What´s the best replacement for AQ271C (or 570) 5.7 GM engine, ideally stroker?

[Scott Danforth]

if you buy a pre-made spec built stroker, it will have cast pistons with 4-relief cuts. basically stock GM pistons. you leave a lot of power on the table (about 40-50hp) when you do that vs picking the proper pistons to work with vortec heads (LCQ style)

cost of a new 6.2 base motor is about $4700-$5300 depending on where you get it (their prices also went up from the beginning of the year)

6.2L - 383 c.i. "Stroker" Base Marine Engine

6.2L - 383 c.i. "Stroker" Base Marine Engine

www.michiganmotorz.com

the pre-made 377 or 383 motors are about 350hp at the crank or 320hp at the prop.

 

[bollerwagon]

I´ve asked the Center State Marine Engines guys, if they´re willing to share what exact parts they use to build the engine, but this is all I got out from them "We use a Mercruiser 383 camshaft in the stroker engine, a SCAT crankshaft and connecting rods, and Sealed Pro pistons."

 

[Scott Danforth]

the mercruiser camshaft is same for the 350 and 383, only difference is the 1.6:1 rockers.

they use a flat top 4-relief piston (not a proper piston for building a 377 or 383)

 

[bollerwagon]

Are there any reasonable priced offers on the market, where you can get a proper build stroker then?

 

[Scott Danforth]

Are there any reasonable priced offers on the market, where you can get a proper build stroker then?

Mast automotive machine shops rhat also support marine and racing. Would seny you to my guy here in Florida, hoewever he retired last year.

A few in the midwest

 

[bollerwagon]

I had a long conversatoin with Tim from Center State Marine Engines and he says for this engine
http://marineengines4less.com/marin...gine-with-intake-replaces-years-1996-present/ they use Keith Black/KB Pistons 9912HC. They have this small table to reduce compression so it works well with low ocatane fuel. Since we only have 95 and higher octane fuel in germany, we theoretically should be able to go up to 11:1 compression.
They might be willing to put in other pistons. If I understand @Scott Danforth right, the surface of the piston should match with the hole in the head to form a nice compression chamber - probably the LCQ style piston. But what exactly should I ask them to use?

Other than than that there seems to me a small safety advantage for the electric fuel pump, so if the engine stalls but still turns, it will not pump fuel. While I write this I realize, since the engine is still turning there might still be oil pressure and ignition fire, so the electrc fuel pump will also continue to pump? Anyway, what do you say? Electric or mechanic?

 

[Scott Danforth]

you pick the pistons based on the combustion chamber shape of the heads, stroke, compression height, deck height and rod length. The KB D-shapped recess with 2 reliefs is a LCQ style piston when used with a vortec combustion chamber. if they are starting with virgin blocks, deck height is a given. if they are dealing with a used block, then then deck height is determined after line-honing the mains and decking the block.

There is no safety for an electric fuel pump itself, only in how its wired. a mechanical pump will be better than electric hands down from a performance/longevity/cost stand point.

a mechanical pump will last many many decades. an electric pump will last about 15 years.

 

[bollerwagon]

The KB D-shapped recess with 2 reliefs is a LCQ style piston when used with a vortec combustion chamber.

How is this piston D-shaped? From the picture it looks round, except the two reliefs.

if they are starting with virgin blocks, deck height is a given. if they are dealing with a used block, then then deck height is determined after line-honing the mains and decking the block.

I would go for the remanufactured block, since it´s 1100 USD cheaper than a new one.
Side story: he explained to me that the higher prices for the blocks this year come from a regulation that forced GM to produce in the States instead of Mexico. And due to higher labor costs the price on the blocks is a bit higher now.

There is no safety for an electric fuel pump itself, only in how its wired. a mechanical pump will be better than electric hands down from a performance/longevity/cost stand point.

a mechanical pump will last many many decades. an electric pump will last about 15 years.

He says I can pick what I want, since they would then just take a block with or without an opening for e mechanical pump-

 

[Scott Danforth]

that isnt a D-shapped piston.

this is

 

[Scott Danforth]

and this is

 

[bollerwagon]

True, I thought you were referring to the KB 9912HC Piston. So what part number would you suggest, considering the availability of a high octane fuel?

 

[Scott Danforth]

you need the quench pad.

make sure the final quench distance is in the .040 range

are they using a used block, or a new block?

the GMPP blocks have the mechanical fuel pump boss machined. the stock GM blocks do not.

 

[Scott Danforth]

keep the compression ratio about 9.4 and dont worry about the fuel.

 

[Scott Danforth]

so..... what heads will you be running?
that is where you start with the determination of piston.

the next question is new or used block to determine bore and deck height

 

[bollerwagon]

They use the 062 Vortec heads and price wise I would use the used block variant (see below).

I would expect a higher compression to make sense performance wise. Or is that not suitable for this kind of antique engine design?

 

[Scott Danforth]

stock blocks with roller cams do not have the machined fuel pump boss.

you want a roller cam.

they could fly-cut the mounting surface and drill the hole for the push-rod and oil return

 

[Scott Danforth]

are they balancing the motor?

 

[bollerwagon]

I understood they can just pick any block with the mechanical fuel pump holes and build on it.

The spec sheat reads "Hydralic Roller Camshaft". Hydralic? Whats´s that? Does anyone know the simpsons episode with the "malk"? Should I be suspicious?

They say the engine comes balanced, they have a machine mo measure all components and it tells them where to take material off to balance it

 

[bollerwagon]

@Scott Danforth, earlier you mentioned that you can build a 6.2 liter with 420hp.

if you want more power, then you need to build a 377 or 383 (vs buying a GM crate motor with the god awful flat-top 4-relief cast crap pistons. you can build 420hp 6.2 liter

If we take the Center Stage engine, put in the D-shaped pistons, what else would be easily doable to have maximum power that does not hurt my wallet too bad and won´t reduce engine durability?
- higher compression is not the way, as I understand?
- maybe order the Edelbrock Performer #2516 intake for a 200$ add on fee

What else would you do?

 

[Lou C]

I understood they can just pick any block with the mechanical fuel pump holes and build on it.

The spec sheat reads "Hydralic Roller Camshaft". Hydralic? Whats´s that? Does anyone know the simpsons episode with the "malk"? Should I be suspicious?

They say the engine comes balanced, they have a machine mo measure all components and it tells them where to take material off to balance it

That’s standard GM practice (hydraulic tappet cam) and roller is big improvement over the previous style flat tappet camshaft actually. Roller is less prone to wear and nearly all GM small block V8s since 1955 were hydraulic lifter camshaft equipped. Just a few high performance applications used a mechanical tappet camshaft.