Aftermarket cam grinds for 4 valve motors
07-08-2005, 04:19 PM
#16
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FWIW, I used elgins to regrind my GT cams - .020" over stock gt, w/968 valves, stock GT springs/lifters and it seems to idle fine, but it does leave big black marks on the driveway (no dyno #'s, but melting a 18/285/50 for over 30' w/ 1/2 throttle pretty much says it all for me)... I changed so much stuff, I really don't know how much is just from the cams, but elgins thought about 25-35hp at the crank was a reasonable expectation for that grind on a 6.4L motor, at 3k-5500k rpms...
according to elgins, anything over that and you'll have issues w/stock springs/lifters and idle/street use w/an AT 928... they also have some custom 928 cam indexing jigs that help keep timing spot on... $700 and 2 week turn around included nitriting... nice guys too!
hope this helps...
you'll also have to make your valves the right ht for the new cam specs, so be ready...
according to elgins, anything over that and you'll have issues w/stock springs/lifters and idle/street use w/an AT 928... they also have some custom 928 cam indexing jigs that help keep timing spot on... $700 and 2 week turn around included nitriting... nice guys too!
hope this helps...
you'll also have to make your valves the right ht for the new cam specs, so be ready...
07-09-2005, 04:16 PM
#17
Lag: "I don't care what the magazines say,"
Well that's a very telling statement...
"I've seen many many many dyno sheets from all over the world, and every single stock Z06 dynos between 340-355 at the rear wheels (..DynoJet). EVERY SINGLE ONE."
A 15hp spread on a motor that's only in the mid 300hp range. Not exactly what i'd call particularly accurate.
As power increases so will the margin of error.
This is why 5000hp top fuel motors(let alone turboprops or locomotives) don't even bother with dynos. The margin of error would be ridiculously large.
"Just because a magazine may have 'discovered' some unscrupulous shops doesn't invalidate the rest of the shops that run their dynos correctly."
No, but there is no denying that there's an inherent innacuracy, as witnessed by your claim that stock Zo6s all dyno within 15hp of one another using the same exact settings on the exact same model number dyno.
"'Wildly overrated IMO'?? That's funny! Just curious, have you even dyno'd a car before?"
Sure have. I was a Pa licensed emisions technician for 5 years, Pa uses a chassis dyno for emissions testing.
This one:
"Nonetheless, that's just your opinion, and you're entitled to it; however, I disagree. A timeslip is GREAT stuff, but there's way too many variables from run to run versus a controlled SAE dyno run."
You simply go by your best ET and best trap speeds, and average the two with the appropriate conversion formulas. It's a very accurate measure of actual useable power.
To me, the only way a dyno is truly useful is if you're using the same one all the time, as Greg stated. It may be off by a set %, but at least it will be 100% consistent in it's error.
But i digress, i don't want to hijack this fellas thread.
Well that's a very telling statement...
"I've seen many many many dyno sheets from all over the world, and every single stock Z06 dynos between 340-355 at the rear wheels (..DynoJet). EVERY SINGLE ONE."
A 15hp spread on a motor that's only in the mid 300hp range. Not exactly what i'd call particularly accurate.
As power increases so will the margin of error.
This is why 5000hp top fuel motors(let alone turboprops or locomotives) don't even bother with dynos. The margin of error would be ridiculously large.
"Just because a magazine may have 'discovered' some unscrupulous shops doesn't invalidate the rest of the shops that run their dynos correctly."
No, but there is no denying that there's an inherent innacuracy, as witnessed by your claim that stock Zo6s all dyno within 15hp of one another using the same exact settings on the exact same model number dyno.
"'Wildly overrated IMO'?? That's funny! Just curious, have you even dyno'd a car before?"
Sure have. I was a Pa licensed emisions technician for 5 years, Pa uses a chassis dyno for emissions testing.
This one:
"Nonetheless, that's just your opinion, and you're entitled to it; however, I disagree. A timeslip is GREAT stuff, but there's way too many variables from run to run versus a controlled SAE dyno run."
You simply go by your best ET and best trap speeds, and average the two with the appropriate conversion formulas. It's a very accurate measure of actual useable power.
To me, the only way a dyno is truly useful is if you're using the same one all the time, as Greg stated. It may be off by a set %, but at least it will be 100% consistent in it's error.
But i digress, i don't want to hijack this fellas thread.
