This is the dyno of the recent heads/cam/UD pulley addition I did on my '01 C5 MN6.
My original numbers were 333RWHP, 345RWTQ.
Here's the link to the graph--(the pic won't post here for some reason)
***EDIT you'll have to copy/paste the addy in a new window-- it won't link to here either <img border="0" title="" alt="[Roll Eyes]" src="images/icons/rolleyes.gif" /> /EDIT***http://temp.corvetteforum.net/c5/mdl...yno4-9-02a.jpg
I'm wondering what all the experience here has to say about the results(including that jaggedness at high RPM). The heads are essentially stock, with smoothing/casting flash removal--but little actual material removal and no reconfiguring--I look at them as optimized stock heads(w/comp springs,Ti retainers, CMoly pushrods, stock valves...)
The cam is 226/226_.591/.591 112.
I used it on the advise of a friend and a tuner from Texas.
Computer reprogramming by Ed Wright.
I'm rather dissapointed with the Torque gains-- only 19lb/ft!! <img border="0" title="" alt="[Mad]" src="gr_images/icons/mad.gif" />
The idle is sometimes embarassingly erratic...and is so rich at idle that you could practically put a match to it and it would ignite...When I first turn it on, it locks at 1500RPM, and won't settle at 1K (where it's set) until I've driven it a bit...even then, it still hunts and surges a lot--(occasionally stalling from diving down to as little as 200RPM!!!) PS--I have drilled the throttle plate 1/8th already--barely helped...it's not as bad as it used to be, but it's still a pretty big issue.
The car feels incredibly strong after 4K, and it literally sounds like a race car at WOT--but it doesn't show at the track--(DISCLAIMER-I'm a mediocre track driver--only a few months experience there <img border="0" title="" alt="[Embarrassed]" src="gr_emb.gif" /> ) I'm up to 116.xMPH from 113.x trap speed, but for the life of me, I couldn't get lower than the previous best of 12.5 (w/Firehawk Run Flats)in the Qtr <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />
So, tech guru's-- please tell me what you think of my situation, and any ways to improve it--
Thanks, and sorry this is so long--just wanted all the variables known <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

<small>[ April 17, 2002, 10:44 PM: Message edited by: MDL-01C5 ]</small>

 

Umm, I don't see a problem.
Looks good!

Depends how they do the graph averaging. Some minor spikes like that are ok. You see more of them as your engine temp goes up. But you aren't seeing anything unusual. You can print the graph in diff modes that smooths out the curves or not. A/F at WOT looks good. Can't comment on part throttle A/F.

 

Possibly just a touch too much timing is causing the jaggedness. You only see the high amounts of timing at the top of the rev range, and it can slighty pull down power. Any clue how much advance you're getting up top? 30 degrees or more? I didn't lose sleep when my dyno looked like that.

J.

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by MDL-01C5:
<strong>This is the dyno of the recent heads/cam/UD pulley addition I did on my '01 C5 MN6.
My original numbers were 333RWHP, 345RWTQ.
Here's the link to the graph--(the pic won't post here for some reason)
***EDIT you'll have to copy/paste the addy in a new window-- it won't link to here either <img border="0" title="" alt="[Roll Eyes]" src="images/icons/rolleyes.gif" /> /EDIT***http://temp.corvetteforum.net/c5/mdl...yno4-9-02a.jpg
I'm wondering what all the experience here has to say about the results(including that jaggedness at high RPM). The heads are essentially stock, with smoothing/casting flash removal--but little actual material removal and no reconfiguring--I look at them as optimized stock heads(w/comp springs,Ti retainers, CMoly pushrods, stock valves...)
The cam is 226/226_.591/.591 112.
I used it on the advise of a friend and a tuner from Texas.
Computer reprogramming by Ed Wright.
I'm rather dissapointed with the Torque gains-- only 19lb/ft!! <img border="0" title="" alt="[Mad]" src="gr_images/icons/mad.gif" />
The idle is sometimes embarassingly erratic...and is so rich at idle that you could practically put a match to it and it would ignite...When I first turn it on, it locks at 1500RPM, and won't settle at 1K (where it's set) until I've driven it a bit...even then, it still hunts and surges a lot--(occasionally stalling from diving down to as little as 200RPM!!!) PS--I have drilled the throttle plate 1/8th already--barely helped...it's not as bad as it used to be, but it's still a pretty big issue.
The car feels incredibly strong after 4K, and it literally sounds like a race car at WOT--but it doesn't show at the track--(DISCLAIMER-I'm a mediocre track driver--only a few months experience there <img border="0" title="" alt="[Embarrassed]" src="gr_emb.gif" /> ) I'm up to 116.xMPH from 113.x trap speed, but for the life of me, I couldn't get lower than the previous best of 12.5 (w/Firehawk Run Flats)in the Qtr <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />
So, tech guru's-- please tell me what you think of my situation, and any ways to improve it--
Thanks, and sorry this is so long--just wanted all the variables known <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">First of all, if you're saying those are stock heads with just alittle material removal but no porting, and then a cam, and you have 404RWHP, I'd be happy, not confused. The most I've ever heard of on a C5 with stock heads was 385RWHP.
It was a 560 lift cam though, and also cam swaps with stock heads is not common on C5s.

