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View Full Version : help me pick out a cam (regrind)



scotte
04-11-2004, 11:39 PM
hi i'm tearing my motor apart to fix a spun bearing so i want to put cam in too i want a very lumpy cam idle without sacraficing the ability to idle (its a street car

i want the complete info from somebody thats done it before

example

you want #%#% cams ger-xxxxx grind and you need X.XXX in long pushrods with stock rockers


btw i'm replacing my lifters to i've heard you can use 5.0 h.o. stuff (new of coarse)

fastsc92
04-12-2004, 12:03 AM
its tough to figure out dude. You wont gain a thing without major head work. In addition its not just an in out deal. You need to understand the full concepts involved. You'll need longer pushrods on any regrind, but it varies engine to engine and matters if you have your heads or block decked ect. When you regrind a cam, you are taking material away from it...hense the reason for longer pushrods. Also, a stock cam is made with a 4 deg advance built into the cam. Once you grind it..you are taking that away, making it have no advance. You'll need to degree your cam, which is an easy process but must be percisly done. If your cam degrees out retard or advanced you'll need to either get the crank or cam gear machined and have another keyway cut into them, or get an adjustable timing set which does the same thing. If you dont degree your cam and its installed retarded then you wont make any power until 3500 and up...which will be dog on the street. If you want a lopy sound...then get a mustang. I cam regring wont have that sound unless you go to a super high lift. Having a high lift means major work to the heads and new springs. The stock heads can handle about a .500 lift cam. Anything more than that and you'll get coil bind. Its a lot to understand and a lot of work to get it installed right and get the most power out of the motor. When i put my cats on the exhaust you cant even notice that it has a cam at all. When the cats are off it def has a lope to it. With this type of car (supercharged) you'll want a double plane durration rather than a single plane. This means the durration should be different from the intake and exhaust rather than being the same. Example is a 205/210 durration rather 205/205. My advice is upgrade the cam only if you are 100% committed on doing it the right way. This means be willing to have the heads fully ported, get large/stronger springs, degree the cam, have a timing set machined, measuring pushrod length, checking rocker arm geometry, ect.
Bottom lines is if you want a nasty lope, get a different car. If you want a lope like that it wont happen with this 3.8. If you're going for a lope that large, with a high lift you WILL have idle problems and the stock computer wont handle it. I only have a small lift with a good durration and the computer has a tough time. I dont mean to be rude, but you cant expect to get the results and have the ease of installation as a mustang or any v8. Try doing a search on this subject and you'll get tons of info. I was in the same boat as you but i learned so much about the subject. I have a sound clip of my car idling with the cam. However the car has no cats so its a lot louder and more lope than with them.

scotte
04-12-2004, 12:41 AM
If you want a lopy sound...then get a mustang, but you cant expect to get the results and have the ease of installation as a mustang



rotflmao

wanna read my sig ;)

so according to you because my engine is in a stang i can get a easily installable cam ??? (j/k)

p.s everything in the valvetrain is stock right now
i have to replace the cam anyway (the one in my car is f###ed lobes arnt shiny :eek: )

i'm going to get the heads ported while their off the motor

btw maybe i didnt state my question correctly

i want a cam with the most lope possible perserving idle (i will take what i can get)

most people i talk to say just use to stock timing chain/gear and to h#ll
w/ the 4 deg.

their has to be some way to tell how long of a pushrod you need
otherwise nobody would have a cam

turbospeed
04-12-2004, 01:31 AM
if you have the $$ get a cam head package from someone like steigmeter (best but not cheap) morana(good and rasonable prices) or coymiller( ultra expensive but excellent heads) or chris wise( one of the best too but you better have a good wallet)

T-bird4vr
04-12-2004, 07:52 AM
I had mine speced out by RGR performance. The cam was reground with a 5 degree advance built into it. I would imagine most regrinds are similar. I believe if you call up crane they have a popular SC cam grind and would be able to tell you what length pushrods you need.

I also thought that is was the duration etc not the lift that gave a loby idle. Mine is at 9inhg vac @ ~650rpm idle.
~.495-.5lift on stock valve springs is about there limit (from what I was told.)
like said before.

