317 to 243s by milling ?
Thread Starter
Staging Lane
Joined: Feb 2013
Posts: 91
Likes: 0
317 to 243s by milling ? I'm curious I've been doing some researching and have found the intakes and exhaust valves of the 317s and 243s are the same at 2.00 and 1.55 aswell as intake/exhaust ports at 210cc and 75cc. So the only real difference seems to be chamber sizing at 71cc (317) to 64.5cc (243). Long story short my question is could you not mill a set of 317 down .036 to make them a 65cc chamber and essentially have a pair of 243s?
I got my math from other threads .006 per 1cc
Going from 71cc to 65cc so 6cc x .006 = .036 ?
Just a thought let me know what you guys think maybe it's not practical price wise I don't know what milling heads down is worth.
I got my math from other threads .006 per 1cc
Going from 71cc to 65cc so 6cc x .006 = .036 ?
Just a thought let me know what you guys think maybe it's not practical price wise I don't know what milling heads down is worth.
one of my friends works at a high end machine shop. We had a conversation similar to this a few weeks ago but it was relevant. I was concerned I might not have enough compression on my build he said we could mill the heads. Now you can only mill them so much before it changes the angle on the intake ports. At that point the intake manifold will leak. We talked about how there could be further machining on the intake ports to restore it to where it would seal however on stock heads its kinda dumb. If you had super expensive heads you had to mill a few times after a few seasons you might be able to get a little more use out of them this way. On stock heads just buy the ones you want and be done with it.
Thread Starter
Staging Lane
Joined: Feb 2013
Posts: 91
Likes: 0
one of my friends works at a high end machine shop. We had a conversation similar to this a few weeks ago but it was relevant. I was concerned I might not have enough compression on my build he said we could mill the heads. Now you can only mill them so much before it changes the angle on the intake ports. At that point the intake manifold will leak. We talked about how there could be further machining on the intake ports to restore it to where it would seal however on stock heads its kinda dumb. If you had super expensive heads you had to mill a few times after a few seasons you might be able to get a little more use out of them this way. On stock heads just buy the ones you want and be done with it.
Fair enough. I too wondered if at a certain point it would even be worth it just figured I'd see if anyone had done it. What started out as budget I feel is slowing turming into a built motor.
100% true. He stated that he could rework the other stuff to make it work. However he said it's only worth it on high horsepower engines where the parts are super expensive.
With an alumn. intake you could mill some to realign the ports some, but with plastic ones no dice-241 heads are kind of in the middle, but not sure about the port vols., I got a set of those to knock a little off comp. on a project.
I milled the heads on my lsx376 to gain compress. I did it because I already had the engine and it was cheaper and easier then replacing pistons or so I thought. I milled my heads .040 to gain 1 point of compression. After I clayed the engine surprise intake valves are now gonna hit. I had some old cylinder head with valves so I welded around the edge and bottom and using a grinder made teeth to clearance the pistons. Then pushrod length was incorrect. This I was not surprised on. Finally manifold wise the Holley highram had never lined up perfect but now it sits perfect lined up with the ports. Go figure. Anyways that is my experience. Didn't really feel a difference in the 1 point compression increase. In my book it was a lot of work for little gain.
Trending Topics
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Milling them a ton also reduces deck strength and the heads ability to seal/hold the HG in place. Some of the companies weld up the CC to bump compression. Always wanted to try that.