I would guess that tuning (Ed Wright) should be able to fix your idle and torque issue. Did you get back in touch with him? I'm sure if you richened it up around the 3.5k-5k band, you'd get some torque back.

 

Don't get me wrong--I'm thrilled with the 70HP increase!!! The only reason I prettied up the stock heads and used them was that the "real" heads, (that me and a friend spent 40+ hours making perfect(and VERY ported/polished)with custom back-cut Ferrea valves at 2.02" and 1.57" w/ competition valve job) were over decked from the guy I bought them from (Ebay)without me knowing it--he evidently ground a good bit off them to make them look good, so when I went to true the surface at my machinist, he had to shave 15 thousanths to get it flat <img border="0" title="" alt="[Mad]" src="gr_images/icons/mad.gif" /> which, as a result of all the material that'd been taken off, combined with the big lift, only left me with 50 thousanths exh. valve clearance--not enough to be safe...rendering them useless with this cam <img border="0" alt="[whiner]" title="" src="graemlins/gr_cry.gif" />
Since I have to redo the "Stage II+" heads,which will take me God knows how long to get around to, and wanted to get the car running again, I just put about 8 hrs of educated surfacing work into the stockers, since they were already off and I could put them right back on.
With this dyno info, you think would Ed really be able to fine tune my program to get more power and idle quality?
Thanks -- Matt

 

TTT--any other views/opinions?

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by MDL-01C5:
<strong>TTT--any other views/opinions?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">First you should raise idle speed with idle adjust screw, an extra 100 rpm would clean up idle big time, and help with idle hunting, second you could run head gaskets on the thick side, advance cam in engine, and run healthy valve springs, and or rev kit from ARE and still use those overmachined heads, if you still cant live with the clearance my suggestions would give you, than have exhaust valves sunk in heads by regrinding seats, this wouldnt hurt flow or power much and would give you more clearance. I think your crazy if you abandon those prepped heads!

 

How do you know you only have .050" clearance? Did you drop the valve down with the piston at TDC? Heads with 2.02 intake valves and only .015" shaved off is not going to have much of a chance of hitting with 226 degrees of duration.

When we measured my heads (cut .050" & 2.02 valves), we were safe in P to V until about 230 duration at .050. Lift is pretty irrelevant since max lift occurs with the piston well down in the cylinder bore.

 

LS1derful--I thought of that, and used the Cloyes Adj. timing chain to advance it 1.5 degrees-- it is pre-advanced 4, and we didn't want to over-do it--the Comp springs are good for the app... I'm unfamiliar with the "rev kit"--what is it? We were '_' close to recessing the valves, but we then had to find a way to compensate the valvetrain geometry...
Patrick-- we measured the P/V clearance by measuring between the tq'ed down rocker and the valve at TDC, as well as the approach of the piston and the downswing. Also, it's important to note that the 15 thousanths was removed by me was just to true it...we don't know how much the seller took off, but it was of course enough to cause all the clearance issues.. the problem was with the exhaust, not the intake--that was fine. the tightness occurred when the piston was traveling up towards TDC and the valve was closing, it was chasing the ex valve on the upswing and at lowest clearance, was ~.050.

 

Ok, rev kit is spring mounted on lifters sandwiched between cyl. head and lifter, it takes some of the control responsibility from the valve spring, by keeping lifters firmly planted on cam, this is done without applying spring pressure on hydraulics of lifter, only on body of it, so it doesnt try to collapse. They are a great idea, and this lifter tension actually helps lifter reliability, by not letting bearings get hammered from bouncing up and down, So did you check ptv with checking springs, and is .050 with cam in 5.5 degrees advanced? It seems kind of weird you only have tight exh. valve clearance, when both valves have less clearance from grinding heads. So you definitely degreed actual int. centerline before testing?

 

ok...I am the infamous friend..lcvette.. the heads were brought to me and appeared in great shape until they were measured under the scrutinous eyes of a seasoned machinist.. they were roll warped from front to back short length and required some milling (.015" to be exact).. unfortunately the seller from ebay brought it upon him self to use a sears belt sander apparantly, as bad as the warpage was, to try and make the heads cosmetically pleasing. this left us with two new dilemas.. the valvetrain was out of whack with the non adjustable rocker arms.. no biggie.. custom length pushrods right! ok so we measure with pushrod checker and get the correct length and then we test our P2V clearances.. all seemed well until the piston was on its exhaust stroke and pinched clearance to .046".. being from the old school, i feel much more comfortable with at least .100" and better with .120" clearance at its smallest tolerance. so we weighed the options.. recess the valves... this is still our most considered and cost effective solution, but i feel .054" is alot of milling and then i would question the integrity of the valve seat.. if the costs became too much this route we thought of notching the pistons with a valve relief cutting tool.. this seemed a bit sketchy on the stock cast pistons.. so we considered new notched pistons in a forged metal. all will be labor intensive... this is where we turn to the mass of experienced LS1 engine techies to help us make an informed decision.. anyone with experience in LS1 specific valve relief cutting, valve recessing, or knows of a place which sells a rev kit which would add some peace of mind for such a tight clearance as we have please submit your input as we respect and appreciate your knowledge and experience. if you have any other questions please post i would be more then happy to bring any information i may have overlooked into the discussion to better reflect the current predicament. Thanks and best regards,

