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The compression height of a stock 350 piston is 1.56" so those Wiseco pistons are the same height as stock. Based on a .025" deck height and the .015" gasket you are right on target for .040" quench. The 4032 alloy used in those pistons will not expand as much as the GM forged pistons so you should expect the bore to piston clearance to be a little tighter by design. Less cold start up piston slap noise is a good thing.
Those rings will likely come pre-gapped but better verify with a set of feeler gauges. Don't be too alarmed if the gaps are much larger than the minimum spec.
The compression height of a stock 350 piston is 1.56" so those Wiseco pistons are the same height as stock. Based on a .025" deck height and the .015" gasket you are right on target for .040" quench. The 4032 alloy used in those pistons will not expand as much as the GM forged pistons so you should expect the bore to piston clearance to be a little tighter by design. Less cold start up piston slap noise is a good thing.
Those rings will likely come pre-gapped but better verify with a set of feeler gauges. Don't be too alarmed if the gaps are much larger than the minimum spec.
I did not see the cam specs posted?
Thanks for the reassurance with the piston compression height and advice on gapping the rings.
just in case the link doesnt work it's Duration 266/270, Lift .485/.495, 112 LSA, 108 ICL. 213 int./217 exh at 0.050. I know this is a pretty tame cam, but I'm looking for useable low end torque. This is a stock 2 bolt L48 and the car is a TH400 auto with 3.08 rear gears, and will not see any racing, so I dont see any point in pushing the power curve higher
One thing I have been thinking about is installing the crank sprocket advanced to move the power curve a little bit earlier and add more dynamic compression. What do you all think? Is the cam already aimed at lower rpms enough?
From: Las Vegas - Just stop perpetuating myths please.
Originally Posted by mongoose87
Just a little update:
I finally got my block back from the machine shop.
It was not decked
bored 0.030 over
crank was ground to 0.010 under size
new cam bearings
he hasn't measured the rods yet, but visually he thinks they can be just boiled and good to go.
Is it as important to match the rod into its original cylinder if it is ground down and bearings replaced?
I put a little sharpie on the rods, but not sure if it will last through the cleaning.
My plan was to get these rod bearings, which don't look like they have the oiling hole in them, but from what I've heard, they dont really need the hole. That hole is more a ford thing, where oil gets sprayed from the rods.
Does this sound correct?
I know forged is better, but not sure my build is aggressive enough to warrant the extra $. If they were available at a reason able price, I'm leaning toward just hypereutectic pistons with 1.560 compression height and 12-15cc dish. I see some examples on summit for less than $100 with the dish, but the compression height is too low, around 1.540.
If I can't find any I'll probably get the ones above and be happy my quench is as close to 0.40 as possible. (Hopefully exactly 0.40, but maybe the copper cote spray I'm going to use on the head gasket may add a hair)
If anyone knows where I can some like stock, please let me know.
I like the Silv-O-Lite pistons like: https://uempistons.com/i-19748-5-7l-...2m139-030.html But they have only a 6cc dish (valve reliefs) so you have to find another 6cc to 9cc volume somewhere. Summit has as a set: https://www.summitracing.com/parts/uem-3437hc-030
IMHO I think you are spending to much on forged pistons for what you want to use them for.
Not to late to have the shop "shave" the block deck.
Well if you recondition the big end of the rod you can reuse the rods in any cylinder but I don't know if cutting the crank down does the same correction. Common practice is to replace the rod bolts with better bolts and recondition the big end but that cost nearly as much as a better aftermarket rod. Choice is yours but from what I read the major failure location for a connecting rod is the bolt.
Why are you trying so hard to find a piston with such a big dish?
Use a 4 eyebrow flattop....generally -5 cc in the eyebrows.......
Even with a small 64cc head.....this is under 10 to 1.....and much superior quench. I see no pics of your heads but 72' had the 76cc chambers.
Buy those Wiseco pistons.....they come with a $100 set of rings so add that to the value.
There is no good reason other than finances or matching number to not deck an engine block. Period. The only other reason is you are installing new heads on an engine in the car.
