383 240z Posted March 8, 2003 Share Posted March 8, 2003 I was told the motor had flat tops when I bought it but buyer beware I found dished pistons with 4 valve reliefs. yuck!!! I have a set of 64cc heads will this bring my compression to a livable level. I'll cc the pistons tomorrow and see what I get. Now this will really change my cam choice. I hope I'm not screwed as I dont have the money for new pistons right now. Keith Quote Link to comment Share on other sites More sharing options...
Mike C Posted March 8, 2003 Share Posted March 8, 2003 Compression may be fine depending on stroke and piston to deck height. Quote Link to comment Share on other sites More sharing options...
Kevin Shasteen Posted March 9, 2003 Share Posted March 9, 2003 I've never seen a true 'Dish' piston that also had valve reliefs. I've seen Solid Dome, Hollow Dome, and Flat Top Pistons that had piston reliefs...but never a real Dish Piston w/Valve Reliefs. I would contact the previous owner & have him confirm what pistons your actually have; get a part# and ph# of the piston mfg so you can confirm what cc's your pistons are. Kevin, (Yea,Still an Inliner) Quote Link to comment Share on other sites More sharing options...
383 240z Posted March 9, 2003 Author Share Posted March 9, 2003 I have a buret here so I will set it up and cc them in the morning you can see a photo of them here http://photos.yahoo.com/bc/rx7260z/vwp?.dir=/V-8+RX-7&.src=ph&.dnm=DSC01930.jpg&.view=t&.done=http%3a//photos.yahoo.com/bc/rx7260z/lst%3f%26.dir=/V-8%2bRX-7%26.src=ph%26.view=t I bought the motor at a swap meet it looked pretty well taken care of and was priced right and was complete oh well Keith Quote Link to comment Share on other sites More sharing options...
denny411 Posted March 9, 2003 Share Posted March 9, 2003 What size rods do you have? I`ve got a set of 11:1 domed weisco`s for 6" rod that I`m not sure what I`m going to do with. Quote Link to comment Share on other sites More sharing options...
383 240z Posted March 9, 2003 Author Share Posted March 9, 2003 I have stock rods on a stock 350 crank. I need to run this motor on 87 octane But I still need it to make some HP. Keith Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted March 9, 2003 Share Posted March 9, 2003 those piston are considered flat top for a sbc, normal for a sbc, i have yet to see a true flat top for a sbc, with no valve reliefs, a dish will have a half moon shape with no valve reliefs, each valve relife is usually 2cc, Quote Link to comment Share on other sites More sharing options...
80LS1T Posted March 9, 2003 Share Posted March 9, 2003 Yeah I'm going to have to agree with Shank on this one, those are considered flat tops. Atleast from what I have seen that are called flat tops. I dont think you can have a dished piston and valve relief? What would be the point of the valve relief if the piston is dished? Guy Quote Link to comment Share on other sites More sharing options...
Guest grinsha Posted March 9, 2003 Share Posted March 9, 2003 Those look like Factory Flattops. I have a set just like them out of a factory engine. Quote Link to comment Share on other sites More sharing options...
Guest the_dj Posted March 9, 2003 Share Posted March 9, 2003 They don't look like my factory flattops Aside from the little relief, mine are perfectly flat. His seems to have 2 levels, with the inner level deeper. Quote Link to comment Share on other sites More sharing options...
383 240z Posted March 9, 2003 Author Share Posted March 9, 2003 The DJ got it right the ring around the outer edge is higher than the middle portion the pistons in my 327 are flat with 4 vr's Keith Quote Link to comment Share on other sites More sharing options...