I'd give crane a call.

click ('http://www.public.iastate.edu/~julian/run1.AVI)
^^hard to tell the idle but there is some lobe. I had someone tell me my T-bird sounds like it has a mean 5.0L in it. I don't know about that one, but it sounds decent.

fastsc92
04-12-2004, 09:00 AM
most people just install their cam because there is a lot of work involved in getting it to degree with the correct specs, so they just hope for the best and install it. When you do degree it...you'll install it in the motor the way it was designed to run its best, and you'll get the most performance out of the motor. Getting a cam decides a lot on what your heads are capable of flowing. Getting a .520 cam is useless if your heads cant flow that much. I'd get the heads fully ported, with bowl work and larger valves. The stock valve springs can handle about a .500 lift like i said, and after that they start to coil bind.
I said if you want an easy installation and cheap install, its much easier on a 302 stang or some other pushrod v8. The 3.8 motor is hard to squeeze power out of, and much more expensive to do so.
If you're not up to getting a lot of head work, then stay with a small lift and more of a durration. I have a .493 lift and 210/220 durration. It uses the most lift it can without getting into changing to a different valve spring which requires machining of the seats ect. Here is a clip of my car idling. After i rev the motor you can hear that it really has some lope in it, but its because i dont have cats. Its idling around 850-900..and once i get a new chip i can prob, get it to idle a little lower. This cam is exactly the same as a coy miller stage one cam..but half the price.
My dilema with my cam was that i did not want to get an adjustable timing set from morana and pay 200 for it. I did however degree it with a brand new timing set and it degreeing in at 105 ICL..rather than 112 like the cam card said. It was advanced 7 deg. This would move the power band down lower. I ended up figuring out where the new keyway needed to be in the timing gears with a little math and some CAD. I used a broaching kit and cut a new keyway. After it degreed in at 113*, it was 1 deg retarded but it was much closer to what the cam was designed to run at.
Like i said pushrod length all depends on the motor, cam grind, and rocker geometry. What determines the proper length is the correct lifter preload and rocker geometry. You'll need to take a stock pushrod and measure the preload on the lifter and add the difference and order a longer set. With my motor i used 7.195" rods from a SBC 305 iroc. I've seen other with the same cam use longer rods such as 7.280". It all depends on your motor ect. Because there aren't parts easily available for this motor its hard to just order a cam and get pushrods from a magazine. I'd like to help you out as much as i can, but i want to walk you through everything involved and the reasoning why its not such a simple task to provide your cam specs. Anyhow...here is the link to my idle.

Jay's Idle (http://home.comcast.net/~fastsc92/my_idle.wav)

scotte
04-12-2004, 09:20 AM
i just called cranes tech line

the guy was a real $&^&&^&^^

i told him i read on a message board that crane had a popular regrind out for these motors

the guy was like " i'm not responsable for what others post on some other site" ~~~ come on here i'm trying to pay this company money and the guy wont even ask anybody (he said their was somebody else there that knew but he wanted me to find out specs)

i'm so sick of f#$#ing companys doing this

scotte
04-12-2004, 10:01 AM
ok thats it i give up i will just put the stock cam out of my 89 motor in

so what should i do get the heads ported ?

my spending limit on the heads is prolly around $400 max (so i can get some stegimiers right :rolleyes: )

but then again i'm not trying to achieve 300 rwhp

what kind of gains are there with a cheapie port job

i dont really want anything that i'm not going to see gains with untill i sell my soul and buy 100,000,000.00 $ on mp stuff

i'm looking to stay with my 94-95 blower

i dont want to spend money on porting i will never use

fastsc92
04-12-2004, 12:51 PM
i ran into the same problem with crane and comp cams. They said that "they dont offer any grinds for my cam" I talked to about 3 people on each end, and they were dumb. I finnaly got one guy who knew his ~~~~~ with our cars and cams at comp. I was talking to him a few times for about 20 min each time. I mentioned coy miller and he was able to help me out. He talked to the guy who deals with coy's cam orders and was able to grind my cam to the same specs, and it cost me 125 rather than 180. I talked to him a few times here and there during the install and he was even kind enough to call me out of the blue the other day and see how the whole project came out. This really impressed me, when i havent talked to him in over two months. Just because i had a great experience with him, i would gladly go back to comp to get one of their cams for any other car. His name was matt maxwell if you are interested in any regrind.

