6.0 LS Build

[pro86tourn]

Too large for the current engine setup (displacement, heads, compression), even considering weight, gears, and transmission type. And you'd be better off with the Edelbrock RPM intake over the Victor Jr.

https://www.hotrod.com/articles/20-l...ifolds-tested/

Okay so I guess even if i shaved the heads .30 and ran a thinner gasket I still would be shy on the compression required. So question is I go to which cam? If i maintain the stock setup. I want a lumpy idle with good power.



2nd option is keep stock heads and swap pistons or swap the head to increase compression and keep the cam suggested above.

[68Formula]

Okay so I guess even if i shaved the heads .30 and ran a thinner gasket I still would be shy on the compression required. So question is I go to which cam? If i maintain the stock setup. I want a lumpy idle with good power.

2nd option is keep stock heads and swap pistons or swap the head to increase compression and keep the cam suggested above.

Either the one I suggested in one of my earlier posts or the custom one that KnightmareZ specified. They have virtually the same overlap, so idle will be same (aggressive, but won't require jacking up the idle speed just to keep it alive). The XER ramp rates are pretty aggressive, so you'll get more valvetrain noise from the quick valve closure, and shorter long term durability for valve seat wear and cam lobe wear compared to the Summit. The extra lift also means a stiffer valvespring (like PAC1218) , so also a little quicker wear on the cam, and higher cost (the Summit can use the GM LS6 factory springs). The XER will probably put a few more HP on the very top of the RPM range (like 5500-6500) with a little less torque below that. Won't make much difference unless you change over to CNC ported L92 heads or aftermarket.

[KnightmareZ]

It's all about valve events and how long you keep that valve open to let as much air in and how much you are able to get out on the exhaust side
Actually the cam you speak of would have more overlap 54.5* vs 51*
Should lope a very little bit more, nothing noticeable
As far as low rpm torque the XER Lobes would close at 64.5* ABDC vs summits at 65* ABDC the lower the closing angle the higher the DCR and cylinder pressure.
But as far as numbers are concerned, trivial and almost dead equal until we start talking about the area between where that valve opens, the ramp rate, the lift and then where the valve closes.
Now when you envision the summit lobe coming off the seat at 274 at .004 and 222 at .050 with a .545 lift vs 273 at .004 and 224 @ .050 with .581 lift its pretty obvious which one took in the most air and will have the most cylinder pressure down low. More air entering the chamber will generate higher cylinder pressures given they are closing at the same time. Or in this case the XER even sooner. This means more torque down low. You spell it out like the only gains would be 5500 to 6500 with loss of torque down low. LOL The XER lobe in this example would drag this soft summit lobe throughout the powerband.

[68Formula]

Actually the cam you speak of would have more overlap 54.5* vs 51*
Should lope a very little bit more, nothing noticeable
As far as low rpm torque the XER Lobes would close at 64.5* ABDC vs summits at 65* ABDC the lower the closing angle the higher the DCR and cylinder pressure.

Which is pretty much what I said:

They have virtually the same overlap, so idle will be same.

But as far as numbers are concerned, trivial and almost dead equal

Which is why I wasn't worried about a couple degrees overlap difference.

Now when you envision the summit lobe coming off the seat at 274 at .004 and 222 at .050 with a .545 lift vs 273 at .004 and 224 @ .050 with .581 lift its pretty obvious which one took in the most air and will have the most cylinder pressure down low. More air entering the chamber will generate higher cylinder pressures given they are closing at the same time. Or in this case the XER even sooner. This means more torque down low.

Between the earlier intake centerline (107 versus 108) and the 2 degrees shorter duration @ 0.50" lift on the Summit, I expected a slight increase in torque down low. With the stock head flow and the fact that you're almost at peak flow by .550" lift, the tiny bit lift difference @ low speeds isn't significant enough to impact cylinder filling. Which is why I wrote:

The XER will probably put a few more HP on the very top of the RPM range (like 5500-6500) with a little less torque below that. Won't make much difference unless you change over to CNC ported L92 heads or aftermarket.

You seem to think I was being hard on the XER cam, when really I considered them virtually equal (only minor differences depending where you were in the rpm band).

However, since you came back with a very strong statement of:

The XER lobe in this example would drag this soft summit lobe throughout the powerband.

