When did they first appear,can gen IV heads be used on these blocks without any mods?Up to what lift can be accomodated with the factory roller setup?I'm planning on using an electric fuel pump anyway so if it isn't machined for it it will be ok.Is .080" a safe overbore on these blocks or do they run marginal cylinder thickness?Can they be strocked to 496 with no problems?Any links to build ups or data on gen V big blocks are welcome.Thanks,HF.

1991 was the first year for GenV.
I dont think GenVs were rollers, mine isn't. What year is yours?
I believe that you cannot use MarkIV heads on the GenV engines the water passage holes will not match between the block and head. I think there is a gasket out there that will allow you to use the older generation heads on the GenV, but I dont know who sells it.
I dont see why you would not be able to get 496cuin out of a GenV block.
You might want to ask more on this forum (www.454ss.com) they are all about trucks but will have much more knowledge and information to your questions than me.

Renzo

Older Mk IV heads on the newer Gen V block is a coolant leaker. The newer heads can go on the older blocks, though.

Victor sells two "special" gaskets, one for left side and one for right side, to use older heads on newer blocks. I've never tried them. Any parts store that sells Victor can get 'em for you. They're listed in the regular Victor catalog.

.060 is about all the overbore you're gonna get.

Far as I know, 4.25 cranks aren't a problem, but of course you'll need one for a one-piece rear main.

I have taken a GEN V 454 Block to .120 over with no problems had it sonic tested and still had good wall thinkness. And u can stroke it to 496 easly. I have also used those conversion gaskets and they worked fine, They were not that high priced either. Also u will need to get retrofit roller lifters because the GEN V block has no center spider hold down studs and would be cheaper to just use retrofit roller cam parts. The best thing to do is get the step nose type camshaft so u dont have to use a thrust button and the cam retainer is like 5 bucks. Hope this helps

Also use a 2 piece rear main conversion kit so u dont have to find a 1 piece rear main crankshaft they go for around 35 bucks

Originally posted by sugarwolfpimp69:
I have taken a GEN V 454 Block to .120 over with no problems had it sonic tested and still had good wall thinkness. And u can stroke it to 496 easly. I have also used those conversion gaskets and they worked fine, They were not that high priced either. Also u will need to get retrofit roller lifters because the GEN V block has no center spider hold down studs and would be cheaper to just use retrofit roller cam parts. The best thing to do is get the step nose type camshaft so u dont have to use a thrust button and the cam retainer is like 5 bucks. Hope this helps =
They must vary a bunch as I just sonic tested two of them for a customer & I wouldn't bore either over .060.
The thicker of the two was .210 in a couple of cylinders on the thrust side.

Won't a custom oil pan also be required?

U just need a pan for a mark5/6 with one piece rear seal all major oil pan companies make them and one is also available thourgh the GM dealer. I called scroggins & dickey down in texas last year on putting the older gen 4 heads on the mark5/6 blocks and there tech guy said they make a plug kit ($35 or so) for the block to put the older heads on them (i belive there put into the block to make coolant passage smaller). He said they have sold many and had good luck with them, in fact they had a hard time keeping them in stock. I was going to put a set of 70 LS-6 106.9cc closed chamber SQ ports on my 1994 502 to make 9.9 compression ratio, but sold the shortblock.

Yea you will need a GEN V VI Pan I am using a moroso one and the 2 pice rear main adaptor works for the Gen V VI Pan

I have a gen V big block and was using gen lV aluminum heads. I bought the kit from Scoogins. You have to use a certain fel-pro gasket. The number on the gasket I beleive is FEL 1017-1. I didn't have any water leaks. If your going to run over sized valves make sure you get valve reliefs cut in the top of the cylinder walls. I didn't and it's going to cost me about $4,000 in repairs.

Originally posted by chris454ss1970:
I didn't and it's going to cost me about $4,000 in repairs. :( That's terrible..... graemlins/sad.gif

Originally posted by chris454ss1970:
I have a gen V big block and was using gen lV aluminum heads. If your going to run over sized valves make sure you get valve reliefs cut in the top of the cylinder walls. I didn't and it's going to cost me about $4,000 in repairs. What exactly happened?? Something doesn`t sound right.

A valve hit the edge of the cylinder wall on #1 and #5 cylinders. It broke the head off of an intake valve and it punched a hole through the dome on #5 piston. It then hydro locked the block and bent a rod. I'm out a set of rods, set of pistons and a new set of heads. Because my old heads had been decked I had to get my intake machined to fit. So I have to get a new intake also. Oh well live and learn.

What size of valves you using when u blew up your motor? I have 2.19 and 1.88 valves and have no problem with my Gen V Block.

Originally posted by chris454ss1970:
A valve hit the edge of the cylinder wall on #1 and #5 cylinders. It broke the head off of an intake valve and it punched a hole through the dome on #5 piston. It then hydro locked the block and bent a rod. I'm out a set of rods, set of pistons and a new set of heads. Because my old heads had been decked I had to get my intake machined to fit. So I have to get a new intake also. Oh well live and learn. Thats strange. I have ran up to 2.25 / 1.88 in 4.125 bore, while close they cleared. It now has 2 years on it at the track . I did have the cylinder walls notched as in a 396 / 375 HP engine . Did you use off set dowels or something?? Maybe a piston to valve clearance problem ?

My block is a '95 gen V, was standard bore, fixing to put it in the shop and get it punched .030. My valve size is 2.250 in. and 1.890 ex. The old hi performance blocks had reliefs cut in the cylinder wall. The gen V doesn't have them, as I found out the hard way :eek: . Oh well live and learn.