Hello guys need a little help? I have pull my engine out and planed on just doing gasket and a clean up on the engine. The engine run strong when pulled no nosies or it didn't smoke. A new timing chain and oil pump but my plans quickly have changed once I got the intake oil pan and timing cover off. Timing chain was shoot I found two weak lifters and a piston that was cracked had a couple of valves seeping oil around them. All the main and rod bearing look good and the cylinder walls hardly no wear so now I'm all in. Would like to get a littke more power out of it now since I'm in a full blown rebuild. My question is should I go with flat tops and a small cam to help out or just go back with stock build? I will be reusing the factory intake and cab and ext manifolds to keep it stock looking under the hood. Anything else I might need to know to keep in mind on the rebuild.

 

You can go with the 10.25 pistons from speed pro and a small cam. Cutlassefi can have a custom cam made for you. Tell us about your car so others may give you some good advice.

 

Well it a 71 supreme auto 350 turbo car with ac I thank that it's a 2.73 or a 2.93 gear in the rear end haven't pulled the cover to check to make sure yet. Not looking to really build a power house of a motor. All I plan on doing is crusein in the car just thought since I was in the motor just to see what the best way to go with it. Would that be to much compression to run on the street with pump gas. Do they make a dish piston that will bring the compression up with a smaller dish. Going to take everything to the mechine shop and see what he has to say about it.

 

I never understood the advertisements of 'X to 1 CR pistons'. There are so many other variables that factor in greatly as to what your actual CR will be. Buy '10.25 to 1 CR' pistons, install them in an engine without decking the block, use thick Felpro gaskets which most do, slap on a set of heads you 'assume' are X cc's because that's what you saw on the internet, and end up with a hell of alot lower than 10.25 to 1 CR.

To make the problem worse, you picked out a cam you thought would match up well with 10.25 to 1 CR, but since your actual CR is alot lower, you are now over cammed. This is why there are so many turds on the road! Don't make that mistake. Figure out what CR you want to go with and get the appropriate pistons, gaskets, and machine work to achieve that in the most efficient way.

 

Speed Pro L2321 6cc dish piston is still available through Jegs. Call them and ask them to call speed pro and do a stock check. My buddy just ordered his they are $549 with shipping.

 

You can get the Speed Pro's for cheaper than that. I think you can get the better/lighter Probes for less than that too.

 

You are correct on both of your posts.

Check with Jeff Dana (jdana24) on here. He did a stock build similar to the way you're headed with Probe pistons, stock heads, intake and Qjet, along with headers. He's posted a couple of vids to show the build and how it runs. This may be helpful for you.

 

Where do they sell 6cc dish speed pro pistons for less?? Part #L2321F30

Just wandering, I am helping a friend with his 350 and we looked up and down for them couldn't find them anywhere besides Jegs. He paid $549.

 

I don't have the part number off hand. Just do a search on Probe pistons for Olds 350 and they'll come up. I've seen them for $460. They're not 6cc dished pistons though. Thay are flat tops with 3cc valve reliefs, but I see them listed at times as being +3cc instead of -3cc though.

 

Remember, they're not only less of a dish but they're also taller so you'll gain the better part of a half point over the Speed Pros. Plus they're much lighter.

http://www.probeindustries.com/Oldsm...s_s/102231.htm

 

Wouldn't that be too much compression?

 

It'll be every bit of 10.0:1, but that's doable with the right setup.

 

Mark, are there .030 over 14cc dished cast pistons available for the Olds 350 or are there just the big 23cc dished ones that are available? Just curious as I just found out my engine builder screwed up my engine build by installing the big dished pistons and not doing the proper machining ( decking the block ) to get my CR where I specified it to be at. I was always under the impression I had the 14cc dished pistons, but apparently not.

 

Sorry to hear that, that sucks.
I'd use the L2321. I have those in mine. With 66cc heads and little deck I'm at 9.7:1. I would guess seeing as how your block probably wasn't decked as much as mine that you'd be in the 9.25-9.5 range. Not sure if that's what you're looking for but that would work fine.

 

Man, I wish I was even close to the 9's in CR! I'm at about 8.1:1 and I specified I wanted 8.8. With 8.8, I figured ( now that I'm not limited by running on the computer ) I could bump up the the CR with a thinner gasket and sleight head milling to get it up in the low/mid 9's and add a sleightly bigger/better cam. NOPE! Those Bozo's saddled me with the big dished pistons which are sitting way down in the hole ( .038 measured by my guy ), thick head gaskets, and then they milled alot off the heads ( 60 cc chambers ) to come up with my craptacular CR. This is what an 'Olds engine building specialist' built me.

