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505 Big Block Build

 
eightyproof
I love my Chevy Chevette!
Posts: 24
Joined: 01/09
Posted: 12/14/10 06:07 PM

I originally started with a 454 .060 over. Was planning a 468 build but found out it would only be about 700 more to do a stroker build. My current plan is to take the block .100 over with domed pistons to get a 10.25 static compression ratio. I am buying a new Scat 4.25 crank that will allow me to use my stock rods. I will be using 336781 oval-ports from 73'. They have 2.19/1.88 valves and have not been ported, but they have been milled down to 110cc's. The reason I am taking it to .100 over is because my machinist didn't like the condition of the cylinders and wants to clean them up nice. The motor is going into a 84' chevy shortwide with a th400 with a shift kit. A ten bolt posi rear with 3.08 gears. Rear -end will be changed someday but will have to wait until later. My question is if anyone has built a similar motor and what cam would fit nicely. I'm definately after a brutal torque curve and Comp recommended a marine cam  XM296HR , It has 242/248 at a .050 with .566 lift on both valves. I have also found a Howards cam with 236/242 at a .050 with .612 lift on both and also a .620 lift with the same duration. I'm leaning towards the most lift with the same duration, seems I would be losing out with less lift and the same duration. I know the comp has more duration but will it outweigh the higher lift on the howards? Plus the Howards comes in a kit with lifters for around $520 Bucks. Any suggestions? Confused  

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tuffnuff
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Posted: 12/14/10 07:42 PM

Are you sure those cylinders will go .100" over,,,
Smile  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

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eightyproof
I love my Chevy Chevette!
Posts: 24
Joined: 01/09
Posted: 12/14/10 08:46 PM

well I kinda gotta trust my machinist on that but CHP says 454 blocks can take a .100-.125 overbore pretty regularly. Right now its at 4.310 and the walls aren't as clean as he would like them. Plus I don't mind the extra cubes. The block was supossedly ready to build, but it looked like they did it in a garage out back at the junkyard next to the dumpster!!!  

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eightyproof
I love my Chevy Chevette!
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Joined: 01/09
Posted: 12/20/10 04:51 PM

anyone else want to chime in?  

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tuffnuff
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Posted: 12/20/10 05:12 PM

Icon Quoteeightyproof:
anyone else want to chime in?


Sure,,, I'll try one more time to point out that I don't think your 454 will go that much overbore,,, .125" is 1/8".
Let me show you the autopsy of a 454, with a hole in the cylinder,,, and how much "meat" there is in those walls.

Bighole

All 5 mains are 4 bolt on this 454 Marine block,,,

Autopsycomplete

Evidently your machine shop knows something I/we don't,,, let's hope his "boring" doesn't strike water.
Good luck,,,

Grin  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

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Dave632
I mow my lawn and find Chevys
Posts: 2253
Joined: 07/08
Posted: 12/20/10 08:26 PM

I would have the block sonic checked before going .100 over.
I knew some guys who went .100 over but they also hard blok-ed the block.  
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tuffnuff
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Posted: 12/20/10 08:33 PM

Icon QuoteDave632:
I would have the block sonic checked before going .100 over.
I knew some guys who went .100 over but the also hard blok-ed the block.



Sure,,, block filler to the frost plug holes "may" work,,, but I visually looked at that hole in the Marine block and the cylinder walls are only 3/16" at best,,, take 1/16" off that, for a .125"+ bore, and we have walls that are only 1/8",,, nawwww, not my choice by far Dave,,, way too dicey for a max effort engine, in my books.
Any core shift at all and disaster strikes,,, one lunched engine.
Grin  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

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Dave632
I mow my lawn and find Chevys
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Posted: 12/20/10 08:40 PM

My last block was a Dart big M which claimed to have .300 wall thickness at a 4.6 bore. I did not cut it apart to find out however. Grin  
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tuffnuff
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Posted: 12/20/10 09:18 PM

Icon QuoteDave632:
My last block was a Dart big M which claimed to have .300 wall thickness at a 4.6 bore. I did not cut it apart to find out however. Grin


Chuckles Dave,,, I didn't purposely put a hole in #7 to see how thick the walls were,,, I paid $400 for the marine block and $100 to have it sleeved,,,
it's fixed now and sits in line to be built,,,

It's the BB in the middle with all 5 mains 4 bolt,,,

Enginesandmoreengines

Grin  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

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skyeking
I mow my lawn and find Chevys
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Posted: 12/21/10 03:43 PM

