If you are considering another 400ci I have one. Never bored, excellent
motor runs great. Contact me if your interested.

 

You can actually take the motown to 4.25 safely, apparently. That's the bore of their 454 small block which uses the same block. I think 4.2 is the max they recommend anyone else take it to, but they take it to 4.25 all the time. That's the route I'm going to take when I get the $$$$ for a new engine.

 

Kalway if you are going to build your own large mouse the dart iron
eagle is the better way to go. wider pan rails, taller deck, raised cam.
You have to run a different pan. timing cover, chain, intake,remote
oil filter. you can run a 4.250 stroke 4.200 bore for 472 cubes.
the raised cam allows a stock length dist and the 4.250 stroke
will work without having to use a .900 base cam. a 4.00 stroke
crank in the motown block has to have a .900 base cam to clear it.
The .275 higher deck allows a longer rod so your not side loading
the block as hard. if you have bags of money scott shafferoff
will sell you a 472 dart 620 HP is the one he says is the daily driver
the one with a little more cam and comp. makes over 700 HP.
Hell just put your motor over to the side and build a 540/572 rat
no sense playing around with small blocks at these power levels

 

Well my idea was to have a 454 or maybe a 427 that can run on maybe midgrade (89 octane) and still have 450 - 500hp. I figure the motown would probably fit under there better and I'll be able to use like a holley commander EFI system on it. I'm going to have a local engine builder build it for me as they can get the parts and put it together for a lot less than it would be for me to make it. I trust their work because they rebuilt my 350 for a rather low price and it runs great.

Real reason I want to stick with a mouse engine is because it's more of a drop in and go routine than a rat. I don't want to horse around with a big block conversion when I get to putting the engine in.

 

I got some updated info from both machine shops. The block is now at the original shop again. He checked the mains with the bearings out and his gauge is saying the mains are almost perfect. I watched them do this in my presence. They are on the lower side of what his book says they should be (forgot the numbers) providing his gauge was set correctly. He has also fixed up the main caps. The race shop checked my running clearance at the mains with the bearings in the caps, torqued down. This is how they got the reading of the mains being too large and out of round. They measured my crank then set their bore gauge to that and checked the mains. I'm not sure which way is the "correct" way to check this stuff, one shop tells me you can do it with the bearings and not get an accurate reading, whilest they check it without the bearings and conclude the mains are perfect. If the main webbing and caps are perfect, crank is turned perfect, then it seems the bearings are not good. Not quiet sure what's going on here. Would tightening the mains with the bearings in and the crank out cause distortion along the bearings? If so, this is why my caps are "out of round" according to the race shop. I talked again to the gentlemen that did the test assembly and he confirmed he used the gauge and got good readings.

Assuming the mains are ok, I had him go ahead and check the cylinder walls since it was bored without a plate. He checked only one side of the block and said one cylinder was about 2 thousanths off. I find out tomorrow morning what the other side looks like. Is this going to be a problem? Don't the rings take off at least that much of hte block during breakin?

I'm still trying to salvage this block as I have some time and money tied up in it, but if all else fails this guy has another 4bolt 400 sitting out back that's never been disassembled or checked. He's willing to trade me block for block if this turns out to be soemthing I don't want. No telling what shape that one is in, could be good, bad or worse. I'm going to cut this one short as I'm starting to ramble and confuse myself evenmore. If anyone has feedback on the questions above please fill me in.

Thanks

 

Race shop did not perform the mains check correctly. To determine mains out of round you don't have the bearings in place. THe limit is .0007", that's 7 ten thousands of an inch. With the bearings in place you are going to get an out of round reading because the bearings are slightly tapered at the parting lines.

If mains check out OK you install the bearings and subtract crank journal diameter from the inside bearing diameter measured at 90 degrees from the parting line. THis is your oil clearance. You buy the correct thickness bearings to get the oil clearance desired.

 

No, not normal to gain 0.002" in bore diameter during breakin ... in a fresh hi-po build, I would not wanna accept 0.002" taper/variation within a bore.

With bearing in place & torqued, the ID of BEARINGS are NOT supposed to be round (this is result of normal "bearing crush" & creates desired "oil wedge").

With caps ONLY in place & torqued, the ID of CAPS & SADDLES ARE supposed to be round.

I have very good quality standards & gaging in tip top shape & calibration ... here's how I measure: I gage torqued caps & saddles with a good bore gage, using it to determine if round & correct ID ... I double check the bore gage by slipping it into a good mike. Then I install the bearings & torque ... then I gage the crank w/ good mike ... then I gage the bearings w/ a good bore gage ... then I slip that bore gage into same mike used to gage crank ... the difference is the oil clearance. Bearing shells (halves) are available in 1, 2, 9, 10, 11, 19, 20, 21, 29, 30 & 31 thousandth's ... it is normal to install different shells ... say one 10 and one 11 in same position (effectively a 10.5) to obtain optimum oil clearance. Guys that build w/ plastigage can't get into such detail; those with decent gaging can ... pros do.

May seem counter-intuitive, but an OE 2bolt 400 is stronger & more desirable than an OE 4bolt 400 ... but studs (arp) in mains will greatly strengthen OE 4bolt.

It's beginning to sound as though the block may be OK ... IF ... if you can get past the bore taper/variation.

 

Ok, so I'm thinking the mains are good then based on what the machine shop told me and what I'm reading here. I dunno what the race shop is doing. Maybe they have some little agreement to buy the block from the other guy if I decide not to use it or something. Anyways, in an hour or so I'm going down to the shop to see what else they found out with the bore taper. I can't remember if he said that .002 was on the tight or large side of the spectrum. If it's tight he can hone it a little with the plate on to make it true, if it's too loose, then I dunno what to do.

 

One thing you can do is tell him straight up you have people you can talk to to verify what he tells you so he won't try and BS you anymore

 

Taper is .0015 on the large side, not perfect, but I think i'm going to use the block. He has the other side to put the torque plate on and check but chances are it is alright too. I don't think he was trying to BS me because he's kept the same story for the beginning. This is the original shop that I did not think too highly of becaus of them letting me have the loose mains. He said it shouldn't have went out that way and his guy just missed it, but he did check the tolerances and everything was good.

My second opinion, a race shop, has me puzzled though from the information I've gathered. They were telling me I need an align bore job because they checked my mains with the bearings in and they were "out of round." From what I've picked up here and the original machine shop, you don't check them with the bearings in because the they cause inaccurate readings.

Anyhow, that's enough for one day. Things are starting to brighten up and now I can save towards that 700R4 conversion instead of starting over with a 2 grand block.

 

You'll probably be just fine. Light tension rings & wavy bores will not work out. Do use standard tension rings. Do fit each ring individually to each bore. Do pay special attention to any with taper ... do fit rings & set gaps with ring squared at tightest part of bore's ring path.

No different from the rest of us ... machine shop folk don't necessarily have superior intelligence; If you have the time & inclination ... learn what they do, how they do it & their terminology ... demonstrate that knowledge by fluency ... then they'll know that you know. Sounds like the block'll be OK ... best wishes.