OK Guys I don't know crap about engine building.
That said, I wanted to put a 427 into my truck. I talked to a very well known engine builder and this is what he said.
A 408 will be alot stronger than a 427 for boosted applications. He said you could up the boost a couple of pounds more to make up the the CID differance. I ask about an Iron block stroked 427 and he said you can't do it. Something about the thickness of the block or something like that.
Any help would be apreciated.
Mark

 

dont go over a 408 on a 6.0L block stroke wise which is a 4.000 stroke and .030 overbore

1slowz71 (i think is his name) tried to do a 418 (4.100 stroke)well he has done it but has had a bunch of problems

im sure youve heard of parish8 he has a 408/turbo with a 10.08 time slip and over 1000hp

 

I highly recommend no more than 4.00 stroke due to the piston pulling too far out of the bottom of the cyl. The pistons rocks too much and causes clearance issues with the counter weight on the crank and not to mention the wear on the pistons when it rocks against the bottom edge of the cyl.

 

If you go with a over a 4.0" stroke you don't have enough room between the pin and the top of the piston to have complete ring grooves.So you can have ring sealing problems in the unsupported areas around the piston pin.

 

For the price difference go with a 408. You CAN have an iron block 427. Throw some Darton sleeves in it and be done with it. The price difference is stupid. Go 408 and be done with it, you will save alot of money. Just an FYI, C5R blocks are about 5500 from GM, and iron block with Darton sleeves will run you close to 3000, a bored 6L block BRAND NEW will run you 800 bucks, 600 for the block 200 for machine work. You get my drift? Atleast 2K for another 20-30hp. For that price difference you could put it towards heads, etc. If it was me and going turbo with maximum effort this is what I would do; New iron block/good used donor, bore to 4.03, C5R main billet caps(made of billet aluminum instead of cast iron), ARP studs thorughout, Lunati 4" crank, Lunati Pro Billet rods(super strong), JE/Wiseco pistons either are a good choice IMO, hellfire or total seal rings(total seal are good but have caused some problems with sealing too well and sucking oil thorugh the valve stems), double roller timing chain, cometic head gaskets(best you can get IMO), cam of your choice, Morel lifters(wouldnt trust stock lifters to high rpm and extra pressure from stiff springs, comp lifters in all types seem to be noisy and hard to adjust and the morels have ahigher oil port for high lift cams), ALL PRO heads(they have EXTRA thick decks for strength in a high cylinder pressure turbo app), Jesel shaftmount pro series(they have adjustable pushrod cups to set valve lash perfectly and damn they are strong), springs should be supplied with your heads. Long *** run-on sentence You building it or someone else. Try to get the lightest pistons you can since it will let the engine rev fast since most likely you will have a little boost lag, throw a ncie fat tripple disk stall in there too and of course and 80e and that should do you pretty good.

I have done extensive research for the rebuild on my 418 so I have already been through most of this since Im going for all top of the line components this time shoot me a PM if you need any help

 

1slow01Z71,
Thanks for the good info,
In a week or so I will PM you.
Mark

 

The 408 would be a better boost motor then a 427.

 

Curious as to why you say that.

 

You'll gain strength in the piston and also have less rock in the piston because of the 4.125 stroke.

We'll gain .075 thou (1/2 of the throw of .125" extra stroke) on the top ring land thickening it up quite a bit.

Instead of a .220" 1st ring land, you'll now be close to a .300 ring land, which is good for 300hp worth of power adder and a very strong piston you'll never hurt.

 

408 and 427 BOTH have a 4.000" stroke, 427 are sleeved LS1/LS6 blocks with a 4.125 bore.