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High compression 360 heads |
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tgoddardamc
AMC Apprentice Joined: Sep/15/2013 Location: vacaville ca Status: Offline Points: 105 |
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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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AMCya!
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purple72Gremlin
AMC Addicted Charter Member Joined: Jul/01/2007 Location: Illinois Status: Offline Points: 16591 |
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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
Supporter of TheAMCForum Joined: Aug/08/2012 Location: Minnesota Status: Offline Points: 4867 |
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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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70 Javelin SST, second owner, purchased 1972
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Moffman
AMC Nut Joined: Sep/28/2011 Location: New Jersey Status: Offline Points: 287 |
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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
AMC Addicted Joined: Dec/14/2013 Location: NH USA Status: Offline Points: 4209 |
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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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Gremlin Dreams
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Red Devil
AMC Addicted Joined: Jul/10/2007 Location: Canada Status: Offline Points: 1743 |
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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
AMC Addicted Joined: Dec/14/2013 Location: NH USA Status: Offline Points: 4209 |
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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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Gremlin Dreams
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Sonic Silver
Supporter of TheAMCForum Joined: Nov/23/2011 Location: East Tennessee Status: Online Points: 7902 |
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White70JavelinSST
Supporter of TheAMCForum Joined: Aug/08/2012 Location: Minnesota Status: Offline Points: 4867 |
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Why not, then go to 13 to 1 and burn E85? The sound difference is tremendous alone, not to mention the horsepower increase. |
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70 Javelin SST, second owner, purchased 1972
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texasamx
AMC Apprentice Joined: Apr/07/2010 Location: Texas Status: Offline Points: 56 |
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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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