 idea!!! Especially for the autocross thing. Torque!!!

1) Open up the stock Intake manifold base.... it doesn't flow enough for the 350 because it was designed for the 305!!! and now you wanna put an engine under it that is 25% larger than the manifold was designed for... The 350 runs out of air around 4800 RPM and the 406 will run out of steam sooner than that. (But will pull hard until then )

2) Keep the SLP Runners and open them up too.

3) The ZZ4 heads are probably too small for this 406... http://www.gmpartsdirect.com/perform...CATID=671.html
especially when you have it paired to a higher reving cam. The intake port is only 165cc which will also choke this engine in the higher RPM zone... maybe alot sooner than you think. Not to mention the 1.94"/1.50" valves which most would consider small for a hot 350. Probably has too much compression as well with the 58cc combustion chambers. Since the pistons are already in the block I say sell the heads and get something with larger ports, valves and chambers...

4) The Lunati cam is large... http://www.summitracing.com/parts/LUN-60104/ and has a operating range of 2200-6400 RPM, which would be a little lower in the 406... probably 1800-6000 maybe less. Which the Intake base and small cylinder head ports won't support.

5) Won't need the stall converter. It will essentially decrease the amount of usable RPM you have to play with. Especially considering the 406 will run out of air in the higher RPMs with the Intake/Cylinder head combo. For example, 2800 to 4500 RPM instead of 1200 to 4500 RPM

A great street car or Autocross car has great torque with usable RPM range... and I think that your 406 engine is a great idea!!!!, but keep in mind what that engine is doing.
I would probably build that engine with the expectation to run under 5000 RPM... and this is due to the amount of air you can stuff into it.

*Open up the plenum
*Open up the intake manifold ports or get an aftermarket Intake manifold and open that up too....
*Port the SLP Runners to match
*Find a Cylinder head that can match what the 406 needs... A 180cc intake port is probably a little small for a healthy 406 but a large cylinder head intake port means nothing if the manifold can't fill it!!! Then try to match your combustion chambers to your pistons for desired compression ratio.
*Find a camshaft that "works" within your operating area (now you can probably go one size higher than you would in a 350 because the 406 will make the engine slightly Duration tolerant) http://www.summitracing.com/parts/CCA-CL12-365-4/ Remember that the cam has to be somewhat computer compatible....
*Sell the Torque Converter. The 406 will make tons of Tq and generally people buy high stall torque converters because the larger cam they have installed doesn't make enough power in the lower end of the engines RPM... Yours Will!!!

Not trying to cause an arguement, Just my

 

dont forget the steam holes in your heads otherwise youll have overheating problems good luck sounds like a fun build

 

This guy looks like he can make an Intake to flow well for a 406.
https://www.thirdgen.org/forums/tpi/...g-project.html

Check out some of his pictures... they are in the link on the first thread.
If you could get a TPI Plenum/Runners/Manifold/Head Combo to breathe well enough to place on a 406 you'd be laughing!!!

I went with a HSR...

 

To me anything over 383 cubes is asking for a mini-ram at the very least but TPI is one sexy intake just not sure the trade off is really worth it, especially if you really want to race it.

 

PM sent.

 

Even with a heavily ported stock base the 400 will still starve it but will be fun down low.

Ditto on the heads not being worth it, cam etc.

The 113 head needs larger valves and a lot of portwork to breathe, its a low rpm motor understood but still its like throwing good money after bad.

 

So its safe to say I will need a new base right? I will add that to the mental check list. I can run a sandpaper roll through the SLP runners / new base and maybe port them open some more for good measure. At the minimum I will be port matching everything.

The way I figure if I can keep it cheap, then whatever. I can afford to play in the under $2,500 area, not saying I have that laying around lump sum. But I wouldn't loose my mind sinking that much money into the car making it fun.

@ Blackdog: I contacted Dr J's porting (who do 90% of the work for the engine masters competition) and they quoted me $800 for porting on my zz4s which would take me into the 270 cfm range and 180cc intake port size all with stock valves. That should be enough to allow the 406 to breathe to 5,000 rpm. And that is $650 cheaper than a set of AFR heads which would be comparable. However if I can replicate 75% of those results by myself (I port junk heads for fun) and then add some better valves, heck im in business for under $300! Oh yeah and to a set of prying eyes...its just another L98 .

Also I was told I can run a 125 shot assuming the timing is VERY happy. I may or may not go that route...leaning towards may. That would help crutch my 1/4 mile times. Also I have been drawing up plans with my welder on welding up my 10 bolt and adding some supports. He only charges me $10 an hour for the labor, so I figure why not. Im not to sure about the stock posi, but if it gives up it gives up. I will toss in a locker and girdle when I can. But the axle upgrades will come when the SFCs do.

Lastly I already own the camshaft, but im not thrilled about it. And being that the camshaft makes or breaks an engine, I will probably just use Blackdog's calculator and call comp cams with the results. I still feel stupid for not camming my L98 when I had it down to the short block 2 years ago.

Does all this sound right to you guys?

 

Good advice. I think that all works. I'd like to see a head in the 200-210 size range for a 406 to get enough CSA, anything smaller will choke it off. Since the OP is accustomed to porting, he may be able to open them up himself to pick up enough CSA.

Additionally, I think if you don't spin this past 5500 to make power, you're cheating yourself. As pointed out in this post too.

 

Still have the problem with 58cc chambers...and if they deck the heads for best sealing surface, they are going to come up smaller. over 11 to 1 is getting out of pump gas territory. Ported heads will feed the 406 to 5000 rpm or so which is in TPI range, so thats not a problem.

You can run the cam you have as long as the runners are fully siamesed and ported out along with the base. A ported aftermarket base would be better as you should beable to get more port area and flow out of the aftermarket base. That cam is a touch bigger than something i'd run but it will work just fine. That 406 will swallow that cam up. My 233/233 single plane EFI 401" motor will peak in the mid 5000 rpm range so the duration is about right for a siamesed TPI setup, but thats with a 195cc head that can flow pretty good, and a 2.05" valve.

Plus, you will need the later intake valve closing point to go with that high compression to get dynamic compression down abit...even tho thats not the end-all-say-all of pump gas compatibility, its a helpful target to use..

I'd seriously consider a dish piston for 58cc chambers or else spend the money on a set of 195-200cc heads and let it eat.