Author Topic: 400 block...  (Read 12075 times)

dutch

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400 block...
« on: October 07, 2008, 06:12:28 AM »
Hi all:
  I've got a chance to pick up a 400 block (a #509 casting but I still have to confirm that) which I'm told is a 2 bolt version and out of a '72 pickup truck for my '68.
   Can anyone share their impressions as to how good a street engine this could be made into with a bore clean up and new pistons /heads and whether it could be a good purchase for that intended useage - assuming it checks out OK?.
  In a first quick look it appeared to have some cylinder ridge but decent bores which means it probably would end up as a 406 - but would this be a good candidate for splayed main caps / roller cam and decent heads to expect a reasonable 425hp - 450 ft lb  street engine to replace my 302 which resides on an engine stand now anyway. Does the 400+ small block version really require 5.7" rods to make it work better or will the stock rotating assembly, assuming it checks out OK, cut it?
   Can a 400 block be easily (and reasonably cheaply) built up to be as good or better than a 383 stroker using the many kits available for both of them or should I pass on it and jusy look for a good 350 4 bold block and do the same 383 thing as everyone else these days.
  The going price for me is in the $150 - $200 range and if anyone has input and experience as to which small block variant works better operation and cost-wise for a somewhat hot street engine I would appreciate hearing the feedback. - Randy

hotrod68

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Re: 400 block...
« Reply #1 on: October 09, 2008, 03:12:07 AM »
I was once told to leave the 400 alone--a 350 would run just as well. Lucky for me I didn't listen. With no more than flattops, stock #291 heads, a hydraulic cam, headers, an ancient Weiand manifold, a Turbo 350 and 3.55 gears, my '68 ran mid-12s. It cost me about $1200 to build that engine--including machine work.
 The 400 is a great engine, but you MUST keep it cool! If it overheats more than a couple of times with forged pistons and decent compression, expect the #7 cylinder wall to crack. A 400 will take a .030" overbore with no problems as long as it's kept cool. You don't need 5.7" rods--the stock rods with ARP bolts will easily live at 6500 rpm at the drag strip--but a 5.7" rod cuts down in internal friction. The stock iron crank will live at 6500, too. Even if it's a 2-bolt, you don't need splayed main caps unless you spin it well over 7000 rpm and have very high compression--that would be a waste of money. Any heads with 200cc intake ports will really wake a 400 up if you're spinniing it to 6500. But remember to DRILL THE STEAM HOLES!!! It will overheat if you don't.
  There is no substitute for cubic inches, and you can build a 400 as cheaply as a 350--and it'll have a lot better torque! For that it's worth, that's my input and good luck!
HotRod'68  1968 SS350 coupe undergoing frame-off resto/rod. 386/350/4.11s
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dutch

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Re: 400 block...
« Reply #2 on: October 09, 2008, 11:22:42 AM »
HR...

  Thanks for your info - great to know it doesn't take much because I'm basically pretty cheap and that sort of fits my budget well right now.
   Good warning about the #7 cylinder area though and I'll pay special attention to that spot when I take a look at the block. Does the cylinder crack in the bottom web area with overheating or anywhere else particular as far as you know? That's obviously the problem with any old engine as they could have had anything done to them and how would one know? I met a guy yesterday who will let me throw it in his hot tank for a few days and let it sit so I can really get a good look at the block cleaned up before I spend any money and time on it...
  I was hopeful that a set of vortec -type heads (possibly aluminum) and Air Gap manifold with a 750 Holley I have might work to continue with the cheapness theme and it sounds like it might and still make good power. I have always heard warnings about the cooling of these and it sounded like the steam holes always fixed the problem - but would you consider with the holes drilled it would be a match for any done up 350 or 383 when it comes to cooling issues or is it still a different animal on its own with the siamesed bores?
   Thanks for your input... - Randy

rich69rs

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Re: 400 block...
« Reply #3 on: October 09, 2008, 03:09:18 PM »
I've read previously that the potential for the Chevy 400 to overheat is linked to the "siamesed" cylinder design which also limits the amount the cylinder can be bored out.  Never have heard the same concerns expressed for a Pontiac 400 though.

Some additional info can be found here: http://books.google.com/books?id=GUC52-afG5EC&pg=PA13&lpg=PA13&dq=chevy+400+siamesed&source=web&ots=HZ-PEpeI4q&sig=T-wXV4o5NiczUlOuSobEpE93ydA&hl=en&sa=X&oi=book_result&resnum=3&ct=result#PPA20,M1

See page 19 and 20.  The author's opinion is that the 400 is a fine block, that the siamesed cylinder design adds a certain amount of structural integrity and that overheating is not a problem as long as a few precautions are taken.

I don't have any direct experience.  Just passing this along for your info.

Good luck Dutch.

