[Greg T]

Howdy.
I have a cam question. I recently had the chance to put my 96 Chevy with a 388 on a chssis dyno and it rersponded with what I thought to be some impressive numbers for it's relatively mild build. BUT, I was wondering about squeezing a bit more power for next year. I'm going to do a tear down this fall just to freshen up the heads and such and was thinking that while I was in there I may make a cam change.
The config consists of an .060 350 block stroked to 388, Edelbrock E-tec 200 heads, roller 2201 cam (specs: 234/238 @.050 and .539/.548 lift with 112 lobe sep.) I've got an air gap intake and custom built QFT 680 cfm carb.
Now, I see that Ede offers the same cam in a 114* lobe sep with everything else being the same. But I was thinking of going to 110* lobe sep. I could easily custom order a 2201 with a 110 lobe sep instead of my current 112.
My power readings on the chassis dyno are, 380 HP and 396 lb/ft torque at the wheels and the peak power is all in by 5800 rpm. So, question: Given all the same specs on the cams, what would be the difference in the engine characteristics if I chose the 114* or the 110* for my motor? Idle difference? Power difference? Power band difference? Expert replies will be greatly appreciated! Thanx,
GT

[S10 Racer]

There is some good info on Comp Cams website about this very topic. It gives you the pros and cons so you can make the best choice. Read here

http://www.compcams.com/technical/FAQ/LSAproperties.asp

[Greg T]

That is a nice summary of events. I'm wondering how much torque increase there will be with only a 2* narrowing of the LSA. May or may not be worth the expense, but a torque increase would sure help the street use of the truck.
Whatever happened to Techinspector1? He used to crunch these numbers!

[cobalt327]

Originally Posted by Greg T

Howdy.
I have a cam question. I recently had the chance to put my 96 Chevy with a 388 on a chssis dyno and it rersponded with what I thought to be some impressive numbers for it's relatively mild build. BUT, I was wondering about squeezing a bit more power for next year. I'm going to do a tear down this fall just to freshen up the heads and such and was thinking that while I was in there I may make a cam change.
The config consists of an .060 350 block stroked to 388, Edelbrock E-tec 200 heads, roller 2201 cam (specs: 234/238 @.050 and .539/.548 lift with 112 lobe sep.) I've got an air gap intake and custom built QFT 680 cfm carb.
Now, I see that Ede offers the same cam in a 114* lobe sep with everything else being the same. But I was thinking of going to 110* lobe sep. I could easily custom order a 2201 with a 110 lobe sep instead of my current 112.
My power readings on the chassis dyno are, 380 HP and 396 lb/ft torque at the wheels and the peak power is all in by 5800 rpm. So, question: Given all the same specs on the cams, what would be the difference in the engine characteristics if I chose the 114* or the 110* for my motor? Idle difference? Power difference? Power band difference? Expert replies will be greatly appreciated! Thanx,
GT

Changing nothing but the LSA by 2 degrees retarded or advanced will not make any more difference in power than the normal differences seen between dyno runs done on different days. It just not enough of a change. And unless the cam was properly phased by degreeing it in and correcting if necessary, there's even less reason to change the LSA by 2 degrees. In my opinion.

[Greg T]

The currect cam was degreed and found to be about 1/2* retarded so I left it alone.



.

[S10 Racer]

Originally Posted by Greg T

That is a nice summary of events. I'm wondering how much torque increase there will be with only a 2* narrowing of the LSA. May or may not be worth the expense, but a torque increase would sure help the street use of the truck.
Whatever happened to Techinspector1? He used to crunch these numbers!

I think Techinspector1 has bowed out of HR.
Here is another article based on 3* LSA differences. They have crunched the numbers at the bottom of the page. Hope it helps.
http://www.chevyhiperformance.com/te...t/viewall.html

[ap72]

Edelbrock cams aren't exactly known for quality. And those heads canuse some porting. That being said good head work and a custom cam from a good grinder would probably get you at least 50hp. You're looking at over $1000 to get that done though.

[Greg T]

Originally Posted by S10 Racer

I think Techinspector1 has bowed out of HR.
Here is another article based on 3* LSA differences. They have crunched the numbers at the bottom of the page. Hope it helps.
http://www.chevyhiperformance.com/te...t/viewall.html

Thanx much. That seems to be just about what I was looking for. Hardly looks cost effective for a couple of lb/ft and a couple of horses. Looks like if I want a noticable increase I'd need to go with heads, cam and larger carb. I don't need a few ponies THAT much!

[F-BIRD'88]

Your money is better spent on a larger carb.
get a 750-850cfm carb.
The 680 carb is too small for max performance
on this motor.

[cool rockin daddy]

Originally Posted by ap72

Edelbrock cams aren't exactly known for quality. And those heads canuse some porting. That being said good head work and a custom cam from a good grinder would probably get you at least 50hp. You're looking at over $1000 to get that done though.

Typical post from you from the almighty Ap72. No doubt you are one of the reasons TI is nowhere to be found. First, Greg says he is happy with his engine's power. Just wants to tweak it. Second, he's asking about a different lobe seperation angle and what he can expect from that change. So, what do you do? You put down his choice of cam manufacturer and then tell him his heads are subpar. Based on what? Your personal opinion? As usual, you don't pay any attention to what the OP asked, you just use the thread to spout off your ambiguous statements about high performance.

[cobalt327]

Originally Posted by Greg T

The currect cam was degreed and found to be about 1/2* retarded so I left it alone.



.

I applaud you for taking the time to degree it, most guys don't bother.

Have you given any thought to changing the cam phasing by advancing it a few degrees? Depending on the whether the cam is ground w/any advance already, that could get you some positive results.