You can save quite a bit of money on that Wiseco piston/ring kit if you buy from Competition Products or CNC Motorsports. Not sure why Summit is so high on it.... but I do believe they will price match if pressed.
United Engine and Machine aka UEM manufactures following three brands:
KB Pistons
ICON Pistons
Silv-O-Lite Pistons.
For this owner's vortecs & mild goals it seems a dish is appropriate
But seems there fewer affordable choices that're both 1.560-1.565 and have a small dish.
I even checked NPR pistons (a large NIP-USA mfg w/ plants in USA who also supply OEM as a tier 1) but their Vortec replacement piston has 1.551" CD... nine thousandths shy
Heck, a set of OE vortec hyper pistons would be great and fit specs and use thin metric ringpak … but they're expensive!
Why are you trying so hard to find a piston with such a big dish?
Use a 4 eyebrow flattop....generally -5 cc in the eyebrows.......
Even with a small 64cc head.....this is under 10 to 1.....and much superior quench. I see no pics of your heads but 72' had the 76cc chambers.
Buy those Wiseco pistons.....they come with a $100 set of rings so add that to the value.
There is no good reason other than finances or matching number to not deck an engine block. Period. The only other reason is you are installing new heads on an engine in the car.
Jebby
I am actually using the numbers matching block, so that's the reason for not decking the block. It seems silly now with all the other modifications done, but I had the machinist check the block deck and he said it looked good. Looking back on it I would have been better off finding an entire used vortec motor and going from there (or find a 454!), but I was initially hoping to not get into the bottom end. Oh well, lessons learned.
I'm running vortec heads that have a 64cc stock chamber, and since I had them resurfaced, I had the machinist remove about 0.020 while he was at it, putting it to around 62cc i believe.
If I was running stock heads, I would have used a flat top as you are saying.
If i were to use a flat top with the vortec head, it seems the CR would be too high for iron heads:
Last edited by mongoose87; Feb 24, 2019 at 11:29 AM.
I took another run at the DCR with 62cc heads and 15cc dish pistons - came up with 9.5 static CR and 7.83 for DCR. If you really wanted to advance your cam 2 degrees, you could. New DCR comes in at 7.94 which is still safe.
I would not advance that cam. You are already pretty high on the DCR at 8.54 and advancing the cam 2 degrees will put you at about 8.6 which is even higher. If you can measure the actual head CC's you might be able to play with the cam timing but it takes some tools to do it. (I will post pix in my build thread of the tools when I get a minute)
And use a intake closing point of 38.5, which yields 8.21 DCR.
I was told the intake closing point calculation is = (LSA)+1/2*(intake duration @ 0.050) - (ground in advance) - 180
Since my ICL is 108, there is no ground in advance, so = (112)+(1/2(213)-(0)-180=38.5
If I advance the crank, wouldn't this yield a DCR of 8.4?
If you can share the calculator you used i would really appreciate it.
I'll be totally honest, I'm not totally sure how the increased DCR will affect power in the end. I know with more DCR the engine takes less advance and better low end torque, but how does that affect the engines power with less advance?
From what I've read, 8.5 should be the upper limit (especially with iron heads), but are there cases where someone increases DCR right to 8.5, properly decreases ignition advance to accommodate the higher DCR, but ends up with less power?
...
IMHO I think you are spending to much on forged pistons for what you want to use them for.
Not to late to have the shop "shave" the block deck...
.
I agree with you. I would have bought hypereutectic pistons if I found them with the right dimensions. I know it's just a crap L48 engine, but it is matching numbers, and I still have the heads intake and all the other parts to put it back to 100% stock if i ever sell it to someone who would like to do that. If the deck is good, it wouldn't seem like much cost savings to shave it just to save some $ on pistons. It would probably cost me another $100 to get it shaved + $150 in pistons + $50 in rings = roughly $300 with no numbers matching block.
Seems like the forged pistons ($500) and keeping it numbers matching is worth the $200, or at least I hope it will be, but I may be delusional.
While I was hoping this to be a "budget" modification in the beginning, this has turned into a "no expense spared" type of situation. ugh
Got the block painted yesterday. I'm hoping to repaint everything to make this engine look brand new by the time i put it back in.