I decided to toss it into DynoSim and see that that said. I already had the LQ4 modeled previously anyway, and it's been validated against published real world dyno data with various camshafts, so it's reasonable accurate.

Using both the 0.50" and advertised duration, stock heads, factory intake, compression, and long tube headers, they were within 1-2 ft-lbs torque difference below 4000rpm. So basically the same. No slight edge to the Summit, but the XER doesn't "drag it" either. The curves are basically on top of each other.

Now above 4000rpm, you can see the power curves begin to separate with the XER on top, but still talking single digit horsepower with only 6hp difference at the peak. So the XER isn't dragging it on the top end either (even above 6k). I attribute that to the added exhaust duration of the Summit. The 317s aren't as efficient on the exhaust side, and on naturally aspirated engine it it helps quite a bit.

Again, CNC ported heads would make a bigger gap between the two (starting from about peak torque rpm up to peak hp rpm). Or maybe if you were using L92 heads with their more efficient exhaust ports, you might see a little more separation.

[badazz81z28]

Just my opinion...how did you come up with that cam? I would avoid shaving .030 off the heads AND running a thin head gasket. You will impact PTV clearance and possibly cause issues for the intake fitment . I don’t know the science behind cams and compression so I copy proven combos. If I were you...I would call Texas Speed and tell them what you are looking for. They will set you up with the right cam to match your desires. The engine being carb versus EFI is an important piece of info when choosing a cam.

There’s a handful of parts you should swap out too while you’re in there...lifters, trays, pushrods, cam retaining plate, timing chain...Texas Speed can advise.

[pro86tourn]

Just my opinion...how did you come up with that cam? I would avoid shaving .030 off the heads AND running a thin head gasket. You will impact PTV clearance and possibly cause issues for the intake fitment . I don’t know the science behind cams and compression so I copy proven combos. If I were you...I would call Texas Speed and tell them what you are looking for. They will set you up with the right cam to match your desires. The engine being carb versus EFI is an important piece of info when choosing a cam.

There’s a handful of parts you should swap out too while you’re in there...lifters, trays, pushrods, cam retaining plate, timing chain...Texas Speed can advise.

Buying cam off a fellow member. I will be swapping the pushrods, timing chain, springs, valve seals. Stock lifters should be changed? or will they work?

[79 Camaro]

LS7 lifters aren't expensive. I'd buy new lifter trays also. That cam is going to be a bit lopey. Are you going manual or auto trans? If auto you should consider some level of stall converter. And maybe 3:73 gears? Be interesting to see how much vacuum you will get with that cam. May affect your brake booster.

[KnightmareZ]

Too much cam for an engine with 9.4:1 SCR in my opinion. Been crunching some numbers and that only nets a 7.2:1 DCR. You need to be high 7s low 8s or you are leaving way too much on the table. Can you provide more info on your ride and plans? Transmission, rear end gear, weight, tire size, which heads and gaskets, shaving or no?

[pro86tourn]

Too much cam for an engine with 9.4:1 SCR in my opinion. Been crunching some numbers and that only nets a 7.2:1 DCR. You need to be high 7s low 8s or you are leaving way too much on the table. Can you provide more info on your ride and plans? Transmission, rear end gear, weight, tire size, which heads and gaskets, shaving or no?

Im not sure what those numbers mean you listed but the car has a T5 now will be switching to a T56, rear is 3:73, weight not sure stock, rims are 16 but will be eventually going 18.

Id like to keep the 317 heads was considering shaving heads/thinner gasket. Will consider other heads if it helps ! any advice on best bang for buck

[KnightmareZ]

Im not sure what those numbers mean you listed but the car has a T5 now will be switching to a T56, rear is 3:73, weight not sure stock, rims are 16 but will be eventually going 18.

Id like to keep the 317 heads was considering shaving heads/thinner gasket. Will consider other heads if it helps ! any advice on best bang for buck

7.2:1 is your DCR with that cam
DCR Dynamic compression ratio takes into account the intake valve closing angle as well as all the other variables for your static compression ratio.
SCR Static Compression ratio- Is a ratio that assumes the intake valve is closed at BDC and takes bore, stroke, head volume, deck height and compressed gasket thickness
Generally, we like to see around 8 to 8.5:1 when running pump gas on a street setup.
Here's what I would do if I were in your situation
https://www.summitracing.com/parts/w...23as/overview/ along with all new bearings and ARP bolts. I'd run the 317s with a .04 cometic and see how you like it. Later on you could send those heads off to get worked or sell them and get something else. This would put you at 10.9:1 SCR and a DCR of 8.33:1 using the cam you spoke of earlier.

