Choosing a piston
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=41059
Printed Date: October-07-2024 at 12:27am
Topic: Choosing a piston
Posted By: KooK
Subject: Choosing a piston
Date Posted: May-13-2017 at 1:43pm
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1979 CC Mustang 17 w/ Ford 302 Commander. Bored 30 over w/ GT40p heads. So I'm over here trying to research what type of piston would be best to go with my boat. Taking into account the ring gap and thermal expansion here I'm a little confused how this works because I can't imagine marine engines operate at the same temperature range or are subject to as consistent conditions as that of a vehicle. Should I be looking at marine specific pistons or do people run into any issues with automotive pistons? |
Replies:
Posted By: TRBenj
Date Posted: May-13-2017 at 1:56pm
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Normally one chooses the pistons first, then has the block machined for them (with the specific application in mind to set the clearances appropriately). Where exactly in the process are you? |
Posted By: KENO
Date Posted: May-13-2017 at 3:08pm
Like TRBenj said pistons first then then .bore Why don't you get in touch with Duane who offered you some basically new 0.040 over pistons for the price of shipping and have it bored for them? Here's the thread with the offer http://correctcraftfan.com/forum/forum_posts.asp?TID=40896&KW=&title=my-oil-pan-was-leaking-but-i-cant-figure-out-why" rel="nofollow - thread It sounds like you decided on pistons back then, Or if you're buying pistons, go with the manufacturer's recommendation for piston to cylinder clearance and ring gap.for their piston. Some ring gap discussion in this thread http://www.correctcraftfan.com/forum/forum_posts.asp?TID=40932" rel="nofollow - thread |
KooK wrote:Posted By: MrMcD
Date Posted: May-14-2017 at 4:57am
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With Pistons you have 3 basic types to choose from. Cast Piston = same as the original piston in your boat. Hypereutectic pistons = an improved version of the cast piston. FYI: Mercury Marine has been buying Federal Mogul Hypereutectic pistons for their engines for many years. They work well in these mostly stock engines. Forged Pistons = a very strong and forgiving piston but the highest priced piston. Forged offer some extra protection inside the engine and can help avoid failure in extreme situations. If you are going to spin 7,000 RPM buy the forged. If your block is a very high dollar and hard to replace block, buy forged. In each piston type, Cast, Hyper or Forged they will have a few compression options you can choose from. Typically a Marine block will be honed to leave a little extra Piston to Cylinder wall clearance to allow for extra thermal expansion and so you have no issues running hot pistons in your marine engine which will typically run at 140 degrees. If the Automotive Piston is recommended to run at .0015 clearance most shops will add an additional .001 clearance for marine use for a total of .0025. If you buy the Hyper pistons you can run them tighter, they don't expand as much. Your machine shop can help decide what clearance is good in your block with the options you choose to run. ------------- |