At my buddies the other day, he had a 327 done .030 over, flat top 4 valve relief pistons. I took my stuff over and see he's right about .050 in the holes. Seems the shop used a rebuilder piston w/o decking the block. Okay, he has a set of .039 compressed Felpros, is there really any point of going with a thinner head gasket? It looks like maybe the block was surfaced, as the numbers on the stamp pad are fainter than you would expect, so hopefully the deck is true...he's using new Al ProComp heads, so hopefully those will be true as well. I have an extra set of Mahle .026 gaskets he could use. Not sure it'd make a difference in how it runs. Cam appears mild, I checked and intake and exhaust lobe, both .30x, so .450 lift. Other possible option would be a .018 steel shim gasket, but I don't know with Al heads if it's advised. Thanks Edit: One thing I meant to mention, the deck...I can't be for sure it was surfaced, the pad might have just been stamped shallow.
Being that .035 - . 045 is recommended , I would think you'd be prone to detonation & a very low compression ratio ..
Your buddy has himself in a real bad spot. Deck height is 9.025". 1/2 stroke + rod + 1.56 compression height = 9.000". This leaves the slug .025" in the hole. Rebuilder pistons usually have a 1.54" C.H. Now the piston is .045 in the hole. Proper quench is .035-.045". Anything more will cause detonation (pinging). I wouldn't suggest decking the block .050". The aluminum heads require require a composite gasket to prevent fretting. The thinnest I know of is .026". Still a terrible .076" quench. So the rebuilder pistons just aren't going to work for a well built engine. The only way out I see is to install a new set of stock C.H. pistons and zero deck the block.
Agreed. I have no idea what those heads cc at, but if he’s planning on high compression ratio it’s going to rattle.
I was thinking along the same lines, Heads are either 63 or 64cc's (spec-not measured) So CR should be in the mid to low 8's I'd guess. I think what happened was he brought in this 180 HP 327 and asked for a rebuild "and a mild cam", well then some time later bought the heads, not really knowing what he had, etc. I don't have the free time to tear the engine down for him, etc, and he doesn't have the $$ right now to take it into a shop. I'm just going to tell him to use my Mahle .026 gaskets and let's screw it together. Kinda of a shame though, but I have a bare block on my engine stand, crank in my lathe to polish a bit and enough SBC to keep me busy for awhile
Yes, kind of a shame. A shame that the machine shop would use rebuilder pistons in a block that was not decked. Also a shame your friend didn't ask for a rebuild that was close to OE spec.
Save a dime in the front end and spend a dollar in the end. Your buddy has painted himself in a corner. He needs to buy a set of real quality pistons like Mahle and deck the block to match otherwise he will have a motor that will be a pooch. Go with 2 eyebrow's.
Yep, if he let the shop choose the pistons, the shop screwed him. I'd have it back to the machine shop asking why they used those pistons. They didn't pay much attention to the details.
I guess the story is he had the engine done 7-8+ years ago, sometime after bought the heads via Ebay. AFter seeing the heads we did some grinding for PR clearance, checked and several valve were not seating well (I'll get to the point soon), so he tried contacting the place he had the engine done at to do the valve job on the heads, but phone was no answer or message option, he went by and shop appeared closed. So maybe shut down for the C-19 issue, unsure, or out of business all together. I know what I'd do if it were mine, but I have my own irons in the fire right now. He's anxious to get this car on the road again, I don't blame him. If I can get him to wait a few months till I get my kids car done and bring his engine over to my place, cool. Tough working on it at his place as he's 35 miles from me. Aw well, I'll run some things by him and see what sticks. Thanks all.
KB Pistons has a comp ratio formula you plug your #'s into, but you need to know them. Cometic has many different gasket thicknesses. I believe 4 eyebrows are 7cc's. That site stayed me a lot of time and $$$$. Good luck.
Warning: Rant Below One of the things that dries me crazy is when someone says "they don't have the money to do something" so they are willing to do something that everyone has told them is wrong. If he ponied up enough money to buy aluminum heads, he can sure save up the money to buy new pistons. He just doesn't want to admit to himself that he needs to part with some money. A decent set of pistons for a smallblock Chevy aren't that expensive, and he can sell the old (new) pistons to offset even that small outlay. Had a young guy show up at my house to repair my cable tv/computer connection last month. While he was here he got a phone call from a collection agency. He went outside the ba*****t door and I could hear him hollering into the phone. He was upset that the bankruptcy he filed didn't cover everything and if he didn't pay something on his bill they were going to repossess his 2005 Camry. He and his girlfriend/roomate both had steady jobs and yet they couldn't pay their bills and have enough left to eat. He had about a dozen tattoos and one of them was brand new. I asked him why he couldn't pay his bills but could afford expensive tattoos? His reply was that his buddy did them for free when he didn't have other customers. Duh! Yeah,right.... Wife told me about several ladies at the Bingo complaining they didn't have money for their utility bill. Or the "lady" who pulled into the gas station with her friend and spied the gullible old fool (me) putting gas in my truck. Came over smoking a cigarette and asked me to buy her something to eat cause she didn't have any money. I asked why she had money for cigarettes but not for food. Or the guys standing next to the road with their dogs saying they need money for food. Yep, when people say they don't have the money for something it usually means they just don't want to spend it on something because they want to spend it on something else. Rant over...........
These guys got the cart before the horse on “rebuilder” pistons with lower pin/compression height. they should really get their **** together and call them “decked block” pistons The other guys making gaskets with different compressed heights ,,, well that’s another part of the same story.
I got tired of this ****. Standard response now is - “You need to find someone who’s less talented, doesn’t know better and needs the work”.
So I have to reply, first off I like your post. Good there. Maybe in your lifetime, you never hit a bump in the road. So, without goung in to my details, let me ask you this: 10 years ago knowing nothing but "someone" told you "pull the engine, have it rebuilt". So you do...you pay your bill and have a rebuilt engine at your place. Then, life happens...no details...but after you picked it up and rolled it into the shop, some time later you are out of a job...you take your stuff to friends places, lose what you have...and then eventually 9/10 years later you are back in the game...just with essentials So, now a year or so later, you have a place, you have all your stuff back, and you want to get things in gear. Now ya not pulling down the 6 fig salary you once had, but you are better than min wage. Feel me? So, looking back 10 or so years you spent $$...like we all have done, ...lets side step...you bought a 2K front door made of solid Oak, ...etc, etc...lost ya job...years later moved into a apartment...and even though you have that door, you be trying to use it...heck, ya paid for it , right? Back to the matter on hand and your comments, guy is now getting solvent, he want's to get his ride on the road. 10+ years ago spent **$'s... So, in closing as my fingers are getting tired, you made a blanket statement I had to respond to. Just FYI, I have learned much from you in your replies to my questions and appreciate the time you do take to respond, but in all honesty if you do not know someones finacial status, you can not ***ume it is the same as yours. Regards
I'm one of those guys that have bought the $95/set ebay rebuilder style pistons on purpose, a low compression street/strip pump gas build that was sprayed to 700hp just to prove that I could do it. Even ran 87oct fuel even when spraying. It was a 2525lb car with 3.73's and no overdrive, ran 5.73 in the 1/8th and still got20mpg down the highway. That Brodix headed engine had around .090" quench, only cranked about 90psi on the starter, and had timing locked at 36. None of the problems typically ***ociated with excessive quench. Grant
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