Cam differences cam identification cam ID cams camshafts camshaft degreeing timing

Posted by fivestardsm, Oct 31, 2002
Cylinder Head & Short Block - 4G63 cams, valvetrain, pistons, rods, stroker kits, 6-bolt swaps, hybrids, etc. Read this Forum's Strict Guidelines.

  1. fivestardsm

    fivestardsm Proven Member

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    Whats the differences in the cams between the 91-6 bolt and the 93-7 bolt blocks? I did a head for a friend and we used the 91 head on the 93 bglock. I would of changed the cams also when I did the head, but the cams were "beat" out of the 93!

    Steve. :confused:
     
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  2. GRNDSM

    GRNDSM Moderator

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    91-94 cams are all the same for 5sp, turbo cars. AT's used different cams (at least one of them was NT speck, as I recall).


    So as long as both engines were 5sp and turbo, you are all set.

    Leon
    RR
     
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  3. niterydr

    niterydr Proven Member

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    actually the 93-94 cams have a slightly higher lift..(someone did a test)..but it is a minor detail..so basically all 1g m/t cams are the same profile, more or less.
     
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  4. larryd

    larryd Proven Member

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    I was told that the 90 had different spec cams then the 91-94 as well.
     
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  5. boostedinwyo

    boostedinwyo Proven Member

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    , cheyenne_wy
    I also heard that the 90 cams have the least lift and duration and that the changed in 91-92 and again in93-94.
     
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  6. Big Woo

    Big Woo DSM Wiseman

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    According to the service manuals I have the 90-92 4g63s all had the same cams. 1993 and later cars were as follows.

    90-92
    intake 1.3974 lobe height
    exhaust 1.3777

    Intake cams
    NT & Turbo w/manual trans 1.3974 lobe height
    Turbo w/ auto trans 1.3858

    Exhaust cams
    NT & turbo with auto trans 1.3858 lobe height
    Turbo with manual trans 1.3974

    Since we know that all year's cams were ground on the same base circle
    one can conclude that there was at least some changes in maxinum lift, based on this data. One could conclude that the most desirable choice would be an intake cam from a manual trans car, and a exhaust cam from a 93 and later turbo manual car. This is interesting since mitsubishi listed a BHP change in the turbo cars between 92 and 93 of 190 to 195 respectivly.
     
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  7. insane147

    insane147 Proven Member

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    on early dsms, you may not find letters stamped on the cams, toward #1 cylinder, but if you do see them it goes like this:
    intake: ID mark A,D: 1.3972-1.4138
    intake: ID mark B,C,E,F:1.3858-1.3661

    exhaust ID mark A:1.3858-1.3661
    exhaust ID mark C:1.3972-1.3776
    exhaust ID mark E,F:1.3744-1.3547
     
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  8. GTM

    GTM Proven Member

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  9. insane147

    insane147 Proven Member

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    being dohc with a belt, the overlap can vary because the intake and exhaust is independant of the other, so milling the head / block or a stretched belt can toss the figures off. my book does not tell me duration or overlap, but i think im going to get my dial indicator and cam wheel out to see.
     
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  10. GTM

    GTM Proven Member

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    "

    That would be useful info, best done if you have a complete assembled spare head and some means of keeping oil pressure feed. Another useful measurement can be taken on an assembled engine with a second dial indicator and a long extension through the spark plug hole to the piston top to record piston travel and cam timing relationships.

    While thinking about it, I used a 1/4" drill and a socket to spin the oil pump/ balance shaft sprocket to prime the oil gallery and hydraulic lash after the head was torqued and cams in place. Use assembly lube or white grease on cam bearings without cam followers, throw a rag over everything unless you don't mind oil everywhere. This fills any collapsed lifter which I realize some books say not to worry; however; with our experince of cam followers falling off and bending valves this was not an option.

    It should be noted on my son's TSi that the piston eyebrows were not correctly placed and the intake valves fouled the tops. Some of the resultant damage could have been averted had they just used modeling clay and pulled the engine through a couple of revolutions when they selected the lowest possible bidder for pistons. Argh!!

    As an aside, I had read that the head was designed by Coventry Climax, can anyone confirm this?? It does resemble a redesigned upgrade to the Lotus twin cam of some years back. Those engines use a domed slipper piston with significant valve cutouts and a steel skirt insert to control piston expansion. Wonder if the pistons are interchangeable, Heppolite(sp?) made a decent after-market racing piston which could be substituted for production engines but needed high octane or aviation gas.

    Cheers,
    GTM
     
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  11. insane147

    insane147 Proven Member

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    why would i need to supply oil pressure? i was just going to give readings from the cams base circle on. i would do it with a crank degree wheel and a dial indicator for each cam. every degree you move the crank, write down the results and by the time you get done with 720 degrees of rotation you should have all the numbers you need to graph out the entire valve train operation..
     
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  12. Big Woo

    Big Woo DSM Wiseman

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    Of the manual's I have on DSM's Haynes, Chilton's, 1990 Eagle talon factory service manual, and a 1993 Mitsubishi service manual, none list the number of overlap degrees. This makes since, since factory/ dealership/ home mechanic repair work will not require such information.

