Blue pill or red pill = 675 or 920

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65barracudaLA

65barracudaLA

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I bet most folks will argue that the 920 heads are better, because they are closed chamber heads. I think they'd be great from what I read!

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Here's the deal, though: I just picked up these 675 heads from a FABO member last Sunday (in exchange for a bottle of Jack Daniels). They were rebuilt 5,000 miles ago with new stock valves and springs. I should be able to bolt these on and go. I got the 920s in a package deal when I bought the transmission that's in the car right now a couple of years ago. I thought they were pretty rough and just put them on a shelf. Well, I just started cleaning them up a bit and turns out they aren't that bad. The bad is that two valves are missing on one head and the other has a broken valve. The good is that none of the valves are stuck, there is no pitting and they should clean up nicely. Here's the real question, though: I want to keep it as cheap as possible. As far as I know the 675 and the 920 both have 1.5 intake and 1.78 exhaust valves. Can I just put new valve seals on the 920 heads and swap the valves and springs from the 675s to the 920s? Is that a bad idea?

:rofl:

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Anyways, this is what they're for: My '65 Barracuda that I recently swapped this '69 318 in. Currently it has 163 heads (mid-seventies to mid-eighties smog heads?) and they are not great. Not sure what condition the valves are in, but there's some rough pitting around the water ports and one of the exhaust studs has a heli coil that I've replaced a few times, but it might start leaking again. According to the seller it's a stock block with stock pistons and cam. It doesn't smoke, so bottom end seems in ok shape?! Edelbrock Performer intake and 1406 carb. Stock manifolds, TTi 2 1/2" dual exhaust, A904 with stock converter, 7.25" sure grip with 2.76 gears, 225/65R15 tires.

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The car was my daily driver for 13 years with a slant 6 and now now that I got most things tweaked on the small block, I'm back to driving it every day. Is it really necessary to swap the heads? Will it make a significant difference? I don't plan on racing the car. I just like to tinker and figure things out. I've never swapped or rebuilt heads before. I like a good challenge, haha. I think I should start by getting a spring compressor and take the valves out of the 920 heads, so I can inspect them better. Thoughts?

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My argument would be it depends on what you're doing.
 
Well the least you should do to them is, do a garage valve job on them, to at least clean up the seats. You can get a hand drill operated gizmo, and some valve grinding compound and do it. Look up "Valve Lapping tool attachment", on E-Bay they're cheap, and work great.
Clean them up good, after you get them apart, in a parts washer. Clean the valves also, a wire wheel on a bench grinder works well on the shafts. A good C shaped valve spring tool is worth it. Its not worth fighting one of those elcheapo things.
You will probably have to replace some valves, so get them from Rock Auto.
Put all new seals on, its worth it.
Clean all threads up with a good thread chaser, or tap.
Use your factory service manual, or get one.

Dave
 
bro, those 920's look tore up from the floor up.

if you wanna keep it on a beer budget, snap on those 675's and ship it.

there's no telling what could be wrong with those 920's-- janky guides, wasted seats, bad deck, cracked, and on and on. i wouldn't run those without a hot tank, mag check and the okay from a machine shop.

and i certainly wouldn't take apart a perfectly good set of heads to play humpty-dumpty with a roached out set of cores.
 
junkyardhero said:
bro, those 920's look tore up from the floor up.

if you wanna keep it on a beer budget, snap on those 675's and ship it.

there's no telling what could be wrong with those 920's-- janky guides, wasted seats, bad deck, cracked, and on and on. i wouldn't run those without a hot tank, mag check and the okay from a machine shop.

and i certainly wouldn't take apart a perfectly good set of heads to play humpty-dumpty with a roached out set of cores.
Click to expand...
X2 plus it looks like one exhaust valve is burnt.
 
675s for the win. Your ‘69 318 should have the higher compression height pistons. Use a pair of Felpro 1008 high performance gaskets.
 
920 heads are great. But, I would have them tanked and magnefluxed first. If good, milled .020, mill the intake side .019, probably need to replace the exhaust valves (stainless steel), clean up the bowls, get a competition valve job, brass freeze plugs, and redo the guides, might as well add 340 valve springs (or equivalent) while you are at it, and use Fepro Viton valve seals. On the cheap, leave the heads on until the next problem occurs, then slap on your "done" 675's. You can also get a set of 360 heads and do the same routine. A good cam would be nice... See how it goes? Now about that 7 1/4 rear...
 
Thank you, I'm not in a hurry to do this. I figured it'd be wise to have them checked by a machine shop. Again, the 920s look a lot worse than they are - the 675s actually have some pitting around the exhaust flanges and as I discovered one of the heads also has a heli-coiled exhaust stud. In the end the difference between the two is probably minimal? I couldn't find that info, but did the horsepower rating for 273's or 318s drop from '67 to '68?
 
All the work you are planning for the 920s in post #8, is a LOT more than I would put into (almost) any iron head.
675s ready to go, bolt em on and fly it.
(How much horsepower better do you think the 920s will be? 20? 30? Think that will be necessary for a 318? Price the machine work you are contemplating, I'll bet you decide not to.....)
 
Honestly, if its still running fine, leave it alone.
New heads all sealed up my find the weak link in the bottom end.
 
If your existing heads are working fine, leave them alone and drive it. If they need changing, I'd just install the 675's and go. I'd wait until I wanted to do a complete build to change to the 920's It may be that installing them will boost the compression ratio up to where you have to run high octane fuel. You don't really know until you compute the actual compression ratio during a build.
 
Thanks for all your input - lots of things to consider. I still like the idea of the 920s, but it'll be an investment to do it right. It's good to know that if I have an issue with the current heads again that I have a backup plan with the 675s.
 
cudamark said:
If your existing heads are working fine, leave them alone and drive it. If they need changing, I'd just install the 675's and go. I'd wait until I wanted to do a complete build to change to the 920's It may be that installing them will boost the compression ratio up to where you have to run high octane fuel. You don't really know until you compute the actual compression ratio during a build.
Click to expand...
agree. if you do need to swap the heads at some point I'd look at upgrading the cam if it's a stock 318 cam.
 
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