Cam swap only worth it?

[jamesjones]

I'm in the process of swapping a cable driven LQ4 from an '05 van into my '72 Blazer. I've been thinking I know I'm going to hop it up eventually but I don't know if I'll go the FI route or keep it NA, so I don't want to get rid of the 317 heads. I'll also be using TBSS manifolds until I can afford to get some custom headers made for space reasons.

I figured since I have the front clip off and such easy access to the engine I'd have a custom cam ground and swap it in with some upgraded springs.

Do you guys think this would be a worthwhile side project to do to keep my right foot happy a little longer than the stock engine once it's up and running?

[BR3W CITY]

No real reason to go with a custom grind for a stock swap. Plenty of good (and now lower in price) entry level shelf cams.

I started mine with pretty much "cam only" (but make sure to do the supporting valvetrain stuff), and was plenty happy with it. I'm going FI but for the cost of the cam stuff, its hard to beat the instant power and sound.

[Custom 68]

Brew got it right, I drove mine for a couple years stock and got tired of that. It ran great and did super on gas mileage however it didn't have that "old truck" sound. I swapped out cam and springs and a new tune and the power difference was huge (from feel). The sound was great and seemed to be where I wanted to be.
Then along cam the FI and of course it is even better I have had that in for a couple years now it seems to be a work in progress.
But I like Brew said just get an off the shelf one there are several proven ones. In stock form the Gen 3 motors run great with a tune, add a cam and retune and even better. I say go for it.

[jamesjones]

There's really not much of a price difference these days between a custom grind and an off the shelf cam it seems, so I figured I might as well have one ground specifically for my application.

So it will be worth while even without all of the other supporting mods?

[Super73]

An oldie but goodie.. Here is a 5.7 wearing stock manifolds. Not exactly your combo as it has better heads (LS6 243). But how is 403rwhp through stock exhaust manifolds?

http://ls1tech.com/forums/dynamomete...-mild-cam.html

[jamesjones]

Originally Posted by Super73

An oldie but goodie.. Here is a 5.7 wearing stock manifolds. Not exactly your combo as it has better heads (LS6 243). But how is 403rwhp through stock exhaust manifolds?

http://ls1tech.com/forums/dynamomete...-mild-cam.html

Funny, that's who I'm planning on getting my cam from.

I'd love to find a set of 243 heads in the cheap and put my 317s away in case I FI.

[BR3W CITY]

Originally Posted by jamesjones

There's really not much of a price difference these days between a custom grind and an off the shelf cam it seems, so I figured I might as well have one ground specifically for my application.

So it will be worth while even without all of the other supporting mods?

If you have an otherwise stock setup....there isn't anything specific TO your application.

[Super73]

Originally Posted by BR3W CITY

If you have an otherwise stock setup....there isn't anything specific TO your application.

Sorry, I have to disagree. Stuff a trex or any version of a torquer cam in it and it won't work so good. The main issue is the stock exhaust manifolds and goal of keeping a semi stock tq band, those are his specifics. Imo the valve events need to be considered to make meet his specific goals.

[mcfarlnd]

If I could do it all over again, I would have done a 4.8 with arp rod bolts, and head studs, on 18lbs of boost instead of building a high compression 5.3. The little things add up after a while and once you cam it, trust me when I say you won't stop there. There are guys running over 20 psi of boost on those little 4.8's producing over 700 hp. Look on performancetrucks.net. And if you pop a 4.8, one can be had in short lock form for next to nothing. In short, I would boost it......

[softballnrd27]

I agree with Super73, every combo is different in some way and with the prices so close why not go with a custom grind.

[BR3W CITY]

Originally Posted by Super73

Sorry, I have to disagree. Stuff a trex or any version of a torquer cam in it and it won't work so good. The main issue is the stock exhaust manifolds and goal of keeping a semi stock tq band, those are his specifics. Imo the valve events need to be considered to make meet his specific goals.

I don't disagree there, but I also wasn't thinking to include them in the range of consideration. When I look at the info provided, I guess aside from the use of tbss headers, an otherwise stock-for-stock swap. This is assuming the use of stock converter, injectors and on and on. This really limits the amount of suggestions that are practical, and I can't see justifying the cost of a custom grind cam against something in the take-out of out of the generals parts bin category. The hotcam etc are popular, cheap, and can be more or less supported on an otherwise stock truck....even if you don't do the supporting valvetrain stuff for some of them.

Maybe I'm just jaded due to Ls1tech, but people like Pat G over there made "custom grind" a buzzword. It gave people with tame cams the feeling of buying custom race parts, and they sold well. I think custom cams are great in a ton of applications, but I just don't think that it should be the defacto advice. More than a handful of times "custom" cams are nothing more than the "closest thing" that the company offers based on what you tell them you have. I don't think that many people really have enough information to know the difference.