So why did I have 'my guy' tearing into an engine with less than 7000 miles on a top dollar 'pro' rebuild? To fix the $hit valve job they did of course! That has been the reason my engine never ran right from day one. When you have 2 cylinders with about 75 and 30 psi cranking preasure, that kinda hurts performance.

Sorry for the mini rant, but I just found all this out very recently and am a bit unhappy about it. At least I was also charged for a 3 angle valve job they never did too....

 

Flat tops and a cam or stock rebuild? It depends on how thick your wallet is. I totally believe in talking at length with your engine builder. A stock rebuild and a correct CR engine are 2 different things and they are a long ways apart in price.
I did this recently and fond out it costs a lot to get a properly machined engine to establish a correct CR (it is worth it to do the extra blueprinting but it's expensive).
You need to talk to a local shop to get the right answers to your particular needs. There are so many factors to look at including the altitude you live at, it costs a crapload to do an engine these days and your local shop is the one that can tell you what you need to do what you want where you live.

 

With all due respect, I find it interesting that both of you guys (Mark and Double V) are running dished pistons but when J Rod asked Both of you recommended flat top that will bring compression up to 10:1, maybe more, that can barely run on pump gas and that may be ping if not set up right.

Can I ask why? Wouldn't be better to run 6cc dish like I mentioned and be safe?? Obviously J rod is not building a race car.

Not everybody wants their engine at that fine line, you know, to ping or not to ping.
Please don't take me wrong, just curious.

 

I ran flat tops .025 in the cylinders with milled heads rouhghly 66 cc's my compression was right under 10 to 1 it was in the 9.9 to 1 range . It ran fine on pump 93 .

 

You recommended Speed Pro 6cc dished pistons and I simply mentioned that the Probes were better ( and cheaper than what you quoted for the Speed Pros ). The Probes have 3cc valve reliefs, so they're only 3cc smaller than those Speed Pros. The effects on final CR would be negligible.

I never even mentioned to Jrod he should even go with flat tops, or even forged pistons for that matter. If anything, I would probably recommend 14cc dished cast pistons if they're still available. I still don't know if you can get those anymore though.

 

Let's assume the 14cc dish piston no longer exists.

There are still some very viable options;

The 2321+.030 6cc piston with a 0 deck, 9cc gasket thickness and #8 heads(79cc); 8.75:1

2321+.030, 0 deck, 9cc gasket, 5, 6, or 7 heads with 68cc chambers;
9.75:1

Probe 3cc +.030 piston, 0 deck, 9cc gasket, #8 heads(79cc), 9.0:1

Probe 3cc +.030 piston, 0 deck, 9cc gasket, 5 ,6 , or 7 heads (68cc), 10.0:1

Obviously deck clearence and chamber size will effect these ratios. Remember the Probe not only has a smaller cc but is also taller than both the 2320 and 2321, meaning less will need to be taken off the deck in order to achieve a 0 deck.

My point? You can still use the Probe piston, a little in the hole and/or with larger (smoothed) combustion chambers, for a compression ratio in the mid 9's. Very streetable in my opinion. And it has a better ring pack and is much lighter than just about any other off the shelf SBO piston.

Hope this helps.

 

Thanks for that post EFI I found it helpful

 

I believe Egge makes them cast, just says L3066 .250" dish, $448 a set. Almost as expensive as good forged pistons. Assuming their calculations aren't BS, supposedly gives 8.75 to 1 vs the Speed Pro 6cc they sell, they calculate 9 to 1 for those. That sucks DoubleV, I thought that place, if any, would do it right.

 

Thank you for the explanation Mark. I have built few of my Chevy's but when I bought my Olds I realized how different things are. This a learning curve for me. As we all know choices are limited when it comes to SBO off the shelf parts. It's good to know few options available.

Personally I still like the 6cc Speed Pro better in MY SBO. IMO Mid 9's is safe for a cruiser with a little more ***** over stock. Too bad they are discontinued and hard to find as they are perfect choice for majority of rebuilds that will never or hardly see the track.

Once again did not mean to offend anybody.
If one doesn't ask one will never know.

