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I bent a valve on a missed shift with stock Vortec springs and a flat tappet cam (.458"). I've since installed Comp Bee Hive springs onto unmodified Vortecs. Original valve seal. No machining of the guides or spring pockets. I regularly spin it up to 6000-6500 rpm running a 276 hydraulic roller. No problems so far and thats a hundred 1/4 mile passes and 30 000 miles.
Check this out.
I looked at the block again and it looks like there is a ridge on the top of the cylinder (feels just like carbon buildup but i'm not sure) the motor has been rebuilt before. Here are some pictures, they suck but they are better than nothing..... also i can see the cross scratches from the boring originally( or what ever they are called). (lots of crossed scratches looking things on the cylinder wall)
You a few decisions to make and they involve money.
I've rebuilt a few short blocks and the first thing to be decided is what the block needs to be reliable. If the bores measure within spec then you might decide to just deglaze the bores and re-ring with your old pistons.
That's the least expensive route.
You'll also have to deal with the resulting low compression. I did a quick calculation using a typical 350 dished piston with about a 17cc dish. Combine that with your 64cc heads, a .025" below deck piston (stock) and a .026" head gasket and you end up with about 8.8:1 static compression. That's pretty low and a cam with any kind of duration will fall on its face.
If you upgrade to a flat top piston with 6cc valve reliefs, you can gain a full point (9.8:1) in compression. That's starting to be significant.
Of course that comes with a price.
__________________ 1986 IROC-Z. 350 010 4-bolt block 10.1:1 static cr. 8.1:1 dynamic cr. Vortec heads w/ competition valve job milled to 63cc. Modified for screw in studs and guide plates. Comp Cams: Bee hive springs, Pro Magnum 1.6 rockers, Pro Magnum push rods, XR276HR cam. 670 Holley Street Avenger. RPM Air Gap intake. Cloyes Hex Adjust timing set and cover. Resized stock rods w/ARP bolts. Polished stock cast crank. Speed Pro coated flat top 4 relief pistons. Balanced assembly. Fluidampr balancer. SFI flexplate. MSD small cap distributor. MSD 6AL ignition box. Hedman LT headers w/ stainless 2.5" y-pipe. 3" Flowmaster no cat back exhaust. 700R4 w/ Trans Go reprogramming kit and upgraded 3-4 clutch pack. TCI Street Fighter 10" convertor. B&M trans cooler. Hurst dual gate shifter. 3" steel driveshaft with Spicer 1350 u-joints. 9 bolt 3.27. Spohn LCA relocation brackets. Boxed LCA's. Edelbrock strut tower brace. Energy suspension polyurethane bushings throughout. McCreary Dirt track 26" bias ply treaded slicks. 12.778 sec. 105.05 mph. 1.70/60'. 3700 lbs w/driver and 1/2 tank of 94 octane. 26(CDN)/23(US) mpg highway.
I went a little further and using the Lunati cam you mention in your first post which specs out at 276/284 adv duration on a 110 lsa, you won't have nearly enough static compression to make it work. Your dynamic cr ends up around 6.8:1 and that's not good.
Advancing the cam will help a little however a shorter can will help build more bottom end torque and be a lot more fun to drive.
Doesent look like much of a ridge to me. Grab a scotch brite pad and some carb cleaner and clean the carbon off a little better. Hard to say for sure but just by the pic it looks like no boring is needed and your just dealing with a carbon buildup
__________________ 1982 Firebird 350/700R4.
Crower Beast cam, RPM Intake, Edelcrap 1406 for the street, 14x3 open element air cleaner, Serpentine conversion, Carter rotary pump, Flowtech Headers 3" exh, cat delete with Ravin muffler. Modified B&M / Transgo shift kit with B&M cooler.
I went a little further and using the Lunati cam you mention in your first post which specs out at 276/284 adv duration on a 110 lsa, you won't have nearly enough static compression to make it work. Your dynamic cr ends up around 6.8:1 and that's not good.
Advancing the cam will help a little however a shorter can will help build more bottom end torque and be a lot more fun to drive.
i want to go with a Comp Cams XE274 cam or at least a XE268 cam.
