[ss396si]

Is it necessary to have a block sonic tested before building a 350 street motor? My target is 350-400hp and torque?

[BOBCRMAN@aol.com]

Depends on the intended bore oversize. Check the block. Is the cam bearing bore well centered in the machined surface of the casting? If not, I would have block checked on anything over .040"

[ss396si]

I plan on pulling a motor from a junkyard, changing the heads and cam

[cdminter59]

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.

[ss396si]

Originally Posted by cdminter59

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.

Now I have a 350 with that casting number. Your saying with a standard bore I dont have to sonic test, I can achieve those numbers.

[LATECH]

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.

[CNC BLOCKS NE]

(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.

[against all odds]

Please discuss further:

1) The quality of mexiblocks.

2) Sonic testing in further detail.

[BOBCRMAN@aol.com]

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..

[LATECH]

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.

[E.Furgal]

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..

[CNC BLOCKS NE]

Originally Posted by E.Furgal

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..

At finish size I look for minimum of .160 on the skirt sides and wrist pin side I look for a minimum of .100 at finish is size.

I have seen guys with stock builds crack the wall of a cylinder and I doubt it was 13:01

Do a search!!

[CNC BLOCKS NE]

Originally Posted by BOBCRMAN@aol.com

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..

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 ???

[CNC BLOCKS NE]

Originally Posted by against all odds

Please discuss further:

1) The quality of mexiblocks.

2) Sonic testing in further detail.

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

[ss396si]

Thank you all for the details on my block. So it looks like I don't need to have a sonic test done. I want a reliable street engine 350-400hp and torque.