Hi guys. I did a search and didn't come up with much on sonic testing, so I'll go ahead and post my questions. I got my 400 block back from the machine shop. It initially went .030"over, but he gouged the number one cylinder when he was about finished. It cleaned up to .040"over. I had it sonic checked AFTER I had everything done. Here is what the readings came out to:

Postion looking from top of block (clock reference i.e. 12 o'clock)
CYLINDER..................12............ .....3...............6...........9
1...............................228..... ..........176...........148........155
3...............................178..... ..........185...........128........195
5...............................205..... ..........176...........159........157
7...............................157..... ..........174...........200........193
2...............................225..... ..........206...........158........165
4...............................145..... ..........196...........144........139
6...............................184..... ..........195...........144........152
8...............................144..... ..........209...........194........147


It's a 511 block ('70-'73 4 bolt block). I'm running a Scat 3.75" crank, 6" Eagle SIR LW rods, 10.2: KB hyper pistons, all internal balance with Fluidamper 6.25", Air Gap intake, Comp Magnum 1.52 RR, Roller cam(haven't purchased the cam or lifters yet), MSD distributor and 6A, 200CC/64CC aluminum Pro Topline heads. I haven't purchased a carb either-I don't think the Edelbrock 600 I had on my Vortec motor is going to work. Anyway, do you engine gurus think those sonic numbers are ok? I plan about 450 HP/ 500ft/lbs tq. Also, what's going to get me the proper quench area I am looking for? Will that be in the head gasket thickness? Oh yeah, before I forget, I had it measured for line bore. It checked dead on, even though someone had swapped the caps around before I purchased the block. Right now, it has the stock bolts in it, but I plan to go with ARP everything. The machine guy says if I go with different bolts, it may warrant line boring. Any thoughts?

 

My "Chevrolet Power Book" recommends sonic testing before boring more than .030", but other than looking for uniform thickness, a specific (or minimum) thickness isn't specified. I am a little puzzled by your numbers. The 12, 3, 6, and 9. indicate readings made every 90* around the bore, but there is no indication of where he started. Is 12 o'clock at the valley? The front of the bore? The back? The book states the that the bore thickness is most critical at the major thrust surhace. The 400 blocks have siamesed cylinder bores. That means that there is no gap between the cylinders. With a 4.40" bore center and a 4.165" (4.125" + .040") bore, that should leave a (4.40-4.165 =) .235" thick wall on cylinders 3, 5, 4, and 6, at two places around the bore, 180*s apart, whether at 12 and 6 or 3 and 9, depending on the 12 position, and at one point on the others. You don't show a wall that thick, anywhere. Could it be a limitation of the measuring device? I can't answer your questions, only raise more. Perhaps your machinist can comment.

Depending on the cam you select and your target rpm range, I think a 700 or 750 cfm carb would be a good choice. I prefer mechanical secondary, double pumpers, but vacuum secondaries carbs are more forgiving and street friendly.

The quench distance is the distance from the top if the flat part of the piston to the cylinder head. Two components make up this distance. The deck clearance and the gasket thickness. My book, mentioned above, states .035" to .040", minimum. Others have gotten away with less. Select a gasket and consider whether you want or will need to have the block decked.

RACE ON!!!

 

The "clock" positions I refer to are if you are looking at the top of the engine(the lifter valley). The 12 o'clock position is at the front of the block, the 3 o'clock position is the area of the bore closest to the lifter valley on the left side of the engine(outside edge on the right side). The 6 o'clock is the "rear-ward" part of the bore and the 9 o'clock would be the left side of the bore. I told my machinist that I thought I read that .250 would be the minimum you would want, but he says that you don't even get that if he was to sleeve a cylinder. I have a 600cfm Edelbrock Performer right now. I kinda need to stick with an Edelbrock because I have a BTO Stage 3 200R4, and don't want to fork out the money for new TV linkage. The block was decked to square it up, but It isn't really clear on what the deck height now is. I'll have to measure that myself. Where is the comprimise of the quench area to the CR when selecting head gaskets? To be honest, I don't really want to take this block back for any more work to be done, including decking any more.

The thrust walls-3 o'clock on the 1,3,5 and 7 cylinders all show between 174 and 185 and on the 2,4,6 and 8 cylinders between 195 and 209. The place that he took the block to get it sonic tested said they were all good numbers. I don't plan on 7000 rpm launches, so I guess it should be ok. I really don't plan to get it over 6000 rpm and even that might be high.

 

Let's see if I understand all this.

1.) Although you don't realize all the ramifications, you are satisfied that the bores are thick enough for your use.

2.) You asked about what carb to use, but now you say you don't want to change carbs.

3.) Despite your inquiry, you are not willing to deck the block to optimize the quench.

It sounds like your mind was made up on all issues, before hand. Was there a reason for this thread? And my lengthy response?

RACE ON!!!

 

No, I am saying that I "thought" that the minimum I should go with was 250, so I was asking if any engine builders could set my mind at ease.
I plan to change carbs, but I am saying I will probably go with a bigger Edelbrock.The block has already been decked-I don't want to spend more money on it. My question was how do I pic head gaskets and adjust for quench while maintaining the desired CR?

 

To really know the required gasket thickness you have to have the bottom end assembled. I ended up with pistons @.020 down in the hole. The closest correct .040 inch quench was Flat Out .021 copper head gaskets. You can't run .015 steel shim gasket between iron block and aluminum heads, but i considered it because I'm below 11:1 on this motor.

 

Mike, your quench and C/R are all products of knowing your stroke, rod length, compression height, and deck height among other things. It sounds to me like you'd be well advised to develop a plan with a competent engine builder. That will necessarily include a rerun in the machine shop I'd think......sorry

George, are you going to be home the weekend of April 2nd? I need to get some breakin miles on a certain motor and there's a chance I might not be in Mexico

 

I can figure out the CR, I have the stroke and rod length. I was just looking for advice-not someone to build for me. I am very competent and my attention to detail is impeccable. I was just looking for input.

 

Is there any input you are still lacking?

RACE ON!!!

 

Sorry Mike, didn't mean to offend you. Sometimes you just can't tell the level of experience with questions like these

 

None taken...Maybe my questions are a bit open ended.

 

i'm like that myself

 

i recommend a Bowtie block.
Find Pete79L82 for advice on wall thickness

 

i recommend a Bowtie block.
Lingenfelter says .200 up OK. Being cheap, and a risk taker, i might fill it 3/4 w/HARD BLOK $66 and run it. More info needed.
Find Pete79L82 for advice on wall thickness

 

in smokey yunick's book, he says .130 is OK.
he has seen as little as .090
i wouldn't let .oo2 worry me on the .128"

 

Yes, I'll be around. I was planning on taking off on a long drive on thursday to breakin my 427.

 

Mike this is not a true statement. You check align boring with torqued main caps. A bolt is a bolt. But if your talking ARP "Main Studs" it could feasably pull the core around.

I'm big on using fully studded motors. You can just keep using them over and over in future products. Personnally I would never use a OEM 400 block, but you might consider a billet main caps and studs.