07-09-2005, 05:07 PM
#18
Three Wheelin'
Originally Posted by m21sniper
Lag: "I don't care what the magazines say,"
Well that's a very telling statement...
"I've seen many many many dyno sheets from all over the world, and every single stock Z06 dynos between 340-355 at the rear wheels (..DynoJet). EVERY SINGLE ONE."
A 15hp spread on a motor that's only in the mid 300hp range. Not exactly what i'd call particularly accurate.
As power increases so will the margin of error.
Well that's a very telling statement...
"I've seen many many many dyno sheets from all over the world, and every single stock Z06 dynos between 340-355 at the rear wheels (..DynoJet). EVERY SINGLE ONE."
A 15hp spread on a motor that's only in the mid 300hp range. Not exactly what i'd call particularly accurate.
As power increases so will the margin of error.
"Just because a magazine may have 'discovered' some unscrupulous shops doesn't invalidate the rest of the shops that run their dynos correctly."
No, but there is no denying that there's an inherent innacuracy, as witnessed by your claim that stock Zo6s all dyno within 15hp of one another using the same exact settings on the exact same model number dyno.
No, but there is no denying that there's an inherent innacuracy, as witnessed by your claim that stock Zo6s all dyno within 15hp of one another using the same exact settings on the exact same model number dyno.
It is no 'claim'; it's a FACT! GO LOOK IT UP!!! And while you're at it, go look up the factory horsepower numbers of a 2001 Z06 versus the 2002-2004 models.BTW, are you not familiar with engineering tolerances, and that one engine from the next will not put out the same amount of horsepower? This is getting ridiculous...
"'Wildly overrated IMO'?? That's funny! Just curious, have you even dyno'd a car before?"
Sure have. I was a Pa licensed emisions technician for 5 years, Pa uses a chassis dyno for emissions testing.
This one:
Sure have. I was a Pa licensed emisions technician for 5 years, Pa uses a chassis dyno for emissions testing.
This one:
"Nonetheless, that's just your opinion, and you're entitled to it; however, I disagree. A timeslip is GREAT stuff, but there's way too many variables from run to run versus a controlled SAE dyno run."
You simply go by your best ET and best trap speeds, and average the two with the appropriate conversion formulas. It's a very accurate measure of actual useable power.
To me, the only way a dyno is truly useful is if you're using the same one all the time, as Greg stated. It may be off by a set %, but at least it will be 100% consistent in it's error.
You simply go by your best ET and best trap speeds, and average the two with the appropriate conversion formulas. It's a very accurate measure of actual useable power.
To me, the only way a dyno is truly useful is if you're using the same one all the time, as Greg stated. It may be off by a set %, but at least it will be 100% consistent in it's error.
07-09-2005, 05:22 PM
#19
Rennlist Member
Dynos....ahh, my favorite topic!
So many factors, so little time!
To minimize the factors, jsut stick to SAE numbers. Each dyno manuf has doen their best to integrate the SAE CF standards and they are all VERY close. The DynioJets may not be tolerenced to the nth degree, maybe +/-3% one to another, but clsoe enough that we can make good judgement o perfromance "trends".
One thing I will state is a fact. Put two 928's on a dyno, the one with the most average hp under the "important" part of the curve (as defined by the trans ratios and "used" rpms) will win the drag race every team.
Drag racing is considerably too driver dependent...and I know I suck at it
Made three runs, barely made it home on a shredded clutch......car never smelled the same 
I have also seen at Sears on Wed nights and watched one car, three drivers, and every time was different.
Marc
So many factors, so little time!
To minimize the factors, jsut stick to SAE numbers. Each dyno manuf has doen their best to integrate the SAE CF standards and they are all VERY close. The DynioJets may not be tolerenced to the nth degree, maybe +/-3% one to another, but clsoe enough that we can make good judgement o perfromance "trends".
One thing I will state is a fact. Put two 928's on a dyno, the one with the most average hp under the "important" part of the curve (as defined by the trans ratios and "used" rpms) will win the drag race every team.
Drag racing is considerably too driver dependent...and I know I suck at it
Made three runs, barely made it home on a shredded clutch......car never smelled the same I have also seen at Sears on Wed nights and watched one car, three drivers, and every time was different.
Marc
07-09-2005, 05:26 PM
#20
Rennlist Member
Rob,
That is amazing pricing on the cams! Damn ... I cant touch it.
