Thread: Another build question

Tweet

In the preassemble stage of checking the piston to valve clearance, is the head gasket reusable after being torqued down to compress the modeling clay? And I suppose you need to check all 8 so you can't mock up with just one piston and rod assembly at a time, correct? If someone would kinda run me through this it would be great. Trying to work less by working smarter.

Originally Posted by jimmyjeep

In the preassemble stage of checking the piston to valve clearance, is the head gasket reusable after being torqued down to compress the modeling clay? And I suppose you need to check all 8 so you can't mock up with just one piston and rod assembly at a time, correct? If someone would kinda run me through this it would be great. Trying to work less by working smarter.

Why do you think you need to check piston to valve clearence?

Originally Posted by erik erikson

Why do you think you need to check piston to valve clearence?

bad erik yes you can reuse it just do not tell any one i have done that just make sure it is put back on the same side you had it on

Originally Posted by pat mccarthy

bad erik yes you can reuse it just do not tell any one i have done that just make sure it is put back on the same side you had it on

Well I know why and when I start to check it I was just trying to get him to give me a little more info.

Originally Posted by erik erikson

Well I know why and when I start to check it I was just trying to get him to give me a little more info.

ok i was thinking you were just given him some

Well I have gotten the message from my mentors here, NEVER take anything for granted as far as measurements. To get the squish right and check the piston to valve clearance, the only way I can rationalize it, from all I've read, is to assemble and then check the compressed clay for clearance info.

Jim, the first question is......is the block square? If it isn't, your measurements will be off by how much the block is out of square. I have checked blocks that were off by 0.008" from one end of the deck to the other. This will not only cause your p/v clearance to check screwy, but your squish and static compression ratio will be off from one end of the block to the other.

I applaud you for learning to do these things in the right way and not just throwing a bunch of parts together "willy-nilly".

If you don't know how to check the block for square, just ask.

By the way, when torquing down the heads, just hold back on the torque by 15-20 pounds from what you'd use on final assembly so you don't fully compress the gaskets. You'll be close enough to check p/v and the gaskets will still be good to re-use. I, like Pat, have done this many times and skated through. Follow Pat's advice about marking them.

Assemble the heads with some old, stock, worn-out springs. You'll want to use them to break in the motor anyway and you might as well make it easy on the cam to do your checking.

I always use solid lifters to do the p/v check with because I'm never sure the hydraulics won't leak down some and give me an erroneous reading. Leave nothing to chance. You should have a set on hand and add them to your specialty tools collection along with an old worn out set of springs. After a quick google, I came up with these on ebay....
http://cgi.ebay.com/ebaymotors/CHEVR...QQcmdZViewItem

Tighten the rocker nuts down to allow about 0.001" to 0.002" valve lash at the rocker/tip interface to do the checking. You can also check the ratio of the rockers at the same time if you want by mounting a dial indicator on the retainer and recording the valve lift for each valve. If using stock Chevy stamped rockers, you'll probably see quite a range of ratios among the 16-piece set you're using. Some of the more savvy stock-class racers used to make friends with the counter guys at the Chevy dealership to be allowed to go through the rocker inventory and check for the rockers with the highest lift ratio. They'd take them home and check them just like we're talking about here, then return the duds and keep the jewels.

I would check all 8 cylinders at the same time, not just one. You don't know if all the seats are installed in the heads the same distance from the head surface, so one or more could be close and you wouldn't catch it. Install pistons without rings, clay all the pistons and have at it. You're looking for MINIMUM 0.080" on the intakes and 0.100" on the exhausts.

Thanks Tech. How do I check for block square the right way?.

Originally Posted by jimmyjeep

Thanks Tech. How do I check for block square the right way?.

Corner to coner with a straight edge.
If I find .004 or more with a feeler gauge it is time to deck the block.
There are a few people that will disagee with what I said.

Thanks a bunch Eric.

