Must sonic test 360/408 stroker for street use?

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femtnmax

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There is no one in my neck of the woods that does acceptable sonic testing. The nearest "speed shop" will test ONE location on each cylinder and call that good enough...really ignorant IMO.
So the question is...I have a LA360 bored .03 over, production date 1979...does the engine block have a good chance of surviving as a 408 stroker for street use (no slicks or track use)?
The cost of taking the block hundreds of miles, overnight stay, etc to find out the cylinder walls may be too thin...thus needing another block, etc is not worth it.
If sonic testing is really the best answer, then my options are either forget it and keep the 360, or go with a 3.79 stroke which would put the rod length/stroke ratio in the middle of current and past OEM production range.

I could pour block fill into the water jackets up to the bottom of the freeze plugs to help shorten the unsupported cylinder wall length. Some folks say this does not cause much if any engine overheat issues. Any opinions on this idea?
Thanks in advance.
 
They call that a "short fill', usually done for real high rpm/compression/H.P builds.Built a 77 360 based 408,ground the reliefs myself.Typical 500 horse street/strip .030 408.Never had a problem with it.Most builds don"t usually use it,unless really dropping the hammer. That would depend,on your combination.Also,less water capacity in the cooling system,can affect cruising speed temps.
 
My opinion......unless that block had some crazy core shift, it's good to go at .030 over. If it was mine, it would be a 408 :D.
 
It's pretty rare to find a block that isn't good at .030 over. Since your using it for street use I wouldn't worry about it unless you visually see something that doesn't look right.
 
79 360 should be fine. Block fill is just fine (up to the core plug holes){farther??}. Use an oil cooler if going the block fill route. (helps with oil temps and durability).
It would be nice to sonic check but if your just goin .030 over, that is usually considered safe almost all of the time.
 
Just curious why the local shop can't be paid extra (like normal shop labor rate per hour) to take more readings? Personally, I would't trust it. I've found just as many failed as passed regardless of the year. If the power level is kept "low" and the rpms kept low, there "shouldn't" be a problem. but I'd rather know.
 
moper said:
Just curious why the local shop can't be paid extra (like normal shop labor rate per hour) to take more readings?
Click to expand...
Thanks to all for the experience and feedback. Looks like a 408 will be in the works.
As to having the shop take more readings...dealing with that shop is two steps forward and one step back. I had them deck the block in their CNC mill...the tooling that slips thru the main bearing bores...they must have thrown the tool at the main caps...bad damage to 2 of the caps, had to hand file the distorted metal so the main bearing shells would lay correctly in the caps. Also a two week quote turned into 6 weeks with no completion in sight because my job kept being pushed back to make room for their friends work. I'm over that place for good (DK motors in Helena MT).
 
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