347 or 352?

Mook · Oct 18, 2004

I am planning on getting a dart block and scat forged internals... I have a choice of going with either .30 over pistons (347) or .60 over pistons (352) for the same price. Is there any reason I should not to get the extra cubes? Is a .60 over the largest standard size piston you can get before going to custom pistons?, would I be better off sticking with a .30 or .40 over bore piston that way if I need to bore it again I would still be able to use a standard piston? Thanks

Gearbanger 101 · Oct 18, 2004

No power advantage, just hotter running cylinders with less forgivness if an overbore is needed in the future.

87'GTstang · Oct 18, 2004

If you have ever found the factory specs on a 302, you will find the bore range to be (recomended) from 4.000" - 4.030", so there is your answer. .040 is pushing it and .060 is an engine suicide waiting to happen. There is no point in going that large of an engine anyway, a 347 is maxing it as it is, safely that is. The difference in power between the two would be similar to the difference in a larger throttle body swap - no real huge gains.

tjm73 · Oct 18, 2004

87'GTstang said:
If you have ever found the factory specs on a 302, you will find the bore range to be (recomended) from 4.000" - 4.030", so there is your answer. .040 is pushing it and .060 is an engine suicide waiting to happen.

The Dart block does not have the same issues or tolerance limitations as the factory block, so comparing it to the factory block is like comparing the atomic bomb to a slingshot. Absolutly nothing in common other than they are both weapons.

The Dart block will take up to a 4.125" bore (something the OEM block can't even dream about), so you could easily go 352. Could go as big as 363 with the 4.125" bore, but you wouldn't have room for a rebuild if something happened. I myself would go 355. Leaves you 2 rebuilds if you need them.

Bore
4.060 = 352
4.080 = 355
4.100 = 359
4.125 = 363

bluevenom867 · Oct 18, 2004

tjm73 said:
The Dart block does not have the same issues or tolerance limitations as the factory block, so comparing it to the factory block is like comparing the atomic bomb to a slingshot. Absolutly nothing in common other than they are both weapons.

The Dart block will take up to a 4.125" bore (something the OEM block can't even dream about), so you could easily go 352. Could go as big as 363 with the 4.125" bore, but you wouldn't have room for a rebuild if something happened. I myself would go 355. Leaves you 2 rebuilds if you need them.

Bore
4.060 = 352
4.080 = 355
4.100 = 359
4.125 = 363

Actuly you can got to a 374 if you use a 3.5 storke crank.Go .06 over and put a 3.5 stroke crank in and you will get a 362 with lots of torque and room for more piston in the future.And yes there is a power advantage because the bore is larger it un-shrouds the valve and has a larger flame front for longer flame travel.

tjm73 · Oct 18, 2004

bluevenom867 said:
Actuly you can got to a 374 if you use a 3.5 storke crank.Go .06 over and put a 3.5 stroke crank in and you will get a 362 with lots of torque and room for more piston in the future.And yes there is a power advantage because the bore is larger it un-shrouds the valve and has a larger flame front for longer flame travel.

I wondered about that. I couldn't find max crank throw specs so I stuck with 3.40". How big of a crank throw can the Dart block take?

bluevenom867 · Oct 18, 2004

tjm73 said:
I wondered about that. I couldn't find max crank throw specs so I stuck with 3.40". How big of a crank throw can the Dart block take?

That is the biggest I think it can go.I haven't seen any cranks bigger than that for the 302 either.

Mook · Oct 19, 2004

Thanks for all the great info guys.... I will check further into the 3.50" stroke idea.. One question I do have is at what size bore do you start getting into
custom pistons .80? .100?, I know that custom pistons can get pricey and would like to keep with standard sized pistons if I can to keep the cost down.

tjm73 · Oct 19, 2004

Mook said:
One question I do have is at what size bore do you start getting into
custom pistons .80? .100?, I know that custom pistons can get pricey and would like to keep with standard sized pistons if I can to keep the cost down.

There are several places that make pistons that are not much more money than a standard set would cost. Talk to the companies that do strokers and see what they have to offer.

bluevenom867 · Oct 19, 2004

Mook said:
Thanks for all the great info guys.... I will check further into the 3.50" stroke idea.. One question I do have is at what size bore do you start getting into
custom pistons .80? .100?, I know that custom pistons can get pricey and would like to keep with standard sized pistons if I can to keep the cost down.

I know SCAT has thous profiled forged cranks for the 302 and you can get a 3.5 stroke.And most bores above .06 are gonna need a custom piston.

347 or 352?

Mook

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