Originally Posted by erik erikson

Corner to coner with a straight edge.
If I find .004 or more with a feeler gauge it is time to deck the block.
There are a few people that will disagee with what I said.

i was not was going to tell him but was waiting for tech the only thing i would add is that the rods could be off that far if stockers with a recon and the block center line could be off to one side more and crank indexs all adds up. so a new machine block could be off .004 easly if not tru deck like BHJ thru cam and main center line .with the rod/crank pistons to you would get stack on that could throw you off. i think .004 you would be doing good on all new stuff. it would nice to see less .so like erik said that would be good .004 but if not how much would you spend to get it better than .004 or there ??what i am trying to say is how much is this worth to you they can be way off and still work making it this good with some parts could be $$$tough

Originally Posted by erik erikson

Corner to coner with a straight edge.
If I find .004 or more with a feeler gauge it is time to deck the block.
There are a few people that will disagee with what I said.

I'm not gonna disagree with you Erik, but that isn't exactly what I had in mind. What I was referring to was.....are the decks square with the crank?

Jim, here's how I do it. First, get the pistons you will run. Clean the block up so you and the machine shop owner won't get greasy handling it.Take the pistons, rods and the block to the machine shop and get the block bored and honed for those pistons and rings. DO NOT HAVE NEW CAM BEARINGS INSTALLED YET. You're gonna hot tank the block later and the caustic soda will eat the cam bearings. Have the rods resized and fitted to the pistons. If you're gonna get the crank turned, do that next. Now take the rod/piston assemblies, crank and block back to your shop. If you're good friends with the machine shop owner, he may let you do this at his shop so you won't have to haul the parts back and forth. Most shop owners though, will not want you to do your own work in their shop for reasons of liability. Plus, you'll be in their way.

Mount the block on your engine stand. Roll it over and install the crank on oiled main bearings. This is a good time to plastigage the bearings if you're gonna do that yourself. If you're not gonna check them, you don't need to torque the mains down, just give them a moderate tug on your ratchet handle. Otherwise, have the machine shop mike the bearings and take their word for the clearances. Now, choose any piston/rod assembly and install it (less piston rings) on #1 rod journal on oiled bearings. Roll the block over and mount a dial indicator on the deck. Bring the piston to approximate TDC and pre-load the dial by about 0.200". (adjust the dial/plunger on the stand so that the plunger moves up about 0.200" against the piston crown with the piston at approximate TDC). Now, jockey the crank back and forth until you see absolute TDC on the dial. Now, place a depth mike on the deck and let the spindle slide down the cylinder wall until it contacts the crown of the piston at the wall. Do this at the 3:00 O'Clock and 9:00 O'Clock positions of the piston as you're standing at the side of the block. If you check at the Noon or 6:00 O'Clock positions, the piston can rock on the wrist pin and give you an erroneous reading. With the block deck free of oil, write the measurements on the deck with a Sharpie. If you get measurements that are very much different side to side on this one piston, then the rod is probably bent. Disassemble the rod/piston from the crank and assemble another one in the #1 hole and check again.

Using this very same piston/rod assembly, disassemble it from #1 cylinder and move it to #7 cylinder. Repeat the above procedure to find the piston deck height on this #7, then move to #2 and #8 so that you will have measurements on all four corners of the block.

If by some act of God the decks are square with the crank, thank your lucky stars and go buy some lottery tickets. If not, you will have the measurements to give your machinist who can then cut the decks to square. You will also know the piston deck heights of all the holes so you can make a revised decision about cutting the decks for matching up the gaskets for 0.035" to 0.040" squish. If you decide you don't have to cut the decks, then follow Eriks advice about checking to see if the decks are flat before you take the block back to the machine shop. If the piston deck heights are square and the decks are flat, go back to the store and buy some more lottery tickets.

On this trip to the machine shop with the block, have it hot tanked and replace the cam bearings.

Oh yeah, last thing. If you did find bent rods, have the machine shop straighten them or replace them with new rods. www.summitracing.com has Eagle SIR rods for $235. per set.

An afterthought: If you can't buy, beg, borrow, steal or rent a depth mike, you can use the slide on the end of a 6" dial caliper to measure depth. The slide has a little scallop cut into it. You want to position that scallop right next to the cylinder wall so that the very end tip of the slide contacts the piston crown. If you can't buy, beg, borrow, steal or rent a dial indicator, you can check for piston at TDC by using a straight edge held on end across the bore and slip feeler gauge blades between the straight edge and the piston crown right next to the cylinder wall. Move the piston up and down with the crank snout until you get the thinnest blades to go in snug.