BKB
04-12-2004, 10:29 PM
You need to talk to Matthew Maxwell [email protected] he works on a lot of SC motors and is a very nice guy. He will spend the time with you to get the right cam. No one can tell you what length push rods to get thats why they sell push rod checkers.

scotte
04-12-2004, 11:37 PM
ok what has the most gains ??

after i get all the stuff for the new cam i will have 300-350 into it

i think i can get a pretty good head porting for that

should i do the heads or the cam ?

David Neibert
04-13-2004, 08:38 AM
should i do the heads or the cam ?

You really need to do both, but if I had to pick one I would do the cam.

David

Rich Thomson
04-13-2004, 10:42 AM
I am using a 520 lift cam in my 94 SC which may not be correct for a NA engine. Eitherway here is the cam spec card. You will need Comp Cam 942 Springs, new roller lifters (5.0L lifters work), Comp cams 7808-16 pushrods, Any bolt-on 1.73 roller rockers (do not reuse the stock rockers) 11mm x 40mm 12.9 allen head bolts and a set of rocker shims just in case. Best to get a pushrod length checker so proper lifter preload can be verified. Comp Cams also sells 5/16" adjustable pushrods part 7702-1.
http://www.mn12performance.com/images/520cam-specs.JPG

scotte
04-13-2004, 10:46 AM
ok what do i need with a cam

i should be able to reuse the stock rockers right?

lifters,new diff. sized pushrods,pushrod length checker,

i will be using a new stock replacment timing set

what can i do myself as far as head porting? will it make a diff.?
i've heard the exhuast side is where the gains are so i would prolly stick with that side i'm very mechanicly inclined so i think if i bought a porting kit (have diff. die grinders but need the specific bits)

XR7 Dave
04-13-2004, 11:27 AM
Geez guys, you are killing this poor man.

I can't disagree with Rich about his recommendation, but it is only a recomendation and it certainly isn't the LOW BUDGET way to go.

Speaking from experience and not theory, there is no reason to have more than $200 in a cam swap. Depending on mileage, there is probably no need to even replace the timing chain. I've never heard of a timing chain on an SC breaking, and they can't come loose due to the tensioners. There is no reason to replace the stock rockers OR the lifters unless you see a problem with the old ones. If the rollers on the lifters are not badly scored and the rockers are not chewed up then leave them all alone. As for pushrods, you will find that you can either use the stock ones or you may need to go to a longer replacement. Stock is 7.135" and 305 Chevy ones are 7.192" if the stockers are too short. Either way just re-assemble everything and as long as you have at least 1/2 turn of preload on the lifters you are fine. If not, then go with the longer ones. It is really that simple. The stock lifters have .180" of travel so you are in no danger of bottoming a lifter.

I did just such a swap 5 years ago on one XR7 that routinely sees 6000+rpm and 340rwhp. It has over 50K miles on it in that configuration and it shows no sign of weakening (and yes I've had it apart for inspection recently).

Advice: do the cam now and worry about heads later. Since the heads are something where you get what you pay for, it is better to wait a little longer and have the heads done right. Here is a better cam grind for use with stock springs. It has under .500 lift and has the properties to support 300+ rwhp. It is also a spitting image of a CMRESI cam. If you have the heads milled .010" you can even use this cam with the stock pushrods as it has only about .030" taken off the lobe base circle.

http://members.tccoa.com/xr7dave/camcard.jpg

fastsc92
04-13-2004, 01:01 PM
i agree with dave...since he helped me out a lot when i was gathering info on my cam swap. The regrind cost me 135 total, gaskets cost about $180, and i did a timing chain for good measure for 35. Like i said i took the time to degree the cam and cut a new keyway in the cam to bring it to the proper ICL which is 112*. My cam card was exactly the same as dave's which is also a coy miller stage one. I love the lope on my car...as you can hear in the sound clip, but it'll only have that lope without cats.

scotte
04-13-2004, 09:09 PM
i talked to matt at comp cams
and here is what he figured out

3160/3161

210 intake 220 exhaust and 110 lobe sep.

