A little known bit of info...
Actually the 1st gen 4g63's have several cam iterations. There are around 4 different grinds from the factory. Yes the automatics had the smallest of them.

 

Hmm.... I thought there were 3 different grinds for 1gs.

Worst- Best
1.AT cams
2.90 cams
3.91-94 Cams

Any others I am missing?

Peter

 

well how do the 1G AT cams compare to a 2G MT cams?

which is better in that sense?

 

2G MT cams are better.

I recently switched from 1G AT cams to 272/256 Webcams, and all I can say is the car now rocks. Before it would fall flat at 5,500 rpm. Now I can rip past 6,500 with ease, and it still pulls hard.

Peter

 

i dont understand how you are comparing the webcam to a stock cam when i'm trying to figure out difference between 1G AT stock cams and 2G MT stock cams.

please explain

 

I answered your question to start out by saying that 2G MT are better cams, as they have a longer duration, and I believe aslo a higher lift.

Then I made a side note, about my experiences with my webcams.

Peter

 

well, still having a hard time finding specs on cams.

would the evo jdm motors have different cams?

any site that would list any of the dsm cam sheets?

from RRE:
"The lift is higher(.010), there is a rocker arm ratio of 1.7:1 so it is even a little more difference than that."

What is rocker arm ratio and why would 1.7:1 be better?
i know this wouldnt be answered in gen tech.,

thanks

 

A rocker arm ratio... basically is a factor that tells what effect the rocker has on the valve lift. For example a camshaft will have a lobe lift of say .229 inches. Multiply this number by the rocker arm ratio of 1.7 and you will get the gross valve lift of .389 inches. These numbers are fairly representative of DSM cams. Alot of V8 guys change their rocker arms to those of a higher ratio to increase valve lift easily. Most Domestic v8s have a rocker ratio of 1.6 stock. If the valve lift is .490 at a 1.6 ratio then upgrading to 1.7 ratio rockers will bump valve lift up to .520 inch. This is like putting a bigger cam in the car...except there is little effect on duration.

On a side note... If you run reground cams in a dsm.. you actually will slightly alter the effective rocker ratio. It will increase slightly due to the change in rocker geometry. Factory dsm's have been listed as having 1.7 ratio rockers from factory.

Peter 92Tsi
The DSM's under different badgings appear to have been treated to different cam combinations. The lasers have smaller cams than the eclipses. Plus the '90 eclipse cams are the best in my opinion. The 4G63 cams all have a letter code stamped on the end of the cam opposite of the pulley end. The letters are A,B,C,D. (A) being the smallest. Both intake and exhaust cams have these same designations. Throughout the years and badges... these cams were installed in several differant combinations. From all that I have seen the 1990 eclipse had the best combination C/D than all the other years. The lasers that I looked at in 1990 had a smaller combo. The automatics were like A/A. All later years from 90 had smaller cam combinations for some reason. It was published somewhere that the 92-94's had increased exhaust cam timing. From what I have seen it looks like all they did was decrease the intake cam timing and leave the exhaust the same as in '91. In all the DSM's I have ever been in.. the 1990 eclipse/talon's have consistantly seemed to be the fastest for the least amount of mods for some reason. I contribute it to the cams. These letters are true for 1st gen's... 2G's may not follow this same pattern.

 

Good info, thanks man.

Peter

 

...The 4G63 cams all have a letter code stamped on the end of the cam opposite of the pulley end. The letters are A,B,C,D. (A) being the smallest...

I can't find it, Do you have a picture of where exactly I can see it? I look at the end of the camshaft but I don't look like to be able to see any A, B, C or D... I only remove the cams from a '90 head... I have the head of my original motor too(another '90) which I can remove to see it but on the first head the intake and the exhaust don't have any letter on the opposite side of the cam spocket...

And I have a JDM motor in the car now and I want to verify the cams too, do you think it should have the same codes on it?

 

the letter is about 3-4 inches in from the end opposite the cam sprockets

about 1/2" in size

 

That's a fast answer! Thanks!

I think I'll take a picture of them to show them to you guys because the only things I can see is O, R6, 04 and 16 in four diffrerent place on the camshaft, that's it... These are suppose to come from a manual '90 4G63... I think I have the same code on my oem engine but I'll check it...

[Edited by Lulutalon on 07-24-2001 at 11:16 PM]

 

I knew there was some reason my car always beats up on crazy modded Talons...

This will sound dumb, but when I first got my car I remember hearing what sounded like burp(at 4K) followed by a pretty intense thrust in the backside. Almost like a second set of lobes coming on line.


90 Tsi

 

The letters that I go by are on the very end of the camshaft. I mean the end. They are very small and stamped on... in alot of cases they are faint and hard to make out. They could very well be somewhere else too but I have never noticed. I will have to look. If you pull the cam position sensor off and shine a flashlight in at the end of the cam you should be able to see the stamping(most times). That is the end I am talking about. Have fun.