OldSoldier

I am attempting to build a #8 headed stroker engine courtesy Mark's stroker crank and piston setup. I initially vacillated between aluminum aftermarket heads and #8 castings, but decided on the #8 in the end because they look more natural than the aftermarket ones perched atop the engine. I procured a set from a CO member a couple years back and finally got around to sending them off for a valve job and porting. I took them to a cylinder head porter in DFW and his machine shop found cracks in one of the two heads. They had more #8 heads laying around so they cleaned those up and both of them were cracked. They found another set and they were also both cracked. So my porter told me he has 5 of 6 that are no good. I understand these things are not new, and decades of wear and tear might cause some issues, but I do not know of or feel like I've read on this message board that there is a problem with 83% of factory iron heads being junk when trying to machine them for a simple valve job (small sample size, I know). These are #8s, all low performance heads.

1) Has anyone experienced such a high failure rate with these castings before?
2) Does anyone in DFW have a #8 that is in known working order that I can buy? I really don't want to ship heads since they're so heavy.

joe_padavano

I'm thinking this is nature's way of telling you that you shouldn't be using #8 heads on a performance build...

Seriously, I've not seen cracks in Olds heads until recently. One of the C heads from my 67 Delta was cracked between the valves in one chamber. Don't know if this is fatigue from thermal cycling after half a century or what.

olds 307 and 403

There was another member with a cracked #8 head but haven't heard other complaints. Other than the 3A heads, Olds heads weren't known for cracking. I have a feeling it is an age thing as well. Where are you located?

OLDSter Ralph

Joe, when are you going to update your car list to show which one was on the Power Tour this summer ?

coppercutlass

I just gave a set to Jim over at J&S machine for some t shirts and gas money lol. I couldn't sell them and they came off an engine I had on the running stand 2 months ago. How high would the compression be with some 7A heads. they usually cc in around 68-72 and that number goes up if you polish the chambers.

OldSoldier

Joe, what better way to build a sleeper than an engine with #8 heads but 427 CI?

I'm in Dallas - Fort Worth.

I have 7A heads on the engine in the car currently. I can CC them to find out what my ratio would be, but with the 79 & 80 cc chambers I measured in the #8 heads I would be running right at 9:1, which is what I wanted. How many CC would I be gaining with a chamber polish? Perhaps I can make up the difference with that and a thicker gasket? Mark specified a cam that works with the lower compression ratio, as I have future plans to add mild boost so I want to keep the CR relatively low.

Kyle's77cutlass

Doing a build right now with #8's. Came off a 73 block, they are okay.

olds403

Why not BB heads and run 93 or E85 ? Its like a free port job. I've done some full port on two sets of heads and flow nearly the same as my ProComps BB heads.

coppercutlass

You can do it with a thicker head gasket. Guys worry about the quench but I have ran it as wide as .065 with no issues @ 10 to 1 compression. polishing the chambers may net you 2 to 4 cc's but you have to be consistent and cc each one as you go .

OldSoldier

Good tip, thanks Copper. I'm still looking around for a #8 head but the 7A may be an option if needed.

Kyle's77cutlass

Where you located?
I could get my spare set of #8s checked

Inline

There aint any reason to skimp on quench in my opinion when doing a motor like thread starter.
You realise that cc difference with 4.125" bore gasket, for example, is a whole 0.52cc's between .040" and .064" quench distance? Thicker gasket to lower compression is worst way to do it.

coppercutlass

I ran .060 quench in a 10 to 1 motor with no issues. I know there is more pros to keep quench tight than not . it may not be much but between .040 and .060 but if he ise running a .040 head gaskets he could possibly order a .065 head gasket depending on where his specs fell. If i remember correct from my research when i wanted to run boost some guys run more quench area some as much as .080 .