Hi T/N,
 Remember last year when you had very little to do??  
skyeking

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Dave632
I mow my lawn and find Chevys
Posts: 2253
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Posted: 12/21/10 04:08 PM

Icon QuoteDave632:
My last block was a Dart big M which claimed to have .300 wall thickness at a 4.6 bore. I did not cut it apart to find out however. Grin

Icon Quotetuffnuff:

Chuckles Dave,,, I didn't purposely put a hole in #7 to see how thick the walls were,,, I paid $400 for the marine block and $100 to have it sleeved,,,
it's fixed now and sits in line to be built,,,

It's the BB in the middle with all 5 mains 4 bolt,,,

Enginesandmoreengines

Grin


Sorry I just thought you had to know how thick it was and you brought out the old import tool, (that wooden handled hammer works well on those imports), to check it out. Grin  
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Pontiacman2
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Posted: 12/21/10 05:29 PM

Grin  
Pontiacman2
Pontiacman2

Professional Hi-performance engine builder

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eightyproof
I love my Chevy Chevette!
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Posted: 12/21/10 06:39 PM

what exactly is sonic testing? I'm assuming they use sound waves to check the thickness of the block?  

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tuffnuff
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Posted: 12/21/10 06:54 PM

Sonic Testing - What, Why, How,,,

In the racing world a sonic tester is used to measure the thickness of metal in areas that can’t be accessed for direct measurement, the most common being cylinder walls and roll bar tubing. I’m going to focus on the engine block’s cylinder walls.

Relative to the induction system, there isn’t much power to be had in the short block, but one of the most important areas is ring seal. The interaction between the rings and the cylinder wall is critical. Rings can handle some irregularity, but there is no question, the better the cylinder wall, the better the power.

How a sonic tester works,,,

Just like a bat or a radar gun, the sonic tester sends out a sound wave and then calculates the thickness of the metal by measuring the time for the reflected wave to return.

Calibration is the key to accurate readings. For the best results you should find two pieces of like material (cast iron), one thinner than typically readings and one thicker, to use as standards. You need to be able to physically measure these pieces and then compare them with the tester to make adjustments. You can try to find areas on the block for calibration or take a sledge to a blown up block and make your own. I was “lucky” enough to have a customer forget to put antifreeze in his block over the winter, which supplied me with the perfect donor block.

Where to test,,,

Major thrust – Located opposite the rotation of the motor. Facing the front of the engine, if it turns clockwise, the major thrust is the left side of each bank (V8). This is the location of the largest loads and thus it would be nice to see the thickest cylinder walls here.

Minor thrust – Located opposite the major thrust and on the same side as the rotation of the motor - Typically the right side of both banks.
Front and back of block – This would be the front of the front cylinders and rear of the rear cylinders. Most manufacturers put a good amount of material in these areas, probably because they had the room.
Between cylinders – This is typically the thinnest section of the cylinder because of closeness of adjacent cylinders and the need to allow room for coolant. I’ve actually seen blocks run with less than .100" on the pin sides.
What’s a good thrust side thickness? .300"+
What’s ok? Over .250"
What’s bad? Under .200" on a thrust or under .100" on a pin side – I’d call this a nightmare or train wreck.

What can go wrong? Egg shaped cylinder walls and worse, a cracked cylinder wall. A good way to know how good a block is without a sonic tester is to see how out of round the cylinders get after a season of racing, good blocks will take next to nothing to clean up, bad ones may take .002"+ every season.

Fixes,,,

Grouting the block - Filling a block with grout is no replacement for having a good block. Grout can be helpful, but for other reasons, that I will discuss in the future.
Sleeving the block - There are so many things that can go wrong with sleeving a block that it’s not worth the risk in my opinion, unless it's a valuable 4 bolt main block.
Offset boring – Offsetting the boring bar away from thin spots may help a fuzz, but unless you’re doing a large overbore you just can’t make enough difference.
A better block – In the end this is the only true fix, with a few more pounds on the nose of the car being the only negative.

Hope this sheds lite on your question,,,

Grin  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

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chevelle83
I mow my lawn and find Chevys
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Posted: 12/21/10 10:22 PM

tuff,,,,,at what power level would you say this info comes into play???? cause I am confident a mild engine would be fine without sonic check.

 In other words I only use (can afford) stock blocks for now and, some time or another I will build an engine with some real power and the though just crossed my mind.  

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