As a rule I replace the rod bolts and of course have them resized. The cam and lifters will definitely be gone. I’ll rebuild the whole thing with quality pieces. Has there been any detonation/ run on problems with the 4bbl open chamber heads? My 400M sure hates cheap gas even with 8:1 ( now probably 5:1) compression on the 2bbl open chamber heads. Also, any header suggestions? Thanks again.
You’ll laugh, but my favorites are the cheapo BlackJack headers. They fit very well (the handful I’ve used), come in and out easily, and leave plenty of clearance, Clarence.They’re cost effective too. FPA makes some nice parts too. http://fordpowertrain.com/351C.htm A little spendy, but worth every penny, imo.
The open chambers don’t spark knock nearly as bad as the American 2v style heads. You’ll still want to run 91 octane in it though. The chamber design of the 2v has a very bad rep for knock and detonation. The 73 4v heads are really good parts all around for a street engine.
Great! That’s good to know. I was concerned about the knock as I don’t want to sound like Uncle Buck when I stop.lol Ford Powertrain does have some nice pieces. I’m still wanting to swap out my old tubular performance headers for their B2/1965 Mustang headers. $700 bucks is a chunk.
Confused by your post Andy, specifically “The open chambers don’t spark knock nearly as bad as the American 2v style heads”. American 2V heads are open chamber (which I’m sure you know). All American C heads are open chamber except the 70 (and 71?) 4V, Boss, etc. Did you mean to say Australian rather than American maybe? What am I missing here?
I’m assuming there’s enough difference that the 4V opens don’t get the hotspots the 2V opens do. That knock condition may be a result of carbon build-up in the chamber also I suppose.
To my knowledge, the open chambers are pretty similar 2 or 4V, another reason I am confused by Andy’s post. Also surprised that Andy says the OC 4V heads are good all around street heads. The 4V port sizes (and resultant low port velocities) can be a big problem on the street (known for low end bog). In my (simplistic) view, you need higer compression and the right cam to make the 4V heads work well at anything but high RPM’s.
For me, Aussie 2V (closed chamber) are the best for street, if you can get the CR right (custom head gaskets is how I did although hoping I won’t ultmately decide a true 10:1 is too much for pump premium), and failing those, American 2V would be my choice (and up the CR with small pop-ups, thinner than stock (.040"?) gaskets, milling the heads or a combination of these).
Again thanks for the input. Well, the only experience on the big heads I have is through my Boss 302 engine. While a bit peaky it still ran pretty good through the whole RPM range ( although my memory is a bit foggy. I’ll let you know again this spring when it fires again). My logic for the OC heads is that I can run a flat top piston. This translates to a good flame travel across the piston. Now, I haven’t done the math yet but I can boost the C/R by lengthening the stroke as the crank is rusty and will need replaced. As far as compression vs octane goes, my brother and his son are running over 10:1 in their 351 Windsor based strokers and I’m running 10:1 on the Harley. I have conservative timing on the bike which will allow 89/90 octane as long as you’re not crankin’ it. We have 93 octane available locally here. I DO have a set of Aussie heads in the garage but I’d like to try the 4bbl heads. The Aussie heads I got for the 400 in my Ranchero.
If you examinate the 73 heads, you’ll note that the ports are more like the 2v sized stuff, while the valves are (edit: bigger…) like the 4v heads. It’s a nice combination.
The chamber design of the 4v parts is different from the 2v American parts. I gaumed up the nomenclature, but the 2v stuff gets a hot spot and spark knock quite badly where the 4v’s do not.
I’ll dig up some parts and take some pics now that I’m done with my Physics finals.
Actually, looks like mustangtek has some of the particulars listed here: http://mustangtek.com/heads/Heads.html
Peruse the differences between the 70 2v head and the 73+CJ head. Then, note the differences between the 70 4v head and the CJ parts.