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You are backwards. The -5cc is subtracted from the piston side which means it makes the chamber volume 5cc larger.
That's where my point is. Like I said, I hope that Summit has the numbers backwards and that the pistons for this motor are actually a +5cc dome so your compression is 11.2:1 like you had calculated. But, if they're a -5cc dish you might be better off exchanging them if they aren't already in the block. If theyre a dish, you could run a .040" cometic gasket and get back up to 10.25:1 or and perhaps mill the heads a bit. Since you've got the valve reliefs, I dont believe PTV would be an issue at all with a thinner gasket and a bit shaved off the heads. BUT, hopefully none of that will be necessary.
Much better! I won't be a dick and double check the numbers this go around but that looks to be much more accurate, haha. Just something struck me funny when I read your original post and saw 11.2:1 compression with dished pistons and no milling or thinner head gasket. I had a Scooby Doo moment and ran the numbers myself to make sure I wasnt nuts.
Another thing you might consider is variations of piston to bore size accuracy. More than likely, your motor will need at minimum a clean up hone. Maybe not, but then again it can't hurt. The likelihood of any aftermarket piston being an exact match for a factory bore motor might be a long shot. So, make sure you size the pistons to the cylinders so you're not screwing yourself on installed ring end gap or issues with the piston size in relation to its corresponding cylinder. If it is in budget, it might be best to strip the block down and order some 4.005-4.010 over size pistons and have the block machined to match each piston for the best fit.
But as far as your initial question goes of a cam recommendation I can't help you one damn bit there. I did basically the opposite of your setup. I took a perfectly good 6.0 block and punched it out to .065 over and put factory LS3 rods & pistons in it and will be running cathedral heads. Have you talked with Martin Smallwood any about it? If not, get with him and give him the run down of your setup and goals and I'm sure he would be able to come up with a good cam recommendation.
WS6Store might be spot on with what you need, I just have no idea because I've never considered or looked into running an L92/LS3 top end and matching bump stick. So I'll keep my mouth shut on all of that stuff lol.
Much better! I won't be a dick and double check the numbers this go around but that looks to be much more accurate, haha. Just something struck me funny when I read your original post and saw 11.2:1 compression with dished pistons and no milling or thinner head gasket. I had a Scooby Doo moment and ran the numbers myself to make sure I wasnt nuts.
Another thing you might consider is variations of piston to bore size accuracy. More than likely, your motor will need at minimum a clean up hone. Maybe not, but then again it can't hurt. The likelihood of any aftermarket piston being an exact match for a factory bore motor might be a long shot. So, make sure you size the pistons to the cylinders so you're not screwing yourself on installed ring end gap or issues with the piston size in relation to its corresponding cylinder. If it is in budget, it might be best to strip the block down and order some 4.005-4.010 over size pistons and have the block machined to match each piston for the best fit.
Was definitely planning to check fit first of course. Rings will be file fit also. Was planning to do a dingle hone or maybe a finger hone if needed. IF I really end up needing to, I will be looking for roughly .005-.008 piston to wall clearance. I don't mind running the engine a little loose if needed.
I am building a bit of an abstract vehicle. It's a 1990 S10 that I just picked up. The simple think to do would be to turn it into a drag truck, however I don't think simple. I want to cage it, stuff some C4 ZR1 17x9.5F/17x11R wheels under this thing with a custom 3 link rear suspension, double adjustable QA1 coilovers and some big Willwood calipers and rotors and make this thing handle. Why a truck? Why not!
So the dilemma I am facing is cam selection (and yes I've spent a lot of time in the cam guide post). It's always easy to just throw a GM Hotcam, TSP Torquer V3 or a LG G6X3 cam in, but it may not be right for what I want the truck to do.
I know PTV clearance can be an issue with this combo. I have decided to purchase a set of aftermarket pistons rather than go the flycut route. I have never done fly cutting and would like to keep this build completely in house. The added security of having a set of decent forged aluminum pistons in there is nice too. For that reason I chose these DSS SX Series Forged Pistons to use.
As for what I am looking for, it may require a custom cam, or maybe one of you more well versed in this area may know of a good off the shelf cam that will allow me to keep the price down. Maybe it's even one of the ones I listed above!
What I am looking for is something that will hold good power up to 6800ish with good mid range response in both power and torque and decent drivability. Peak power numbers don't mean as much to me as a nice broad and healthy torque and power curve. The flatter the curve, the better to me for what I want. I would really appreciate some input from anyone willing to edumacate me. I will be topping this engine off with an Edelbrock RPM Performer Intake and a worked over Holley 750cfm 4bbl carb. The truck will see some road course use, some street use and some strip use and will primarily be run on 93 octane, however I do have access to 110, 112 and 116 pretty much any time I want from the speedway where I race my oval car that is a mile and a half from my shop.
Compression Ratio for Combo with Stock .053 Head Gasket: 11.2:1
Compression Ratio for Combo with Cometic #C5751-070 .070 (4.060 Bore) Head Gasket: 10.73:1
Compression Ratio for Combo with Cometic #C5751-066 .066 (4.060 Bore) Head Gasket: 10.84:1
Compression Ratio for Combo with Cometic #C5751-060 .060 (4.060 Bore) Head Gasket: 11:1
Thanks in advance!
-P
Originally Posted by box_dime
You know, I feel pretty dumb because I didn't even realize that TSP provided dyno sheets on their website that go with their camshafts.
The power and torque curve of that cam in the LS3 crate they dyno'd it in, looks fantastic and it looks like it makes 400hp+ from about 4400rpm on. I A/B/C'd it between the Stage 2, 3 and 4 just for comparison sake and to satisfy curiosity and the Stage 3 is definitely the best to me.