i told him i wanted it lumpier at idle and he recommended the 110 lobe separation over the 112 he said it would take a little top end away but give me a little more low end grunt in small amounts and i'm fine with that

i shipped my core in today does anybody have any comments on the change in lobe sep. ?
if i want to change it i have to call him before the cam arrives ;)

XR7 Dave
04-13-2004, 09:40 PM
Or you could have just gone with 220/220 duration and kept the 112 or even gone to a 114 seperation. Don't know if they can grind that on your core, but it would surely make it sound "lopey". :cool:

fastsc92
04-13-2004, 09:41 PM
you might have your info mixed up. On any regrind, you cant change the lobe serparation angle, and it must remain at what the stock separation angle is. He might be grinding the cam so that its made to be installed at 110 Intake center line, or ICL. The info for my cam was a .493/.493 (280 lobe lift)lift, and 210/220 durration, and to be installed at 112 ICL. IF you install it at 110..you'll get more low end, but its nothing drastic. If i had to install mine again i would install it a little advanced just to get some more low end. It pulls hard up top ( 3500-5500), but stayed the same on low end. Retarding the cam just moves the power band up higher.

I'd say you're fine with that...what lift are you running. I told you...matt was a great guy to deal with, and like i said, he randomly checks back with me to see how my set-up was going. Its people like him that make Comp who they are today.

scotte
04-13-2004, 09:51 PM
yup matt was great to talk to and seems to really know his stuff

he said .493 lift and he said that whatever they set a 110 is ground into the cam and makes it have more of a lope

does this sound right?

fastsc92
04-13-2004, 10:10 PM
ya but the lobe separate isn't changed because its a stock cam core. They set up the machine to grind it at 110 ICL, thats all. Which would give it more lope and more bottom end, not by much...but more. Seems to be that after i talked to him about getting the same grind that coy does...and its a proven set-up, he's been recommending it more and more. When i sent mine in, he wasn't sure what was a good set-up. He asked if he could profile my cam to see what the stock specs were and such. This took more time for a grind, but he said that it would help develope NEW cam cores in the future. I think the stock specs were something like .443/.452 lift and 183/203 durration. Clearly the durration alone is what makes the power with the new grind. Good luck man..you wont be disapointed.

scotte
04-13-2004, 10:52 PM
f%$%$ing cool

cant wait to hear it idle (or try to :D )

i will defenitly be taking the last two cats off (gutted the primarys)
or i will get a long tube/offroad h-pipe setup

fastsc92
04-13-2004, 11:07 PM
did you hear my sound clip of that same exact cam? Also i wouls still recommend that you degree it, that way it will be installed where it was designed to be run. If you need the cam timing to be changed let me know because i made a special broaching kit that fits the timing gear exactly to cut a new keyway and it.

scotte
05-02-2004, 12:23 AM
matt said he left the factory advance in

now i measured my needed pushrod length and its 7.200

so i bought the pushrods and installed them

now after its sat for a couple hours i can wiggle the pushrods a little

im assuming the lifters are just bleeded correct? i have the apropriate amount of preload on them

so when the engine is started (hopefully someday/week/month/year here the lifters will pump up and do their thing corect?

David Neibert
05-02-2004, 09:51 AM
so when the engine is started (hopefully someday/week/month/year here the lifters will pump up and do their thing corect?

Yes...that's correct.

David

scotte
05-02-2004, 12:31 PM
cool

thanks for the info

gbabione
05-02-2004, 01:36 PM
I don't know much about cams, but why is everyone reggrinding the stock cams instead of buying a new one with the specs they want? Also what are good specs for a better than stock without any lope?

turbospeed
05-02-2004, 02:43 PM
I don't know much about cams, but why is everyone reggrinding the stock cams instead of buying a new one with the specs they want? Also what are good specs for a better than stock without any lope?
becasue its cheaper ,a new cam core costs about 300+ bucks.

scotte
05-02-2004, 11:04 PM
or because the unground core were not avalible untill recently (right after i got my regrind :( ) as for your wanting a well performing cam without the lope i think it is possible to a degree but the performance would suffer possibly negating any gain or making it not worth it in hp to $$ ratio

personally i would have got one even if there where no gains just because i WANT a BIG LOPE :D :D :D

turbospeed
10-05-2004, 01:35 PM
so xr7dave i remember you recommened a cam that a wa lil better thna the one you had what were the specs?