Edit- Never mind. It already has 5 degrees of advance ground in (107 degree intake c/l on a 112 degree LSA).

No need for 1.6 rockers, the lift is sufficient as-is for the heads. I'd say cam-wise it'll take a new cam to gain anything.

Is the QF 680 a DP or vacuum? Annular boosters? Those carbs are hard to beat. It might be giving away a bit of peak HP but everywhere else it ought to kick ***.

[S10 Racer]

Originally Posted by cool rockin daddy

Typical post from you from the almighty Ap72. No doubt you are one of the reasons TI is nowhere to be found. First, Greg says he is happy with his engine's power. Just wants to tweak it. Second, he's asking about a different lobe seperation angle and what he can expect from that change. So, what do you do? You put down his choice of cam manufacturer and then tell him his heads are subpar. Based on what? Your personal opinion? As usual, you don't pay any attention to what the OP asked, you just use the thread to spout off your ambiguous statements about high performance.

Butt he got one of them thar pecces of papr that say he is eddicated an he talkin lik a 26 yer old high performunts perfeshnuls. Butt whez all no hez jus a guessin at them thar questchuns an makin a ful of hisself. Ben readin to menny books insted of gettin hes hans derty. I dont thenk no one lessin two hem anyway.

[ap72]

Fwiw edelbrock isn't a cam manufacturer, they just box and ship them.

Also for the runner and valve size the flow numbers are not spectacular at all. Flow is not everything of course but its a good start.

As for all my pieces of paper I'll be the first to say they are way too easy to come by and I still don't have a phd, which is the only degree that means anything any more.

Also I get my hands dirty but perhaps less than others as those silly little books ensure I get it done right the first time. Only in America would working smart instead of hard be frowned upon.

[Greg T]

Originally Posted by cobalt327

I applaud you for taking the time to degree it, most guys don't bother.

Have you given any thought to changing the cam phasing by advancing it a few degrees? Depending on the whether the cam is ground w/any advance already, that could get you some positive results.

Edit- Never mind. It already has 5 degrees of advance ground in (107 degree intake c/l on a 112 degree LSA).

No need for 1.6 rockers, the lift is sufficient as-is for the heads. I'd say cam-wise it'll take a new cam to gain anything.

Is the QF 680 a DP or vacuum? Annular boosters? Those carbs are hard to beat. It might be giving away a bit of peak HP but everywhere else it ought to kick ***.

I know the carb is a bit small for peak HP, but I didn't want to lose the low end and drivability on the streets. This truck may see the strip once or twice for a test and tune session but it really doesn't need it. It's been done on a dyno so I know it's damn close to optimal. The carb is an HR model vacuum because it's a 3800 pound truck. TI had run three potential scenarios for me with minor parts changes. According to Desk-Dyno I would gain about 17 lb/ft and 7 HP with an 800 carb but the power peaks would raise about 300 RPM. 1 3/4" primary tubes would also net me another 6 lb/ft and the same HP. So, not much sense in that because that huge carb would not run well on the street. Right now the low end with this 680 is just sick. I can roll into the throttle already doing about 30 mph and break the rears loose without effort.

We have no machinists around here so porting, and basic engine machining must be done about 60 or 70 miles away. Can't even get a valve job here anyomre. Years ago we could go into any parts store and have heads done, block bored/honed , balh blah. Not now. So, shelling out the cash for AFRs or Trick Flows, plus a cam, etc to gain 50 HP is just not cost effective. What I will probably do is pull the heads, lap the valves, gasket match the intake and intake ports on the head and reassemble. Fine tune again and then run the dyno at Fun Run next year just to check the difference.
Plus, TI came up with about 441 HP and 471 lb/ft on desktop dyno. Well, my numbers are 380 and 396 respectively at the wheels,. Using the standard 20% loss for an automatic trans that brings me to about 475 HP and about 495 lb/ft of torque. Thats not bad for a pretty mild small block.

[ap72]

Originally Posted by Greg T

I know the carb is a bit small for peak HP, but I didn't want to lose the low end and drivability on the streets. This truck may see the strip once or twice for a test and tune session but it really doesn't need it. It's been done on a dyno so I know it's damn close to optimal. The carb is an HR model vacuum because it's a 3800 pound truck. TI had run three potential scenarios for me with minor parts changes. According to Desk-Dyno I would gain about 17 lb/ft and 7 HP with an 800 carb but the power peaks would raise about 300 RPM. 1 3/4" primary tubes would also net me another 6 lb/ft and the same HP. So, not much sense in that because that huge carb would not run well on the street. Right now the low end with this 680 is just sick. I can roll into the throttle already doing about 30 mph and break the rears loose without effort.

We have no machinists around here so porting, and basic engine machining must be done about 60 or 70 miles away. Can't even get a valve job here anyomre. Years ago we could go into any parts store and have heads done, block bored/honed , balh blah. Not now. So, shelling out the cash for AFRs or Trick Flows, plus a cam, etc to gain 50 HP is just not cost effective. What I will probably do is pull the heads, lap the valves, gasket match the intake and intake ports on the head and reassemble. Fine tune again and then run the dyno at Fun Run next year just to check the difference.

If you can gasket match its not that much harder to work the bowl area- that is where the real gains will be made. Work the bowls and get a proper cam and you'll come close to seeing that 50hp. The majority of your flow increase is a half inch either side of the valve seat. Not by the intake manifold.

As for the carb, if you're happpy with it keep it but a well tuned 800cfm or larger carb that is properly built will show gains from idle to redline, but its not cheap.