Because of budget reasons I'm reconsidering building the 374cid stroker engine right now. I have a '76 block in good condition (never been overhauled). I'm thinking if I simply re-ring the engine and replace the #8 heads with some #7s I can get the compression up to around 9:1. I'm running out of money and would rather get the car running with the stock engine; I can build the stroker engine later on after my checkbook recovers.

The engine builder (who was to build the stroker engine) wants to bore the block and install new oversize pistons, but I want to reuse the original pistons to avoid the huge 24cc dished replacement pistons. Here are my questions:
1. Can I just hone the cylinders and reuse the stock pistons? The block is very nice, no ridge at the top of the cylinders, but haven't checked the taper of the bores.
2. How much piston skirt clearance is too much when honing the cylinders and fitting new rings?

Thanks!

 

Is the engine still together? I picked up two 76 350's that had good compression and nearly perfect crank and bearings. These motors with tall gears and being so neutered couldn't hurt themselves. I know forged pistons need .005" piston to wall or scuffing can occur. I believe someone mentioned not going past .006" with cast pistons. If the block needs bored, get Speedpro flat tops and reuse the #8 heads. All those heads need to flow is the lip under the exhaust valve removed. I too hate vehicles sitting undriveable.

 

The engine is apart and at the machine shop. I was getting ready to start the stroker build, but need to hold-off because of money needs. I asked the machine shop if they would just hone the cylinders, re-ring the existing pistons, and install new bearings, timing chain, freeze plugs (basically freshen up the short block) but he said he doesn't build motors that way. I'm pretty sure he hasn't checked the cylinders for wear or taper, but he has checked the block for cracks and says it's good. I've heard Olds blocks are much harder than Chevy blocks so the cylinder wear may be minimal and within honing range.

 

he doesn't want to hear horror stories about oil burning due to poorly seated new rings.

Maybe if you sign a waiver accepting consequences of ring/ cylinder problems?

You can always buy a $100 dingleberry hone and spend a couple hrs doing the cylinders yourself. In theory if the taper was not objectionable before it will still be OK, and the fresh hone will seat the rings right.

What about clean out the pistons' ring grooves and oil return holes and put it back together with the same rings and pistons? Too late for that?

 

Octaina:
I'm meeting with the machinist tomorrow to see how they tore it down and make sure I'm not missing any parts. It might be too late to put it back together and get the pistons in the correct holes, rod caps mated to the correct rods, etc. The pistons and rods were going in the trash for the stroker build so it wouldn't surprise me if they didn't catalog all the parts when the tore it down. If everything is in good order, I may ask him to hot tank it and install the cam bearings and freeze plugs; I can hone the cylinders and reassemble the short block myself. Thanks for your comments.
Rodney

 

I ran a re ringed 350 with max .006 clearance on a few pistons. it was a 10 to 1 engine using CAST flat tops. I beat the living snot out of it for a season and a half until the skirts cracked and it started making noise. I regularly spun it to 6k rpm. It didnt smoke all i did was dingle ball hone it and used stock replacement rings. Its amazing how much abuse old stuff will take.

 

I can't understand why you would throw these away instead of selling/giving them to someone who needs them. The rods are still useable and if the pistons had low miles they may have been useable, too. Why throw them in the trash?

 

Ken:
It was just an expression, I meant they wouldn't be used in the stroker build. Unless they were damaged in some way, I would offer them for sale in case someone needed them. Replacement parts for our cars are getting harder to find, absolutely need to recycle good used parts.

Rodney

 

14 cc pistons will bring about 75 to 100 bucks .

 

If you can afford it, do what 307/403 suggested. Bore the block and install flat top pistons on the stock rods. Resize the rods with new ARP bolts to .0022+/-. Then, use the #8 heads to get 9 to 1 CR. You won't have to get the other heads and you will have a fun streetable cruiser. If you decide down the road you want more, then bolt on some older heads with a cam upgrade, knowing the bottom end is in good shape. At this point, you are almost better of finding a running 350 or 403 than putting yours back together, IMHO.

 

You'd be surprised what you can get away with until you actually do it. I've been accused of being cheap, and that's fine. Truth is, I am the most precision guy you'd ever meet. And I got the tools to back me up.

I won't go into detail with the things I did that would be considered "sub-par" but I can tell you that if you know what you are doing, you can make your engine run.......and run well.

I would get the parts back from the machine shop, and then beg, borrow, or steal a bore gauge. See what you got for cylinder wall straightness. When it is out of the realm of what everyone here would recommend, go ahead and get a dingle ball hone and put a nice 45* crosshatch on the cylinders, get the cheapest cast iron rings you can find, put it together, and if you actually did a good job it will run and run well.

Your #7 heads will need to be milled around .060" to get 9:1 compression. Your intake will need to be milled to fit. When I was a young buck, I did the same thing to a 350 of that era with #7 heads and went 13.04 @ 104mph in a 3500lb Cutlass.......and if I knew a thing about converters back then, I would have been much faster.

 

ps- if want to go this route, I will send you a good used cam and good used double roller timing chain for this build.....just pay the shipping.....my only request is that you put the motor together. You will need a set of new lifters though.

