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Old 01-03-2017, 08:24 AM
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Hey guys new here just got 350 block

Hey guys new here to this site names billy I'm 22 just got a new old 350 block
It's a 72 350 4 bolt with a forged crank, I was also in the process of ripping apart a 69 327 2 bolt cast crank so now I'm stuck on what I should build first I leaning towards the 350 it might go into a c10 or g body coupe, the 350 needs to be bored 30, pistons are speed pro H345DCP 30 with rings and pins, gonna keep stock rods new main and rod bearings my question is will I need to get the crank balanced due to the pistons would be heavier right??? Oh and the heads I got are a set of 461
And 462 fuelie heads this is my first sbc build Any feedback will be greatly appreciated thanks and have a good one.

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Old 01-03-2017, 08:51 AM
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Those pistons are rebuilder specials, with a reduced compression height of 1.548" instead of the standard 350 compression height of 1.560". They will be 0.012" further down in the bore with the piston at top dead center and will make it impossible to achieve a tight squish/quench, even with a steel shim head gasket. Right now, the piston will be down in the bore by ~0.037", so that even using a steel shim gasket, the tightest squish/quench you could build into the motor would be ~0.053". The whole idea of squish/quench is to set it at between 0.035" and 0.045" to help prevent detonation on pump gas. You will either have to have the block decks cut or use standard 1.560" pistons. Either way, it's going to cost you $150. If it were my build, I'd use the H345 pistons and cut the decks to a new block deck height of 9.008", so that the piston is 0.020" down in the bore with the piston at top dead center. Then use a Fel-Pro 1094 head gasket (0.015" compressed) to set the squish/quench at 0.035". Cutting the block in this manner will give you a new flat surface for the shim gasket to seal up with and will also square up the block so that the heads will sit squarely on the block and the intake manifold will sit squarely on the heads, as well as equalizing the static compression ratio hole to hole. For bulletproofing the whole build, have the shop take a very light cut on both cylinder heads so that they are both flat.
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Old 01-03-2017, 09:30 AM
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If you plan to run up over 5500 rpm very much, I would strongly recommend that you have ARP rod bolts put in the rods and the rod big ends resized. Resizing is a near mandatory rebuild requirement as used rods are rarely ever round on the bearing bore after 40 years of use.

You will likely find that resizing the stock rods and adding the new bolts cost-wise comes darn close to a set of brand new Sportsman level aftermarket rods like the Eagle SIR or SCAT ProStock I-beams.....and the new rods are better material and have zero cycles on them, where the stock rods likely have a cyclic count well over 1 Million cycles.

I don't even bother with stock rods anymore, just not worth the work.

The minor difference in piston weight doesn't make balancing necessary unless you are going to rev it up above 6800-7000 rpm a lot. The new rods wil come balanced closer than the stock rods, right out of the box. Everythin will still be within the factory balance tolerance.

You could also mix and match your parts....take the 4-bolt 350 block and bore it .030" over, the large journal 327 crank, the H345DCP pistons, and a set of aftermarket 5.850" rods(Eagle makes 'em in the SIR line-up) and have yourself a long rod 331" engine. Parts stack for that combo comes out to 9.023", fits right into the 9.025" stock block and allows you to use a common composition gasket at .038-.041" thick to arrive at near perfect quench clearance. Light skim cut to clean each deck of the block and your good to go.
For those guys who like the little 327 combos.

Last edited by ericnova72; 01-03-2017 at 09:38 AM.
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Old 01-03-2017, 09:41 AM
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You will have fuel octane problems with those heads and a 350 CI + .030" engine. You may have problems with fuel octane requirements with the 327 CI engine. If the deck clearance is excessive, you will have overheating problems.

My 1962 Chevrolet Bel Air has the original 327 CI / 300 HP engine bored OS to 331 CI with 461 heads, original forged 327 crank turned .010" on rods and mains, Speed Pro forged flat top Pistons, L79 "151" cam, Pertronix Stock Look distributor, a 1967 Rochester Q-jet 800 CFM carburetor and intake manifold. The block was decked .010" flat corner to corner. It runs well on 97 octane Texaco or Exxon/Mobil with the initial advance at 10-12 degrees. It runs at 180-200 degrees on a 105 degree day with the original Harrison radiator and a good clutch fan. . I give the tank 5 gallons of VP C12 108 octane racing fuel to 15 gallons of Exxon/Mobil 97 pump gas and then advance the initial timing to 13-15 degrees, if I want to get serious. That boosts the octane to about 103 which is on the ragged edge of detonation with 15 degrees initial advance.

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Old 01-03-2017, 05:38 PM
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Hey guys new here just got 350 block need help!!

Get a set of these Summit Racing pistons. They won't break the bank. https://www.summitracing.com/parts/s...make/chevrolet Rings - https://www.summitracing.com/parts/s...9-30/overview/
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Old 01-03-2017, 05:47 PM
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Hey guys new here just got 350 block need help!!

With the 461/462 fuelie heads and using a .039 head gasket and having the block decked to zero the compression ratio will be 10.244. Use this set of pistons https://www.summitracing.com/parts/s...make/chevrolet with the fuelie heads for a 9.559 c.r.

