i wanted to ask some of you 383 guys how much clearence you had when you built your 383's

i'm worried that i might not have enough and when heat expansion takes affect bam, big problem!!!!

from your experiances on your 383's what types of clearence and luck have you had with your motors?

how many miles do you have with your clearences???

i guess i'm just scared but i just want to know if i'll be ok with what i have as of now......

 

According to Penton Publishing, the thermal expansion coefficient of ductile, nodular, and gray iron is 10.4x10-6" / °F. What this means in your engine is that in a worst case, if the crankshaft heats to 800°F (the annealing point of iron at which it would fail anyway) and the cooling system manages to keep the block at 200°F (not coolant, but iron temperature), then the crankshaft would expand about 0.054" more than the cylinder case, or 0.027" on a side. If you have less than 0.027" of clearance now and intend to run your engine to the point of near melt-down, you might have some thermal clearance issues. Other than that, whatever you have now should remain relatively constant as the engine heats.

One interesting side note is that steel expands slightly less, so with a steel (forged) crank the clearances would actually increase with temperature. Unfortunately, the growing case would lower the compression ratio a few thousandths of a point, so you'd lose power with a steel crank in a hot engine - in theory.

How much do you have at this point? I'd be a little more concerned with cetrifugal forces elongating the metal and reducing clearance than thermal ones.

 

I went with .040 on mine and I haven't had any problems.

 

certain places i have 1/4 of and inch and others well???

i think were i messed up was using my stock rod to clearence the block....

i took a stock one, or 89 tpi l98 350 one and honed out the hole were the pin goes though so it would slide in and out of the piston.... i mocked each cylinder up one at a time making my cuts as i went.....

once thats was finished i had everything balanced and rods and rings put on....

i started assembling the shortblock and noticed that the rods come close to hitting the top of the oppising cylinder...... it didn't have this near miss with the stock rod....

like you said, i'm worried about the wear and oblonging of the parts........

i just hope the 1/4 will not shrink over time

i'm not so good with the decimals but isn't 1/4 like .200??

so i should be fine???

i don't know if it's just jitters or what, i just don't want to see anything else go wrong, $$$$$ is the factor........

vader, so heat wont really mean anything for my application?? i'm going for like 160* all the time.... i hope it helps

 

if you are good with decimals you maybe ought to get someone to double check your work since most if not all engine assembly is in thousandths or ten thousandths of an inch. 1/4" is .250. crimp a loop of music wire in a short piece od copper or steel tube for a clearance tool, use a couple of sizes for a go and no go gage.

 

well, right now i'm still attending college and thats where the motor is being assembled.....

my teacher an ase master, told me it's ok, as well as the machine shop instructor across the hall........

i can stack about 3 quarters together between the clearences in places, and at least 1 quarter in others......

note: this should not be the way you measure a block clearence...
but my dumbass is !!

anyway, if i'm good as far as heat expansion goes what about mechanical wear, or oblonging as vader spoke of???

that could be disasterous, like rods wising by my head after a nitrous run!!! lol.....


thats why i asked so that people that has a few miles what kind of luck they had........... ahh lord i guess only time will tell.....

thanks adam

 

Things don't expand all that much, either from heat or whatever. .060" is minimum, shoot for .100" if you can get it. Even alot of stock motors have places with less than .250".

Like ede said, music wire makes a good cheap flexible wire type feeler gauge.

 

I'm a guitarist, so I can even tell you the exact thicknesses of each string, if you really wanna know.

 

does anyone know how thick .200 is????

if i could have somthing to relate to i would know if it's ok.......

 

i think the e string is .024, but it's been a while since i need music wire.

 

.200" is one-fifth of an inch. Look at a ruler.

 

I used a 5/64 allen wrench as a feeler gauge. Flat-to-flat it's 0.078125" across.
Eng hasn't been run yet, but everything should clear.

 

your gonna need a bass guitar for that one

lol

 

well i got to cecking and i have about .200 in some and at least .100 in others...

will this be ok??

i will throw some pics up tonight......

 

.100" of clearance should be OK. Be sure to check the clearance with the camshaft (and timing chain) installed. Cam will need to be degreed to where you plan to run it.

 

see next...

 

thats cool....... it's hard to belive that .100 will last 100,000 miles...

i thought of somthing today.... the only way the clearence could get lesser is if the rod actually got bad enough to elongate to do wear...

it would more likley knock before a clearence problem would occur..... when it decided to go this time i took it home immediatly and started tearing it down......

as for the cam problem, i think everyone here knows about that lol!!!! j/k

i had to send my comp xe282hr cam back for a small base circle version......

is it true that you only need .050 cam to rod clearence or would you guys reccomend a little more???

i took some pics, this is the best one the rest were blurry as hell.
sorry, it's a ****ty camera!!!!

i'll get some good one's monday

 

The same clearance specification should be acceptable for the camshaft lobes.

Incidentally, it's encouraging to see you're using a crank socket to turn the assembly, instead of a flywheel or balancer bolt like too many others have tried. Good thinking...

 

well, i was using the flywheel bolts and a screwdriver to turn it...... but when i found out we had the sockets i changed immidiatly!!!!

hopefully i'll be able to get better pics monday.....