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+--- Thread: Larger valves and pistons om617a displacement assistance (/showthread.php?tid=5761)
Larger valves and pistons om617a displacement assistance - mdeming - 08-06-2014
Hi all
I've finally gotten around to putting the om617a engine back together (really I'm tired of tripping over greasy parts).
I've stripped the head and am nearly ready to send parts to the machine shop but need some guidance.
I've searched several forums for quite a few days now and have found very little on head modifications beyond people saying they ported theirs or JTY doing some mods but, at time of posting, he hadn't yet updated his thread with photos of that portion of his build he had on another hard drive.
(Bear with me, there is a question coming). I'm a huge believer in larger valves on gas engines, my toyota 2f has a new head with larger valves from a small block Chevy (an engine mine was based on) and it now runs like nobody's business.
I plan to have a larger element ip and of course the higher turbo boost so oft discussed. What I want to know is: has anyone installed larger intake/exhaust valves on their head and/or is there an existing valve size from another engine that would work well for this process? Do you have photos of this?
Also, While I'm not in the market to buy new pistons, I can add .10mm of special ceramic to the skirt for about $50 ea. Has anyone done this? I don't see any other options for larger pistons.
Also wondering if there has been a follow-up on different con rods for lowering compression?
I'm trying to gather this info so I can contact some of the recommended cam shops (Delta sounded like a great deal). So I can better plan my build up.
I appreciate any input you can provide.
Matt
RE: Larger valves and pistons om617a displacement assistance - Simpler=Better - 08-06-2014
Cams-there's a guy up in Canada who does TDI cams, and can do a 617 cam for around $300-$400. I forgot his name, he owns a cam shop
Valves-whatever fits, make sure it can take the heat. Stock valves are sodium filled. See my build thread for blurry photos, the short side radius needs porting. Be very careful with valves-the piston sticks above the deck at squish time
Rudolf Diesel on here ran 18.5:1 with a thicker HG, you cna read his thread for more info on that
Prechambers are the hot thing to mod now-check out what captain america's got to say about that.
Users OM616 & MF90 don't have a ton of faith in the coatings when using a diesel, there was a thread on it earlier. I think the coating eroded pretty quickly YMMV
Shameless promotion-buy my shit and weld up a sweet exhaust manifold once your head's ported out.
RE: Larger valves and pistons om617a displacement assistance - MFSuper90 - 08-06-2014
Coatings aren't bad, but unless your running a super high performance engine they normally aren't worth it in my opinion and I don't think they would be able to take the heat cycles of everyday driving. Coating the skirts won't do anything besides lower friction between the skirt and the cylinder wall. If anything I would coat the top of the piston, but to get a good coating that will actually be beneficial, I'm sure it will be pretty expensive.
As far as lowering compression goes, just shave a little off the tops of the pistons! I'd have to look at my spare set to see how it could be done, but that is by far the easiest route.
RE: Larger valves and pistons om617a displacement assistance - mdeming - 08-06-2014
Thanks all, great info. Simpler=better I've read your build thread a few times recently. Unfortunately, most of the photos (including the head photo) won't load from the page. I wonder if there is an already determined size of valves that are possible? Surely there's something off the shelf. I wonder what larger valve size is beneficial for better breathing vs at what point the torque drops too much.
My coating remark was for larger size rather than the friction benefits. Swaintech will add .101mm to a piston. They market it to firm up sleeve fittings but since mine are in spec it would effectively make my pistons that much larger without a large cost (I think $50 each,$30 for just the skirt)
I figure $150 for both the size and friction isn't bad bc I'm not buying new pistons. MFSuper90 I'd like to know what you find out re shaving the pistons and keeping the swirl patterns when you take a look.
I do plan on the pc mods too but I'm trying to find out the valve/piston options while keeping it as off the shelf inexpensive as possible (I know, I know). I figure if I can get these metrics and call the cam guys then the machine shop can work their magic so I can assemble it and then move on to the other mods.
S=B I like your manifolds too. Hopefully I'll get to that point soon enough.
Matt
RE: Larger valves and pistons om617a displacement assistance - MFSuper90 - 08-06-2014
I'll be home in a couple days, take a couple picture of the piston tops and post them up.
Then we can see what we think
RE: Larger valves and pistons om617a displacement assistance - Simpler=Better - 08-07-2014
You can always cut threads on an SBC/SBF valve and ream a valve guide to match. I'd measure the stockers, the bore clearance, and then find something domestic that's close.
I'll check on my thread-that shit shouldn't go anywhere