Ok , I know I'm going to get different Opinions on this , and that's great. I bought a project cutlass 1970, with a 350.
All of my life , I have rebuilt car motors to stock. But this one I want to build to have fun, (not drag race it) but fast, choppy sound. This is what I know from past owner, by the way motor is torn down to short block. This is what came with car: Magnaflow stainless exhaust with the tru X pipe, headers, a Edelbrock Performer RPM Intake Manifold 7111, heads are #6 and the person told me they are rebuilt to W-30 specs, ( I don't know if that's true). the block is the 1970 block, but has a .30 bore. I was thinking of installing a thumpr cam with Hydraulic Lifters.
My question is , is this a good set up for what I want? should I go with a different cam? lifters? springs? what about stall converter? If I need more info, let me know ,and I will try to get it on here. This motor has been ran once, the man said he put a high pressure oil pump in it, and it blew the seal for oil filter off and covered everything in oil, I will not be using that oil pump! Motor has been on engine stand for last 6 years, so I will be taking it apart to check it out, if nothing else, to re-gasket it, and paint it.
I look forward to all your input. Joe , cutlassefi, I know you will have good advice. Thanks.

 

Can you measure the depth and diameter of those piston dishes? They look kinda large to me, which would mean not as much compression as you need for the build you describe.

The 6cc dish pistons are .077" deep x 2.54" diameter; the 14cc dishes are .130" deep x 2.88" diameter, and the 25cc dishes are .215" deep x 2.92" diameter.

 

I am betting those are the huge dish 24cc pistons. I would pick up a set of L2321 forged pistons and get them pressed on your rods. They need a minimum clearance of .004", it may need a hone to have enough clearance. Looks like the W31 valve sizes were used.

 

Well i would say flat tops are your best bet for gaining usable compression. Get them pressed and the rotating assembly balanced. Im running a lunati voodoo cam and its pretty rowdy but had great street manners.

My 355 has 10 to 1 compression , luntai voodoo cam 522/539 lift 233/241 duration. 3.73 gears 3000 stall th350 trans . In my car ran danm near mid 12 sec. e/t's which makes for nice little fast street car. Thats the skinny of it but its a full street car, driven to the track and back and makes enough vacuum for power brakes. Runs on pump gas.

I can give more details to the build if you would like but i dont wanna eat up space lol. My build is brutally basic and bare bones yet effective and has the e/t slips to prove it.

 

What octane fuel do you want to run on? He will also need a 3000 stall and a minimum of 3.42 gears with 10 to 1 compression. Is 3000+ rpm at highway speed OK for you? I would CC the heads too. He can go with a mild converter, 3.08 gears and have some lump/power with the 6CC dish and probably get away with regular fuel with the low-mid 9 to 1's those pistons provide.

 

I run 93 but ran 91 in a pinch last summer on my way to the track. I don't actually have a true 10 to 1 I'd you wanna get technical it's like 9.97 to 1. 9.75 to 1 would be the least amount I would run with the cam I have personally. 3.42 gears are great on the street and if racing is not gonna be something you do then they will be adequate imo. For stall the 3000 is not bad it scares people off but I got a good unit that has minimal slip around town cruising but a 2600 2800 unit would be good on the street .

 

x2 on L2321, that's what I built my 350 with. Why take a chance when there are options. Around here we only have 91 octane.

Also I would stay away from thumper cam, talk to cutlassefi for a cam.

 

The small dish Pistons are 20% more expensive than flat tops:-( but they seem to be the appropriate selection for 91 octane.

I am figuring out my 350 build as well.

Ryan

 

You can dumb down the compression when using the flat tops by polishing the chambers smooth which will add cc's and actually help performance. Remember most sbo cyl heads have closer to 68cc's NOT 64cc's . I had my #6 heads milled .024 , and with a .040 head gasket and the piston about .025 in the cylinder im right under 10 to 1 compression so there is alot of controlable variables there imo . I would rather get the flat tops.

