[~JM~]

I posted this up on the Camaro board & figured I should probably get an opinion from you folks also.

I've been slowly collecting parts to build a 406.

So far I have a 509 block (that still needs to be machined), a Scat cast steel 6" rod-internal balance crank, a set of 6" Lunati rods, set of aluminum Pro Topline 200cc angle plug heads with 64cc chambers, set of 1.6 Comp roller rocker arms & a few other small pieces like ARP stud kits, etc.

Last night I ran across a good deal on a Scat cast steel 6" rod-internal balance crank for a 383. It's one of their lightened cranks.

So now I'm trying to decide wether to build a 406 with a factory 2 bolt main block & all the potential problems that may or may not occur with a factory block. Or play it safe & build a 383 with a 4 bolt main & what is probably a more stable block.

I'm a big believer in the more displacement theory but I don't want to put the time & money into what may be a short lived block.

Intended usage, is a fun street car ('78 Malibu) that must be well mannered & run on pump gas. Low maintenance is a high priority.

Now here's a curve ball... Lately I've been thinking about turbo's.

So... What do you guys think? I would really like to hear from someone who has built, thrashed on & possibly destroyed both.

Thanks.
~JM~

 

[Chevelle408]

I say go with the 406. What problems with a factory block are you referring to? From my understanding the 509 castings are the toughest of the 400s.

 

[driver]

Another for the 406..

 

[furball8994]

I've had both. A 383 with 10.5-1 comp. and a 280* cam in a 73 nova. Car ran very well. Street manners were OK. Best 1/4 was a 12.72. Later I had a 74 nova with a 406, 9-1 comp. 273* (I think) cam. Drove the car all the time. Even on 100+ mile trips. Very well mannered, Best 1/4 was 12.18. The 73 was an auto with 3.08 gears and the 74 was a 4-speed with 3.42's I regularly pounded on both these cars. Shifted the 383 at about 7800 and the 406 at about 7500. The only issue I ever had with either was caused by me. The 406 had so much low end, I got into the habit of not downshifting when I made turns. I would lug the engine down to 700 to 800RPM then just hit the gas. This caused it to wear out two bearings. There was no damage to the block or crank. I replaced the bearings, Put about another 5-6K on the car then sold it.
I think there are pro's and con's with either. But the bottom line is, Like you said your self. There's no replacement for displacement.

 

[Camaro_fever68]

The 406cid combo is extremely close to my planned engine build with the 2-bolt 509 block. The combo will live fine in the GM block but adding a turbo will be questionable. If you're really leaning towards the turbo idea, I don't see any reason to chance the 400 block. The 4-bolt 350 block will likely live longer at higher hp levels. The only replacement for displacement is power adders If you are unsure of the turbo idea, build the 406.

 

[DOUG G]

Both can be built for about the same money, both can be stock - wild.

I would go with either and set the other to the side or sell it to re-coup some $$$

Same parts,compression,ect.,ect., the 400 sould be ??? .1-.2 faster in the 1/4 ??? maybe.

 

[kirkwoodken]

406. Make REAL sure the person doing the machine work knows what he is doing. Failure of 400 blocks has more to do preparation than any structural flaws. Must be plate honed properly. Must be balanced properly. Must be line honed properly. Don't take to the guy on the corner just because he is close. Shop around and find someone with a good reputation. Like you said, you don't want to do it over. If in doubt, send it to one of the guys that invest their time in this site. JMHO. You can read about satisfied customers on this site. You can also read horror stories about Bill Mitchell and his ilk. Go where the satisfied people are.

What size chambers in your heads?

If you are serious about the turbos, I'd go with a 350 block. Better gasket grip between the bores. Any size engine will make any amount of power with a turbo. A 1000 hp 350 is not unusual. When you get to those power ranges, any detonation can cause gasket problems.

 

[jbird]

406

 

[Pavement Pounder]

Are there steam jackets that are to be drilled as well ?406 is the way to go and the combos for that are endless !Good luck

 

[animal69]

There is no substitute for cubic inches- 406.

 

[.GEARHEAD.]

I vote 406. I've had many over the years, and I believe the a 400 2-bolt splayed block is one of the best platforms for all around performance. That being said, all things being equal, the difference between a properly built 406 and 383 is about one tenth in the quarter. I just happen to error on the side of cubes based on personal preference.

Jim

 

[~JM~]

I guess I should've known what to expect from a bunch of big block Chevelle lovers.

The heads that I have are small chamber, 64cc I believe.

Piston selection & price favors the 383. Not as much available for a 6" rod 400. I'd like to keep the compression around 9.5 or 10 to 1 for a naturally aspirated engine.

The turbo is an after thought. I just happened to meet a few turbo guys & I'm real impressed with what they are doing. I've also been trying to learn more about the LS series engines for later on down the road.

Anybody know of a trust worthy machine shop in the Portland, Oregon area?

Thanks
~JM~

 

[kirkwoodken]

Don't know how I missed your chamber size the first time around. Small chambers and dished pistons make a nice setup. That being said, I still like flat tops that allow a large quench area for maximum turbulance. Keep your quench close, .035-.040" which ever way you go. If you go with hypereutectics, it can be even closer. The problem with most pistons is their short compression heights, leading to taking a lot off the deck surface to get good quench.

