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High compression 360 heads

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tgoddardamc View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tgoddardamc Quote  Post ReplyReply Direct Link To This Post Topic: High compression 360 heads
    Posted: Sep/12/2017 at 6:29am
I'm wanting to get some opinions about increasing the compression of my 78 360. It will be replacing my 1973 gremlins 304. I have long tube dog leg headers and an edelbrock performer intake on the 304 that I would like to swap to the 360. I'd like to get a decent power increase over the 304 but the 360 is a low compression motor and I don't have the budget for aluminum heads. Could I mill the heads or just try to find the earlier high compression heads? All of the pistons I have found are the stock dished type units. I'm not trying to build a track monster but I'd at least like to make my efforts worthwhile. I'm also planing on a nice streetable cam. Any suggestions would be appreciated.
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purple72Gremlin View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote purple72Gremlin Quote  Post ReplyReply Direct Link To This Post Posted: Sep/12/2017 at 7:49am
Make sure you run a 360 flywheel.or faceplate. The 360 will run much better than the 304 in stock form...
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White70JavelinSST View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote White70JavelinSST Quote  Post ReplyReply Direct Link To This Post Posted: Sep/12/2017 at 9:27am
Milling the heads enough to change the compression significantly will mean the intake manifold will need to be milled as well. The compression height of the piston will need to be checked too, so they don't contact the head or valves.

What heads do you have now for the 360? Are they 502s? Look under the valve cover between the valve stems, there should be a head casting part number there.

The 319-291C heads are the smaller chamber higher compression ratio from 1970 and 1971. They are still around. These heads will have studs instead of bridged rockers. FYI, by the time you refurbish a pair of 291C heads, you may have as much in them as Edelbrock Aluminum heads. It all depends on the cost of parts and machining. Aluminum heads are less prone to pinging and combustion knock because they dissipate heat better..

Bulltear Industries can get any piston you want for a 360. They will be forged and at whatever compression you ask for. Matt is very good at it, listen to his advice as well.

Better yet, if your 360 heads are not 502 heads, (which I think they aren't because of the 78 model year) find a pair of 502 heads, they are touted as being the best breathing head that AMC made. Have them machined for rocker studs and hardened seats. Have a set of pistons made to your spec for compression and go from there.
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Moffman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Moffman Quote  Post ReplyReply Direct Link To This Post Posted: Sep/12/2017 at 10:00am
If you haven't picked out/bought pistons yet, that's probably the best way to go about bumping the compression up. Milling to achieve especially with later bigger cc heads get complicated and geometry gets changed as White70JavelinSST said, you have to mill the intake as well to match so if you ever want to swap forgot selling it and it's a pain.

On my 360, I used stock cast pistons to save a couple bucks but in the long run probably spent more and was definitely more work then needed.  Had to find a set of 291C 51cc heads, machine to accept sbc rocker studs (that was for the rocker geometry on higher lift cam though), block was decked, heads milled, intake milled. Lots of machining costs and I've ended up around 9-9.5:1.
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Boris Badanov View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Boris Badanov Quote  Post ReplyReply Direct Link To This Post Posted: Sep/12/2017 at 11:28am
As said above, milling for compression is a no no.

You will cut into the intake valve seat well before you get
a substantial increase in compression.

Pistons are the answer. If you are lucky enough
to have a 63CC chamber flat top pistons will
rock your world. 58CC will require a small dish.


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Red Devil View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red Devil Quote  Post ReplyReply Direct Link To This Post Posted: Sep/12/2017 at 11:51am
If the 360 is in otherwise good condition, simple bolt-on parts will get a noticeable power increase without changing anything internal other than a cam change to something in the 210@0.050" duration range, e.g. https://www.lunatipower.com/Product.aspx?id=1481&gid=287. Fit springs to match and a new timing set if stock is worn.

Add a good dual exhaust to match to your headers and Performer intake. Depending on transmission, a bump in stall speed and/or more rear gear would also help. Adjust timing, tune carb and enjoy.

Hope this helps,RD.
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Boris Badanov View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Boris Badanov Quote  Post ReplyReply Direct Link To This Post Posted: Sep/12/2017 at 3:33pm
I agree, but there is NOTHING like a bump from 8:1 to 11:1
with a mild performance cam. The difference is stunning.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sonic Silver Quote  Post ReplyReply Direct Link To This Post Posted: Sep/12/2017 at 4:42pm
Originally posted by Boris Badanov Boris Badanov wrote:

I agree, but there is NOTHING like a bump from 8:1 to 11:1
with a mild performance cam. The difference is stunning.
11:1? What do you use for fuel? 
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White70JavelinSST View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote White70JavelinSST Quote  Post ReplyReply Direct Link To This Post Posted: Sep/12/2017 at 4:42pm
Originally posted by Boris Badanov Boris Badanov wrote:

I agree, but there is NOTHING like a bump from 8:1 to 11:1
with a mild performance cam. The difference is stunning.


Why not, then go to 13 to 1 and burn E85?

The sound difference is tremendous alone, not to mention the horsepower increase.
70 Javelin SST, second owner, purchased 1972
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texasamx View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote texasamx Quote  Post ReplyReply Direct Link To This Post Posted: Sep/12/2017 at 5:00pm
Mad Dog  racing may offer the pistons you need, just keep compression under 10: 1  so you can use pump gas.  also if going to stud type rockers use the ford studs as they will give you more adjustment.
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