305PhoenixAm

Is it necessary, in every case, to grind reliefs into the oil pan part of the block to accept the stroke of a 400 crank? I haven't yet bought the crank, but I'm looking at a scat 9000 series nodular steel one that's been on ebay forever. It can be seen at http://cgi.ebay.com/ebaymotors/ws/eB...category=33616 .
I have some issues I want to clear before buying it, though. First, I was understanding that the only clearance issues I would have to worry about are the ones I mentioned earlier, about grinding into the block on the oil pan rails. On the information for the crank it also has something written in, though.
"Note: You cannot use 5.565" and 5.7" rods with this crank because of counterweight to piston clearance issues. "
I did searches and saw that people tend to prefer 5.7 rods to something longer. Is this just an issue with this specific crank? What size rods should I look into with this crank?
As for the grinding, I'm going to have full access to a rather large high school auto shop next year, (For some reason, my high school has a lot of money pumped into the auto program compared to other schools.) so what would be the process and what would be used for doing the grinding myself? I'm not too happy about the thought of spending 100+ just to get something like that done.


Also, a little off topic here, but I think I understand this, I just want to be sure. The block was made in the late 60s, early 70s. This would make it a 2 pc rear main, right? Does this have any effect at all on whether I should buy an externally or internally balanced crank?

Thanks for any help you can give. These are my last concerns before I have the block hot tanked and begin my 383 buildup.

contactpatch

305, you might want to think about using a
350 style mains, with spacers, 3.75 stroke, internal balance type crank. Be sure to get the two peice rear seal type crank, for
a 1970 era block.

RB83L69

That is a 400 crank. It will not fit in a 350 block, because of its main journal diameter (.200" too large).

If you're buying a new crank anyway, get one that's specifically made to fit 350 blocks; i.e. a 383 cank, not a 400 crank.

The reason it has to be used with longer rods is because it's made as internally balanced. The reason the factory 400 is externally balanced in the first place, is because of the short rods; there's not enough room under the bottom of the piston, for enough counterweight to fit. But that doesn't matter because it's the wrong crank for your block. However, internally balancing your motor is a good idea, because then you dodge the damper & flywheel issues.

The reason people prefer the 5.7 rods is usually their cost (lower than non-stock lengths such as 6"), more than anything technical.

It will almost certainly be necessary to drind the block at the oil pan rail and the bottom of the cylinders. How much, will depend on what rods you use.

Yes your older block will have a 2-piece rear main seal.

305PhoenixAm

Sorry, stupid mistake on my part.
Here's the part
http://cgi.ebay.com/ebaymotors/ws/eB...tem=7914953199
It's an internally balanced 2 pc..took me a while to find again, actually.
Anyway, it still has the note on piston clearance issues, So I guess I'm going with 6.0" rods and there's no way around that. Thank you for clearing that up.

And back to the grinding. Can this be done with just a dremel or does it have to be done another way? The block is one of the high nickel content ones, btw, in case that makes any difference.

RB83L69

In theory you can do it with a dremel; I hope you're a very patient man though. It's tedious enough with a die grinder, and will probably take 4 or 5 times as long with a dremel.

But again, the amount required, will depend on the rods you use.

305PhoenixAm

Well, die grinder then. I was asking what tool you'd recommend. I guess I'll figure it out though. I'm probably going with 6.0" rods. Don't see any way around it.

305PhoenixAm

[edit] nevermind. I didn't realize you have to have externally balanced cranks for 383s

RB83L69

You don't have to have an externally balanced crank for a 383. If you use rods longer than stock 400 rods, it's possible to put all the necessary counterweight on the crank where it naturally belongs, and not have to locate any of it outside the engine. The tradeoff is a less stable and shorter-lived ring package... a tradeoff the factory wasn't willing to make, as they considered the external balance to be the lesser evil, at the time.

A cap-screw rod will typically require less grinding. That type is also much more likely to clear the cam.

305PhoenixAm

Well, not just because of that, but I don't want to spend the extra 150 or whatever to get the block honed to +.030". Mine is still 4" and I can't find pistons anywhere for a standard bore 383. I can barely find 383 pistons for 6" rods anyway. That would mean I'd have to go ext balanced to get decently sized pistons, which means money for new flexplate and dampner, and then my compression ratio will be in the neighborhood of 12:1 with the 305 heads, so then there's more money I'd need to spend on getting new heads. It just doesn't seem worth it. I barely make enough money to pay for insurance with this car. I think I'm just going to go 350 and when I get enough money, grab some good heads, and buy a stroker kit later on. I just don't have the budget right now.