Judging by the fact that my engine will be a 6.0 vs the 6.2 LS3, but will have pretty much the same compression ratio I can only assume that I would probably lose 10-15 numbers off of their peak numbers with the loss of displacement, however I am not sure how the Edelbrock Performer RPM intake setup with the Holley 750 on top will affect that.
Thanks for the info and suggestion, this one has been bookmarked and is at the top of the list for sure. Curious to see anyone else's insight or input too, but you very well may have just made the decision for me lol
Originally Posted by box_dime
Yeah, it's kind of hard to beat what you showed me already for sure. The only thing that would make me change my mind from the TSP Stg 3 cam is something with a little more of a boost in lower rpm power and torque, but from my understanding from what I have read about the LS3 heads, you give up a little bit of that regardless due to port design.
If my curves ended up anywhere near what the TSP dyno sheets show, it will definitely perform perfectly for what I want. I may even go after a .066 compressed head gasket to bump it to 10.84:1.
Are you taking into account the -5cc DSS Pistons I linked that I will be using to avoid flycutting? When I go to 0cc for OE Flat Top pistons, I get 10.54:1
Originally Posted by box_dime
With the -5cc piston, according to how they figure it with Summit, you are effectively removing 5cc from the combustion chamber area. -Xcc pistons are dome, +Xcc pistons are dish. In this case, the -5cc piston is effectively giving me a 63.4cc combustion chamber on the LS3 heads with the engine at TDC.
The piston I chose is linked to Summit's site. They list their dome pistons as (-)cc and dish pistons as (+)cc, using their calculator with stock gasket, I get 11.2:1 this is why I use Summit's link for calculator and to reference parts specs.
Originally Posted by box_dime
I'll be on the phone with DSS once I get off work at 5. I will post the result here.
Hello box_dime. I did not see where you specified which transmission that you intend to run. This would affect which camshaft that I would recommend. I would also want to know your full exhaust configuration.
On the compression, I think you will find that the piston you are referring to is a flat top design that has -5cc valve reliefs in the piston. If you look at the DSS catalog, you will see that dome pistons are listed with +cc volumes while dish pistons are listed with -cc volumes. This would mean that those pistons will decrease compression over a true flat top piston with no valve reliefs.
Also, I did not see where you said how much you were going to bore the block for the new pistons. It appears they are available in STD, .005", .030", .040" and .060" oversized. The difference between .005" over and .030" over is about 1 tenth of a compression point.
In addition, the piston which you are considering appears to a "0" deck height piston as opposed to stock which is .005-.007" out of the hole or "positive" deck height. This will also reduce compression.
So, with a stock 68cc combustion chambered head here is what I show your compression to be with the piston that you mentioned assuming a .030" over bore:
Now, if you use a "0" deck height piston, you could go to a thinner head gasket like the .040" FelPro or Cometic and increase the compression a bit to this:
If you still would like more compression, you could mill the heads .030" and get this:
If you have the heads milled at a talented and reputable machine shop, you could also have a good competition valve job done to the heads while in the machine shop to improve performance even more.
As for a shelf camshaft saving you money over a custom, we do not charge extra for custom camshafts. We have 5150 steel alloy camshaft for $399.00 and we have our renowned 8620 steel alloy camshafts for only $449.00. So, getting exactly what you need or want is completely affordable.
Hello box_dime. I did not see where you specified which transmission that you intend to run. This would affect which camshaft that I would recommend. I would also want to know your full exhaust configuration.
On the compression, I think you will find that the piston you are referring to is a flat top design that has -5cc valve reliefs in the piston. If you look at the DSS catalog, you will see that dome pistons are listed with +cc volumes while dish pistons are listed with -cc volumes. This would mean that those pistons will decrease compression over a true flat top piston with no valve reliefs.
Also, I did not see where you said how much you were going to bore the block for the new pistons. It appears they are available in STD, .005", .030", .040" and .060" oversized. The difference between .005" over and .030" over is about 1 tenth of a compression point.
In addition, the piston which you are considering appears to a "0" deck height piston as opposed to stock which is .005-.007" out of the hole or "positive" deck height. This will also reduce compression.
So, with a stock 68cc combustion chambered head here is what I show your compression to be with the piston that you mentioned assuming a .030" over bore:
Now, if you use a "0" deck height piston, you could go to a thinner head gasket like the .040" FelPro or Cometic and increase the compression a bit to this:
If you still would like more compression, you could mill the heads .030" and get this:
If you have the heads milled at a talented and reputable machine shop, you could also have a good competition valve job done to the heads while in the machine shop to improve performance even more.
As for a shelf camshaft saving you money over a custom, we do not charge extra for custom camshafts. We have 5150 steel alloy camshaft for $399.00 and we have a renowned 8620 steel alloy camshafts for only $449.00. So, getting exactly what you need or want is completely affordable.
~Steven
Steven, man do I appreciate your post. But I feel bad that you essentially wasted half your time lol While you were posting this, so much changed in the numbers thanks to a great catch by zachm89 and ss454327.
I did go through and modify everything and all the numbers should be now correct along with a new piston. I admittedly haven't gone through your post completely yet. I only skimmed it real fast and noticed it was still all the original info with pistons and wrong compression ration due to my error.
I'll look through what you posted and respond again. Thanks!
Steven, (and I will edit the OP also) the transmission I will be using is a T56. The exhaust will likely be Patriot S10 swap headers with 1-5/8" primaries and 2-1/2" collector and then 2-1/2" exhaust out. I will have electric cutouts on the truck to dump the exhaust before the mufflers when the truck will be driven hard. I do not plan to overbore unless needed, I also do not plan to mill the heads or have valve work done aside from lapping the valves.
06-01-2017, 02:34 PM