When are you dynoing the engine ... sounds like it should make about 400 - 425 rwhp based on components.
The best we ever made with stock GT cams was 440 rwhp. Most end up at 400 +/-15.
Marc
That is amazing pricing on the cams! Damn ... I cant touch it.
When are you dynoing the engine ... sounds like it should make about 400 - 425 rwhp based on components.
The best we ever made with stock GT cams was 440 rwhp. Most end up at 400 +/-15.
Marc
07-10-2005, 05:58 PM
#21
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BTW, are you not familiar with engineering tolerances, and that one engine from the next will not put out the same amount of horsepower?
I don't trust everything the mags and OEMS report - ever since 0-60 became the "rolling start 0-60", it just got too wierd for me... kinda like unemployment numbers only counting those currently elgible for unemployment benefits..
Rob,That is amazing pricing on the cams! Damn ... I cant touch it.
When are you dynoing the engine ... sounds like it should make about 400 - 425 rwhp based on components.
The best we ever made with stock GT cams was 440 rwhp. Most end up at 400 +/-15.
Marc
When are you dynoing the engine ... sounds like it should make about 400 - 425 rwhp based on components.
The best we ever made with stock GT cams was 440 rwhp. Most end up at 400 +/-15.
Marc
should know next week or so... was hoping for around 400-425rwhp, but as we all know - lots of little stuff can affect the numbers/devil is in the details for sure - it's an AT car, so that alone is a bit of a handicap for RWHP numbers... guess we'll see what all the goodies did to help offset that - as long as it melts tires, passes smog, and isn't a maintenance nightmare I"m going to consider it a success - getting lucky in it wouldn't be bad either!! ha!
of course, if my numbers are "just too low", that x-pipe of yours will be the 1st to go!!! hahaha!
but like I said - it's easily melting tires already w/out ANY tuning or even the cold air intakes or airbox on!! yeehaa!back to cams: IMO, application is the key factor when considering options w/cams, port sizes & valves - changes in geometry can yield some great rpm specific power #'s, but at a price in reliability/drivability more than any other NA stuff (spring tension/idle issues etc vs changes in displacement/stroke/FI) ... it just all leads back to that "all part of a balanced system of tradesoffs" thing, what's right for one app will be a disaster for another, so you need to establish the usage/goals before you can effectively determine the suitablilty of any deviations from OEM specs....
07-10-2005, 06:17 PM
#22
Rob,
That is amazing pricing on the cams! Damn ... I cant touch it.
Marc
That is amazing pricing on the cams! Damn ... I cant touch it.
Marc
They quoted 400 pounds, which is about $750 USD. Also they said, without seeing them, they didn't think the cams were nitrided. They thought probably just black phosphate coated. They would investigate when the cams turned up. Does anybody know for sure if they are nitrided or not?
Still haven't got my 86.5 cam back as yet, but will post photos when I do.
Cheers Greg
07-10-2005, 11:12 PM
#24
Drifting
i also had piper regrind my GTS cams closer to GT specs, have posted the duration/lift numbers before in other threads. finaly im getting very close to having the engine installed in the car and seeing it running at which time i will report more about the performance.
07-11-2005, 05:27 PM
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hey greg, guess I got lucky w/elgins, or maybe it's a personal thing! ha! does help if you talk to the right guy for sure - camgrinder hangs out on the rennlist from time to time, was quite helpful... IIRC, he's the shop manager... but I suspect/ hope there's more than 1 competent shop on the planet 
IMO, main thing is to get the indexing right, and use specs that are right for your app/build... I'd love to use some overlap, but smog #'s would've gone down the toilet... lots of trade offs/compromises for street cars...
IIRC, there's about .070" "play" in the OEM hydraulic lifters, but once you go beyond .020" over or so, it's time for solid lifters, different springs, different valve lengths, etc... whole different ball game, but awesome results at higher revs...
FWIW, specs I used are:
GT stock - .214 //.393 Intake
stock - .199.9//.353 exh
new - .218 //.404 intake
new- .208//.374 exh
all gains from reducing base circle, pretty modest changes...
dont' overlook coatings - IMO, the cams probably benefit more than most stuff w/a good nitriting/low friction coating process... lots of coating choices too - I used nitriting cause it was cheap/proven, although more exotic $tuff is out there (IIRC Brendon had a line on some interesting coatings)/might be worth trying for someone more adventurous/running more aggressive revs, pressures and lifts/etc....
