383 or 406 sbc
 

a guy around my way has two blocks that have been through the necessary machining and reassembled what im asking is what would most of you racers go with the 383 is a fresh 30 over 350 block with a 400 cast crank external balanced with 400 rods forged flat top pistons


and the 406 2 bolt block cast crank 10-10 5,7 rods cast flat top pistons decked .10 both for around the same price would really love to have some help with this guys

I wouldn't want either one with both having cast cranks. But that's just me.

What do you plan to do with the engine? And what type of car? Need more info?

Re: 383 or 406 sbc
 

i built my budget 383 to hold me over till i got my 406 built.... it has all stock bottom end with keith black pistons and lunati cam and stock alum heads off a 85 vette.... i been spinning it to 7k though the traps for over 2 years now in the 1/4 running 10.60 et ... not a problem yet :) now my 406 is all high end stuff :wink:

guys i know it should be forged all the way. but ive built engines with cast cranks and cast pistons for yrs and ive only had a few come apart. and when they did they were gettin old.ive left the line around 7000 a few times and missed shifts(cheap shifter) and watch my 12,000 grand tach say 10,000 and still drove it up on the trailer to go home. but ive also sweep up a few ponds of metal for the trash man too. but mostly they stay together. dont ask me how but its true.ive run 13.1 pistons on a cast crank.stayed together. that did come apart one day when we decided to put the juice to it and it had a tunnelram on it so we gave it a little to much i quess,cause thats one of the ones i swept up..lol should never smoke pot and think about cars.ever lol.. but i was young so what the hell it was only money and metal!!!!!!!! and a whole lot of fun!!!!!!!!!

i hear ya... i was playing around with the rpm/shifting chips and got distracted and i hit 7500 when i forgot to put my shifting and rev limit chips back in my car...... going down the track and i hear the motor just screaming and shifted by hand.... then it hit me i didnt finish what i started ...:oops:

Go with the 383 stroker but thats just my opinion... :D

I ran a 406 back in the mid 80s with a cast crank and 305 rods forged 12.5 pistons ( i did not build it) and it turn 8300 every pass 10.40s in 2600lb car 5.13gears for two years. I put the spray to it a few times and after a few times of that it ran slower on motor so when i pulled it down i found three bent rods. I think if you have a good balanced engine and turn it with in reason it will hang in there. I have ran both engines and had good luck and alot of fun.

Its all in what he plains on doing, really need more info!

I love both stories (wazup & fastvega) about the budget motors & cast bottom ends (and stock 305 rods) in motors running in the 10's & spinning 7K to 8300... that is awesome!! Gives us hope & courage to build on a budget with results!! Of coarse- like wazup says within reason & balanced well.

my motor was balanced and no noticeable vibration at all and 100 pounds of oil pressure going do the track... 45 pounds at idle :wink: i was told by a few old racer/motor builders including the man that builds my motors ... that for every 10 pounds of oil pressure...you can spin a motor 1000 rpm's.... i like to leave a buffer zone and never fully tested their theory..... lol they say the crank/rods fail when the oil barrier between the two fails and you get metal on metal.... it made sense to me and they been racing long before they had all these aftermarket parts now days :)

Re: 383 or 406 sbc
 

Wow, thee are still too many variables and too many questions to be answered before making a call on either one...
1st: When you say a 400 crank in a 350 block, with external balance, I am assuming it is a good after market stroker crank and not a cut down stock 400 crank...?
2nd: I have never heard of 400 (5.565") rods in any 383 combo...? I don't think you could find the correct compression height pistons for that...? Most assemblies have either 5.7" rods or 6.00" rods.
3rd: if that is true, and you have a 4.030" bore, with 3.75" stroke, and 5.565" rods, the short rod/tall compression height "forged" pistons would be incredibly heavy... a scary excessive balance risk...?
4th: If the 400 block is a true "406" (4.155" bore x 3.75" stroke), with 5.7 rods, that combo would be much lighter piston weight and easier on the rotating assembly.

The only real difference between a 383 and a 406 is the bore size, 4.030 vs. 4.155. Either 5.7" rod/piston or 6.00" rod/piston rotating assembly combination should be pretty much equal parameters between both blocks. Howerver, what 400 block number is it, that may be a critical factor? You can scan these forum threads for many arguments over different 400 blocks...

I have heard many arguments that a stock GM 2 bolt main frame with cast crank is more flexible and less prone to 'snap' under hard load/unload...?
You really need to tell us the application and intended usage before anyone can make an educated recommendation... JMHO...

I have heard this theory too; but I assume you would need to be more concerned about valve float & failing top end before the bottom would fail?? Wazup's motor shifted at 8300 & you shifted at 7K... could you really see that much more gain out of the power curve w/ 1300RPMS more above 7K? I assume this must have been a bigger difference in cam specs & head flow? I could build a motor similar pretty cheap & maybe reduce the comp some & run pump gas for street w/ 4spd.... it would be fun & cheap... sorry for the hi-jack on this thread.

Rigsby, here is the best part when i took it apart the rods were ground on the cam side to clear the cam lobes (630 roller). I was amazed how long this engine ran. I bought the car turnkey and the man that owned it was in his 70s and had won with this car all over the place. The car was called the "Dirty Bird" out of savannah Ga. All i can say is i know i put around 300 plus passes on it all 1/4 mile, hell i ran every weekend all over the place,Fa.,Ga.,Sc., so i might have put more than that on it and dont know how many was on it when i bought it. I sure know i had alot of fun.

