jonlabree Posted July 25, 2011 Share Posted July 25, 2011 Is there a chamfer at the top of the cylinder walls?Jon. Link to comment Share on other sites More sharing options...
2seater Posted July 25, 2011 Share Posted July 25, 2011 My notes don't indicate any substantial chamfer, just a smal edge break to facilitate piston installation. Pistons are over .040" down the hole. Combustion chambers are < 40cc's. Perhaps Recian has further input having just had the heads off? Link to comment Share on other sites More sharing options...
Guest Recian Posted July 25, 2011 Share Posted July 25, 2011 (edited) what exactly do you mean by a chamfer at the top of the walls? If youre referring to the fact that they shave the corners off where the deck is and the head gasket goes they dont. At least mine didnt. If it was it was incredibly minor and i didnt notice it. The edges of my pistons were chamfered but not the deck Edited July 25, 2011 by Recian (see edit history) Link to comment Share on other sites More sharing options...
Guest Recian Posted July 25, 2011 Share Posted July 25, 2011 here's a pic of the deck up close so you can see yourself Link to comment Share on other sites More sharing options...
jonlabree Posted July 26, 2011 Author Share Posted July 26, 2011 Thanks, That what I wanted to know. Some engines are chamfered at the top of the cylinders.The reason I ask is the a lot of the headgasket manufactures are selling headgaskets the are over size for the cylinders, so I needed to know if I need to buy an over sized headgaskets. Some are over 4.0" and larger., way to big for a 3.80 bore. I don't want to loose any compression fron the headgaskets. Link to comment Share on other sites More sharing options...
Guest Recian Posted July 26, 2011 Share Posted July 26, 2011 my head gaskets fit perfectly with what i've got. You definately dont wana lose compression on this engine, If anything increase. V engines rely alot on compression especially this GM engine unless you intend to turbo it but supercharging is more common Link to comment Share on other sites More sharing options...
2seater Posted July 26, 2011 Share Posted July 26, 2011 (edited) The stock GM gaskets @ 3.84" were the best that I found. The FelPro's I received were over 4", 4.10" to be exact. I don't have the old stock gasket to show for comparison. Sorry for the quality of the photo. Maybe you can zoom in to see better detail. This is the FelPro. Edited July 26, 2011 by 2seater (see edit history) Link to comment Share on other sites More sharing options...
Guest Recian Posted July 26, 2011 Share Posted July 26, 2011 i used fel pros on my engine. i didnt take measurements but they fit the cylinders perfectly. they werent too big or too small. i know .20 isnt too noticable to the eye but i ran my hands around them and they matched my bore Link to comment Share on other sites More sharing options...
2seater Posted July 26, 2011 Share Posted July 26, 2011 (edited) It is possible there is more than one part number for FelPro's although looking through their catalog reveals only one. These are 9556PT. The ones illustrated came in a kit for the top end. My bad on the measurement, it is actually 4.01". The overall distance over the adjacent fire rings is .225". Edited July 26, 2011 by 2seater (see edit history) Link to comment Share on other sites More sharing options...
Guest Recian Posted July 26, 2011 Share Posted July 26, 2011 that's what I used. It was actually a HS9556PT Link to comment Share on other sites More sharing options...
2seater Posted July 27, 2011 Share Posted July 27, 2011 Not a big deal, about a 1/3 cc different @ .040 thickness, unless you are after maximum compression ratio. It does increase the crevice volume slightly but will probably fill with carbon anyway? Aftermarket stock replacement pistons are way worse for dropping the compression ratio. Usually destroked, meaning lower compression height, assuming the block will be decked, and dish volume in piston may also be larger. This works good for a boosted engine. Link to comment Share on other sites More sharing options...
Guest Recian Posted July 27, 2011 Share Posted July 27, 2011 actually i should slap myself for not realizing this earlier. the head gasket you measured at 4.02 is a new un used gasket. once you install the heads and torque them this gasket crushes in which causes the bore of that gasket to shrink. thats y its got an extra .20" to compensate for that Link to comment Share on other sites More sharing options...
2seater Posted July 27, 2011 Share Posted July 27, 2011 In this case, the gasket is only sort of unused. It was not run, but it was installed and torqued in place. I had misgivings about the bore dimension, in hindsight, (I was going for max. compression ratio at the time), so I removed them and replaced with the GM gaskets. It also cost me another set of torque to yield headbolts. Personally, I like, and use, FelPro gaskets, and the bore diameter in this case was just picking "nits" due to what I was trying to accomplish at the time, (+.050" comp. height pistons). Link to comment Share on other sites More sharing options...
Guest Recian Posted July 27, 2011 Share Posted July 27, 2011 i wouldnt think theyd make a gasket that precise with a .2" varience in bore. you didnt by chance measure the gm gaskets b4 installing did you? Link to comment Share on other sites More sharing options...
2seater Posted July 27, 2011 Share Posted July 27, 2011 Yes, I did, although I don't remember if it was 3.84" or 3.86" I believe it was 3.84", the maximum overbore recommended, but for some reason, I did not write it down. At some point I want to pull the engine down that I installed them in to check for damage from my first turbocharging effort but that won't be for a while. You don't have your old gaskets yet? Link to comment Share on other sites More sharing options...
Guest Recian Posted July 27, 2011 Share Posted July 27, 2011 I threw out my old gaskets recently. The combustion chambers were WAY out of round and blown out so there was no way to get a good measuremnt. However news as of today i have to pull the engine so if i do put rings in it i'll check my bore on thoe crushed gaskets Link to comment Share on other sites More sharing options...
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