My Vortec Combo disappoints
Race Director
Joined: Oct 2000
Posts: 15,055
Likes: 79
From: central FL, near the beach.
I did live in NJ, back then a choke was needed. 17F is low there.
Here in FL no choke on my cars. Do have a hand throttle on my 61, and a fast idle solenoid on my 72 for cold starts.
Yes i'm spoiled
This was the whole idea living in NJ; i needed to save up $$$ by driving old cars so i could afford to move to FL.
Looks like i will have to cut the grass. it has been in 70's last 2 weeks. 76F right now.
Here in FL no choke on my cars. Do have a hand throttle on my 61, and a fast idle solenoid on my 72 for cold starts.
Yes i'm spoiled
This was the whole idea living in NJ; i needed to save up $$$ by driving old cars so i could afford to move to FL.
Looks like i will have to cut the grass. it has been in 70's last 2 weeks. 76F right now.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
He could try advancing the cam 4 degrees. Might pick up the low end torque he feels its lacking. Comp cams says that if you have to advance a cam that its the wrong cam.
Look at the dyno chart the peak torque should have occurred very early in the rpm range not post 4000 rpm. A xe262 peaks around 4000 rpm on the comp cams website and that is on a 218/224. So yours on a 212/222 should have a lower rpm peak torque.
Do a compression test.
A cam installed just 4* retarded would represent a loss of 609 lbs of pressure on the cylinders at low rpms. Don't know how much hp that is but sounds significant enough to me.
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
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'
I drove my 61 like that for 4 or 5 years! It was fun, i admit that. But it got 11 mpg.
Still have the 4.11 in my 61 and it now gets 15-19 mpg at cruise. still just as much fun, even more as it doesn't need any warm-up(to drive off gently), even down to 38F. Same 270 magnum cam, just a fully divided dual plane. 1000-6000+ power band. That is my point, i'm not giving up anything, and, as my 72 proves, a 3.08 works great with the 4 holer base gasket. If someone needs more rpm than the 6000 the ex262, or more power,go right ahead with a larger cam, higher stall, steep gear, whatever. Just keep the 2 planes fully divided for more fun and decent mpg at cruise.
The op should be checking that carb base gasket! 4 hole only! No cut down divider! No unused cross passages in the carb base!(plug them) The devil is in the details!
'
I drove my 61 like that for 4 or 5 years! It was fun, i admit that. But it got 11 mpg.
Still have the 4.11 in my 61 and it now gets 15-19 mpg at cruise. still just as much fun, even more as it doesn't need any warm-up(to drive off gently), even down to 38F. Same 270 magnum cam, just a fully divided dual plane. 1000-6000+ power band. That is my point, i'm not giving up anything, and, as my 72 proves, a 3.08 works great with the 4 holer base gasket. If someone needs more rpm than the 6000 the ex262, or more power,go right ahead with a larger cam, higher stall, steep gear, whatever. Just keep the 2 planes fully divided for more fun and decent mpg at cruise.
The op should be checking that carb base gasket! 4 hole only! No cut down divider! No unused cross passages in the carb base!(plug them) The devil is in the details!
Le Mans Master
Joined: Dec 2009
Posts: 6,397
Likes: 649
From: Saskatoon Saskatchewan
Today its forcasted to go slightly above freezing which is very warm for this time of year. The past several weeks its been -20 to -30 which is typical for this time of year.
Le Mans Master
Joined: Dec 2009
Posts: 6,397
Likes: 649
From: Saskatoon Saskatchewan
I think you got the solution. The cam is plenty short to have good bottom end. Cam was probably not installed correctly.
Look at the dyno chart the peak torque should have occurred very early in the rpm range not post 4000 rpm. A xe262 peaks around 4000 rpm on the comp cams website and that is on a 218/224. So yours on a 212/222 should have a lower rpm peak torque.
Do a compression test.
A cam installed just 4* retarded would represent a loss of 609 lbs of pressure on the cylinders at low rpms. Don't know how much hp that is but sounds significant enough to me.
Look at the dyno chart the peak torque should have occurred very early in the rpm range not post 4000 rpm. A xe262 peaks around 4000 rpm on the comp cams website and that is on a 218/224. So yours on a 212/222 should have a lower rpm peak torque.
Do a compression test.