[pro86tourn]

7.2:1 is your DCR with that cam
DCR Dynamic compression ratio takes into account the intake valve closing angle as well as all the other variables for your static compression ratio.
SCR Static Compression ratio- Is a ratio that assumes the intake valve is closed at BDC and takes bore, stroke, head volume, deck height and compressed gasket thickness
Generally, we like to see around 8 to 8.5:1 when running pump gas on a street setup.
Here's what I would do if I were in your situation
https://www.summitracing.com/parts/w...23as/overview/ along with all new bearings and ARP bolts. I'd run the 317s with a .04 cometic and see how you like it. Later on you could send those heads off to get worked or sell them and get something else. This would put you at 10.9:1 SCR and a DCR of 8.33:1 using the cam you spoke of earlier.

I was hoping to leave the bottom end intact... I guess running a thinner gasket and shaving the heads wont get me where i need to be? Leaving the bottom end in tact which head choice would be best? I guess I would have to weigh the cost of pistons vrs/heads

[pro86tourn]

LS7 lifters aren't expensive. I'd buy new lifter trays also. That cam is going to be a bit lopey. Are you going manual or auto trans? If auto you should consider some level of stall converter. And maybe 3:73 gears? Be interesting to see how much vacuum you will get with that cam. May affect your brake booster.

In that case ill buy new lifters/trays. I will being going manual trans & 3:73

[79 Camaro]

If you decide to go L92 or LS3 heads check out the parts for sale section. There is a LS3 intake with fuel rails and injectors. $350 is a great price. The LS3 intake has 42lb injectors. I don't know the seller just FYI.

[79 Camaro]

Sell the 317 heads to the turbo guys unless you are headed that direction.

[pro86tourn]

Sell the 317 heads to the turbo guys unless you are headed that direction.

Im staying NA. Which heads would you use I have been hearing so many people say keep stock heads they fine, use L92 but they make power up high, use 5.3 heads bla bla bla no one seems to have an exact answer

[79 Camaro]

That's the trouble there are way to many good choices. I had a 73 Z28 with a L92 out of a 2010 Silverado. Added a Texas Speed cam. 225I/230E .600 lift. 114 CL.It ran great thru out the power range. Down low plenty of torque. Ran great in the upper rpms. It had a TKO 600 with 3:73 gears. Did the Power Tour a few years ago and on the back roads at 60 mph it did 25 plus mpg.

I'm a fan of the L92/LS3 heads. With the right piston / head combo you can easily run 10.0-10.5 CR on 91 octane and a mild tune. We can only get 91 octane around here.

As far as milling the 317 heads. Talk to the guys on LS1 Tech forums. I'm sure they can help.

I've been down the "too big" cam road. Sounds cool at first but after a short time it gets old.

[KnightmareZ]

A 224/228 using Comp XER lobes with a 112 separation and 4* advance would get you to a DCR of 8:1 and would still rip up top. That's about as aggressive as Id go in this setup. You'd also have quite a bit of lope at 51* overlap, I forgot to ask about how you wanted it to idle.

[68Formula]

A 224/228 using Comp XER lobes with a 112 separation and 4* advance would get you to a DCR of 8:1 and would still rip up top. That's about as aggressive as Id go in this setup. You'd also have quite a bit of lope at 51* overlap, I forgot to ask about how you wanted it to idle.

Agreed. He's going to have fun getting the tune right with the cam he listed. It's going to be doggy on the low end, and pull no better on the top (maybe even worse, without adding a lot more compression and/or more cubic inches displacement), than the one you suggest listed above. Basically sacrificing street manners with no added benefits over choosing the matching cam for the rest of the setup.

[79 Camaro]

Since you are going to disassemble to check everything just unbolt parts and send to the machine shop hot tank. Stuff like coils and other more delicate parts clean by hand with degreaser.

[btmatt]

Tape it up real good and use some purple power and power washer. Awesome stuff