How Can I Know if I have a 347?

90silverstang · Feb 2, 2011

Is there a way I can test a engine to verify it is a 347, without tearing it down. I know its based on bore and stroke, but how can I measure the stroke?

stykthyn · Feb 2, 2011

Not sure if its possible without tearing into it.

clement · Feb 2, 2011

pull the heads off and measure the stroke of the piston

giddyup306 · Feb 2, 2011

They have tools where you close both valves and then screw in the calibrated tool to see how much air moves this little ball.

clement · Feb 2, 2011

P&Gs start around $900. its cheaper to pull a head

robo · Feb 2, 2011

there's a long skinny pedal on the right. push it down with your foot real hard and see what happens.

or, pull a head like mentioned before.

S&B · Feb 2, 2011

Carfox ?

85_SS_302_Coupe · Feb 3, 2011

You could try to remove a spark plug and measure the distance the piston travels in the stroke...that should give you at least some kind of idea how much stroke it has....at least enough to know if it's stock or not.

FastDriver · Feb 3, 2011

that only works if the spark plug is perpendicular to the surface of the piston.

Here's a thought: fabricate your own tool.
1. Get the hose from a compression tester that screws into the spark plug hole.
2. Get a big syringe, or just use a balloon or bag that you can make air-tight to the end of the hose
3. remove the rockers from the valves on the cylinder you're testing and rotate to BDC
4. plug in your fabricated tool
5. Rotate to TDC
6. Measure the air that is pushed through the spark plug hole. A 347 should have 347/8 = 43.375 c.i. of air or 710.79 c.c. or mL (1cc=1mL)

FastDriver · Feb 3, 2011

I couldn't find any syringes big enough so I started looking for other ways to measure the volume of the air.

I'm not sure how accurate this is, but this is supposedly how to calculate the volume of a balloon: How to Measure Air Volume | eHow.com

Also, since the balloon actually pressurizes the air a big, I don't know how much that will throw off calculations.

Alternately, you could make another tool from a bottle that's at least 1L, preferrably glass, and a 50mL syringe or a Measuring cup with pretty accurate markings:
1. fill the bottle 50 or 100mL at a time with your syringe or measuring cup, and mark the bottle's water level
continue to do this until you can measure the water level up to 800mL
2. fill your bottle with water
3. Fill your sink with water
4. turn the bottle upside down and ensure that it is held in place above the water level in the sink
5. empty the air you trapped into the bottle and use the measurements you made to determine how much air you have. To avoid placing pressure or vacuum on the air in the bottle, raise or lower the bottle so that that water level in the bottle is at the water level in the sink

for reference:
302 = 618.6cc or mL per cylinder
331 = 678cc or mL
347 = 710.8 cc or mL

cjrpony · Feb 3, 2011

If you can, pull the oil pan and look for markings on the crank and for clearance notches in the block. One of my 331's actually had the stroke and part number etched right on the counter weight.

90silverstang · Feb 3, 2011

FastDriver said:
that only works if the spark plug is perpendicular to the surface of the piston.

Here's a thought: fabricate your own tool.
1. Get the hose from a compression tester that screws into the spark plug hole.
2. Get a big syringe, or just use a balloon or bag that you can make air-tight to the end of the hose
3. remove the rockers from the valves on the cylinder you're testing and rotate to BDC
4. plug in your fabricated tool
5. Rotate to TDC
6. Measure the air that is pushed through the spark plug hole. A 347 should have 347/8 = 43.375 c.i. of air or 710.79 c.c. or mL (1cc=1mL)

How about using some kind of air flow meter. (Cubic feet per min). Problem with that is it would be hard to measure because air is not flowing at a constant.
Thanks for some of your ideas

90silverstang · Feb 3, 2011

FastDriver said:
I couldn't find any syringes big enough so I started looking for other ways to measure the volume of the air.

I'm not sure how accurate this is, but this is supposedly how to calculate the volume of a balloon: How to Measure Air Volume | eHow.com

Also, since the balloon actually pressurizes the air a big, I don't know how much that will throw off calculations.