A cam installed just 4* retarded would represent a loss of 609 lbs of pressure on the cylinders at low rpms. Don't know how much hp that is but sounds significant enough to me.
Last edited by Priya; Jan 15, 2013 at 11:59 AM.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
The OP said he was getting 260 rear wheel horsepower after modifications which if we assume a 10% drivetrain loss with the 4 speed transmission (taking into account Sharkracer's caveats) that equates to about 290 net horsepower, a 65 horsepower increase over the L82's stock 225 net horsepower which to me is pretty darn good considering he now has less cam than the stock L82 did. I've been studying similar cam/head/intake combos producing this level of horsepower for a year or more now and from what I've seen that's exactly what the OP should expect his combination to produce. I think everything is installed and working correctly, the only mystery to me is why the OP couldn't notice any seat of the pants difference with an aproximately 65 horsepower net increase - I'd have thought you'd feel that difference for sure, but maybe not?
Today 09:45 AM
Today 09:45 AM
A late closing intake valve due to cam being installed retarded will have a significant effect at low rpms on torque. Once the rpms come up to around peak torque then the effect of a late closing intake valve is not as apparent due to the valve events occuring much faster and the air does not have as much time to escape via the overlap period. So now the dominant power factor becomes more affected by the entire stroke of the engine (ie the SCR) and not the dynamic compression ratio which is directly related to intake valve closing angle. It's all about his low rpm torque levels not the ultimate power produced. That 260 RW HP was probably in the 5000 to 5300 rpm range.
Le Mans Master
Joined: Dec 2009
Posts: 6,397
Likes: 649
From: Saskatoon Saskatchewan
It's not how much HP he is producing that is the problem it's where that power is being produced. At what RPM the torque is being produced in other words.
A late closing intake valve due to cam being installed retarded will have a significant effect at low rpms on torque. Once the rpms come up to around peak torque then the effect of a late closing intake valve is not as apparent due to the valve events occuring much faster and the air does not have as much time to escape via the overlap period. So now the dominant power factor becomes more affected by the entire stroke of the engine (ie the SCR) and not the dynamic compression ratio which is directly related to intake valve closing angle. It's all about his low rpm torque levels not the ultimate power produced. That 260 RW HP was probably in the 5000 to 5300 rpm range.
A late closing intake valve due to cam being installed retarded will have a significant effect at low rpms on torque. Once the rpms come up to around peak torque then the effect of a late closing intake valve is not as apparent due to the valve events occuring much faster and the air does not have as much time to escape via the overlap period. So now the dominant power factor becomes more affected by the entire stroke of the engine (ie the SCR) and not the dynamic compression ratio which is directly related to intake valve closing angle. It's all about his low rpm torque levels not the ultimate power produced. That 260 RW HP was probably in the 5000 to 5300 rpm range.
Makes sense, but unless I missed something the OP didn't post a graph with the torque and horsepower curves so this just sounds like speculation to me. With 3.36 gears and given that low rpm generally means significantly lower horsepower than higher rpm to me its not unresonable to think that he could build this motor correctly have it produce all the power it has the potential to do and still be disappointed at the lack of improvement at low speeds. I just think he should notice a seat of the pants difference on average over the whole rpm range.
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Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
No the OP did not post a dyno chart. I'm advising him to check the dyno chart to either confirm or deny my suspicion. More can be interpreted from a dyno chart other than just the peak HP and torque levels. Look at where these events happened.
Torque is what you feel in the seat of your pants not HP. Hp is more a function of rpms. Notice on any dyno chart for a 350 where lots of hp is produced it occurs at high rpms. That is why a 350 is limited by the duration of the cam for high HP output. It takes lots of duration on the cam to get high rpm performance. It takes cubic inches to produce torque. More cubes more torque. Then multiply the high torque by moderate rpm and you get high HP numbers. Or lower torque by higher rpm to get same HP.
Torque is what you feel in the seat of your pants not HP. Hp is more a function of rpms. Notice on any dyno chart for a 350 where lots of hp is produced it occurs at high rpms. That is why a 350 is limited by the duration of the cam for high HP output. It takes lots of duration on the cam to get high rpm performance. It takes cubic inches to produce torque. More cubes more torque. Then multiply the high torque by moderate rpm and you get high HP numbers. Or lower torque by higher rpm to get same HP.
Last edited by REELAV8R; Jan 15, 2013 at 12:58 PM.
