I have been reading a lot on my next build since it's going to put out a lot of power. I'm just looking for some people to answer me a few questions if they can. I already have a 406 in my car making 573 flywheel HP, I have another 400sbc that I was going to build. Since reading I have really begun thinking about going with a aftermarket block, particularly the Motown block or the Dart Little M. I have also been toying with a aluminum block but the weight savings isnt worth the 3k extra price tag. The next motor is going to get a substantial amount of power increased over the current engine too.

So here are my questions....

1. Is it worth it to go with a aftermarket block over a stock GM casting thats been machined, studs, splayed mains etc.

2. Is a aluminum block worth the price? What are the pros and cons?

3. How big should I go? Stock block can safely be a 427ci sbc while still having some extra clearance. A aftermarket block can go up to 472ci sbc...****in monsters.

4. Heads... I have a very nice set of cast iron heads that flow as well as AFR 195cc heads but should I upgrade to aluminums? I've been told the castirons can take more of a beating especially with nitrous, but aluminums can run a point higher compression and have the weight savings. Do I upgrade?

Thanks for any help guys.

 

After market block for shure you will want a dart block as it takes less money in machine work to prep it. And if you want big inchs or biger than a 4'' stroke you are going to need a dart rocket block with wider pan rails and raised cam. Stock blocks are good to around 650hp give or take 50 hp thay love to crack on #1 main and the steam holes will crack into the cylinders. as for heads to feed this you are going to need a good set of heads somthing like CFE 15 deg heads if you go 434 or larger with some comp. You can not make HP with out good heads.

 

I wasnt planning on going huge, more in question about the blocks. plan on putting a blower on it and a nitrous setup.

 

1: Yes. Aftermarket blocks will always have better castings than production blocks.

2: Typically designed as race only for those who are trying to cut weight down as much as possible. There's no other performance advantage other than weight. For the average person, is the extra $3000 worth it? No.

3: Stock block to 427? Not in a Gen I casting. The LS castings have that ability. It would be cheaper to build a 540 BBC than a 572 SBC.

4: The price of aluminum heads makes them a very cheap upgrade now. Years ago they were an exotic upgrade. They're very affordable now so anyone can afford to buy them. Big engines need more air to breath. I think 195's are good enough for a 350/383 but may be at the limits for a good 400 block. Depends on the power level and rpm range the engine will run at. Big heads also cost more. Big heads on a SBC are more expensive than similar sized small heads for a BBC. HP costs money. I've seen SBC heads that out flow my BBC ones but I couldn't afford them.

There comes a point where you make enough power that production stuff just doesn't cut it any more. Although factory stuff can still be made to work, it doesn't become reliable. The only thing "factory" on or in my engine is the alternator and the distributor hold down. Everything else is aftermarket.

 

Thanks for the info. I need to decide which casting to pick now. The GMPP blocks are nice as are the Dart and World blocks. I have contemplated doing a BBC many time but something tells me to stay with the SBC's. I got a great deal on some castiron heads that flow extremely well and have been ported out from a 200cc casting. I plan for about 700hp on the next motor and I didnt think the stock block could take it and wasnt worth investing in it to try and make it stronger when the price of a Little M block is pretty cheap.

 

I would go with the dart block and some afrs 227's if the budget allows.

 

Whats the diffrence between the Little M and the Motown? Both seem very similar to me. Is it just the bores come finished on the Little M?

 

Dart blocks are just better blocks. All bare blocks need finishing. My BBC uses a Dart Big M block. The other choice was a Merlin block but the casting isn't as good. Dart castings in SBC and BBC are very good.

Another option is to buy a short block or even a long block. It will save you a lot of time and money.