Probe compression height is taller than Speed pro. More compression even with 3cc valve reliefs. The end result is ALMOST the same as running Flat Tops.

 

But if you're doing a full on rebuild, and you're going to be decking the block, using the Probes, you wouldn't need to shave as much off if you wanted to zero deck it. If you want your pistons to sit far down, then that may be a different story, though some claim the poor quench that would result from that would make the engine just as/more prone to pinging than if you would've just went with the slieghtly higher CR and better quench. If poor quench isn't a concern to you and you wanted to keep your CR from being too high while using the better Probe's, you can just run a thicker head gasket and/or not mill as much off the block.

 

If you read his post he is not building a race engine so why would he want 0 deck, he was asking for something little better than stock.
In his words "All I plan on doing is crusein in the car just thought since I was in the motor just to see what the best way to go with it. Would that be to much compression to run on the street with pump gas. Do they make a dish piston that will bring the compression up with a smaller dish."
Why would you recommend 10:1 for a mild build?? Speed pro is about same compression height as stock, so a little smaller dish would do the job for any cruiser.

If he was building something to take to the track and wanted to get every possible HP out of that SBO than you are right Probe are the better option. But he is not 0 deck and 10:1 a bit much don't you think?

 

I'm not. Try re-reading this thread without the preconcieved notion I'm telling Jrod he 'needs' Probe pistons and to build his engine with 10:1 CR and maybe it'll become a bit more clear to you.

You're accusing me of things I'm not saying. Race motor or not, in a full on rebuild you deck the block not only to true it up but help achieve your CR goals whatever they may be. Zero decking isn't a race car thing and either way I never said he needs to do that. He needs to figure out what CR he wants and what his goals are, then pick out a piston that'll achieve that. If anything, you're the one who brought forged pistons in the first place. Aren't forged pistons for 'race cars'?

 

Yes you deck the block but no need for 0 deck. Read the damn question that he asked: Do they make a dish piston that will bring the compression up with a smaller dish?
Aren't Probe forged?

 

Where did I tell him to do that? I didn't. Please stop bringing it up.

Is there really any need for the attitude?

I don't know. If you actually read my posts, you'd see that I actually asked Mark this very same question and again if you would have read my posts, you'd see that if they did have a 'stock replacement 14cc dished piston' available, that's what I would probably recommend.

Yes, the Probes are forged.

Bottom line, IMO, any build ( let's say 'most' builds ) that would work 'require' a 6cc dished Spreed Pro piston, would work just as well with the Probes plus the Probes are lighter and have a better ring pack ( and are apparantly cheaper too ). Will you end up with a tad more CR with the Probes vs Speed Pro's? Yes, a little, but then you could just run a thicker head gasket ( or not shave as much off the heads or block ) and bring it down to the same CR you'd have with the Speed Pro's.

So those are my thoughts. There's no need to get bent out of shape about anything 70cutty. So please stop accusing me of telling Jrod he should 0 deck his block, use Probe pistons, and run 10:1 CR OK?

 

Thanks for the help. Didn't mean to get anyone in to a up wore. Talk to guy about that's doing my engine. Just a little more info about my engine they are number 7 head. They are stock just doing a valve job and new seals. Using the stock crank and rods. Crank will use std rod and mans just polishing it. Check the bore on the block and it will need to be bored over do to some wear. Probably going to take it 30 over. Still not sure what piston I'm going to use. Would like to to make the engine around 9.0.1 cr little more then stock. Will be using felpro gaskets like most going to mill the heads and deck the block to true everything up and to compensate thicker head gasket. Going to do a little more research on piston. He is checking on pistons to to see what he can get. More and likely go with a set of speed pro pistons. One more question is cam just go with a stock cam because of us using stock springs, and not going crazy with the motor? Or maybe a small cam to help out on power?

 

Talk to Cutlassefi for the cam, you will be happy.

As far as the pistons, to keep it in low to mid 9 Speed Pro 6cc is your best bet.
They are discontinued but you can still get them from Jegs.
part #L2321F30 for .030 overbore.

 

Thank you

That piston, with a little deck and stock heads, will give you about 9.5:1, give or take. Very streetable.
I'd seriously consider putting in new springs anyway, whether you're changing the cam or not. I don't think it makes much sense to put 40 year old springs back in. Just sayin, and new ones aren't that expensive. Cam, lifters and springs will run less than $350.00 to your door.

Thanks.