Machining a block, how it´s going???

-
the skirt and the pin height are different for 340 vrs a 360
the crankshaft counterweights on a 360 crank will hit on a 340 piston...
Mel.
 
yep exactly.. the 358 crank in the 360 wil hit piston skirts.. the 360 pistons har slightly shorter .. the 360 piston is also lower deck due to the decreasing compression after year 69 - 70.. i used the 360 .030 piston in my twin turbo 340 some years ago.. unforged for better handling of heat.. they worked super no problems at all, until the 904 tranny spragg gave up.. mmm with an old broken 360 crank radiused to 340 mains ofc.. yea the 6.25 rod lenght is same on all the mopar sb.. so swaping 3.58 , 4 or 3.31 stroke pistons wil make a big bang in any case lol
 
mmmm and, the americans r bit crasy in some ways.. inches.. ehhh 7/5/44/8847//4586/765/654... and so on.. we measure in mm.. .001 mm far more easy.. lol. anyways some blocks yea bored .030 , 40 60.. and so on.. is not to scary for std cast pistons that stay pretty mutch the same in whatever temperature.. now with the forged pistons whatever type, tend to move more with the heat.. they are far smaller than the bore... mmmm so the clerance should be super presize.. so yes he will need to have the pistons first.. h could do a test bore yea to c if .030 will clean it up.. but as moper say.. the bore cant be .030 then honed.. u bore typical .028 29.. then hone the last hundreds for the use of the engine.. typical .0040 street .0045 street/nitrous .0045 towing .0050 turbocharged ...... just took those piston to wall clerances from an old KB sheet i had laying in the shop here.. mmmmmm now u c its not ony ca .030... if someone say otherwise..mmm then i am wrong:happy10:
 
Hello again,

i did the measurements yesterday in the evening - and found out that the badest part of the bore is at the top of cylinder 1 (think you call it ridge, right?), it measures 4,012 Inches.

I did all the measurements terry (demon seed) recommended and found out the bores are tapered from top to bottom and out of round (in load direction), i think this is typically for engines.

So now i feel good when ordering the pistons .030 over - this should clean up the walls.

Thanks for your support,

Michael
 
BJR Racing said:
there custom pistons. They just share the same bore and CD.
Click to expand...

Um... not according to industry standards. But I'll agree they not a factory stock type replacement. Thought I mentioned the build tho... These are stocked catalog/shelf part number pistons for BOTH 340 and 360LA based 4" stroke engines using LA type rods. Tomato/tomaahhto...lol.

360Z - no need for the added block expense for this engine. Simple main studs and good machining and it will live just fine. Plus I was pleasantly surprised at how thick the bores were. Only one hole had core shift and it wasn't too bad. This block's going +.040 but it could go .060 with a 4" arm and have plenty of meat left. of course, that would mean a true custom piston by industry standards and again, we're sticking to a budget.
 
moper said:
360Z - no need for the added block expense for this engine. Simple main studs and good machining and it will live just fine. Plus I was pleasantly surprised at how thick the bores were. Only one hole had core shift and it wasn't too bad. This block's going +.040 but it could go .060 with a 4" arm and have plenty of meat left. of course, that would mean a true custom piston by industry standards and again, we're sticking to a budget.
Click to expand...
a while ago i picked up some late 70's 360 blocks from the local bone yard..
picked one at random at sent it out to get:
1. the bores sonic tested.
2. measure everything up.
2. decide on the machining.
turns out that minimum water jacket thickness between the cylinder bores is .150" and that the minimum thickness between
the cylinder bores is .125". you can calculate the maximum bore allowed on a given bore center. using a small block bore center
of 4.46", the two minimum bore walls calculate to .275" .180" in the major thrust direction .095" in the front-to-rear direction
and then add in the water jacket .125" for a total of .400", which means that the biggest bore possible with a water-jacket
is 4.115” and still keep a margin of safety. i bet that the other cylinder blocks are simular. prolly in the 4.08-4.12 range. this was
a virgin casting..
 
You must log in or register to reply here.
-

Back
Top