Not much to report, but the project continues... New oil pan arrived and will be painted as soon as time, temperature and humidity are aligned in harmony. Pistons are all cleaned up, and I'm going to pick up my heads tonight! I'll post pics before I start on them, and continue as I make progress cleaning them up, swapping the springs, paint, etc. Before I get started, got any do's and don'ts for cleaning these heads up? Is it okay for instance, while they're assembled, to just go to town on the whole thing with a cup brush? The intake ports probably have some carbon buildup... I was thinking I might flip them on their sides and pour in some Chem Dip. How about the valves? Wire brush okay on those if I don't go nuts, or to I need to just dip them?
I clean my own heads and ported the exhausts too. Wire cup wheel to clean the valves and combustion chambers. I passed a magnet thru all the ports to retrieve the metal filings, then washed em with a pressure washer. None of the valves leaked while doing all this. If you do this and they leak, then they'll at a minimum need to have the valves relapped. I don't trust the one remaining machine shop in town to do my work and the next best is 20 miles down the road, there's one guy closer, and he's the best, but when you leave parts there, you're looking at 6 months minimum before he'll get to em.
Chem dip in the ports????????????????? If you have an electric drill...............go get some bore brushes like for cleaning guns...........or some http://www.summitracing.com/parts/SAI-260013/ to clean the carbon out of the ports.............are you going to match the ports............if so then buy the kit which will include these in it, http://www.summitracing.com/parts/SAI-260001/?rtype=10 And like The ShadowMaster said............have a machine shop clean the heads, check the spring pressure and installed height and either give them back to you to assemble or have them do it for you.......IMHO
I missed this post the first time around... There are no holes in any of the pistons, that's just a casting mark. Notice how this pic from Summit shows the same "hole" you see in the top my my piston:
Damn that's some deep reliefs. The "hole" as you call it is probly to determine the "front" of the piston.
So, about the heads. Now that I finally have them in hand, they have turned out to be a whole lot cleaner than I expected them to be. They've been in the custody of a very helpful friend who is not at all knowledgeable about cars. To him they looked nasty as hell... I'm not sure that they need to be professionally cleaned, and in fact if I wasn't changing the springs on them I might consider running them like they are. But I will go ahead and degrease them, run a brush through the ports, get all the soot out, etc. Not that I'm trying to halfass it over $40, I just really don't think they're that bad. Here's a puzzle for you guys though... I have yet to find a reliable source for the true combustion chamber size on these GT40 heads. (side note: I have determined that if one were to make a chart depicting the collective intelligence of all the car forums in the Internet, like those charts that try to show Man's evolution from ape, you would find the Mustang forums just one step above Honda-tech.com.) Misinformed people aside though, I've seen other, supposedly good sources that conflict. For my casting number, F3ZE I've seen 60cc, 64cc and everything in between. This means my compression might range anywhere from 9.4 to to 9.8. Is that enough of a difference to care about in terms of cam selection? If I find out they really are 64cc heads should I consider having them milled, or is 9.4 an acceptable ratio for what I'm trying to do here?
I didn't call it that. I think you are right though. And yes, the reliefs are pretty deep. 12cc, practically a small dish.
The only way to know your true chamber cc is to measure them yourself. A drug store syringe marked in ml/cc and a piece of plexiglass will get you close enough.
That's what I'll do then. Had to do the same thing to measure the dish in the pistons on the previous 351w. ...Now, as for whether 9.4 is an acceptable ratio, I think I've answered my own question. Went to playing with the simulation software again. With 9.4 compression and the 279TH cam it shows peak hp as 369.6 @5500, peak tq 400 @4000. 9.8 shows 376 and 406. I don't think that's enough of a difference to care about in my situation. Found out something else interesting too. While I was going through all these different cams there was just one thing that bugged me a little about the 279TH. It showed peak torque about 20 lb/ft lower than some of the other cams with similar peak HP. It wasn't the highest peak HP either although it was close. BUT- I was only paying attention to the peaks, not the averages. Looking at average HP and TQ over the whole range, the 279TH is the best of them all. And that's with 1.6 rockers. So right now if I go flat tappet, the Thumpr 279TH is my number one choice. It was high on the list already but not at the top. Because of Shadow's recommendation I decided to pay more attention to it and I'm glad I did.
And moderators wonder why I get pissed off and rip the hell out of people over misinformation. 9.4:1 is decent enough. Although I'd rather see a bit more compression by doing a .010" cut. Regardless of the cc's I'd still give them a skim cut to ensure they are flat and will seal the head gaskets.
I could venture a guess, but I'm not going to! You've been extremely helpful to me in this thread. I was just about to ask who you really are, and warn you that the real Shadowbastard is going to be very pissed when he sees you've been using his account...
Regarding lifters... There was some concern mentioned about substandard Chinese hydraulic flat tappet lifters floating around, and I've heard elsewhere that even the major manufacturers may have snuck those into their kits at some point. I found some Elgin branded lifters that are advertised as made in the US. I've heard of the company, I've never heard one way or another about their quality, and of course I'm planning to use a cam made by Comp rather than Elgin, so I don't know if that's a potential cause for concern. My question is, should I stay with Comp for the lifters and buy them together with the cam, or should I get the Elgin lifters?
The conflicting info stems from the fact that the GT40 heads used on the Cobra Mustangs were given an extra pass on the milling machines to give them a smaller chamber, these are listed as having a "nominal" 60 cc chamber. All other iron GT40 heads had a "nominal" 64 cc chamber. Nominal means that the chamber can vary by as much as 2 ccs either way.
