Steve Bryant

iTrader: (1)

Does anyone know if there have been any in depth magazine articles on building a 408 iron block. I am about ready to get a block machined and install an Eagle Kit. This will be NA @ 9.5:1 CR for a daily driver/tow vehicle.

Thanks,

Steve

Steve Bryant

iTrader: (1)

TTT
Anyone?

bluecajun5.3

iTrader: (31)

check out gm hi tech performance mag.

02sierraz71_5.3

iTrader: (2)

http://superchevy.com/tech/0312sc_dm15/
http://www.chevyhiperformance.com/te...30/index1.html

good info in this article
http://popularhotrodding.com/tech/0404phr_sonic

this is what I find interesting
"Sonic testing this .030-over small-block Chevy block (which at this size would have normally been unusable for a performance application) showed it had plenty of wall thickness and could go .060-over. With the Scat 3.75-inch stroker crank this produced 388 inches instead of the usual 383 inches from a .030-over block."

I thought you would have to sleeve a small block after taking that much out. hhhmmmmm

budhayes3

iTrader: (19)

This seems to be old school sbc info...find anything on the GENIII stuff?

02sierraz71_5.3

iTrader: (2)

no

GenIII53

I will tell you guys this...Hae ANY block sonic tested BEFORE ANY machine work is done. I have 2 buildups going on, one for my 71 Challenger (528Ci Hemi) and a 408CI for my 05 CCSB 5.3. Anyways, I dropped off my $2500 BRAND NEW HEMI BLOCK from Mopar Performance at my machine shop. and there was ALOT of core shift in the block. Meaniing some cylinders were ALOT thicker than others, the block was still good, BUT, number 1 cylinder had a thickness at the top of the cylinder wall, on the thrust side..of .292". A machines shop typically likes to see .200, some will take .175..mine like to see .200 on the thrust side. And remember, my block is a SIAMESE BORE BLOCK, meaing no coolant passages around the cylinders, and it was STILL thin on #1. After the sonic testing we were able to come to the conclusion I cold take my block .090 over to get to thickness of .205. Well, you say, that is .090 over...WEll, this being a Siamese block, they are known to be able to handle .100-.125 over easy, not my block. Also, I want to point out I had a thickest reading of .729". Think about that for a minute...I had only .292 (little over a 1/4") to a max of .729" (almost 3/4") That is a HUGE difference is numbers for a block to have. And before you guys go "Well, Mopar junk for ya" You can say it all you want, but when I dropped my block off, I asked him what a report would look like, he pulled one out of SBC that had just been done, and stock bore (not GenIII) but a Gen II block was all it could handle. In fact, at stock bore it had a thin spot of .177, which after a .030 over would have left it at .162 (you take half of the over bore .030=.015 and subrtract that from .177) which we would be un accetable. I paid $52.xx for my sonic test, and from now on (this was my first after many of years of telling people no thanks) Maybe I had been lucky???? Maybe machine shops like to err on the conservative side???? All I know, after this, all my blocks will get sonic tested. A little rant....

Steve Bryant

iTrader: (1)

Thanks guys. The kind of information that GenIII53 is suggesting is exactly what I'm looking for. I have some experience with rebuilding engines as I used to be a full time Detroit Diesel mechanic. I know what I want to do on my block. I will have it clened, magnafluxed and sonic tested. Then I can know if I can safely overbore beyond .030" and have enough durability and margin to do a second overbore/rebuild in a few years which is what I want. Once I know where I stanc regarding cylinder wall thickness after boring and honing we'll do the machine work. I'll have the Crank and caps align honed, then square and equalize the deck height, verify the cam bore axial alignment and dimaters and align hone if necessary, then align bore and hone the cylinders.

Older school blocks cast iron and aluminum did not have the same metalurgy as today's blocks and they tended to be beefy in all ways including wall thickness for strength and where vehicle mass/weight was not the consideration for Corporate Average Fuel Economy (CAFE) that it is today.

With thin cylinder wall thicknesses like is used in the 4.8/5.3/6.0 (as well as the aluminum LS series blocks) a significant weight reduction can be made while increasing heat transfer to the coolant.

With an aluminum block, you're going to resleeve it to increase bore to any degree. With an iron block, if you overbore too much and the cylinder axis is out of alignment slightly or the molten metal has shifted to the bottom or the side or wherever, your wall thickness will be too thin.

I've just never seen a good article on iron blocks and I'd like to find one. I may concact Engine Masters at Primedia on this.

Thanks again to all,

Steve

GenIII53

Good points made Steve. If I knew how to post pics on this site, I would post one of my sonic test for ya'll to see. To see that much core shift in a block that a company charges $2500 for it, is kind of mind blowing if you ask me. You know, if this was a production block that I was picking out of a bone yard, OK then, mass produced means les quality. But, I was on a 6 month waiting list for this block, and to pay that kind of money, you ask me, that is is unaccetable

gonzo 6.2

iTrader: (8)

[QUOTE=Steve Bryant]

With thin cylinder wall thicknesses like is used in the 4.8/5.3/6.0 (as well as the aluminum LS series blocks) a significant weight reduction can be made while increasing heat transfer to the coolant.



The 5.3 can be bored out .120 to accomidate 5.7 pistons.I wouldnt consider that to be thin walled.