Is it wrong to get one? Heck no. If you have a more defined list of all the parts you plan to use or what other mods you want to make, then maybe we can suggest something more specific, but no matter what you do, just get it tuned.

[Andy4639]

Well now,

I'm just going to sit back and wait. I plan to run the 6.0 stock for now with headers and a good street tune I hope. Maybe in a year are so I will put in some rollers and a nice cam but for now I think the stock motor will be good for me.
Much later maybe even a supper charger!

[Super73]

I understand where you are ciming from. There are a lot of "custom" cams that are lets say a degree or two off of a shelf cam. Or the lsa is set a couple degrees advanced/retarded. Their are probably shelf cams geared towards an l92 head that would work goid with stock manifolds since they are designed with a wide split to compesate for a lower exhaust/intake flow ratio.

People thought I was nuts putting a 223/228 108/108 on XER lobes in a 347 with ls6 heads. Goal was stock ls6 power band with more under the curve. I was told it would not run well. Drove great on a stock verter and made great power.

[BR3W CITY]

Your also not afraid to put it in, run the piss out of it...then change it if it doesn't work. Many folks are in the one-and-done mentality of mods. Even something simple like swapping tbss's for some DT's can make enough of a difference to warrant experimentation,.

[Super73]

Me.. Never... I don't change parts.... Experimentation, the only true way to see if something works the way you want. When it doesn't, the next question is how long can you live with it before you start changing more parts out. If only I could be a one and done type..

[ls1nova71]

Originally Posted by Super73

I understand where you are ciming from. There are a lot of "custom" cams that are lets say a degree or two off of a shelf cam. Or the lsa is set a couple degrees advanced/retarded. Their are probably shelf cams geared towards an l92 head that would work goid with stock manifolds since they are designed with a wide split to compesate for a lower exhaust/intake flow ratio.

People thought I was nuts putting a 223/228 108/108 on XER lobes in a 347 with ls6 heads. Goal was stock ls6 power band with more under the curve. I was told it would not run well. Drove great on a stock verter and made great power.

Not to hijack, but is a "cam only" swap really doable? I'm getting conflicting information. Some say you need a stall and others say you may not? How much does a stall really help?

[BR3W CITY]

This comes to symantics.

A TRUE cam-only swap means popping off the timing cover and putting a new cam it, and walking away. Like tossing in a z06 cam and hoping the computer can get enough injector duty to let it run. This can work in basic cases, but on efi trucks more often than not you need supporting mods to get the real advantage
SO
It becomes generally accepted cam-only means a cam swap (usually including the valvetrain stuff, possibly oil pump) plus any expected bolt on parts like intakes and headers. Depending on the situation, it can even mean to include supporting parts like injectors and fuel pumps, but usually does so with out "saying" it directly. This description also tends to ignore non-engine things like stall converters, and tuning.


So with that said, a stall helps because it allows you to target the trucks shifting and USE of the power, within the new power band that a cam provides. A sluggish convertor will makes a peaky cam feel slow because it "Wastes" time in the early rpms, where the cam isn't making peak efficiency. Same goes for the torque curve....you can pair a torquey cam with a very tight convertor, and find that it puts down too much too early, and runs out of breath.

[softballnrd27]

Well said BR3W. Unless you are swapping in a "stock" GM cam then you will need all those supporting mods. If all you are going for is the "sound " of HP then you won't need the converter. If you want to take full advantage of your new cam then you will need to do more than just a cam-only.

[Super73]

I am going to add a little more to the posts from both Br3w and Softball.

Depending on LS motor you buy (Gen3 and Early Gen 4), the stock cam typically produces a peak TQ at 4,200-4,500rpm.

Most stock stalls you will be lucky to see 1,600-2,000 rpm out of them when coupled with an otherwise stock motor. If memory serves my wife's TBSS will stall to 2,000 on the foot break WOT. This is with an LS2 making 400ftlbs from the factory (more on this in a minute).

Proven fact that putting your stall converter at peak tq rpm produces the quickest initial acceleration provided you have the traction.

So with the above, there is already a large delta between a stock cam's tq peak (4,200-4,500) and a stock stalls stall speed (1,600-2,000) meaning acceleration could be majorly improved.

TQ plays a major role in stall speed. Put any given stall behind two drastically different torque outputs and the stall speed will change. This is why I mentioned my wife's TBSS and the 2,000 stall speed. I doubt a NA 4.8 in stock form with that converter would break 1,400-1,600rpm stall speed.

As you go bigger with a cam, you generally increase overlap. When you increase overlap, you generally shift your TQ band further up in the RPM softening bottom/midrange TQ. When this happens, the initial acceleration suffers even more as the delta between peak TQ rpm and stall speed widen.