(Looking at this again, I think i may have to touch up the water pump areas)
And use a intake closing point of 38.5, which yields 8.21 DCR.
I was told the intake closing point calculation is = (LSA)+1/2*(intake duration @ 0.050) - (ground in advance) - 180
Since my ICL is 108, there is no ground in advance, so = (112)+(1/2(213)-(0)-180=38.5
If I advance the crank, wouldn't this yield a DCR of 8.4?
If you can share the calculator you used i would really appreciate it.
I'll be totally honest, I'm not totally sure how the increased DCR will affect power in the end. I know with more DCR the engine takes less advance and better low end torque, but how does that affect the engines power with less advance?
From what I've read, 8.5 should be the upper limit (especially with iron heads), but are there cases where someone increases DCR right to 8.5, properly decreases ignition advance to accommodate the higher DCR, but ends up with less power?
The first law of thermodynamics is "there aint no free lunch"....increases in cylinder pressure are good all the way up to the limits of the fuel octane. You can swap out ignition timing for excessive cylinder pressure at the upper limit but it will be a wash at best. Nothing is free.
I think your cam has 4 degrees of advance already in the grind.
The calculator I use is by Pat Kelly. I can take another look when I get back to the keyboard with the software on it. I may have fat fingered something.
Meanwhile... maybe you can check and post your advertised open and close points at .050" tappet lift from the cam card. Really need the advertised intake close point to see for sure.
Last edited by stingr69; Feb 24, 2019 at 07:37 PM.
Since i have the motor and trans out, I have been reading more on transmission shift kits. My TH400 was working well before, from what I can tell. No slipping or anything and the kick down was functional. I remember the previous owner saying he changed the fluid, and that was about 1.5 years ago. The fluid still looks red.
I already ordered a new seal kit, because it leaks like crazy, so I have to open it up anyway. I would also be nice if it shifted just a little bit later, or higher in the rpm range.
Is there anyone who put in a "level 1" or basic shift kit who found the shifting to be too harsh?
I always hear about the trans-go kits, but if anyone has another I should look at, please let me know.
From: Las Vegas - Just stop perpetuating myths please.
Originally Posted by mongoose87
Maybe I'm going about calculating this wrong, but I don't get those DCR numbers.
I was told the intake closing point calculation is = (LSA)+1/2*(intake duration @ 0.050) - (ground in advance) - 180
I'll be totally honest, I'm not totally sure how the increased DCR will affect power in the end. I know with more DCR the engine takes less advance and better low end torque, but how does that affect the engines power with less advance?
From what I've read, 8.5 should be the upper limit (especially with iron heads), but are there cases where someone increases DCR right to 8.5, properly decreases ignition advance to accommodate the higher DCR, but ends up with less power?
Intake closing point is using the full duration number - in your case 266 degrees - not using a 0.050" lift number. So 1/2 full duration (133*) minus ICL (108*) = 25* BTDC. I have to look at a cam timing chart myself to figure it. But most mfgs use a valve open/close point of 0.006" or less. Now stock GM cams have such a long open and close ramp it they can't be compared directly to other aftermarket cam open/close numbers - that's where the industry started to use the 0.050" lift mark for performance comparisons but this does not work for DCR calculations.
I have to say something here about pistons. Your trying very hard to find pistons that leave you with a good quench height. Thats good but you may not realize that a large dish pistons doesn't have much good quench area. So what I'm saying is good quench is nice but possibly not worth what you will spend compared to what you will get out of large dished pistons. And if you take the time to think about it very few stock engines have good quench - quench height or quench piston area. Don't get hung up on quench height as something else I will say is quench benefits diminish with lower compression ratio. You get less quench benefit with a static compression of 9.0 than 10.0 c.r.. In fact I've heard there is not much quench effect less than 9.0 c.r. take it or leave as I'm no dyno testing expert. You could easily get by with hyper pistons or even regular cast pistons in your power level.
I've used a bunch of Trans-Go kits. Always set them up for Police/Taxi per the instructions. Shifts are firm but not uncomfortable unless you get into heavy throttle positions.
The 266 degrees of intake duration centered on a line at 108 degrees after TDC gives you an intake close point of 61 degrees after bottom dead center.
