400 sbc build
- Thread starter Jbug.jbone
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I have a set of.035 wiseco pistons 4.160 in flat top stock rod length but I don’t know if you can get a set of drop in rings for them 1.55 pin
Or use them to do a 377 stroker
Or use them to do a 377 stroker
If you are considering going with a stock 400 block, be aware that the most they can be overbored is about .040. .030 is about the practical limit. The reasons behind this issue is that the sleeves are both thin wall and siamesed, To get the bore the factory wanted, they literally installed the sleeves with no room between them for water to move past and used a thin wall design to get them as close as possible to each other so that they could use the existing architecture and not have to create a special casting just for that CID.
Being thin wall, they lose the ability to be overbored as far out as the smaller blocks can be. it also makes them susceptible to overheating and warp because they cannot dissipate heat as effectively as, oh, say, a 350 can.
I have a 400 block in the shop right now and the plan for it is to go Eagle and get a matched reciprocating assembly including pistons and rings. For the pistons, for the street,, probably hypereutectic; the middle ground between the stock iteration cast pistons and forgings. I am lucky in that this block is a stock bore and has no ridge at the top of the sleeves. Mentioned elsewhere that I scored it from a neighbour who used to race late model dirt and who had planned to build it for that purpose. Never happened and the block came my way.
As for heads there are several good mfgrs out there who offer a number for the 400. Just make sure that the drilling for the steam holes in the heads match what is in the block for both location and number.
Nick
Being thin wall, they lose the ability to be overbored as far out as the smaller blocks can be. it also makes them susceptible to overheating and warp because they cannot dissipate heat as effectively as, oh, say, a 350 can.
I have a 400 block in the shop right now and the plan for it is to go Eagle and get a matched reciprocating assembly including pistons and rings. For the pistons, for the street,, probably hypereutectic; the middle ground between the stock iteration cast pistons and forgings. I am lucky in that this block is a stock bore and has no ridge at the top of the sleeves. Mentioned elsewhere that I scored it from a neighbour who used to race late model dirt and who had planned to build it for that purpose. Never happened and the block came my way.
As for heads there are several good mfgrs out there who offer a number for the 400. Just make sure that the drilling for the steam holes in the heads match what is in the block for both location and number.
Nick
okay fellas im pretty mechanically inclined. But I’ve never messed around with internals before.
I’m looking at two motors, one is just the block fresh from the machine shop. Guy says he has everything to put it back together.
Second one, guy says he pulled it out of a RV 509 block 70k miles, been sitting 10 years.
Thinking about buying that one tossing in a cam and some heads?
I’m looking at two motors, one is just the block fresh from the machine shop. Guy says he has everything to put it back together.
Second one, guy says he pulled it out of a RV 509 block 70k miles, been sitting 10 years.
Thinking about buying that one tossing in a cam and some heads?
What is your overall budget for this build. We all love spending another gearheads money 
So here is your decision tree.
Do you buy the freshly machined block and the internals from the one vendor or do you buy the crusty lump from the other vendor?
Regarding the fresh block. Much as I hate to put it this way, you have only the word of the seller that the machine work was done correctly. As such you are potentially purchasing something of a pig in a poke because any warranty on the work typically just stays with the first owner and cannot be transferred to a followup buyer. You also only have the seller's word that the new internals that are supposed to come with the block are, in fact, both new, and correct for the application. PLEASE BE AWARE that I am not trying to slam your source here. However, almost everyone here on the site, in the various forums and threads, as a collective group, have a least one horror story apiece about what they thought they bought not being what they got or wanted or could use, or had hidden issues that never were mentioned prior to sale/buy.
Moving on to the lump. In this case you have access to what may or may not be a complete engine. By complete, I mean still wearing all the parts and accessories it would have needed to be a running mill when it was in service. So the first question here is, how complete is it? Second Q., is, how long has it been sitting? And the third Q., is, where and how was it stored, warm or cold, dry or wet, out of harm's way or somewhere where it regularly got banged around or run into?
After that, how many miles are on it? Was it original to the RV from which it was pulled? Why was it pulled? Issues with how it ran or did it overheat? R-V's aren't noted for having engine bays that offer a lot of air circulation and cooling to the engine.