Sorry the pictures suck but i took them on my phone.... i'll get some better quality ones soon.
Well, its not the best pictures, but it does in fact look like you may be able to go with pistons without a bore. As posted above get some scotchbrite pads and clean up that carbon at the top of the cylinders. Then you can get the best idea of what you are looking at. And dont forget, even if they look great, take the time to measure. Its always cheaper to check twice than to build twice.
i want to go with a Comp Cams XE274 cam or at least a XE268 cam.
Stats: 350 std bore, 64cc Vortec heads, stock piston height .025" below deck, Victor Reinz .026" head gasket (5746), stock 350 dished piston w/ 17cc dish.
Static c.r. is 8.8:1
w/Comp Cams XE274 w/ 274/286 adv duration installed on a 106 ICL the dynamic c.r. is 7.16:1.
w/Comp Cams XE268 w/ 268/280 adv duration installed on a 106 ICL the dynamic c.r. is 7.3:1.
If you opt for a .015" steel shim head gasket you bring your SCR up to 9:1 and the dynamic ratio is a little less than 7.5:1.
I've read that a performance street engine should have a DCR between 7.5 and 8.5:1.
you got a lot of guys giving you bad info bro ,listen to skinnyz he seems to understand engines (theorectically) if you want some good advise on your build then ill talk to you about my iron headed 355 in my 92 firebird and yes you can go more aggressive on the cam as long as you folow some basic principles hit me back if you want to discuss this with no bs involved good luck guy bigzeke92bird355
you got a lot of guys giving you bad info bro ,listen to skinnyz he seems to understand engines (theorectically) if you want some good advise on your build then ill talk to you about my iron headed 355 in my 92 firebird and yes you can go more aggressive on the cam as long as you folow some basic principles hit me back if you want to discuss this with no bs involved good luck guy bigzeke92bird355
I think he has figured out what he wants, and the BS was sorted out in the beginning.
I guess I wasnt paying attention. He asked about pistons, so he was talked through it. He asked about cam, and decided on what to do. Heads were resolved. What other thick BS is there?
Calibration isn't a one-time thing, you'll need to do it every time you change the anvil or disturb the dial indicator in its sleeve. Set the micrometer to a size close to the size of the bore you're measuring. The actual size isn't important as long as you record it. Put the dial indicator between the barrel and anvel of the micrometer and note the reading on the dial indicator. Then measure the bore with the gauge and note the reading on the dial indicator again. Calculate the difference in the two dial indicator readings, and add or subtract to the reading on the micrometer to get the bore size.
i couldn't get the stupid gauge set up right, so i took my digital caliper and measured cylinders 1 and 3.... they measured side to side 4.023 and top to bottom 4.018.... both measured the same....
i couldn't get the stupid gauge set up right, so i took my digital caliper and measured cylinders 1 and 3.... they measured side to side 4.023 and top to bottom 4.018.... both measured the same....
Thats not good. Something doesnt jive right to me about that. The carbon ring at the top would make the cylinder smaller, and you are coming up with .020 over side to side and almost .020 top to bottom. Are you sure the engine has standard pistons in it? To me it seems like you may have a .030 engine with some carbon at the top of the cylinder.
Thats not good. Something doesnt jive right to me about that. The carbon ring at the top would make the cylinder smaller, and you are coming up with .020 over side to side and almost .020 top to bottom. Are you sure the engine has standard pistons in it? To me it seems like you may have a .030 engine with some carbon at the top of the cylinder.
The engine WAS rebuilt at some point in its life.... i cleaned the carbon off the cylinder at the top and its smooth all the way to the end(does not feel like a carbon buildup anymore).
The engine WAS rebuilt at some point in its life.... i cleaned the carbon off the cylinder at the top and its smooth all the way to the end(does not feel like a carbon buildup anymore).
I got the engine from a friend, it had 60k on it when i got it and now it has 73k, i would imagine it was bored maybe .020 over?
I got the engine from a friend, it had 60k on it when i got it and now it has 73k, i would imagine it was bored maybe .020 over?
Can you measure the piston diameter? 90 degrees to the pin bore, below the ring lands.
There may even be a part number still visible on the top of the piston. .020" isn't uncommon.