Chris

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by LS1derfull:
<strong> </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by MDL-01C5:
<strong>TTT--any other views/opinions?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">First you should raise idle speed with idle adjust screw, an extra 100 rpm would clean up idle big time, and help with idle hunting, second </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Y-Bodies lack a cable driven TB, our is throttle by wire <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

 

Jagged could be detonation or it was breaking up a little. Tell us about the mileage on the cars, and the plugs you are using and the gap.

Surging is a sign that the car is rich down low. Autotap down low and send that data to Ed Wright.

 

Hey John-- the mileage on the car seems to have taken less of a hit than I expected it to-- my instant HWY is ~28MPG-- only a 2-3 mpg hit.
I'm using champion plugs gapped at the stock 60.
(I realized at the last minute that I forgot to get some good ones <img border="0" title="" alt="[Embarrassed]" src="gr_emb.gif" /> )--NGK 55's will be her in this weekend. (How do you think I should gap them, BTW?)
I'm actually wondering if that could be having an impact...your thoughts?
I don't have any access to autotap or any other diagnostic/tuning software, unfortunately...
Thanks...

 

Matt,
Generally with a gapping tool.. but in your case i would drop them from approx. 4' on the concrete threads down until the electrode touches <img border="0" alt="[jester]" title="" src="graemlins/gr_jest.gif" /> just kidding.. i forgot you put those nasty champions in there..... get some good plugs.. the NGK's are great, i use Autolites.. i know i know, the cheap *** autolite have lasted longer and cleaner without fouling or misfiring up high then any other plug i've ever used.. go figure.. im hooked!!!

everytime i decided to try a different plug i wind up dissapointed!! im sticking with the cheap ones!!

<small>[ April 25, 2002, 08:53 AM: Message edited by: lcvette ]</small>

 

I'm going to order the .078 Cometic head gaskets which will give me a .023 increase in clearance for the good set of heads. Then, I'm going to have the ex. valve seats recessed the remainder of the way to aquire 100 thths. PV. which is ~.025. At that point, I should be good to go with the original heads. Any opinions on this course of action?
Thanks-- Matt

 

I'd go with a .048-.050 gap.

 

Matt,
you need to machine both intake and exhaust valves and have our machinist level the valve stem tips to the same height.. if you don't you will require two different sizes of everythihng from spring shim heights to pushrods, you want to keep everyhting the same the sake of valvetrain geometry. i will talk to you more about that this afternoon when i see you!!

Chris

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by lcvette:
<strong>ok...I am the infamous friend..lcvette.. the heads were brought to me and appeared in great shape until they were measured under the scrutinous eyes of a seasoned machinist.. they were roll warped from front to back short length and required some milling (.015" to be exact).. unfortunately the seller from ebay brought it upon him self to use a sears belt sander apparantly, as bad as the warpage was, to try and make the heads cosmetically pleasing. this left us with two new dilemas.. the valvetrain was out of whack with the non adjustable rocker arms.. no biggie.. custom length pushrods right! ok so we measure with pushrod checker and get the correct length and then we test our P2V clearances.. all seemed well until the piston was on its exhaust stroke and pinched clearance to .046".. being from the old school, i feel much more comfortable with at least .100" and better with .120" clearance at its smallest tolerance. so we weighed the options.. recess the valves... this is still our most considered and cost effective solution, but i feel .054" is alot of milling and then i would question the integrity of the valve seat.. if the costs became too much this route we thought of notching the pistons with a valve relief cutting tool.. this seemed a bit sketchy on the stock cast pistons.. so we considered new notched pistons in a forged metal. all will be labor intensive... this is where we turn to the mass of experienced LS1 engine techies to help us make an informed decision.. anyone with experience in LS1 specific valve relief cutting, valve recessing, or knows of a place which sells a rev kit which would add some peace of mind for such a tight clearance as we have please submit your input as we respect and appreciate your knowledge and experience. if you have any other questions please post i would be more then happy to bring any information i may have overlooked into the discussion to better reflect the current predicament. Thanks and best regards,

Chris</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">We've notched the stock pistons in a solid roller application with no problems. The motor is still going strong with no sign of pistion trouble, this was the motor in Jason99T/A's Trans Am. It is very easy to do with the notching tool. We also had to increase the size of the reliefs in my forged Lunati pistons (it did use up 2 cutters unfortunately--sorry Geoff)

Shane

<small>[ April 26, 2002, 12:19 PM: Message edited by: XtraCajunSS ]</small>

 

I've decided to recess valves 30 thousanths, and go with .078 steel gaskets from cometic-- I'm wondering now how you think I'll do...