Alternately, you could make another tool from a bottle that's at least 1L, preferrably glass, and a 50mL syringe or a Measuring cup with pretty accurate markings:
1. fill the bottle 50 or 100mL at a time with your syringe or measuring cup, and mark the bottle's water level
continue to do this until you can measure the water level up to 800mL
2. fill your bottle with water
3. Fill your sink with water
4. turn the bottle upside down and ensure that it is held in place above the water level in the sink
5. empty the air you trapped into the bottle and use the measurements you made to determine how much air you have. To avoid placing pressure or vacuum on the air in the bottle, raise or lower the bottle so that that water level in the bottle is at the water level in the sink

for reference:
302 = 618.6cc or mL per cylinder
331 = 678cc or mL
347 = 710.8 cc or mL

Are you saying to displace the water in the pre measured bottle with the air thats flowing from the cylinder, to see if the air pushes out 710.8cc of water?

FastDriver · Feb 4, 2011

Yes, exactly. First, trap the air in a bag, balloon or whatever using the first tool, then empty the air into an inverted bottle that you've marked and see how much water is displaced.

90silverstang · Feb 4, 2011

FastDriver said:
Yes, exactly. First, trap the air in a bag, balloon or whatever using the first tool, then empty the air into an inverted bottle that you've marked and see how much water is displaced.

The bottle should be filled with water, correct? If it has air in it already I dont think the measurement would be accurate. I may be wrong.
I think the syringe method would work because you can set the plunger all the way down (no air in the syringe). The air from the cylinder would displace the plunger (if the syringe is large enough). If you can some how mark the syringe in cc's you would not have to use the water method.

FastDriver · Feb 4, 2011

Most syringes are marked in cc's. However, I've never seen a 1L syringe before.

And the answer to your initial question is yes.

85_SS_302_Coupe · Feb 6, 2011

If you have a stock 302 to compare it to, you can pull spark plugs on both and stick a coat hanger in the cylinder while the piston is at the bottom of the stroke and park it with a marker, then stick it in the engine in question and see if it goes in just a bit further. Like is said it's not very accurate but it should at least be enough to show if it's a longer than stock stroke. It's better than nothing.

faststang90 · Feb 6, 2011

not the best way but put a small rod in the spark plug hole.u will need to hold the rod from moving around then turn the motor where the rod stops. then mark it. then turn the motor to where the rod comes up. when it stops mark the rod. the mearsure the distance between the rod. if u get alittle less than 3.1/2 u have a 347. if u have 3.1/4 u have a 331.

FastDriver · Feb 7, 2011

342-347c.i. is 3.4" stroke, 327-331c.i. is 3.25", 302-306c.i. is 3.0"

Are you sure that going through the spark plug hole will be perpendicular to the surface of the piston? If not, then you're going to get longer measurements than the above, anyway. If you're off by one-quarter of an inch, you'll be convinced you have a 331 when you really have a 302.

85_SS_302_Coupe · Feb 7, 2011

I'm just sayin, it should be a repeatable process, and if you measure a known stock 302, regardless what it measures you should measure something different on a stroker and that should tell you that it's at least not stock. I know it's not a scientific way to get a real measurement but if you don't wanna pull the head it should at least tell you something, and it's not like it's a lot of work.

How Can I Know if I have a 347?

90silverstang

Member

stykthyn

I want to measure mine. It doesn't look that tall.

clement

giddyup306

clement

robo

Member

S&B

I hate my CT. :(

85_SS_302_Coupe

it sucks (I know) to be on the receiving end

FastDriver

I was uncomfortably high & wearing a helmet

FastDriver

I was uncomfortably high & wearing a helmet

cjrpony

Member

90silverstang

Member

90silverstang

Member

FastDriver

I was uncomfortably high & wearing a helmet

90silverstang

Member

FastDriver

I was uncomfortably high & wearing a helmet

85_SS_302_Coupe

it sucks (I know) to be on the receiving end

faststang90

FastDriver

I was uncomfortably high & wearing a helmet

85_SS_302_Coupe

it sucks (I know) to be on the receiving end

Similar threads

How Can I Know if I have a 347?

Member

I want to measure mine. It doesn't look that tall.

Member

I hate my CT. :(

it sucks (I know) to be on the receiving end

I was uncomfortably high & wearing a helmet

I was uncomfortably high & wearing a helmet

Member

Member

Member

I was uncomfortably high & wearing a helmet

Member

I was uncomfortably high & wearing a helmet

it sucks (I know) to be on the receiving end

I was uncomfortably high & wearing a helmet

it sucks (I know) to be on the receiving end

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