Race Director
Joined: Oct 2000
Posts: 15,055
Likes: 79
From: central FL, near the beach.
REE
with the 320* intake duration, what is the DCR?
9.6 SCR. must be really low dcr. like what 5.5:1?
The cam is both too big(seat to seat) and too small 212 at 050.
XE262 would perk it up, with proper base gasket of course.
with the 320* intake duration, what is the DCR?
9.6 SCR. must be really low dcr. like what 5.5:1?
The cam is both too big(seat to seat) and too small 212 at 050.
XE262 would perk it up, with proper base gasket of course.
Le Mans Master
Joined: Dec 2009
Posts: 6,397
Likes: 649
From: Saskatoon Saskatchewan
Yes, it would be helpful if he'd post a dyno chart. As it is now we have his subjective opinion that no change was felt and the only objective fact is that it produced 260 rear wheel horsepower at some point I was on comp cams selection program for a couple of days looking at 350's with Vortec heads and cams producing between 310 and 350 (gross) horsepower. They were all similar to the one the OP used with maybe up to 10 percent difference in total lift between some of them but not a huge variance in horsepower figures and all produced peak horsepower at about 4500 rpm with only a few hp dropoff at 5000 rpm and a more signiciant drop at 5500 rpm
Le Mans Master
Joined: Dec 2009
Posts: 6,397
Likes: 649
From: Saskatoon Saskatchewan
For example, a couple of the cams I looked at with the 350 vortec (tuned port injection) combination:
1).449 lift intake .456 exhaust intake, 212 intake duration at 50thou, 218 exhaust duration at 50 thou, 112degree centerline
344 hp @ 4500 rpm, 341 hp @ 5000 rpm, 310 hp @5500 rpm
max 477 ft/lb torque at 2000 rpm
2).464 lift intake .470 exhaust intake, 218 intake duration at 50 thou, 224 exhaust duration at 50 thou, 114 degree centerline
346 hp @4500 rpm, 345 hp @5000 rpm, 315 hp @5500 rpm
max 468 ft/lb torque at 2000 rpm
1).449 lift intake .456 exhaust intake, 212 intake duration at 50thou, 218 exhaust duration at 50 thou, 112degree centerline
344 hp @ 4500 rpm, 341 hp @ 5000 rpm, 310 hp @5500 rpm
max 477 ft/lb torque at 2000 rpm
2).464 lift intake .470 exhaust intake, 218 intake duration at 50 thou, 224 exhaust duration at 50 thou, 114 degree centerline
346 hp @4500 rpm, 345 hp @5000 rpm, 315 hp @5500 rpm
max 468 ft/lb torque at 2000 rpm
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
My total objective with my C2 is 500+ Hp, low rear gearing, 6 speed manual, Decent street manners, an extra 150+ HP with the nitrous and good MPG. Looking for the C6 performance package with C2 styling. Never good enough but I will eventually get there.
Safety Car
Joined: Jan 2009
Posts: 3,736
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From: anchorage ak
bluedawg
So uch earlier do you get up, to get to work on time idling just reduces engine life. All those r's and no forward movement.
35-40 mph takes about 10 hp, and the engine can't tell the difference between that and idling.
BUT, with an opeen base gasket, my 61 would sometimes stall if i tried to drive off gently on a cold start. 4 holer fixed that quirk. And it only needs 1000 rpm for fast idle. Open gasket, it needed 1500-2000 and it would still stall
sometimes, very annoying, even dangerous when pulling out into atlantic ave.
BUT, not ever again, since 2007 when i sealed off the 2 planes, and blocked the extra carb cross passages.
So uch earlier do you get up, to get to work on time idling just reduces engine life. All those r's and no forward movement.
35-40 mph takes about 10 hp, and the engine can't tell the difference between that and idling.
BUT, with an opeen base gasket, my 61 would sometimes stall if i tried to drive off gently on a cold start. 4 holer fixed that quirk. And it only needs 1000 rpm for fast idle. Open gasket, it needed 1500-2000 and it would still stall
sometimes, very annoying, even dangerous when pulling out into atlantic ave. BUT, not ever again, since 2007 when i sealed off the 2 planes, and blocked the extra carb cross passages.
he can probably tear down and rebuild a carb blindfolded better then some of us can do with our eyes open and a manual
Race Director
Joined: Oct 2000
Posts: 15,055
Likes: 79
From: central FL, near the beach.
