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sonic test

5K views 28 replies 8 participants last post by  ss396si 
#1 ·
Is it necessary to have a block sonic tested before building a 350 street motor? My target is 350-400hp and torque?
 
#4 ·
If it were me and I had a 3970010 350 block that is a standard bore that needed to be bored .030 or .040 I would not have the sonic test done. Now if the block has been bored and I needed to have it bored again I would have it done. If I had a standard bore block and wanted it bored .060 I would have the test done.
 
#6 ·
Reason he said that is he knows well enough how thick a standard 010 block is. A standard bore going to .030-.040 is safe as the thickness in the block as produced was sufficient back then to provide material for an overbore without any guess work involved.Older blocks tend to be heavier or "overbuilt" as you might say.
With a block thats allready bored, its best to know if it is thick enough to take another overbore, for the horsepower rating it will be built to, and for the material to be sufficient for heat transfer/absorption so to promote good cooling.
Newer blocks are lighter and have less material due to that, so sonic testing is a good idea to ensure no problems will arise.
 
#7 · (Edited by Moderator)
(1) I have bought brand new blocks from GM that did not pass a sonic test.

(2) Don't go by core shirt that does not work either as I have seen many block with zeor core shift and fail a sonic test and on the other hand I have seen block with alot of core shift pass a sonic test.

(3) The cylinders on the older blocks are no thicker then the newer blocks and actually the newer blocks befre made in Mexico were beter because of better technolog of casting and better equipment.

(4) I have at least 15 block where one cylinder failed a sonic test make the block junk for a performance build.

(5) ********************

(6) On non siamese castings like 350 block the thin part of the cylinders are the wrist pin side.

(7) Take from someone who sonic tests every OEM that comes through the door have it sonic tested before anything is done as it does not have to be cleaned to do this task. I have about 45 blocks in storage that have failed a sonic test.

A few years ago I bought 6 blocks and out of all of them only 2 pased a sonic test for a performance build.
 
#14 ·
The quality of Mexican block is not as good as the ones I bought out of the Tanawanda plant in NY. I am talking about machine work like cylinder bore placement, lifter bore placement and cam tunnel placement and deck heights ETC.

I CNC machine my blocks and every block that goes through my machine goes through a probing cycle to check for cylinder bore placement, bore size, and deck heights before I start which also tells me the quality of the work the was done by the manufacturer.

I have seen cam tunnels off .016 and cylinders off .035 from intake to exhaust and from front to rear never seems that bad.

I have seen crates in circle track racing 355 horse under 10:01 break a cylinder wall and those are 355 horse engine
 
#9 ·
We are talking a 350-400 hp engine here. Plus no oversize stated. A very common situation.

Yes, weak cylinder walls can be found in production blocks and old blocks. I have had new blocks sonic checked and still unusable from sand/air inclusions (one a mexican block from Summit). Just had a 283 from an old boat checked and it was junk from massive corrosion in water side of cylinder walls .

But, for the average guy building a 350 street engine. I will not insist on sonic check.. If I did. I would have been out of business 45 years ago..
 
#13 ·
WOW I have been sonic testing for 30 plus years now and still in business What are you doing wrong ?????????

It only costs 40.00 and about 10 minuts to do but guys don't mind spending 40.00 to find out they have a good piece to start with. 99% of the engines I build are performance only.

I have two 400 blocks here that are less then .125 and one cylinder per block and one guy was guessing say it was good because of core shift WRONG.

I sonic test for alot of shops in my area before they start a build cause they don't want to see any problems.

How does a sonic test find a sand inclusion ???
 
#10 ·
I had my 65 389 bored from 4.0625 to 4.120. I did some research and found that these old blocks can be bored pretty far. I felt comfortable going .0575 with mine, as I asked a very reputable Pontiac builder before attempting it. I used forged sealed power 400 pistons .5140 rods.
When in doubt...get it tested.
 
#11 ·
I've had sonic tested blocks blow the webbing onto the track,through the pan.. and had a 50 junker run 3 seasons on spray...
it's the luck of the draw..
even when some blocks don't pass the test.. it's not that a 13 to 1 n/a engine will have the pressure build to blow a whole in the wall..
detonation does that..
 
#20 ·
What bore ?? I have guys bring in 454 for a 496 build and not have it pass a sonic test and on any of those blocks it was one cylinder that failed the test.

I check every block cause I don't need the practice of doing the job twice because of a split cylinder or poor ring seal.

I have seen a few guys in my small area have build another engine out of there own pocket ecause they did not pay attention to detail.


You have to remember your dealing with OEM blocks that made how much power when stock ?
 
#21 ·
ive never built an engine before and looking at other options rather than buying a crate motor. If I try my luck at a big block junkyard special. Id be saving money. but its still a risk because its a junkyard motor and i could be throwing my money away. Another option would be buying a short block and putting the heads,rockers etc etc together. First start up is another nail biter..
 