 

Good point, all the factors add up, if I can leave a decent CC volume and gasket, may be able to use the flat tops:-)

Also have too see how far piston will be below deck after decking the deck:-)

Ryan

 

measured them 2.88 X .130 so 14cc !

 

91 octane, but I could bump up to 93. I was thinking 3.73 gears.

 

Also , I have 3 automatic transmission he gave me with car. TH350, 400, 200R4. what trans would you use, if it where your car? And thanks for the advice, it helps a lot.

 

If you are not doing a lot of highway driving a TH350 with some upgrades will be fine. If you build up a TH2004R even a 4.10 gear would be liveable on the highway. If your planning 91 and can get 93, then Flat tops should work. If they are 14cc pistons, you will have around 8.5 to 1 with Felpro head gaskets.

 

3.73's aint bad and you can do what i do and run a short tire 26 in. at the track to get a little more gear and run a taller tire on the street like 28 in or 29 in tall tire to keep the rpms down. I recently went to 3.90's but i didnt mind driving home with the drag radials 26 in. tall and 3.73's which comes out to roughly a 3.90 ish gear since baseline is 28 in. tall tire .

 

great info, thanks for the input. I'm looking at L2321F piston on summit, but the picture is dish pistons, and has that in description. Do I have right # , because I thought these are to be flat!

 

You want the LF2320F pistons for flat tops.

 

As I said at start of this thread, I don't build go fast cars, I build factory stock cars. With that said, please no angry responds . motor is bored .30 over, and going with flat top pistons, what head gasket do I use? Do I need a larger bore opening, for .30 or do I use a stock size? New ground for me.

 

Go fast or not it all has to be planned out. Right cam for the compression , right gear , etc etc. It's not just go fast stuff. You should know that a .030 piston will need to bored .030 over. If it's already .030 over then you need to check for adequate clearance and hone it to get the desired piston to wall clearance.

 

Yes, it is already .30 over. I think you are the one running a Voodoo cam? thanks for the input, I don't plan to ever race it, it's just the person I bought it from has had all the machine work done, he is looking for the specs of the cam that the engine shop put in, and he had a lot of aftermarket parts, so I thought I would finish it the direction he was going. I don't know what will work with what, that's why I asked for input, at start of post is what I have to work with.

 

Before you can think about a cam. You need to figure out where everything will be. Chamber cc's , how far the piston is gonna be in the cylinder then also the head gasket thickness and if you can find it the cc's it will add. Some companies have that info available on their gaskets. The voodoo cam I have is pretty agressive but has great street manners.

 

Copper, thanks for the info, it is helping me, I'm taking baby steps here. the heads I have now are 62 CC , this is using plex with hole in it and sealed on head. is this right, do you think 62cc? the pistons in motor right now are 14 cc, I was going to order flat tops , but if dish will work, I will keep them. the pistons are 1/16" from block deck. please see pictures

 

Wow that seems excessive. If they are aftermarket perhaps the pin height is off as has been mentioned before. 1/16 is appx .060 check it with a straight edge and feeler gauges and make sure the piston is at the very top of their rotation. If it really is that far down in the cylinder I would try to find a diffrent piston like the speed pro. With your cc's I would use dished but you have to make sure where you piston is at in relation to the deck height. Can't guess it.

 

calculating what you already have you will only have 8.4 to 1 compression using the standard felpro gaskets .040. In the one picture it looks like the piston is sitting much higher than in the one picture where you have the straight edge. double check that.

 

copper, just checked with filler gauge and flat edge .035 piston is at tdc.

 

Ok if you use a .028 thick head gasket which rocket racing and performance sells but are not cheap . you can have appx. 9.1 to 1 compression. which if you are not racing will be fine but you wont be able to run a big choppy sounding cam but you can have a nice cam with a good exhaust tone to it. also be sure your pistons are 14cc. You could use whats there.

Hopefully this link helps. https://www.rbracing-rsr.com/compstaticcalc.html

 

Copper thanks so much. I will go out now and get the rest of the Measurement I need and plug them in.

 

Great info guys!!!

Ryan