OK, its been hijacked sorry.

The engine was a 406 with 2 bolt block 4.155 bore, stock cast crank,5.7 305 rods, trw 12.5 pistons, bowtie heads 205and1.6 valves fully ported, (junk porting) 630-630 roller setup, eldbrock tunnel ram with two 660s and 5000 stall w/gluide. Rear end 12bolt w/5.13. The only thing i did to it was intake and carbs oh ya nitrous only used a few times with this engine.

I didnt shift at 8300 but 7000, 8300 is what it went thru the traps at

I've been watching this thread from the beginning and was reluntent to weigh in on it but, but now it's time. First of all the cast steel crank is junk, and all of the MFG'er reconagise this, they say don't turn it over 6500 RPM and with good reason it runs around like a jump rope (flex's) and will eventually beat out the main bearings.
Secondly the stock 400 crack is a Nodular iron crank and is much less flexable and stronger. If you have a large C'clamp around you can tighten it until is distorts/bending ugly but it won't break they are also made of nodular iron. A couple yrs. ago i built a cheap 388" motor for a guy (649.00 rotating assm) cast steel crank, SIR rods, Hyperutectic pistons) on alcohol. It ran 6.29@112 in a 3,000 LB Camero, he was spinning it 7600 RPM with 5.86 gears. At about 50 passes it broke a valve head off. When the engine was pulled apart, it had also beatout the front 2 main bearings and broke the 2nd main web all the way up to the lifter bores. All this due to excessive RPM's O'h he had fun, but it was not repairable.
I guess i'm saying it's flip of the coin, the cranks will work within reason, but i would rather have a stock GM 400 crank anyday of the week than the cast steel crank from China.

JMO

Zip.

383
 

wow, never heard of a cast iron crank turning 10,000 rpm. but hey who knows......

Re: 383
 

my gut say the same thing

Also on the 383 combo, check to see how much clearancing was done on from EACH rod-to-block ....?

If they used stock rod bolt type rods and had to grind a bunch off the caps to clear the cam, or had to clearance a lot at the bottom of certain cylinders because of a bad 'centerline offset' from a bad mold pour, skip the 383 and go for the 406...

Just my honest opinion...

well brother there are a few things i dont do and lying is one of them, and why lie to a bunch of guys that have been there and done that on this board.these guys can catch a bs story quicker than hell!

383
 

well, as you see i said i never heard of a cast iron crank that would hold 10,000 rpm, and i also said who knows........ but i have to say that i do not think a cast crank not to even go to the required valve train parts that could hold 10 grand, these are just my thoughts, if its true, way to go, you dodged a nuke.

Many of us have had or ridden in something that had a motor that was exceptional... a freakish motor that should have not been capable of what we witnessed. Weather it was exceptionally balanced, or whatever, it ran better than anticipated. Mine was a 2-bolt w/ cast crank SBC truck block from a 75 chevy p/u. unknown cam, unknown internals, Holley spread-bore carb, headers & Weiand intake. Nothing special, probably half worn out before I had it. I could tell you how it propelled that 69 Chevelle @ 3800LBS & 4 speed, but you would have had to be there to witness it to believe me... it was FREAKISH. Defied logic. No time slip/no dyno chart. Ran like a RAPED APE!!!

Wazup didn't claim 10K rpm's, he hit 8300 through the traps in his freakishly bullet proof motor from the 70's... I misunderstood the shift point.

All I am saying is that a guy could build a ratty SBC/stoker street/strip motor on a budget & he might fool many with his times when they find out what it is really made of. I could build a dirt cheap SBC & preserve my #'s matching SBC too.

lol..I have turned the guts out of everthing known to man...lol


What I am surprised I have not read yet it is that the life and the amount of punishment an engine can take relies a great deal on who put the thing together...the difference between a Gene Fulton and a mail order engine is all in the tolerances (excluding parts)...Dont get me Wrong a cast crank is a cast crank,,,its Metal what will it handle and for how long ...who knows....????

but Don't mistake the durability of a skilled builders engine with near perfect tolerances and a few other secrets Gene Fulton would never tell you....Notice I said Builder not assembler..

383
 

did i read his ad to say something about 10,000 rpm? i sure thought i did, but i did go back and read it and could not find that, if so sorry.....you know how us old guys lose thoughts.

I think the high RPM's was mentioned with a missed shift or something broke when it happened. You have to realize and engine may do that when it's not under load (flash RPM) but they won't live under load, no matter who builds them. Look at NASCAR engines 3.625 stroke runs 500 mi. running up to 9500 RPM's, but cost a Zillion dollars. Case in point, was a cast crank VS a forged crank. A cast crank would not last 10 laps in a NASCAR engine. Like i said in a previous post, the mfg'er don't recommend turning them over 6500, and that's for a good reason.

JMO

ZIP.

depending on the all factors in what u doing I take the 4O6 have line bored make sure the holes 45 deg. to the crank, fill the block get a 3.0 or 3.25 stroke crank and run like the super stock guys