#22 ·
Not that I'm opposed to junk yard engine's but you really don't know if you have a rebuildable block till it's been stripped, cleaned, and Magnafluxed. That happens before you even put it on the table to check the alignment and dimensions. So by the time you find out; first, is it even a candidate you've put in a fair amount of effort and some cost. Second comes the dimensional inspection where you find out if the bearing bores for the crank and cam are straight or not, whether the cylinder bores are perpendicular to and centered on the crankshaft, and whether the head decks are equadistant from and parallel to the crankshaft also how flat and square they are. And more inspections if youre hunting big power like how centered is the cam, do the lifter bores meet the cam at the correct angle. Etcetera! This leads to what will it cost to correct the imperfections.

So there's a lot to be said for the purchase of a remachined block from the major hot rod catalogs as much, if not all, of this has been done for you and the cost is pretty reasonable as this is what they do en-mass so you save money because they can make specific inspection and remachine set ups that do blocks in quantity at each station.

The good news is that 350-400 horsepower and foot pounds of torque from a 350 is not difficult to acheive. This doesn't tax the engine structure all that much if this is a mostly hot street and occasional strip engine so the vast majority of SBC blocks are up to this. Certainly if you do enough of them you'll hit the exception and maybe the hobby builder will hit one but the odds are way in your favor that statistically you won't hit a bad block either a new GMPP or a remacined from a reputable source.

Going racing is a somewhat different propisition because compared to the street the engine is being used on the high side of its power output all the time, it sees big and sudden changes in power settings and when mounted ahead of a manual transmission has to absorb all the clutch pressure changes as it's engaged and dissengaged buy way of reaction this thrust load out of the crank at the thrust cap and putting it into the block. So racing is a situation that will quickly find marginal strength areas and bust them. Automatics are somewhat gentler in this regard but that depends on how aggressivly they are set up.

An unmolested post 1974 used block should take a .030 to .040 without having to sweat out the wall thickness even for a mild racer but especially for a good hot street motor that isn't being blown or juiced. If going to .060 I do recommend sonic testing as these things are thin wall castings. The pre 1974castings are thicker some of the early blocks like the 283 and some 307s will safely bore .120.

Bogie
 
#26 ·
You can do that Chevy High Performance magazine did an article several years ago where they took the Goodwrench and went through a long series of dyno tests where they started stock then went through a series of tests replacing the GM intake and Q-jet with an Edlebrock Performer RPM and 750 Holley. Then stepped up the heads with stock but ported, L99/ZZx out of the box and ported, Vortec out of the box and ported, AFRs I think as well. This thing grew from stock out of the crate at 230 hp or so to about 410 with the stock bottom end. Of course a couple handfuls of dyno pulls isn't the same as honking down the street for a hundred thousand miles but it shows a 400 horse engine can be done on the Goodwrench foundation.

My biggest issue with the Goodwrench as the basis of what is approaching the level of an upper end high performance engine is the piston crown configuration. GM, who isn’t alone in this, uses those circular dished pistons to control overall compression. These things essentially cheat the engine of a considerable amount of squish/quench by reducing the flat surface of the piston that opposes the squish/quench step of the combustion chamber because the stepped down portion of the crown is too far from the head to be as effective as one would hope for. While not the end of the known universe, it does increase the engine’s octane requirement by 4 or 5 points so you can't run as much compression ratio or spark advance as would maximize fuel efficiency and power development. Still, like I said, CHP got over 400 horses from the thing with better heads and cam, and a bunch of what's considered bolt on stuff like an almost racer intake, big ol' Holley and headers. This happened under 6000 RPM if I remember this article correctly. They also didn't do anything under the oil pan either, such an engine especially as it starts getting on the 6000 RPM line could benefit from a windage tray, a rear pan baffle and a crank scraper, this would minimally insure that the oil got pulled out of spinning crank, put under the tray to lose the entrained air, and the baffle helps keep it in the sump instead of the rear crank counterweight when accelerating the car hard. These are things a dyno doesn't do so it's not so critical to have these parts in the bottom end when the engine isn't being maneuvered by the vehicle.

For a few dollars more you can buy one with vortec heads check this link out >>> 5.7 Ltr - 350 C.I.D. - GM ENGINE 1996-2002 New 12530283 <<<. This is a 4 bolt Vortec with a roller cam. The ponies can easily be pumped up with an aftermarket roller, this gets around the flat tappet break-in issues and eliminates the downstream risk of smoking lobes and tappets because you can't get high zinc oil. Since you would stick Vortec heads on the low end Goodwrench anyway the 600 bucks on top of the Goodwrench closes a lot of the cost gap and you end up with a much stouter 4 bolt bottom end. The cam, intake and headers would be the same for either, so for about 400 dollars cost delta you have a much better engine, and no extra heads taking up garage space. The only addition to get this into pre-1986 vehicle will be the purchase of a one piece rear seal mating flexplate and an electric fuel pump.

Really for an entry level upper end high performance 350 engine you've got a lot of choices and the 12530283 as a new 4 bolt block with Vortec heads a very good starting place.

Bogie
 
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