Richard
« Last Edit: October 09, 2008, 03:31:40 PM by rich69rs »
Richard Thomas
1969 RS

dutch

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Re: 400 block...
« Reply #4 on: October 10, 2008, 03:34:39 AM »
Rich
   Thanks for the good read. It sounds like the 400 has been given a somewhat undeserved reputation as a problem heater. The article makes it sound like it's a fairly decent addition the small block family and I hope to get a look at the one I can purchase in the next few days to see if it looks decent enough to warrant the price and trouble.
   The part that appeals to me about this smc variant is that it is a torque producer over all of the others apparently, and that always works well in a street driven car...  Thanks - Randy

bcmiller

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Re: 400 block...
« Reply #5 on: October 10, 2008, 04:01:08 PM »
dutch,

Why not rebuild the 302 that you have on the engine stand ???

If that is the correct engine for your car and you have no plans to all out race the motor, just rebuilding that should be fine.
If you are keeping the engine for origiinality and just going to build the 400 to save the 302 for some future rebuild, then
I understand.

The 400 small block Chevy is a good engine, if built correctly.  In my opinion if you are buying new rods and pistons for the
400, I would switch it to 5.7 rods clearanced for the 400 stroke.  There should not be a lot of additional cost for that.

The is no substitute for cubic inches, but then there is no substitute for the quickness and high rpms of a 302 either.
 
Bryon / 1968 Camaro SS 396 coupe - now old school 468 big block
1967 Camaro RS/SS 396 coupe L35/M40 - 4 generation family project
Looking for 68 Camaro with body # NOR 181016

dutch

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Re: 400 block...
« Reply #6 on: October 10, 2008, 05:16:11 PM »
dutch,

Why not rebuild the 302 that you have on the engine stand ???

If that is the correct engine for your car and you have no plans to all out race the motor, just rebuilding that should be fine.
If you are keeping the engine for origiinality and just going to build the 400 to save the 302 for some future rebuild, then
I understand.

The 400 small block Chevy is a good engine, if built correctly.  In my opinion if you are buying new rods and pistons for the
400, I would switch it to 5.7 rods clearanced for the 400 stroke.  There should not be a lot of additional cost for that.

The is no substitute for cubic inches, but then there is no substitute for the quickness and high rpms of a 302 either.
 


dutch

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Re: 400 block...
« Reply #7 on: October 10, 2008, 05:34:07 PM »
dutch,

Why not rebuild the 302 that you have on the engine stand ???

If that is the correct engine for your car and you have no plans to all out race the motor, just rebuilding that should be fine.
If you are keeping the engine for origiinality and just going to build the 400 to save the 302 for some future rebuild, then
I understand.

The 400 small block Chevy is a good engine, if built correctly.  In my opinion if you are buying new rods and pistons for the
400, I would switch it to 5.7 rods clearanced for the 400 stroke.  There should not be a lot of additional cost for that.

The is no substitute for cubic inches, but then there is no substitute for the quickness and high rpms of a 302 either.
 

I'll try again as I screwed up the last response...

  My 302 is original to the car and sits fully rebuilt and dyno'd in my workshop. It's very hard to get decent gas to run it around here and I built a 350 and used some of the 302 components on it so I can pull up to any unleaded high test pump and fill up if I so choose. Mainly the 302 sits for that reason along with the fact that aside from how nice it sounds it isn't really much fun to drive around unless one is winding it up all the time with so little torque down low.
  The 400 was a thought because of the torque output and therefore the ease of driving the car around town and I have heard and seen a couple of Chevelles locally that really honk with 406 engines and roller cams with a heavier body so I figured if I ever came across a decent 400 block it might be a good winter project to do. Have to put the car away in a couple of weeks anyway until next mid May, so the 400 deal sounded like a good way to keep occupied for some of that time.
  I will at some point drop the 302 back in if for no other reason than just to hear again how nice it sounds...

                                                                                                                                                                                Randy

bdl16703

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Re: 400 block...
« Reply #8 on: October 11, 2008, 12:20:54 AM »
Years ago I worked at a local machine shop for about a year, stay away from the four bolt main blocks. We tried six 4bolt blocks all magnafluxed bad!

hotrod68

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Re: 400 block...
« Reply #9 on: October 11, 2008, 02:35:06 AM »
   The cylinder cracking isn't a problem in a stock 400--the problem with #7 is that #5 and #7 fire one after the other--if the engine is modified and gets hot or you have crossfire in the wires and get into detonation, it beats the hell out of #7. It'll crack toward the bottom on the piston thrust side--this is because of the siamesed bores. But again--as long as you keep it cool and there is no detonation, it'll live a long and healthy life. I always route the #5 and #7 plug wires far away from each other, especially with an MSD box.
   The Vortec heads are basically the same as the Z/28 #291 heads, and they'll work great on a 400 up to around 6000 rpm, espcecially if you pocket-port them. You can use a 400 gasket as a template to drill the steam holes, and it won't hurt the Vortecs if you want to use them on another engine sometime--a 4" bore head gasket will simply cover the holes. Just remember, you can't cool a hopped-up 400 with a 2-core 327 radiator! I bought a 4-core 23" radiator and it keeps my present 406 around 190 degrees in stop-and-go traffic in summer.
   There is no doubt the scream of a 302 is music, but when you hit the loud pedal there is simply no comparison. The 400's torque makes it a blast to drive--even a 350 can't come close to it. That's my humble opinion. Good luck!