SO what EXACTLY do you need to determine if my car can take new pistons without a boreing? I don't really want to take my connecting rods to get machined, what kind of cam can i get that will allow more power at a max of 6k? or should i really have the rod bolts upgraded? Thanks
i just measured the piston skirt and its reading 4.028-4.030. maybe its bored .030 over?
Now that you've established you have a 30 over rebuild you ( by the measurement of the piston ) you need to determine if the piston bore is not worn out of spec. Some may say,"to hell with all the measuring, I'll just take it to a shop and have them do it". That's ok if that's what you want. Otherwise take the bore gauge you just bought and use it find out if the bore is ok or not.
If it is you can probably just do what we hot rodders have done for years and give the cylinders and good going over with a deglazing hone and properly fit a new set of rings onto the existing pistons.
At the very least, if the engine is'nt too badly worn, you should good results with a fresh set of cylinder heads.
Lots of compromises, however it is low dollar.
Well i would like to change to flat top pistons....
That makes it easier. If you are changing pistons, the machine shop will tell you the next available overbore when they measure for the new pistons. You still have the option to spec out the available valve relief or piston dish.
well i would like to not rebore and just install new pistons..... is that possible? Otherwise i will probably just keep whats in it and just upgrade other things.
Also I've been looking into camshafts, I want one where it will make max hp under 6k.... i don't want to change the rod bolts... I might if i can change the pistons, otherwise i don't really want to.
well i would like to not rebore and just install new pistons..... is that possible? Otherwise i will probably just keep whats in it and just upgrade other things.
You are at the point that you have some serious decisions to make. You need to figure out your dial bore gauge. If you need more help I can see what else I can do for you. But you really need to know what the specs of the bore are. You can take it to the machine shop and ask them if it can be honed and have the same size pistons installed without boring. They will charge a fee, but it wont be that much. Or, if you still cant figure out that damn tool, find a shop where you know somebody, and offer 20 bucks to a mechanic to show you how to use it. Any mechanic worth a damn should be able to use it, and show you how. At least if you go this way, you will have learned a life long skill. I wish I could push it through the net to you, I would.
As far as the rod bolts go, you need to get a to the pin bore of the pistons so you can find out if they are press fit pistons. If so, you are going to the machine shop anyway to have the pistons pressed on. I dont know what they charge for this alone, but i know around me 80 bucks gets the old pistons pressed off, resized and the new ones pressed on, plus the cost of new rod bolts. Rod bolts arent that expensive, considering what they are worth to the engine if one fails.
If you are going to put pistons are you going to replace the bearings and oil pump, just because you are there anyway?
Building a budget engine is cool, especially when it all works out and it runs great. However, one must remember, there is an old saying that for the most part is always true:
You are at the point that you have some serious decisions to make. You need to figure out your dial bore gauge. If you need more help I can see what else I can do for you. But you really need to know what the specs of the bore are. You can take it to the machine shop and ask them if it can be honed and have the same size pistons installed without boring. They will charge a fee, but it wont be that much. Or, if you still cant figure out that damn tool, find a shop where you know somebody, and offer 20 bucks to a mechanic to show you how to use it. Any mechanic worth a damn should be able to use it, and show you how. At least if you go this way, you will have learned a life long skill. I wish I could push it through the net to you, I would.
As far as the rod bolts go, you need to get a to the pin bore of the pistons so you can find out if they are press fit pistons. If so, you are going to the machine shop anyway to have the pistons pressed on. I dont know what they charge for this alone, but i know around me 80 bucks gets the old pistons pressed off, resized and the new ones pressed on, plus the cost of new rod bolts. Rod bolts arent that expensive, considering what they are worth to the engine if one fails.
If you are going to put pistons are you going to replace the bearings and oil pump, just because you are there anyway?
Building a budget engine is cool, especially when it all works out and it runs great. However, one must remember, there is an old saying that for the most part is always true:
Cheap, Fast, and Reliable. Pick two.
Yes i'm going to be replacing the oil pump and crank bearings. I'll try to use the bore gauge again. It just doesn't seem to have the right sizes in it, its iether too big or too small. I can't get within that little amount or preload it needs.
