Sonic test results help!

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71swing

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Got my 340 results back. I not sure what the the minimum recommendations are. It a 340 that turned out to be bored .040 over already. So I sent it off to have sonic tested before boring to 4.100" for a 4" cranked 422.

My results came back with the lowest a .094 on cylinder 4 in the middle. And the bottom was a .098

I tried searching for results but all I find is the idea of testing but nobody talking results.

Is this block crap?
 
Who did the testing? There are places on each bore that can be thinner (along the pin axis) and some that can't (major and minor thrusts). Where exactly is the thin spot and how big is it? How were the bores tested?
 
I'm not positive. Im going to stop by and check it out on Thursday. Its at a machine shop in a town I commute to for work. So I was waiting to stop by after work rather than make a special trip. What are recommendations for the pin axis or for the thrust sides?
 
recommended thicknesses depend on the use
high HP race .200 thrust min .140 pin axis min
street motor can use about .030 or so less
I can tell you from experience that a 340 at 4.1" bore will most likely be quite thin, but you don't know till you check.
 
If you want to use that block have it sleeved and use a standard bore. The few cubes you'll give up won't make that much difference. Otherwise if you just want to build cubic inches with a big bore get an R3 block. Or you could use a run of the mill 360 block and put a 4.125 crank in it

I used a run of the mill 360 block, .030 over, tall filled with hardblock to just below the front water holes, main studs and probably a worthless girdle but it's there.

I had to clearance the girdle for the H-beam rods with a 4" stroke so with a 4.125 there problem wouldn't be much left to it.
 
If I turn to a 360 everything I have is interchangeable right besides the pan,balancer, and flex plate right? Everything is the same correct? like the oil pump, distributor bushing, timing cover and chain or anything else?

Is there anything else I need to change to switch over to the 360?
 
rumblefish360 said:
Crank
Click to expand...

Yeah sorry, Im going to stroke whatever I use with a 4" anyway.

Here is my sonic chart, My engine builder only advice was there are really no set giudelines on minimums, but that they did a 350 last week for circle track that had a .075 wall and it didnt last. My block is already over .040 @ 4.080 to clean up I would have to go another .020 to 4.100 leaving me with only .088 & .084 on a few of the pin axis and low .100's on some cylinder thrust like #6.

what do you guys think, should I be shopping around for a 360? when I do find one what are the key points to check out before purchase. Im just afraid to spend $200 or more on a 360 block then get it to the shop and end up in the same problem.

dsc05976z.jpg
 
71swing said:
Yeah sorry, Im going to stroke whatever I use with a 4" anyway.

Here is my sonic chart, My engine builder only advice was there are really no set giudelines on minimums, but that they did a 350 last week for circle track that had a .075 wall and it didnt last. My block is already over .040 @ 4.080 to clean up I would have to go another .020 to 4.100 leaving me with only .088 & .084 on a few of the pin axis and low .100's on some cylinder thrust like #6.

what do you guys think, should I be shopping around for a 360? when I do find one what are the key points to check out before purchase. Im just afraid to spend $200 or more on a 360 block then get it to the shop and end up in the same problem.

dsc05976z.jpg
Click to expand...
This block is used up. Any cylinder with a thrust side thinkness of less than .150 such as #3 is shot.
 
That block is fine, use it.... i've built engines under .080 on thrust sides and they lived for years going down the track, banging 7-7500 rpm's.
 
Hmm, the major thrust side is intake 1, 3, 5, 7 and exhaust side 2, 4, 6, 8. I wouldn't use this for a race block, but as a stock type streeter she'll be fine.
 
Well I have a line on a 360. Will be checking it out this weekend. It’s a little frustrating that there seems to be no standards for the wall thickness and how low you can or should go. This by no means is a racer, but it may see the local track once a year. Lots of cruise/show time and the occasional punks that want to play. I'm looking to popping out mid 400's at the tires and I’m not sure what to think about this lasting under that power. I don’t want to invest thousands to have it crack in 2-3 years. This is long term, maybe even it till I pass it over to my kid.

Could he just sleeve #3?
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Be honest sleeving isn’t even worthy. This is no matching numbers car (originally a /6) I can get a 360 block for nearly the price of sleeving. Not to mention going with a 360 is going to save me money on the custom pistons I was going to need for the 4.100 bore. I’m losing out on the block prep up to this point but the money I save on the pistons for the 360 may cut me even to my original budget, unless I decide to go with the forged crank which I’m still on the fence about.
 
71swing said:
If I turn to a 360 everything I have is interchangeable right besides the pan,balancer, and flex plate right? Everything is the same correct? like the oil pump, distributor bushing, timing cover and chain or anything else?

Is there anything else I need to change to switch over to the 360?
Click to expand...

Quoting myself here lol

I didnt realize that the Scat kits come internally balanced. I should still be able to use my 340's damper and flexplate then right?
 
273 said:
Could he just sleeve #3?
Click to expand...
You can sleeve it with 3/16 (.1875) thick 4" i.d. bore sleeves, but then bored out to 4.1 the cylinders will be .1375 thick. Not much gain there, and sleeves usually run $180ish installed. In my neck of the woods you can find 360 blocks for that money, thank goodness :toothy8:. A block this thin will run hot anyway, not good for a street cruiser.
 
Mid 400 HP at the tires? Go get another block. I'd look for a wall minimum of .200" major/.180" minor and .140" front and back.
 
So how many 340's do you have to test to get one like that????

Kinda like how many licks does it take to get to the center of a tootsie pop LOL
 
I would just sleeve the 340... Then at least your car would have something cool in it.

If you go to a car show, and someone comes by and you tell them it has a 340 in it, they'll think its cool. If you say it has a 360 in it.. Not as much
 
MRL Performance said:
So how many 340's do you have to test to get one like that????

Kinda like how many licks does it take to get to the center of a tootsie pop LOL
Click to expand...

One, I hope.

Those wall thicknesses for that power, it's just an opinion Mike. People use less.

I've got only one 340 block and it has never been tested. The last 340 made 500 flywheel HP and the shift was so bad you could look at the back of the block and see that the mains and cam tunnel were no where near the centers of the casting. The wall thickness? Dad just said, "Thin!" It was an engine for a family member that we would just replace if needed. It's still running today as far as I know, somewhere in Wyoming.

When dad was building the Dodge Nascar engines in the late 70's they were making 620 HP. They used the 340TA blocks and just immediately sleeved all 8 cylinders.
 
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