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Old 01-05-2017, 09:41 AM
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New 302/327/350 build

Sweet guys thanks for the feedback greatly appreciated so I didn't get the 350 I might've gotten a 3970010 302 short block previous owner said it came out of a 69 z28 it's a 4 bolt cylinders are rusty Pistons stuck, forged crank I have to pull the crank and check part numbers I can't find the engine Id cause I'm guessing it was decked at one point so I'm going off of word of mouth, well I'm trying to understand squish/quench never really heard of this term, I used a compression calculator and got 9.92:1 numbers I used bore: 4.030, stroke: 3.48, cylinder head volume: 64cc, eff Dome volume: 6.90 for those speed pros, deck clearance: 0.025 (found that on a quick Google search correct me if I'm wrong) compressed gasket thickness: 0.026, cylinders: 8, I'd like 10:1 compression ratio that's why I chose those Pistons and I'd like to turn 6k rpm, other ?s I have parts stack never heard of that sorry I'm new to all this thanks guys
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Old 01-05-2017, 12:27 PM
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Quote:
Originally Posted by Chevy6610 View Post
Sweet guys thanks for the feedback greatly appreciated so I didn't get the 350 I might've gotten a 3970010 302 short block previous owner said it came out of a 69 z28 it's a 4 bolt cylinders are rusty Pistons stuck, forged crank I have to pull the crank and check part numbers I can't find the engine Id cause I'm guessing it was decked at one point so I'm going off of word of mouth, well I'm trying to understand squish/quench never really heard of this term, I used a compression calculator and got 9.92:1 numbers I used bore: 4.030, stroke: 3.48, cylinder head volume: 64cc, eff Dome volume: 6.90 for those speed pros, deck clearance: 0.025 (found that on a quick Google search correct me if I'm wrong) compressed gasket thickness: 0.026, cylinders: 8, I'd like 10:1 compression ratio that's why I chose those Pistons and I'd like to turn 6k rpm, other ?s I have parts stack never heard of that sorry I'm new to all this thanks guys
If you find you have a 302 then you've got a real find worth some good money. As to the squish, stack, and why not trusting the factory 9.025 thing is important, Tech can guide you great there. I will say if you have a straight edge such as a level and some feeler gauges, you can figure out what your deck height currently is.
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Old 01-05-2017, 01:55 PM
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I have those things I'll check for it later, do you think there's any other engine ids anywhere other than the pad thanks.
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Old 01-05-2017, 04:47 PM
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Here's how to find the piston deck height with a steel rule and a set of feeler gauges......
http://lh4.ggpht.com/_oLX99Wx-rS4/TM...0/IMG_3112.JPG
Rock the crank back and forth to find absolute top dead center before measuring. As you are standing at the side of the motor, take your reading at 9:00 O'Clock and/or 3:00 O'Clock. Taking it at Noon or 6 PM will allow the piston to rock back and forth on the wrist pin and give you an erroneous reading.
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Old 01-06-2017, 07:09 AM
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Quote:
Originally Posted by techinspector1 View Post
Here's how to find the piston deck height with a steel rule and a set of feeler gauges......
http://lh4.ggpht.com/_oLX99Wx-rS4/TM...0/IMG_3112.JPG
Rock the crank back and forth to find absolute top dead center before measuring. As you are standing at the side of the motor, take your reading at 9:00 O'Clock and/or 3:00 O'Clock. Taking it at Noon or 6 PM will allow the piston to rock back and forth on the wrist pin and give you an erroneous reading.
Ok thanks techinspector1 I'll try it when I get home tonight
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Old 01-06-2017, 07:14 AM
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Ok thanks techinspector1 I'll try it when I get home tonight
So I would read that measurement as 9.005 in that pic sorry I'm confused new to all this but wanting to learn.
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Old 01-06-2017, 08:14 AM
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Originally Posted by Chevy6610 View Post
So I would read that measurement as 9.005 in that pic sorry I'm confused new to all this but wanting to learn.
correct,,,
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Old 01-06-2017, 08:17 AM
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Quote:
Originally Posted by Chevy6610 View Post
So I would read that measurement as 9.005 in that pic sorry I'm confused new to all this but wanting to learn.
What the photo shows is that the piston is down in the bore by 0.005" with the piston at top dead center, it does not show you anything about the stack of parts that are in the block.
With the steel rule and feeler gauge method, all you're measuring is the gap from the top of the piston to the block deck. In other words, how far the piston lacks coming to the very top of its bore. Normally, that would be somewhere in the neighborhood of 0.025" (twenty five thousandths of an inch) down to zero (piston crown even with the block). This photo shows that this particular build will put the piston at 0.005" piston deck height, nothing else. To reach a tight squish/quench, the builder might use a Cometic gasket that compresses to 0.036", thereby setting the squish/quench at 0.041".

If, for instance, the piston was 0.025" down in the bore, a fellow might want to use a steel shim head gasket that compresses to 0.015" when the head is bolted down. The 0.025", added to the 0.015", would make a squish/quench measurement of 0.040", right in the middle of the desired 0.035" to 0.045" squish dimension that best works to prevent detonation on pump gas.