The cam is a Comp XE268. I'll help you out with as much info as possible.

 

Rocket:
Wow, I'm touched by your offer! Thank you. I'm really amazed at the generosity of the CO members on this site; it restores my faith in this world knowing there are people who will go out of their way to help others.

I haven't met with the machinist yet, but plan to get with him next week. I had a good idea about the cost to build the stroker engine from a few conversations with Mark (CutlassEFI); but I didn't want to send everything to Florida so I found a reputable local shop. The local guy wouldn't give me a price until I brought him my motor. So I dropped off the short block and after 2 months of phone calls he finally got around to looking at it and said my block was OK. I told him I wasn't about to start building this motor without a budget, but he still didn't have a price for me. Two more weeks of phone calls later, we sat down together and put together a very rough budget (a lot of "rods should be this much", "pistons should be this much" talk). His estimate was $1500-$2000 more than Mark's budget. I've already got $1800 worth of parts (heads, rockers, intake, distributor/coil, oil pump, water pump) and need to rebuild the Q-jet, buy a starter, and put headers on it. I was prepared to spend $6k-$7k on the engine (total) but I'm headed to $10k if I go any farther with the local guy.

I think I would rather just rebuild a stock engine and spend the leftover funds to finish the car. Sorry for the rant.

 

You can also go with the CP pistons which only require a block hone to install, if your block is that nice. BTR has them with rings for around $650. The are lighter than Speedpro or cast pistons withmuch better 1.5 mm rings. The #8 heads will equal early heads with minor bowl work. I went with milled and ported early heads with 14cc pistons. I think the CP pistons, bowl work with a 2" or 2.07" intake valve and minor milling on your #8 heads will get you where you want. Just go with ssomething better than a generic 204/214 cam or you will be disappointed.

 

I think the whole point of the thread is that he wants his car up and running. If he gets new pistons, he will be balancing the crank, resizing rods, paying for piston R&R, might as well go .030 over at that point with a good piston, grind crank, deck block, install larger valves, hell.......complete cylinder head rebuild........you see where this is going?

I took stock #7 heads with stock small valves and no porting to low low low 13s with a stock 1973 bottom end. Why would you suggest he waste more time and money screwing around with #8 heads and CP pistons?

 

#8 heads aren't bad, unlike 3-5A and J heads on the exhaust side. A skilled hand can do alot in an hour with those heads, really just that lip under the valve. So 40 year old heads are bolt on and go? Yes if everything is there, sure slap it together but he should do it himself. He will have guess where the pistons go back. That shop wants It done right and seems pretty pricey. Do you already have early heads? What other parts do you have?

 

I would agree if he did not already have it apart and out of the car. At this point, if I just wanted to go drive it, I would find a running 403/350, then build the other block as time permits. By the time he buys gaskets, parts, and fluids he will have more in it than a decent used engine, IMHO.

 

+1.

- Eric

 

Thanks, it just makes sense. Why spend hundreds of dollars on gaskets, etc, plus all the time and work for what will basically be a "used" engine with a half-azz re-ring. And like 307/403 stated, most older 350 heads are going to need work, too.

 

To re ring an engine buying through summit on the 350 I mentioned earlier I spent appx 700 on the parts.

 

 

I need to see if the machine shop kept all the parts organized and numbered when they tore it down so the short block can be reassembled properly. More than likely the parts all mixed up in cardboard box with no numbering. I was planning to run some Bernard Mondello, ProComp heads for the 374cid stroker, but they would be too big for a stock, re-ringed 350. I do have a set of #7a heads with stock valves and a recent valve job that I bought used for $150 before I started thinking about going the stroker route. I only have $100 in this 350 block and the machine shop wants $75 for the tear-down labor if I decide not to build the stroker and just pick up the pieces. I agree with Captjim, If my engine can't be reassembled with pistons matched to their respective bores, I would just look for another '73-'76 sbo to re-ring and run with the #7a heads, and build the stroker at a later date with the current block.
I want to say a big thank you to everyone for the comments and advice. I'll post more info after I meet with the machinist next week.

 

I have found two decent 76 350's for giveaway prices. Just depends on your area on price and availability. My last one had 140-142 psi all eight cylinders and 15 hot at 600 rpm in gear, 45-50 hot oil pressure cruising. This after adding the compression dropping Performer cam. It ran mid 15's with coil issues, initial engine cost was $150. I since bought big valve milled and ported #6 heads and put them on. Honestly do a compression and oil pressure check before tearing apart a perfectly good motor. Those mid 70's 350 were incredibly durable and were so neutered, it took a lot of abuse to hurt them.

 

Fwiw i recently took in a 73 350 shortblock in for 80 bucks i measured all the pistons. and measured the block i was going to use which was a 1968 350 block. the biggest clearance was .006 all the others fell in between .0045 and .0055 you wanna do it cheap go on ebay and buy the stock style re ring kits from sellers like flacon. I priced out a nice simple "dirty" build for that short block i took in and had i stuck to my plan i would have had it all done for about 1600 all in all but i had an iron in the fire that needed that 1600 and by iron i mean another engine i have been working on for some years now.