   
HotRod'68  1968 SS350 coupe undergoing frame-off resto/rod. 386/350/4.11s
Butternut Yellow    black standard interior

bcmiller

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Re: 400 block...
« Reply #10 on: October 13, 2008, 10:02:09 PM »
dutch,

I now understand the reasoning for building the 400.  If your 302 is original for the car, I guess I would NOT put it back in the car for
daily driving.  It is too valuable.

Build a 400, but make sure you do it right.  Find a good 2 bolt main 400 block, build it with the 5.7 rods and 10:1 compression (which
will depend on your piston and cylinder head combo) and you will have a blast.   
Bryon / 1968 Camaro SS 396 coupe - now old school 468 big block
1967 Camaro RS/SS 396 coupe L35/M40 - 4 generation family project
Looking for 68 Camaro with body # NOR 181016

NHBandit

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Re: 400 block...
« Reply #11 on: November 15, 2008, 06:03:54 PM »
As an old circle track racer I came up with a combo that gives you the same quick revs due to a big bore & a short stroke you get from the 302 but with a bigger displacement. This combination was developed due to the 355 cubic inch limit we had in the class we were racing in at the time. With short track racing the race is won by the guy who can get the revs up the quickest coming out of the turns while building power all the way down the straights. We used a 400 block with a 327 large journal crank using the same bearing spacers they make for putting 350 cranks in 400 blocks. 5.7 rods with custom made pistons. Comes out to roughly 348 cubic inches with a standard bore and slightly over 350 with a .030 bore.  We were using forged steel cranks from 68 Vette motors because they were still available new from GM back then but any 327-307 large journal crank would work.  This may sound like alot of work & extra expense to go through to build a roughly 350 CID engine but the difference between these & a normal 350 is like night & day... We never told our competition what we were doing different and they never figured it out..

dutch

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Re: 400 block...
« Reply #12 on: November 16, 2008, 02:36:40 AM »

   Finally had a chance to go back and look at that 400 that I mentioned at the start of this thread yesterday and took some numbers down. Maybe people will correct me with my code designations / meanings - but its a 3951509 block casting - 1-14-0 casting date - very hard to read, F 0921?(poss 3) (I or T) M block with H28 and WB cast onto the front of the block behind the timing chain cover area. Heads stamped 458642.. didn't get a date cast for these...

   I take it to be a 400 block possibly cast Jan 14th probably 1970 in Flint and if the T in the suffix is correct (its also very hard to read) it is from a truck... I would have thought it would be a 4 bolt from a truck (which I'm told it was pulled out of) but who knows where it started it's life? I didn't pull the pan since this was another just quick look see, but the guy who wants to get rid of it says he took a look since at one point he was going to rebuild it and doesn't have the time or money and says he saw it was a 2 bolt. Maybe the IM suffix that I sort of saw is thusly correct rather than a possible TM and it means something completely different. The block is painted yellow and I'm sure that isn't OEM - so it may have been pulled out of something else, painted in the process and transplanted into the truck at some point.
   anyone want to comment further on my guesses as to the codes and possible OEM origin?
  The guy wants $200 (possibly less as that's the inital $$ figure) for the whole works - no flex plate but w/dampner, water pump, heads, some newer style of Holley carb, and headers of unknow make or origin - which don't appear to be in too bad shape.
   I am told the bore is standard and I did feel from my first quick look a month ago, a ridge - so it will obviously need to visit Mr. boring bar... but may go .020" or .030" if the walls are decent. Unfortunately he has it under a workshop area and the lighting is very poor and if I decide further to persue this I will take a better look once I see where the actual price lies - Thanks for any opinions - Randy

hotrod68

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Re: 400 block...
« Reply #13 on: November 16, 2008, 04:52:07 AM »
For my 2 cents--BUY IT!  At $200 the thing is a steal. 400 blocks are getting harder and harder to come by, and you could easily resell it and make twice what you paid for it just from the block! The early blocks are even better because they supposedly had more nickel in the iron, and the heads were better than the later ones. You have a great deal staring you in the face, friend. Good luck!
HotRod'68  1968 SS350 coupe undergoing frame-off resto/rod. 386/350/4.11s
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Tinkerr

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Re: 400 block...
« Reply #14 on: November 16, 2008, 02:36:29 PM »
I met a older guy at a cars show he had a 68 Camaro w/ a 406, roller cam, brodex track 1 alum. heads, victor jr. intake, 750 holley with turbo 400, 12bolt with 3:73's he ran 11.60's thru the mufflers w/hoosier quick time tires. he drove the car to car shows as far away as the Carolina's (were in MD). this guy was a engineer and his computer progam (that he used to design the motor) told him if he stepped up to the largest hyd. roller he'd pick up 50 more hp. and still shift at 6200 rpms. He was making easily 425hp.

 

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