383 240z Posted March 9, 2003 Author Share Posted March 9, 2003 Well here is the bad news. with the piston at TDC I get a cylinder volume of 25.5cc my head gasket volume of 9.1cc and the heads I'm planning on using measure 64.5cc if my math is right (please feel free to double check me) my compression ratio is 8.21:1 Is there any way to make decent power with this ratio? or do I have to pop for new pistons? I can find a cheap set of cast pistons with rings on E-Bay for about $100 (sealed power w/ cast rings. The wife is getting PISSED if I spend any more money on this car she is going to kill me!!! what started as a simple cam swap is turning into a total rebuild. Keith Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted March 9, 2003 Share Posted March 9, 2003 CR of 8.21:1. Sounds like the start of a good blower motor..... Of course, the significant other factor would probably kill that idea. Quote Link to comment Share on other sites More sharing options...
383 240z Posted March 9, 2003 Author Share Posted March 9, 2003 Thanks Jim just kick me while I'm down Keith Quote Link to comment Share on other sites More sharing options...
Kevin Shasteen Posted March 10, 2003 Share Posted March 10, 2003 Those pistons do look like dish pistons w/VR's. Surely they are the factory low comp.pistons. Dont look at what you dont have instead look at what you do have. You said yourself you want an engine that runs on 87 Octane: yes/no? The only problem is that you cant make serious HP & still run on 87 Octane w/out serious mods to your engine. Serious Mods=MONEY. So, in order live in the restraints of 87 Octane that you have placed on your project...you modifications must be slight. Any Cyl.Head or Piston swap you make to take advantage of a cam swap cant to be to terribly radical, otherwise you will find yourself needing 92 or 93 Octane. What I would suggest is you upgrade to a mild cam swap and then concentrate on decreasing the restrictions to your intake & exhaust systems. This way you'll get a little more punch w/out serious bucks and still remain w/in your 87 Octane requirements. Kevin, (Yea,Still an Inliner) Quote Link to comment Share on other sites More sharing options...
383 240z Posted March 10, 2003 Author Share Posted March 10, 2003 Kevin I just faxed crane cams an info sheet looking for a cam rec. I think that I can use my low comp pistons I'm just looking at all the options. I pulled the motor this morning so I could measure the CR for a cam swap. I was upset that the motor was not what I was led to believe it was. I changed the intake and carbed it for a higher compression motor. I hope there is a way to leave the pistons in the car. Keith Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted March 21, 2003 Share Posted March 21, 2003 I am late with this but, Yep, like Jim Powers said, I think they picked off a blower or an EFI/nitrous setup. Would you buy again like that or would you insist on pulling a head first? Better get the little woman a job to fill in the gaps. Put some wrenches in her hand. Make like you doing all this so she can drive it. Get her opinion on paint color and upholstery. Spray inside with you aftershave (or her fu-fu) and have her sit in it and strap in so you can measure something or whatever. Keep things neat and clean as possible (including your clothes and don't track dirt into the house. Bag your filthy clothes out in the garage and do the laundromat with em' (showing your consideration and concern for her valued houshold labors). This is a critical item because if she insists on doing them herself then you got a hook on the whole situation. . Clean those fingernails. Poke around and find her weak spot. Threaten to Enlist in the Marines cuz' you are so discouraged and if that dont' work, do the opposite and threaten to quit your job and start working out of the house at something brash. I love to tease the women. Because we spend so much time on these conversions/rebuilds, many women get jealous of "That Car"! But, if you can really shake her up then she will come over to your side carwise. Why? Because she loves her man and it's a woman's God given nature to follow him! If necessary, even keep her away from her mother as much as you can. Get her to read a few simple articles about the car for you because you are not sure what they mean. In other words, slyly suck her into the picture eh? You're welcome and NO CHARGE! Quote Link to comment Share on other sites More sharing options...
383 240z Posted March 22, 2003 Author Share Posted March 22, 2003 Spiirit you should meet my wife. She can drive your ass off. I wish I could cut a light as well as she can. She used to run my RX-7 at the local auto-X and embarresed many a male driver. She has just given me the go ahead to build the 383 I have sitting here. And as for her getting a side job to "fill in the gaps" she makes considerably more money than I do. Keith Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted March 22, 2003 Share Posted March 22, 2003 Alright there, glad to hear that! So how come she let you buy a sealed engine at a swap meet? Just kidding.....LOL Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.