When removing the engine out of my 75 parts car, I noticed that it didn’t look like your typical 350. After seeing the three freeze plugs on the side and running the numbers, I realized that it was a 1973 400. In preparation for rebuilding my matching numbers 327, I decided to build up this 400 as good practice. The 400 was running perfectly when removed. I plan to switch it once finished into my 76 to replace the stock 180 hp. I am aiming for around 350-400 hp for only street use.
I have disassembled the block and stared the clean up process. While doing so I came up with a few questions. I have never brought an engine to a machinist so please excuse my amateur questions.

1. How do you know if a block needs to be honed or bored? The walls and pistons look fine but there are a few very fine marks here and there. Do I need to get a dial bore gauge?

2. How far can the stock parts go? In other words should I be replacing the crank, rods, and pistons or would they be able to hold up fine for my application?



3. Is there anything else that I should have the machinist do in relations to the short block?

 

Good score! 400's are great motors!

As far as cylinder wear...the machinist caan mic the pistons and bores to determine wear and taper. The pistons look pretty dry..so that's a good indicator.

He might be able to just run a hone through it to make everything pretty and run our old pistons since you aren't planning on High HP or RPM. If you have to bore it...try to stay at .020-.030" and at that time I would use some forged pistons....but that's just me. I hate to take chances.

The stock crank is good as long as bearing surfaces are fine and even the stock rods will work OK. If you get into new pistons and rods that need work...I'd shoot for some 6.0" rods and pistons for a combo to lighten up the pistons and make it an easy balance job.

Just looking at the pics....I'd be inclined to put some rings and bearings in it and call it a day given what you're after. Get a good cam....decent heads and you'll make well over 400 HP without trying.


JIM

 

I have the same engine on the stand now. If it was a good running engine have the crank polished and order a rebuild kit from Summit with pistons. Line bore and crank grinding isn't nessary IMO . The reason for new pistons is the low compression 400 come with suck! .030 over will give you a nice 406 and the machine shop will tell you which crank bearings you need after polishing. That why you don,t order the summit rblt kit until the crank is finished than order it up and the machine shop will match your pistons to the bore when they do the hone. Good Luck
PS get arp main and rod bolts if your hard on your motors

 

1. Almost every GEN I SBC is going to have wear that will require a bore/hone - not just for the surface, but to address taper and to establish correct piston/bore clearance. The shop will measure this and give guidance - you can absolutely get a bore gauge and mic set and do it yourself...but they are going to do it regardless

2. The stock 400 cast crank is fine to about 1 HP/CID and about 5200 RPM, and no use of power-adders (NOS, forced induction, etc.) The rods become an interesting question; the 400 uses a shorter rod - they're fine, but getting them resized often costs about the same as decent aftermarket rods that are longer. As for pistons - hypereutectic pistons are fine unless you're going with a power-adder.

3. The machinist will clean, mag (test for cracks) and pressure test the block to ensure it's solid. They'll then measure all the parts and provide guidance on what machine operations need to be done. Bring ALL the stuff with you to the shop, since typically a shop will throw all the stuff (tins, etc. ) in the tank at the same time - saving you a few bucks if you reuse the tin. It's unlikely that the engine is in-spec such that you can bottle hone, and change rings/bearings...but you've already got the thing torn down.

Job one here is to come up with a realistic budget. Without a budget, it becomes really hard to make decisions as the options are endless...but all bound by $$$

 

I don't have a comment about your build. I just like this picture of your dog trying to beat the heat by laying on the cold garage floor right under the fan. It made me laugh.

 

read both of these from chevy hipo mag ... then back up & think it thru ... deep-dished pistons, iron gm Vortec heads & a $110 cam&lifter kit will work wonders

http://chevyhiperformance.com/techar.../148_0306_406/

http://www.chevyhiperformance.com/te...imp/index.html

 

Have a competent machinist tell you what it needs.Your intended usage (rpm range)will determine what it needs also.
Vortec heads is a good idea just check on the steam holes for a 400 as I don't know if they have them.

 

They don't - but they're fairly straightforward to drill.

 

Ask around for an honest machinist too, one that will do only the work required, buddy even screws me some time in his shop, there's a fine line between what needs to be machined and not and after it's been machined it will be fine but did it need it in the first place, the almighty dollar rules.

Get him to go through with you what needs to be done and ask him why certain things need to be done. One shop will do the procedure while another might think it's not necessary.

Aside from a rering and new bearing for a stock rebuild if you need new rods or pistons or....you should be building a mild 406ci IMHO I hate those stock rods, I don't even like to look at them

 

Thanks everyone for such a quick and detail reply. It was a very nice surprise to find out that I had a 400 and double humps in the parts car. I thought it was stock until I took it out for a test ride. Since this is just a fun build I am trying to keep the budge as low as possible. Plus the 68 frame off tends to keep money always low.

Like the first article said, “By the time we found a block, paid for the machine work, and spent hours building it, we would be better off with a Coast High Performance 406ci short-block”. The way I figure it is that by the time I get new rods, pistons, and new or polished crank I will be in the $500-$600 range. And then with hone/bore, cam bearing installation and any other necessary machining it will be around $300-$500. Then add an extra hundred or two for anything in between and I’ll have a short block minus cam, lifters, water pump, and timing chain, for well over $1000. Not terrible but just by searching through craigslist for a few minutes I found a complete short block with all the work done and new parts with asking price at $1000 and I would be able to sell off my current block to make that price even more affordable. I rather not go this route because I would like the experience of rebuilding this engine from the ground up but at the same time I don’t want to have too much money in a 350-400 hp engine.

So I guess it comes down to this; after the machinist has looked over the block and any necessary work is done, can/should I use the stock crank, rods, and pistons without any problems for my application of street use or would that be a bad choice? If not it might be easier as well as financially better to go with an already assembled short block and modify it from there if needed.

I would like to build it from the ground up but at the same time I want to make the financially smart move.

What do you guys think?

Here’s the Craig’s list add.

http://lexington.craigslist.org/pts/2477217630.html

 

It's always a toss-up between crate and doing it yourself financially. Usually just about a wash, but the difference can be that you can pick *exactly* what you want done when you build your own. Your numbers are about right - even at the cheap end of the spectrum you're in the $1500 range for a short block at least. Figure another $500+ in the heads...and these numbers all assume a good foundation and smart decisions.

It doesn't cost all that much to get stuff cleaned, tested and measured - IMHO, I'd take it at least that far as at that point you know what you have and can make a decision - and the block is more saleable if you've got a shop ticket showing it's solid.

As for buying someone elses' asembled shortblock - it's a real crapshoot. You're betting that the work was all done, and done right. Receipts help...but overall you're taking an expensive bet on what you're going to get. You'd certainly want to see what pistons are in it.

 

Take it to the machine guy & see what he says. It great to be able to build your own engines then one does not worry about engines.

 

offered multi-stage impersonator build articles as only a guide ... to show which parts really make a diff & those that don't matter.

the piston skirt in pic looks almost new ... suggesting 400 may've been rebuilt before?

if the bearing & journal surfaces both look & mike good ... maybe no more shop time than hone bores, polish crank & hot tank.

if "the 400 was running perfectly when removed" ... machinework could be VERY little, depending on how you choose to build. Perhaps a budget-minded mix ... of what JIM & I suggest.

-add-
that said ... an otherwise stock 400 but w/ $110 cam&lifter kit, flattops, 4bbl carb, all in good tune ... will easily make 350fwhp.

 

Get some oats under that 400 and youll never want a 327 again.