Priya
isn't comparing a XE256, 256* at .006" with a 320* at lash cam folly? there is at least 40* more duration with the 320. it has to be doggy at low rpm, doesn't it?
bluedawg
Below zero temps require special techniques not familiar to me. The coldest i drove a vette was 17F and as soon as i could drive off without having it stall, was good enough for me. Never had any engines fail ever.
isn't comparing a XE256, 256* at .006" with a 320* at lash cam folly? there is at least 40* more duration with the 320. it has to be doggy at low rpm, doesn't it?
bluedawg
Below zero temps require special techniques not familiar to me. The coldest i drove a vette was 17F and as soon as i could drive off without having it stall, was good enough for me. Never had any engines fail ever.
Le Mans Master
Joined: Dec 2009
Posts: 6,397
Likes: 649
From: Saskatoon Saskatchewan
Safety Car
Joined: Jan 2009
Posts: 3,736
Likes: 56
From: anchorage ak
I would love a new zr1. I think a cheap attemp to gain lower rpm would be to to advance the cam 4 degrees, from the way you guys talk about the cam the op is running its an old design with slower ramp rates. So maybe a modern design would be beneficial.
Mat you do run an open hole devider? I hear thats the new nitrous...lol. just joshin ya. Your hate for the cut down divider is fasinating to me. So much ill probably investigate that more this summer.
I know that people have good results with vortecs, bk's combo works well for him. I beleave that the foundation for any performance build should be the heads, the better your heads flow the smaller camshaft you can get away with running, hitting the powre goal, and maintaining ones ideal of streetable. I always suggest afrs, runner volume depending on cubic inch and rpm range. You always get they cost so much, but only a rich man can afford cheap parts. Along the same lines if your building a small block for perfomance, building a 383 instead of a 350 makes it easier to hit the desired power goal with out loosing streetability, and doesnt cost much more if you have to replace the crank and rods any how.
Mat you do run an open hole devider? I hear thats the new nitrous...lol. just joshin ya. Your hate for the cut down divider is fasinating to me. So much ill probably investigate that more this summer.
I know that people have good results with vortecs, bk's combo works well for him. I beleave that the foundation for any performance build should be the heads, the better your heads flow the smaller camshaft you can get away with running, hitting the powre goal, and maintaining ones ideal of streetable. I always suggest afrs, runner volume depending on cubic inch and rpm range. You always get they cost so much, but only a rich man can afford cheap parts. Along the same lines if your building a small block for perfomance, building a 383 instead of a 350 makes it easier to hit the desired power goal with out loosing streetability, and doesnt cost much more if you have to replace the crank and rods any how.
Last edited by bluedawg; Jan 15, 2013 at 03:01 PM.
Le Mans Master
Joined: Dec 2007
Posts: 6,422
Likes: 591
From: McHenry Illinois
Hey bluedawg, I spent 18 yrs on the slope, the off time is awesome, but the work away from home started to suck, I feel for ya! Stay warm!!
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
REE
with the 320* intake duration, what is the DCR?
9.6 SCR. must be really low dcr. like what 5.5:1?
The cam is both too big(seat to seat) and too small 212 at 050.
XE262 would perk it up, with proper base gasket of course.
with the 320* intake duration, what is the DCR?
9.6 SCR. must be really low dcr. like what 5.5:1?
The cam is both too big(seat to seat) and too small 212 at 050.
XE262 would perk it up, with proper base gasket of course.
I just looked it up and looks like your right.
http://www.gmpartsdirect.com/results...umber=24502476
Ok so maybe it is timed in right. He could still benefit from advancing it some....maybe. Ultimately it needs to be a shorter duration cam. This must be a very old school cam for that slow of a ramp.
Not sure I'm doing this right because the numbers look crazy to me, but when I put in numbers to get a 9.6:1 SCR for a 320* cam with a 112 lsa (guessing that one) it comes up with a DCR of 5.82. Also gives me an intake valve closing angle of 92.5*. That sounds crazy late to me.
I'd say mystery solved. Thanks matt I hadn't bothered to look up the cam and made some bad assumptions. since I'm new to this I had no idea that a cam could be a 320* lash and have a 212@.050. Wow!
You'd have to kick up the SCR to around 12.5:1 to get the SCR up to something reasonable.