 

Well I picked up the block and internal parts today from the machine shop. Although they mated the rod caps and the main caps to keep them together, they did not mark the pistons as to which cylinder they came from. I guess in his defense, I was planning to replace the rods and pistons so no need to track their original locations. I'm really kicking myself right now, because I seriously considered numbering the top of each piston with a sharpie before I dropped off the short block. In hindsight I should also have waited until the machinist gave me a price. Live and learn.
So this brings up many questions if I want to install new bearings and rings and reuse these pistons:
1. Is there any way to "match" them back to their respective cylinders?
2. Does it really matter that the pistons go back in the same holes?
3. For a mild street motor, what could it hurt?
4. Can I measure the bores and the pistons and try to match them for the most consistent sidewall clearance? Not sure if I'm using the correct terms here.

 

No
No
Nothing
Yes, this is done with new parts as well. Contrary to popular belief, they are not perfect. Match a rod that is a gram light with a piston that is a gram heavy, etc.

 

Measure it up and put it back together with new rings and bearings. Dingle ball hone the cylinders and get some gaskets and a new timing chain and it will run fine. Just make sure the chamfers on the rods are facing the right direction. When we were racing poor years ago we find this many times just to get back on the track and junkyard sbc would live spinning 7000 rpm in an Imca modified for quite a while. It's funny because we never broke a motor when we ran everybody's used parts until we started building ones with good parts.

 

Which way do the chamfers go?

The chassis manual shows a "spit hole" that faces the center of the block, but I don't see anything about chamfers in the manual.

 

To the edge of the crank journal not next to each other on each rod.

 

The rods are paired on each crank journal the the chamfers out and the non-chamfered sides are together. Is this correct?

 

Yes

 

What's the best way to clean up the pistons? They have a little carbon on the tops and in the oil ring grooves. Can I soak them in carburetor cleaner or is there something that works better?

 

Parts cleaner or carb cleaner and green scotch brite. Soak them then scrub with the scotchbrite they will look like new.

 

The rods and pistons are still assembled, correct? If so, the notch on the piston faces forward.

 

Yes, rods and pistons are still together. There is a "v" notch on the piston and the letter "F" stamped on the pin boss. One of the piston skirts is more shinny than the other side, I'm assuming from the thrust of the power stroke. Shouldn't the shinny skirt face the outside of the block with the less shinny skirt facing the middle of the block? Pg6B-27 of the Chassis manual shows the orientation of the pistons and rods with a "spit hole" facing toward the middle of the block. Is the spit hole the notch in the rod for the bearings? Here's some pics:

Page 6B-27 "Spit Hole"



Is this the Spit Hole?



Piston "V" notch

 

IMAG1210_zps0bc1eb12.jpg

You can see in this picture that the notches face forward. Just take the 4 left and 4 right, put the largest piston in the largest hole. Generally speaking, cylinders #1 and #2 will have more wear.

 

Will I know the left pistons from the right pistons by placing the shinny skirts to the outside of the block?

 

Forget the skirts, they will all look the same after you clean them up. The notches go facing forward, 4 will be one way, 4 the other.

 

Fwiw. On the 350 I mentioned I used rods from a 72 and 70. I had 3 rods that where slightly bent . So I got 3 from a 72 and put them in in no particular order. The pistons where from a 68 w31 . No shakes no shimmies . As long as the rods where in the correct location and the pistons where facing the correct way is all that mattered.

 

I spent much of last night cleaning pistons and taking inventory of all the parts and pieces, nuts and bolts, etc. I bought this engine for $75 (mostly for the bloc as I planned to stroke it) so the condition of the motor is very much unknown; and since I am now considering rebuilding it "as is" I'm carefully inspecting everything looking for warning signs of problems. It looks like the timing chain was replaced (no nylon cam gear) but the steel shim head gaskets lead me to believe the engine has not been opened up.

I've soaked and cleaned 5 pistons (can only soak one at a time) I've found the A-B-C-D factory markings on the piston crowns (used to match piston size to bore size) and so far have mostly "B" pistons and one "C" and one "D". The chassis manual says that the block should be similarly stamped but I haven't found these markings. Anyone know if the CSM is correct and where I should be looking for these markings? Through the process of elimination, this would help me reacquaint each piston to its proper cylinder. The "F" face forward, the chamfers on the rods face away from one another, and match the lettered pistons to the lettered bores. I've been inside five Olds engines in my lifetime and I've never noticed the piston lettering before. Call me a geek, but I'm having fun with this.

I've looked over all the rod and main bearings; although some have noticeable grooves in them, none are worn into the back layer of the bearing shell. I took this to be a good sign, but may still need to have the main journals ground to eliminate the grooves. All of the main bearings have centered slots (for oil flow) except one. Is this correct? This puzzled me because I thought the bottom bearing shells were solid (no slot) to handle the stress of the downward power stroke. The CSM only shows a flat bearing on the front main cap and doesn't mention the other bearings.

"B" Piston


"D" Piston


Bearings