IMO, main thing is to get the indexing right, and use specs that are right for your app/build... I'd love to use some overlap, but smog #'s would've gone down the toilet... lots of trade offs/compromises for street cars...
IIRC, there's about .070" "play" in the OEM hydraulic lifters, but once you go beyond .020" over or so, it's time for solid lifters, different springs, different valve lengths, etc... whole different ball game, but awesome results at higher revs...
FWIW, specs I used are:
GT stock - .214 //.393 Intake
stock - .199.9//.353 exh
new - .218 //.404 intake
new- .208//.374 exh
all gains from reducing base circle, pretty modest changes...
dont' overlook coatings - IMO, the cams probably benefit more than most stuff w/a good nitriting/low friction coating process... lots of coating choices too - I used nitriting cause it was cheap/proven, although more exotic $tuff is out there (IIRC Brendon had a line on some interesting coatings)/might be worth trying for someone more adventurous/running more aggressive revs, pressures and lifts/etc....
07-30-2005, 02:41 PM
#26
Intermediate
Rob,
I left Elgins to start my own cam grinding business last November. Right after you bought your set of cams I believe.
Nitriding is highly recommended on 944 and 928 camshafts after being reground. After nitriding the phosphate coating is applied.
The .070" play you refer to is the lifters plunger travel. The typical lifter has about .050" preload. After regrinding the preload is reduced by .020".
I left Elgins to start my own cam grinding business last November. Right after you bought your set of cams I believe.
Nitriding is highly recommended on 944 and 928 camshafts after being reground. After nitriding the phosphate coating is applied.
The .070" play you refer to is the lifters plunger travel. The typical lifter has about .050" preload. After regrinding the preload is reduced by .020".
07-30-2005, 04:37 PM
#27
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Originally Posted by Camgrinder
Rob,
I left Elgins to start my own cam grinding business last November. Right after you bought your set of cams I believe.
Nitriding is highly recommended on 944 and 928 camshafts after being reground. After nitriding the phosphate coating is applied.
The .070" play you refer to is the lifters plunger travel. The typical lifter has about .050" preload. After regrinding the preload is reduced by .020".
I left Elgins to start my own cam grinding business last November. Right after you bought your set of cams I believe.
Nitriding is highly recommended on 944 and 928 camshafts after being reground. After nitriding the phosphate coating is applied.
The .070" play you refer to is the lifters plunger travel. The typical lifter has about .050" preload. After regrinding the preload is reduced by .020".
glad you're still around!!! a grinder speaks - lots of questiions for you here!!! you should get your sponsorship going - not too many cam pros around!!! like: what's the pro word on using 85 cams in later MY heads???
regards!!
07-30-2005, 06:54 PM
#28
Hi Rob and Dr Camshaft, good info Rob, glad your having fun too. I agree, I don't see any down side in Nitriding. I would like to know the specific benefits of the nitriding or why it is needed, my cams are in England now and they are waiting on the headflow figures.
I will also post shortly, photos of my 85 models cams that have been modified, they cost me $440 AUD or about $325 USD to be done. Not cheap but I had sold my GT cams and I did want that slightly different timing on the intake due to the increased revs I have planned.
Cheers Greg
I will also post shortly, photos of my 85 models cams that have been modified, they cost me $440 AUD or about $325 USD to be done. Not cheap but I had sold my GT cams and I did want that slightly different timing on the intake due to the increased revs I have planned.
Cheers Greg
07-31-2005, 06:12 PM
#29
Intermediate
The factory 28 2v and 4v cams have a "tennifer" heat treatment . This heat treat is super hard, but is not very deep ( less than .005"). When the cam is reground the heat treat is removed. The tennifer heat treat process used cyanide gas, which is not allowed in the U.S.A.
Nitriding is highly recommended to restore the factory level of hardness.
"like: what's the pro word on using 85 cams in later MY heads??? "
I would have to look up the different specs on monday at the shop. The big problem with different
year cams is the factory lobe centers.
Nitriding is highly recommended to restore the factory level of hardness.
"like: what's the pro word on using 85 cams in later MY heads??? "
I would have to look up the different specs on monday at the shop. The big problem with different
year cams is the factory lobe centers.