With aluminum heads, you should have no trouble with 10:1.

 

[greg_moreira]

Not exactly sure what you were planning to spend on pistons or where you were looking, but check out SRP pistons. For example, have a look at part number 259620. Its a -21cc dish for a 6 inch rod 400 bored .030 over.

With a 64 cc head and around .040 quench give or take a little(which Id shoot for right around .040 as close as you can)....this piston makes roughly 9.9:1 compression, which puts you right around where you say youd like to be naturally aspirated. Depending on all the fine details and the actual piston/overbore, it can vary a little, which may equate to a hair more or less comp....but for the most part......this piston gets you right in that range youd like.

There are others out there as well.

Oh yeah, I too would use the 406. The 509 block is a great starting point. And yeah, the two bolt block is the preferred starting point for a 400 block. A good 509, 2 bolt block splayed for 4 bolts is definitely preferred over factory 4 bolts.

 

[greg_moreira]

One last thought....if you did go the turbo route....Id still start with the 400 block DEPENDING on the power level you build for. Obviously if your thinking about some 1200 horsepower, higher rpm thumper it might be a half descent idear to start taking a look at aftermarekt blocks.....but a mild build with a mild amount of boost from a turbo that still makes good power is doable.

Id start with the larger bore 400 block(good breathing with the large bore), 3.48 crank(to make around 377 inches).....and the shorter stroke leaves even more room for a dish(meaning you can knock the comp down further to allow for boost). Some of the "shelf" pistons advertised for this sorta configuration can get you arond 8.75:1 with a -26cc dish and your 64 cc heads. And Im sure if you work with them....you can nock it down a little more without going to a larger chamber.....so that leaves some room for some boost.

 

[~JM~]

Don't know how I missed your chamber size the first time around....

Ken,

You didn't miss the info. I went back & added it after you asked about it.


I'm a big believer in the smallest combustion chamber possible.

Has anyone here read about or experimented with SOMENDER-SINGH grooves?

Interesting concept. I'm trying to decide if I should try it out or not.

Here's a link to some interesting reading. http://somender-singh.com/

 

[kirkwoodken]

Now we are getting somewhere. I believe the SOMENDER-SINGH grooves are simply a crutch for sloppy tolerances in engine building. Ideally, the piston should come within .001" from the head at all RPM. That promotes maximum turbulance. Putting grooves in the pistons simply makes it hard for the mixture in the grooves to burn. Running minimum quench requires research with any piston/rod/ring combo to get the pistons as close to the head as possible. That takes the kind of money that most people don't have.

The old Gurney/Westlake engines used an angled flycut on the tops of the pistons in an effort to increase turbulance. Two strokes use a squish band to achieve the same effect.

The lack of turbulance is what makes hemi's the combustion chamber of choice for fuel burners; You don't want to be compressing liquid fuel in a quench area.

The auto makers do have a problem with quench; they need to provide enough area for carbon build-up over time. It is also said to make engines noisier. Who cares about that? That is something most of us hobbiest need not concern ourselves with.

My present 406 is running the piston .005" out of the hole. I wanted .015", but I hated to take another .010" off the top of the block since we had to grind way too much off to use KB pistons.

If you haven't bought a crank yet, I would talk to Wolfplace about using a 3.810" stroke crank with the KB pistons to see if that could eliminate grinding a lot off the deck area. That's what I'm looking at for my next 406/415.

A lot of people don't like the KB pistons. I have one of the first sets they made for the 406, and I haven't had any trouble with them. I'm using them with .0025" clearance. Next time, I'll go .0015" and .010 quench. I'm not saying you should do that, but that's the way I'm leaning toward my next street engine.

Also, check out The Old One's website. http://www.theoldone.com/ Endon has done some interesting head studies, most of which make sense to me. I wish he lived next door. It's all about sucking the maximum amount of heat energy out of what we are burning. There is still room for improvment.

 

[69chevelle355]

i have nothing to add, but are you by chance the JM from over at cowboy seven?

 

[Busted Knuckles]

kirkwooden, if the piston comes within .001 of the head at TDC, isn't your quench .001? I know that's ideal, but with piston rock, etc., it's not really possible. I've run as little as .025 measured quench on a steel rodded street engine without any problems but you really need a good machinist to get that spot-on as you well know.
Jim Moore (posts a lot on Team Chevelle and Bracket Talk) likes to run minimum quench - as I recall, he said he had one where the piston left "witness marks" on the heads - and he jokes that it keeps your rods from stretching

 

[kirkwoodken]

Minimum quench makes power. Something to consider is the piston stops at the top of the bore. Although it looks like a violent stop, it really isn't. The piston is slowed quite gently at the top and bottom of the stroke. If it weren't, engines would self destruct almost instantly. So, when you run close quench, even if you tap the head slightly, nothing happens because of slow piston speed. I've also seen other peoples motors with witness marks from the pistons, and it hasn't hurt anything, but I've never done it on my own motors for fear that MY gaskets will compress to .035" instead of .039". I think that with hyper pistons and tight clearance, .010" is doable without problems. The main problem is most after market pistons have compression heights that are way to short and would require about a .060" cut off the deck surface. With a stock block, thats a lot of metal to remove.