If, for instance, the piston was 0.010" down in the bore, a fellow might want to use a composite gasket that compresses to 0.028". The 0.010", added to the 0.028", would make a squish/quench of 0.038", again, right in the middle of the 0.035"/0.045" standard that we shoot for.

If, for instance, the piston was at zero, even with the block deck, a fellow might want to use a composition gasket that compresses to 0.041", to make a squish/quench of 0.041".

If, for instance, the builder used a rebuilder piston with a shorter than standard compression height, the piston could be as much as 0.045" down in the bore, leaving no room for a head gasket if the builder was savvy about squish/quench. In this case, the block must be machined to reduce the height of the block decks and therefore bring the piston closer to the deck so that a proper gasket could be used to effect the proper squish/quench.

If, for instance, the piston popped up out of the block, perhaps because the block had previously been decked for a rebuilder piston and the current builder was using a standard compression height piston, then you might want to use a thicker composition gasket to set the squish/quench. Let's say that the piston breached the block by 0.012". You might use a gasket that compresses to 0.062". Deduct 0.012" from 0.062" and you find that you have engineered in a squish/quench of 0.040".

And again, do not confuse piston deck height with the stack height. Stack is the sum of the radius of the crank added to the connecting rod length added to the piston compression height. For instance, on a 350 Chevy, the crank radius (half the stroke) is 1.740", the connecting rod length is 5.7" and the standard piston compression height is 1.560". These 3 values add up together to make the "stack" dimension. In this case, the stack would be 9.000". The nominal block deck height from the factory is 9.025", so with a 9.000" stack fitted into the block, the piston crown would be 0.025" down in the bore and you would use a 0.015" gasket to make a 0.040" squish/quench.

This is where most amateur builders screw the pooch, they fail to know the stack and the block deck height ahead of time and end up in trouble with the piston deck height.
.

Last edited by techinspector1; 01-06-2017 at 08:37 AM.
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Old 01-06-2017, 10:07 AM
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Originally Posted by techinspector1 View Post
What the photo shows is that the piston is down in the bore by 0.005" with the piston at top dead center, it does not show you anything about the stack of parts that are in the block.
With the steel rule and feeler gauge method, all you're measuring is the gap from the top of the piston to the block deck. In other words, how far the piston lacks coming to the very top of its bore. Normally, that would be somewhere in the neighborhood of 0.025" (twenty five thousandths of an inch) down to zero (piston crown even with the block). This photo shows that this particular build will put the piston at 0.005" piston deck height, nothing else. To reach a tight squish/quench, the builder might use a Cometic gasket that compresses to 0.036", thereby setting the squish/quench at 0.041".

If, for instance, the piston was 0.025" down in the bore, a fellow might want to use a steel shim head gasket that compresses to 0.015" when the head is bolted down. The 0.025", added to the 0.015", would make a squish/quench measurement of 0.040", right in the middle of the desired 0.035" to 0.045" squish dimension that best works to prevent detonation on pump gas.

If, for instance, the piston was 0.010" down in the bore, a fellow might want to use a composite gasket that compresses to 0.028". The 0.010", added to the 0.028", would make a squish/quench of 0.038", again, right in the middle of the 0.035"/0.045" standard that we shoot for.

If, for instance, the piston was at zero, even with the block deck, a fellow might want to use a composition gasket that compresses to 0.041", to make a squish/quench of 0.041".

If, for instance, the builder used a rebuilder piston with a shorter than standard compression height, the piston could be as much as 0.045" down in the bore, leaving no room for a head gasket if the builder was savvy about squish/quench. In this case, the block must be machined to reduce the height of the block decks and therefore bring the piston closer to the deck so that a proper gasket could be used to effect the proper squish/quench.

If, for instance, the piston popped up out of the block, perhaps because the block had previously been decked for a rebuilder piston and the current builder was using a standard compression height piston, then you might want to use a thicker composition gasket to set the squish/quench. Let's say that the piston breached the block by 0.012". You might use a gasket that compresses to 0.062". Deduct 0.012" from 0.062" and you find that you have engineered in a squish/quench of 0.040".

And again, do not confuse piston deck height with the stack height. Stack is the sum of the radius of the crank added to the connecting rod length added to the piston compression height. For instance, on a 350 Chevy, the crank radius (half the stroke) is 1.740", the connecting rod length is 5.7" and the standard piston compression height is 1.560". These 3 values add up together to make the "stack" dimension. In this case, the stack would be 9.000". The nominal block deck height from the factory is 9.025", so with a 9.000" stack fitted into the block, the piston crown would be 0.025" down in the bore and you would use a 0.015" gasket to make a 0.040" squish/quench.

This is where most amateur builders screw the pooch, they fail to know the stack and the block deck height ahead of time and end up in trouble with the piston deck height.
.
Wow great write up now I completely understand the squish/quench concept/method I'm gonna get the measurements for this "302" block cause it's been decked before, let's just say it was decked 10 under putting it at 0.015 what piston compression height would I expect? Thanks for everything I wanna do this right the first I've learned my lessons on past builds lol.
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