Weav's Vet

I feel like I have the wrong cam in my motor. I've been thinking about advancing it to shift the rpm range down so I can get more torque. All of my dyno results have shown low torque. 338 was its highest. I was doing some online research and ran across this post in a thread on another forum.

The short story is, if you have to advance or retard a cam to compensate for anything, you've chosen the wrong duration. Either you've chosen a cam that is too small and you retard it, or you've chosen a cam that is too big and you have to advance it to recover the low end.

This is one place where dyno simulation software is valuable. It might not accurately predict your final output, but it will tell you how duration and timing affect the trend for your combination.

So this has me thinking now about just getting a different cam.I was wondering if any of you guys have a simulator you can plug my numbers into so I can come up with a better duration to suit my needs. I guess I could just call Comp Cams or any other cam manufacture and get this answer but I thought this may be a little more accurate. Or perhaps some of you have similar mods and are happy with the cam you have and will share that info with me.

Thanks,
Mike

neat

I don't think you've got anywhere near too much duration. I would have went bigger if it were my car. The crew on here will preach to you about how "the most common mistake is over camming" but in the really real world, you aren't even close to too big.

What RPM are you beginning the dyno chart at? Sometimes, with an auto, you have to start the pull at an RPM that is higher than the torque peak.

If it's not a dyno issue, then I would look at stuff other than the cam.

Does the car feel sluggish or anything at low RPM? Do you have any data logging gear? Any idea what kind of timing curve the engine is using? You can dink with the fuel curve to make the car feel more torquey down low if you want, etc...

I think you've got a pretty solid combo, it's on the milder side (IMO) but it looks like you picked decent parts.

Marv02

What size motor, What are the cam specs, What heads and size runners do they have, And intake which one Base plate and runner size on them, Auto Or Man, Rear end gears.
Exhaust also matters.

I not a Car builder god.

But after Many Many years of racing and bulding bikes I Know even you have the best parts in the world if they don't macth up for what you want the motor to do You have a slug of a combo.

I had a El Camino once I was off 1 tooth on the distributor it would run but no bottom end I just advance it 1 tooth and it fixed every thing.

STL94LT1

Midnight 85

This is just my opinion but your duration looks good but that sure a lot of lift. If it were me I would be talking to Comp Cams, they are the experts in cam selection.

383vett

If your motor is a 350 I wouldn't go with a longer duration cam, but I don't think it is too large. Do you have the stock compression? Is your combustion chamber larger than stock? Did your tuner add in enough advance? Your numbers should definitely be higher.

Weav's Vet

The dyno start rpm issue is being addressed on my next set of pulls. Up to now the operator has had to get past it drop shifting to start the pull about 2200 or 65 mph I think. Tuner is going to disable that feature in 3rd so he can just floor it from the get go when it hits 3rd gear. Maybe that will show better results or at least a better torque curve.

The car feels pretty good actually starting off. I probably need a little more stall though. It always seemed sluggish on the top end. Changing to the 1 3/4 headers seems to have fixed that. It just wants to run when it's all over at the track.

Yes have logging gear. Spark tables are beyond my comprehension.

I played with some different wot AFR tunes last night. It seems to like 13.3 the best.

vader86

I think that cam is fine for the engine as it is, and I agree I'd probably have given it a little more duration if it was in my car.

I'm surprised it is not higher output though, and again second the datalogging necessity to see if something is not tuned right.

Weav's Vet

Stock bottom end. 026 head gasket and stock compression numbers. 58cc chamber. I'm in his hands as far as spark advance goes.

Cam card

Weav's Vet

Thanks Vader this is exactly what I feel. I really wanted this data logging thing to work but I may have to just get a dyno tune to get it maxed out. I hate that, 400.00 here.

neat

The only way I know to disable the shifting deal results in a good bit less line pressure in the trans. That can be pretty hard on the trans for a WOT dyno run. Your tuner might know another way to do it without dropping the line pressure, but it might be worth asking about.

You might try contacting Craig Staples up in Raleigh/Durham. He used to have shop up there, but it closed about a month ago. He was probably the best LT1 guy around.

Depending on what you needed as far as a tune, his base price was $300 give or take a bit. I dunno if still has the dyno kicking around somewhere, or even if he is still doing performance work, but it might be worth tracking him down. You should be able to find him on www.horsepowerjunkies.com if you ask around.