Have you been able to physically inspect it for any external damage, pull the dipstick to check the oil for color and smell? Can you grab the crank pulley and turn the crank? I'd suggest maybe trying to rig it for a test fire but if it has been sitting for any prolonged amount of time, the oil pump and galleries would have to be primed before anything like that might be tried. Does if come with its starter and could you do compression tests on the cylinder?
So, fresh and ready to build or possibly needing a rebuild? Fresh motor versus crusty lump? You building it versus a shop? Accessories and finishing parts extra versus all there but needing to be cleaned and inspected?
And, as noted above, how fat a budget to you have for this exercise?
Oh yeah, if you haven't already taken a peek at the lump, take a buddy along. Two viewpoints can be better than one.
Nick
Do you buy the freshly machined block and the internals from the one vendor or do you buy the crusty lump from the other vendor?
Regarding the fresh block. Much as I hate to put it this way, you have only the word of the seller that the machine work was done correctly. As such you are potentially purchasing something of a pig in a poke because any warranty on the work typically just stays with the first owner and cannot be transferred to a followup buyer. You also only have the seller's word that the new internals that are supposed to come with the block are, in fact, both new, and correct for the application. PLEASE BE AWARE that I am not trying to slam your source here. However, almost everyone here on the site, in the various forums and threads, as a collective group, have a least one horror story apiece about what they thought they bought not being what they got or wanted or could use, or had hidden issues that never were mentioned prior to sale/buy.
Moving on to the lump. In this case you have access to what may or may not be a complete engine. By complete, I mean still wearing all the parts and accessories it would have needed to be a running mill when it was in service. So the first question here is, how complete is it? Second Q., is, how long has it been sitting? And the third Q., is, where and how was it stored, warm or cold, dry or wet, out of harm's way or somewhere where it regularly got banged around or run into?
After that, how many miles are on it? Was it original to the RV from which it was pulled? Why was it pulled? Issues with how it ran or did it overheat? R-V's aren't noted for having engine bays that offer a lot of air circulation and cooling to the engine.
Have you been able to physically inspect it for any external damage, pull the dipstick to check the oil for color and smell? Can you grab the crank pulley and turn the crank? I'd suggest maybe trying to rig it for a test fire but if it has been sitting for any prolonged amount of time, the oil pump and galleries would have to be primed before anything like that might be tried. Does if come with its starter and could you do compression tests on the cylinder?
So, fresh and ready to build or possibly needing a rebuild? Fresh motor versus crusty lump? You building it versus a shop? Accessories and finishing parts extra versus all there but needing to be cleaned and inspected?
And, as noted above, how fat a budget to you have for this exercise?
Oh yeah, if you haven't already taken a peek at the lump, take a buddy along. Two viewpoints can be better than one.
Nick
I 100% agree w/@CopperNick. The .040 over 509 short block that I have is not what I was told it was. The description listed aftermarket crank/rods but it seems it's a factory crank turned .020 & standard GM 5.7 PM rods. Not bad..... But also NOT what it was supposed to be. It was part of a package deal of parts so it was a gamble that I didn't win big on. I didn't really lose on it either so I'd say I broke even since it wasn't junk. The problem I ran into was the combo just doesn't suit the same type of build described in this thread (typical street-only driver; a hot-rod w/no intention of track time or racing). I did score some AFR heads along the way thinking I could make a decent street combo but the options seem to be limited w/o going off track.
Decent mild compression & a mild cam on 87octane w/a >400ci motor would be fun in a g-body while still being street friendly.
If that 70k mile RV 509 set-up wasn't well maintained while in service or stored properly during that 10yr hiatus, that can mean trouble internally. It's a gamble. Cost would be a deciding factor for me.
The already machined block 'fresh from the machine shop'.... Is there a legit dated receipt that verifies that fact? What supporting parts come w/it? If they're not parts that support the style of build you need, that doesn't do much for you so their benefit is debatable w/o knowing the details. This also would come down to the price tag as a deciding factor.
What price are these possible options? What sort of budget were you looking to come in under for the running motor? Be honest w/your numbers & the collective group should be able to help you navigate the waters as long as you continually remind them of your end goal (torquey cruiser vs street terror).
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