Can a cam be designed to have mostly stock valve events and still produce more power with in a stock power band. Absolutely! Will it still suffer the same drawbacks a stock converter plays, yes, but not as bad provided you were able to increase TQ under the curve with the new cam. This is essentially what a stock cam paired with 1.8 rockers does.

My extreme example of how TQ increase plays a roll on stall speed. My 347ci motor made a peak of 380ftlbs @ 5,700rpm and the converter would flash to 4,500 rpm (was really too tight for NA). When I put my 418ci motor in, it made 460ftlbs at the same 5,700rpm. The converter instantly became a 6,000rpm stall. It shifted stall speed 1500rpm.

One other quick example, gearing even has an effect on stall speed. When you think about it, gears are a leverage being applied to the tire. I found that the shorter the gear with the same chassis weight provided a lower stall speed. That 4,500 rpm converter was once a 4,800 with the same 347ci motor but with 3.73 gears. Stall speed went down when I went to a 4.56. Reason is due to the different leverage force put on the verter..


Sorry for the very long post, but I thought I would add some real world experiences.

[softballnrd27]

Super, you have tested and proven/dis-proven many "theories" and you always pass on the knowledge. That makes you a pretty fair guy in my opinion. LOL Thanks for sharing your experience and making so that is understandable.

[jamesjones]

Originally Posted by Super73

I am going to add a little more to the posts from both Br3w and Softball.

Depending on LS motor you buy (Gen3 and Early Gen 4), the stock cam typically produces a peak TQ at 4,200-4,500rpm.

Most stock stalls you will be lucky to see 1,600-2,000 rpm out of them when coupled with an otherwise stock motor. If memory serves my wife's TBSS will stall to 2,000 on the foot break WOT. This is with an LS2 making 400ftlbs from the factory (more on this in a minute).

Proven fact that putting your stall converter at peak tq rpm produces the quickest initial acceleration provided you have the traction.

So with the above, there is already a large delta between a stock cam's tq peak (4,200-4,500) and a stock stalls stall speed (1,600-2,000) meaning acceleration could be majorly improved.

TQ plays a major role in stall speed. Put any given stall behind two drastically different torque outputs and the stall speed will change. This is why I mentioned my wife's TBSS and the 2,000 stall speed. I doubt a NA 4.8 in stock form with that converter would break 1,400-1,600rpm stall speed.

As you go bigger with a cam, you generally increase overlap. When you increase overlap, you generally shift your TQ band further up in the RPM softening bottom/midrange TQ. When this happens, the initial acceleration suffers even more as the delta between peak TQ rpm and stall speed widen.

Can a cam be designed to have mostly stock valve events and still produce more power with in a stock power band. Absolutely! Will it still suffer the same drawbacks a stock converter plays, yes, but not as bad provided you were able to increase TQ under the curve with the new cam. This is essentially what a stock cam paired with 1.8 rockers does.

My extreme example of how TQ increase plays a roll on stall speed. My 347ci motor made a peak of 380ftlbs @ 5,700rpm and the converter would flash to 4,500 rpm (was really too tight for NA). When I put my 418ci motor in, it made 460ftlbs at the same 5,700rpm. The converter instantly became a 6,000rpm stall. It shifted stall speed 1500rpm.

One other quick example, gearing even has an effect on stall speed. When you think about it, gears are a leverage being applied to the tire. I found that the shorter the gear with the same chassis weight provided a lower stall speed. That 4,500 rpm converter was once a 4,800 with the same 347ci motor but with 3.73 gears. Stall speed went down when I went to a 4.56. Reason is due to the different leverage force put on the verter..


Sorry for the very long post, but I thought I would add some real world experiences.

Great info. My TC is a slightly upgraded stock one from when I had my TH-350 built several years ago. I think the stall is 1400-1600.

What range of stall do you think I should consider going to with a slightly bigger cam and upgraded valve train?

[Super73]

Will you do any towing?
What trans is in it? Still the th350?
do you have as good trans cooler?

[jamesjones]

Originally Posted by Super73

Will you do any towing?
What trans is in it?

It's a TH-350HD. No towing, it will be strictly street and high speed off road stuff.

[BR3W CITY]

IMO the dividing line starts at about 2800 rpm. Above that, depending on the converter, you can start to "notice" it a LOT more.

The first time I drove a high stalled street car I thought it was broke.

[Super73]

The looser the converter the more heat you see in stop and go unless there is a lock up verter involved, short shift 1-2 and lock it in 2nd almost right away. Your th350 will not allow this. Its all what you are ok with.

My truck converter will flash to 4,600 off the two step/transbrake. I have a glide and 4.56 gears. It will run 180-200 degrees cruising down the freeway. Stop and go it will climb to 250 degrees pretty fast.
when I had the 80e/4500 verter, stop and go was 160 degrees for the reason I explained earlier. Lock up verter really help streetability.