112 degrees of lobe separation gives you the 4 degrees of ground-in advance.
Static Compression Ratio is 9.51 and DCR is 7.83
Your math you posted above..... "So 1/2 full duration (133*) minus ICL (108*) = 25* BTDC"..... with that, you are calculating the INTAKE OPENING point of 25 degrees BTDC.
Your calculator is using .050" tappet lift numbers.
The one I am using with my solid lifter cam uses cam card .018" tappet lift numbers. (NET .005" valve lift)
You want to find the intake CLOSING point which is going to be 133 degrees AFTER the lobe center. 108 degrees ATDC (center of lobe) + 133 degrees more duration = 241 degrees ATDC, or if you subtract 180 degrees to get the ABDC number.... you come up with 61 degrees after bottom dead center for the intake close point.
Last edited by stingr69; Feb 24, 2019 at 10:01 PM.
I am actually using the numbers matching block, so that's the reason for not decking the block. It seems silly now with all the other modifications done, but I had the machinist check the block deck and he said it looked good. Looking back on it I would have been better off finding an entire used vortec motor and going from there (or find a 454!), but I was initially hoping to not get into the bottom end. Oh well, lessons learned.
I'm running vortec heads that have a 64cc stock chamber, and since I had them resurfaced, I had the machinist remove about 0.020 while he was at it, putting it to around 62cc i believe.
If I was running stock heads, I would have used a flat top as you are saying.
If i were to use a flat top with the vortec head, it seems the CR would be too high for iron heads:
It is NOT too much compression. That number is perfect......the Vortec chamber is much more efficient than the old GEN1 heads.......so much so that it even only requires 34 degrees of advance rather than the usual 36+.........also the quench is better with the flatop and you are at .052 piston to head. That will work fine......
Make sure you have a good curve in the distributor.
I personally have built a few 96-98 Vortec 355's for 4x4 trucks with the CPI and all three were 10 to 1 compression...in a 5500 truck with 35" tires and no ping or computer pulling timing with 93 octane fuel.
BTW....DCR does not work because it does not take into account VE (Volumetric Efficiency).....these calcs leave it out, which makes the numbers not applicable.
Jebby
Last edited by Jebbysan; Feb 24, 2019 at 08:40 PM.
It is NOT too much compression. That number is perfect......the Vortec chamber is much more efficient than the old GEN1 heads.......so much so that it even only requires 34 degrees of advance rather than the usual 36+.........also the quench is better with the flatop and you are at .052 piston to head. That will work fine......
Make sure you have a good curve in the distributor.
I personally have built a few 96-98 Vortec 355's for 4x4 trucks with the CPI and all three were 10 to 1 compression...in a 5500 truck with 35" tires and no ping or computer pulling timing with 93 octane fuel.
BTW....DCR does not work because it does not take into account VE (Volumetric Efficiency).....these calcs leave it out, which makes the numbers not applicable.
Jebby
The DCR calculation does not take any VE into account BUT the GUIDELINES are targets that come from empirical evidence.... Real world experience with running engines that "worked" and engines that had difficulty running on available fuels.
From: Las Vegas - Just stop perpetuating myths please.
Originally Posted by stingr69
You need the intake closing point.
The 266 degrees of intake duration centered on a line at 108 degrees after TDC gives you an intake close point of 61 degrees after bottom dead center.
112 degrees of lobe separation gives you the 4 degrees of ground-in advance.
Static Compression Ratio is 9.51 and DCR is 7.83
Your math you posted above..... "So 1/2 full duration (133*) minus ICL (108*) = 25* BTDC"..... with that, you are calculating the INTAKE OPENING point of 25 degrees BTDC.
You want to find the intake CLOSING point which is going to be 133 degrees AFTER the lobe center. 108 degrees ATDC (center of lobe) + 133 degrees more duration = 241 degrees ATDC, or if you subtract 180 degrees to get the ABDC number.... you come up with 61 degrees after bottom dead center for the intake close point.
Ooops! Your right stinger. I posted a number for the intake opening point. Your number is correct for intake valve closing. Thx for the second check.