383vett

Just for ducks, maybe slap on some drag radials and take it out to the track and see what it runs. A lot of times, too much time is spent on the dyno and too much emphasis placed on dyno numbers. It's the real world that counts and 1/4 mile times and mph will tell you alot about your combination.

dizwiz24

.530 is not a lot of lift. In fact, with his AFR heads, he should have more lift than that.

There is almost no such thing as too much lift. This is another area the LSx motors improved upon the LTx motors was lift. They run 1.7:1 (and I think Z06 may have 1.8:1) roller rockers vs. our stock 1.5:1

Scorpion does make 1.7:1 roller rockers. You need pushrod guideplates though, but they work and are reliable.

A guy on here going by the name of nathan plemons (if he is still around the board), ran 1.7:1 roller rockers on an amateur-ported stock head/cam/lt headers/ electric water pump stock displacement 92 lt1 and made some 375 rwhp.

aboatguy

He has a 4L60E so the shifts are controlled by the ecm.....

Mike you have the right cam.....however, I believe your compression is a little lower than stock due to your 58cc combustion chambers, but the chamber size will help you out when you finally build a stroker.


MIke

LD85

100% I would even have went with a 230 or 233 intake duration

856SPEED

Well,

You had me curious and I had to break open my file on my engine specs....
first off 377rwhp is nothing to make light of, personally.....I think those are decent numbers in its own right.........338rwtq...not bad at all really b/c looking at your cam, this thing should make power a little on top with a 111 lobe sep. (valve overlap) and the short runner intake of the LT1 lends itself to lower torque (although flat) througout the range.....to put into perspective, my L98 (at the time) with the AFR/TPIS heads, ZZ9 roller cam made 380rwtq but it was a torque monster but only could hand over 296rwhp with the Edelbrock base/runners......that was on a fresh rebuild 355 (.030 overbore) back in 2004......

I am now running the miniram with the same cam, heads, etc. and it really woke it up well beyond the 4500 rpm range.....but anyway I was just looking at my ZZ9 roller cam from TPIS........

duration at .050: 212/226
lobe separation: 112
seat duration: 280/287

although the engine builder blue printing records show:

Adv. lift: 510/537
duration at .050: 209.5/226.25

my cam is installed at 107.25 degrees......per the engine builder spec. sheet...whatever that is worth

rather mild cam I have but I was worried about emissions at the time....not so much any more.....car does not require it due to age now.....

anyway........strong numbers..nice build.. in my opinion...........

Weav's Vet

Did that last night and this is why I'm so beat up over it.

Feb with stock heads in some really good air. Stock heads same cam. DA was 102' Relative Density was 99.7. Corrected to 12.3 @ 109



A month ago with 1 5/8 headers and AFR 195 st elim heads. DA was 2317'. Relative Density was 93.4%. Corrected come out to 12.2 @ 111



Last night. 1 3/4 headers DA was 2398' Relative Density was 93.17. Corrected to 12.1@111mph



So my point here is what did gain with 2400.00worth of heads and headers? Two tenths and 2 miles per hour? Maybe that's about right and I expected to much.

Weav's Vet

So let me see if I have this correct. My cam is basically ok for what I have compression wise. A better tune will probably help. No need in advancing the cam to move the peak torque range down any. Even though I'm not really happy about spinning this 98K motor to 6600 rpm ( although I shifted from 2nd to 3rd last night at about 6200)at the track to get the best numbers I can get. Correct?

856SPEED

wow....you are running real close to me......I run 111-112 mph in the quarter...but my times suck compared to yours....I can't muster better than a 2 second 60ft. with that six speed and worn out Dunlop 275's....I run 12.6's (with a 1.99 60 ft.) to 12.8's

shift at peak hp based on your dyno....compare different shift points.....I would think based on your set up, 6200 RPM is right wear you want to be maybe 6500 with your cam

mike100

Well, ok..long term you're gonna go 383 or better, which will solve the port volume and sluggish low end issues if you're having that...so don't spend too much money right now.

try advancing the cam a degree or two and put back on the 1 5/8's while youre running the 350. I don't see you dropping lower than 110 mph and you should be able to sport up the mid-range response to help out the time-distance issues that the track needs vs. the dyno racing aspect.