Ok, I have a Mark IV block 4 bolt main bored .60 over. I have 2 sets of iron heads, one set of oval port, and one set rectangular. I have a used set ( very low miles, was used in an airboat, less than 100 hours) of forged .60 pistons, forged rods and forged crank. The crank has a nick in it and will have to be turned, also I will need to buy one piston and one rod because the motor dropped a piston.

Option #1 Buy a piston and rod and have the crank turned. Also buy a new set of aluminum heads, 325cc w/ 2.30 valves.

Option #2 Buy a 496 Stroker kit with new forged pistons, rods, and crank. I will have to used the iron heads and port them myself.

Both options will cost about $2,000. I leaning HARD towards Option #1 because I'll be saving weight (100lbs of the front end) plus more HP and TQ then the ported iron heads. Plus with the aluminim heads I'll be able to run a higher compression ratio.

What are your opinions??


[Modified by Thad, 10:39 PM 10/8/2001]

 

Someone HAS to have an opinion on this??!! :D

 

Ok lets see:
1. You lost me on option 1 because you said you have a used set of .30 over pistions but you claim you are thinking about boring the motor .60 over. How do your .30 over pistions work with that? Don't you now need .60 over pistons so now you need to buy a complete set or am I missing something?
I like the aluminum head option for the wieght drop and the performance on this option though.
2. When anyone mentions the word stroker I get excited. More cubes more cubes more cubes. As far as the heads are concerned if you can port them yourself I would get a try and see how things works out.


:chevy

 

I'll take extra displacement over aluminum heads any day of the week! Build the bigger motor, then make the aluminum heads next winter's project.

 

I agree on the issue with the .030 pistons and the .060 bore. Huh?

The 496 and rectangular port idea sounds pretty good. Depends on how much cam you're going to use and how much you want to rev, gearing trans etc.

Either one will work, just depends on what yuor plans are.

Give more details.


Jim

 

Sorry guys didn't mean to confuse you. The block was bored .30 over and recently borded .60 over and a rod was bent. So I will need to order a piston and rod. True, 496 cubic inches sounds a lot better than 468ci, but let me add I plan WITHOUT a doubt to use Nitrous on this motor. I ran both motors on my desktop dyno and both the 468 and the 496 made the same peak hp, 650hp at 6,000rpms and the tq difference was only 30lbs difference across the rpm bad peaking at 655tq at 4000 rpms for the 496 while the 468 peaked at 625tq at 4,000rpms. I plan to have everything balanced and not turn over 7Krpms. So I was looking at 325cc heads w/ 2.40 valves.

So I will most like go with the 468 and put a 200hp-300hp shot of N20. With forged internals and a 4 bolt block she should hold up fine. My dad built a 468 for a friend that turned 1250hp with a shot of N20 for his tractor (tractor pull).

Any other opinions???

 

Thad... a few things to remember if you are not already aware of them-

1) Any combination of pistons and cylinder bore you use must be measured (mic'd) before assembly to determine piston to wall clearance. You should start by measuring the cylinder bores. Saying a block is ".060" does not always guarantee a specific bore size. Block bore sizes can vary considerably between the "low" side and the "high" side of a spec. Same thing for pistons... one manufacturers .060 piston may be a different diameter than another manufacturers. Some manufacturers run low, some run high. To build an engine correctly, when a block is bored, the machinist must have at least one of the intended pistons in his hand to determine the actual final bore size. The block should be bored to match the piston, and the final hone (bringing the block to its final bore size) should be done to match the intended rings.

2) The bore may have to be honed to match the type of ring you choose. The final finish (grit) and hone pattern (degrees) determine if and how well piston rings will seal. This is critical to the performance & longevity of your engine. The final hone may take a thousandth or more off the bore size.

For example, boring a block for a set of cast pistons and iron rings is much different than boring a block for forged pistons and chrome faced rings.

You should not just assume everything out of a catalog will fit properly.

Every engine I build, I always approach as a "system" of parts. I Mic each hole in the the block and each piston. If I am recycling used pistons (almost never), each piston must be measured and matched to its best fit bore. This is the only way to build an engine that will both perform and last. Also, any engine that will see any form of abuse, I balance.

You probably already know all of this, but I thought I would mention it just in case. I've seen many people build engines only to find out that the new engine burns oil and has excessive piston rock/slap. The engine lasts a month and then has to be rebuilt again. So... just be careful how you put together your "system" of parts.

 

I think I would go with #1. With that and a 250Hp shot you should move along pretty well.

 

when 427 were all there was GM said to the race officials that they needed to drop weight yup guess what they did the bored the cylinders so big that you could put you hand through in a fist they save alot of weight :yesnod:

ZD