Cylinder Head decision

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perko

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I've got a decision to make and I thought I'd run it by the great people on this forum. Apologies for the poor grammar and spelling I'm on my phone pretending that I'm working. Never buy a PANTECHphone !

I've got a miss in my valve train (1973 318) and it seems that there'sgoing to be valve work of some kind in my future. i thought that while I'm at it I should try to raise the compression. iI bought a set of 920 heads on a whim while I was on a work trip. Unfortunately since I was at work I didn't have the time or tools to take them apart i just had to assume that they were crappy . Upon further inspection, there'saat least two bad seats and some valves that are pitted and mild rust from sitting. My question is to you think it's worth having my local machine shop make these nice again or should I just find another set. I found a company called CME engines that offers rebuilt 302 heads fully asembeled for about 400 before shipping. However, I haven't found a lot of feedback about them . The engine is old and tired, I mostly want something i can tool around. thanks
 
The miss might be caused by the cam starting to go bad. Find out what is wrong first and make decision based off of that. Save you money this way.
 
Just put the cam in. The #6 exhaust lobe was fried and backfiring through the carb something fierce. I think that may have contributed to valve fryage. Don't remember the compression results off thetop of my head but it suggested valve issues.
 
I'd get a set of 302 from the junkyard and take them to the machine shop myself. The 302s will already have the harden seats in them, they're closed chambered (a bump in compression) and they have a swirl design give you more flow. That's what I'd do. buying a set of head that are already "rebuilt" I'd still take to my machine guy and have them looked over.
 
Yeah, I was looking at the 302s, but ended up with the 920s falling in my lap. They are closed chamber as well. The only reason I was thinking about them is because I already bought them when I was bored on business trip, they are supposed to be less prone to cracking, and they are also closed chamber. The lack of a hardened seat is a bummer, but the valves to not appear to be too receded. I was really wondering if there were any opinions on CME engines, because it looks like their prices wouldn't be much more than getting the 920s re-worked.

http://www.cmengines.com/CylinderHeads/PerformanceHeads/tabid/69/Default.aspx
 
What cam did you put in? To high of lift and not cutting the guides downs can make for a bad time. So tell us more about your engine. Cam or new cam choice, intake, carb, intended use, expected performance level, budget, etc.
 
cc your heads and the ones that you plan to use to make sure that you won't drop too much compression.

Here's a thread that can help you cc the heads at home:

http://www.forabodiesonly.com/mopar/showthread.php?t=278215


I just found some 67 273 heads at 63 cc when the books say they should be 57...

Just because they are closed chamber, doesn't mean that they are smaller chambers...

However, I also checked a set of 68-72 318 heads and found them at 79 cc ---> way bigger than they are supposed to be "by the book"...

check your parts to see exactly what you have and where you are going...
 
Huh, I didn't know that they could be that far out of wack from what the book says. guess I'm not surprised though. I'll have to check that out.

For Dano: its a really mild summit grind similar to the 360. (# K6900). The intake and carb are the stock 2bbl, but I do have an eddlebrock 4bbl intake that I will put on at some point. Basically I just want an ugly pos that I can have fun with and drive when my pos daily driver inevitably breaks again. With any luck I will always have at least one pos running.
 
krazykuda said:
check your parts to see exactly what you have and where you are going...
Click to expand...
Anything that's not new can be non-stock, and there are several factors that can affect the ccs so yes- definitely. Assumption can hurt very, very badly. No matter what you should know what they are rather than what they're supposed to be. Milling can drop it way down and excessive port work can raise the chamber ccs.

I think $400 is too much to have in 302s- or a 302 headed motor. In any case having some heads done local should be cheaper. Cracking's a common problem with all hardened seat heads- open or closed chamber from every manufacturer- I've even heard of it with some propensity in certain pre-unleaded heads. I think the bottom line there's they'll all crack if they get too hot and though the smog motors do run hotter, normal operation doesn't usually cause it.

If you left the stock springs the cam's likely got too much lift for the springs if stock. As far as I know- they tended to pair the springs to the cams very tightly and the 318 cam's tiny.
 
Well that cam is mild and would work well if you have a Performer intake. As per heads, you need to cc them as stated above to see what you will get. I will say with that mild cam, higher compression is a bit of a waste of money. Why do you think your exiting heads are hurt? If you wiped a cam lobe then I'd think you'd have larger issues with metal in your engine. If the engine is indeed tired then heads and cam will not do much good if any. Do you have compression numbers, oil pressure numbers at idle and cruise, does it use oil? If the motor shot then you should rethink heads and plan a rebuild or replace.
 
I may be reading this wrong, but it seams like you just want her back on the road at this point?

If it was me, I'd do a local/cheap cleanup of the original heads, do another 6900 cam.....only break it in properly this time :banghead:, and run the "wee' out of that tired 318, as long as it will last.

You can always put together a "tight" engine build down the road that will fit your usage and budget.

Keep in mind, a good exhaust, intake, and carb upgrade, will give you way more performance then a few 10ths of compression with new/shaved heads...
 
If your are sticking with the mild 318 long term, then a compression increase is certainly going to help the torque at the lower RPM's, particularly with a mild cam that has an early closing point. You could also achieve some better lower RPM torque by advancing the cam. But the increase will be limited with the 318's low compression height in the pistons (the tops 'down in the hole').

But the results will be questionable if the bottom end does not have good rings and compression as said.

Do you know what heads are on the car now?

I would not bother with a cheap valve job on the 920's; with a couple already recessed, you can count on putting seats in all chambers and had better put in t new guides to make sure things are sealing right or is can become a waste of time and $$.

I can't see how the CME heads are any particular type, open or closed chamber, from their ad that you attached. So how do you know what you are getting for that low price?
 
If I were in your shoes and short on funds I would look for a decent running 5.2 (or 5.9)Magnum and not mess with the 318 unless you want to rebuild it after you verify the short block is tired.

Still, you wiped a cam lobe, your concern should be metal in the engine. Have you addressed that?
 
dano said:
If I were in your shoes and short on funds I would look for a decent running 5.2 (or 5.9)Magnum and not mess with the 318 unless you want to rebuild it after you verify the short block is tired.

Still, you wiped a cam lobe, you concern should be metal in the engine. Have you addressed that?
Click to expand...

Have to agree,you can buy a 318 or 360 magnum for less that $400.00 for those 302 heads.
Magnums have great heads compared to 302's. Double quinch pads,flow on intake and exhaust is way better stock and ported.
1.5mm rings and stock with hyperutectic pitons plus a roller cam,all win win.
Also the magnums have nodular iron cranks and l.a's,we'll I've always heard just plain cast other than of course the early steel crank 318 and truck 318-3 cranks.
 
dano said:
If I were in your shoes and short on funds I would look for a decent running 5.2 (or 5.9)Magnum and not mess with the 318 unless you want to rebuild it after you verify the short block is tired.

Still, you wiped a cam lobe, you concern should be metal in the engine. Have you addressed that?
Click to expand...
This. A 360'd probably be more than the heads, but a 318 should be right around that range. Larger roller cam, 1.6 rockers, likely compression's the same- but the valvetrain should be in better shape on the newer motor. Can't use thermostatic choke on a Magnum but even smog-compliant there are some options with electric chokes. (at the least- a JY Quadrajunk from an '85-'88 truck/van or Thermobog from an '84-down truck/van)

By his statements and timing it sounds like the old cam wiped and the K6900 replaced it. Dunno for sure though- and dumping the oil's obviously a must and short change intervals would likely be a good idea shortly thereafter.
 
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