    Checking it is not hard but you do need to have the necessary equiptment for degreeing a camshaft. Degree wheel, pointer, TDC stop, dail indicator with mount, for DOHC motoes its nice to have two or four so you can watch intake and exhaust simultaneously. Four can be helpful if the cams your using do not open and close the two intake or exhaust valves at the same time. Some start one a few degrees ahead of the other to promote swirl. Something else that is handy is a four inch travel dial indicator so that you can map piston posistion in relationship to cam timing.

    I could dig up some of the overlap numbers from the cams I have degreed in. I have some info on HKS, WEB, Crower, and Reed cams, but I have never taken the time to do the stock cams. That may be a good winter project, I will post the results after new years.

    I hope this helps
     
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  13. GTM

    GTM Proven Member

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    Hi All:

    "

    That would be useful for even with stock grind relocating cam opening and closing could improve performance especially when operating at higher RPMs.
    .........................
    insane147:
    The only reason for having pressurized the oil system besides the obvious lube would be if you are trying to determine where the piston is in relationship to the valve opening. Since you have no adjustment available to the cam follower which is ascribing a slight arc, having it reflect running position when chasing pistons is necessary. This is not to say you can't temporarily shim the top of the valve to keep the follower in the approximate position, all this is _only_ necessary if you want to know the relationship between valve and piston _IF_ you are going to play with the cam timing. It's all useless info if you are building a stock engine and never get close to redline, tweak the ignition timing, spark plug gap or torque, etc. for performance. To perform these checks you don't need to use a new head gasket or torque to specs for you can even assemble without and then know you will have a bit more clearance as a safety factor. All this can be done with just one 1" throw dial indicator and 10¢ 180º protractor projected on a piece of 10" cardboard cut round with a hole in the center. (necessity is the mother of invention) :)

    Just sanding new valve stems with #800 paper parallel will get you 200-600 rpm when running knurled guides (less friction) before float occurs. Adding a reverse helix valve spring will greatly reduce spring bounce harmonics and valve float rather than a single heavier spring. I've not followed racing rules for many years so don't know what's permissible if class racing is your thing, but if you enjoy tweaking things for cost effective performance then having a good grasp of where to look for reliability vs performance it then becomes critical to have the info available. I don't recommend playing around with some mom's, housewife's or girlfriend's engine for hard starting, rough idle, poor stop light acceleration may suffer if not prepared to kick the rpms up which is especially true with an automatic and playing stop light grand prix.

    Cheers,
    GTM
     
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  14. insane147

    insane147 Proven Member

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    rochester, rochester_new_york
    ah, i see where your coming from, i was just interested in taking it from the cam lobe, but the valve would definately be the best place as you put.

    on the side here, have any vendors or tuners played with degreeing their cams? if so, what were the ranges you got? what cams and piston combo do you have also, thats very important, from the intake and exhaust valve also as they are different sizes and have different clearance issues?
     
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  15. steve

    steve DSM Wiseman

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    Maybe I don't know what I'm doing but it seems that you can calculate the overlap by simply looking at when the intake opens and when the exhaust closes.

    Based on what I can tell from the service manual the 1G 2.0L cams differ as follows: (specifications pages, timing is in one place, lobe height in another)

    Intake NT opens 26 BTDC close 46 ABDC lobe height 35.493 (34.993 limit)
    Intake MT opens 21 BTDC close 51 ABDC lobe height 35.493 (34.993 limit)
    Intake AT opens 21 BTDC close 51 ABDC lobe height 35.200 (34.700 limit)

    Exhaust NT opens 55 BBDC close ATDC 9 lobe height 35.200 (34.700 limit)
    Exhaust AT opens 55 BBDC close ATDC 9 lobe height 35.200 (34.700 limit)
    Exhaust MT opens 55 BBDC close ATDC 9 lobe height 35.493 (34.993 limit)

    From this I come up with the NT intake cam being 252 duration, the turbo intake at 257 and a duration of 244 for the exhaust. NT has 35 degrees overlap (26BTDC + 9ATDC) and turbos have 30 (21+9). These are seat timings. From the point where the valve first starts to move.

    Is my math correct?

    Steve
     
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  16. GTM

    GTM Proven Member

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  17. insane147

    insane147 Proven Member

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    damn, wish i remembered the days when planes flew supersonic over houses... i always wanted to hear/see that.

    the NT has 35 degrees overlap...everything else looked right. if you increase the overlap to 33 how luch will you suffer from reversion. the main reason they try to limit the overlap is so the high turbo backpressure does not blow the intake charge back up the intake.....then again if your going all out, want top end and have a really well flowing manifold and turbo this would be a good move...btw, thanks for the cam numbers and math.
     
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  18. GTM

    GTM Proven Member

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    We only get it once in a great while from the space Shuttle landing at Edwards AFB when weather is bad back east. There are actually 2 shock waves produced, from the nose and the 1/4 wave aft which because of the speed is a full second later. .........

    I understand some of the rational behind intake plenum designs but see some very pretty polished stainless exhaust manifolds which have made no attempt to utilize sequence or even displacement.
    This sort of takes the design beyond the home garage design bundle of snakes when trying to project how a paticular size and length will behave if you are looking for those shock waves for an additional push. What then happens to the down stream turbo??

    Cheers,
    GTM
     
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  19. insane147

    insane147 Proven Member

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    if you made runners and primaries the proper length for say a 7500rpm+ target, you may have weak low band power and then a sudden wooosh of power, light bulb on off type thing. all types of racing use long exhaust primaries, look at the lemans cars for example, works of art in stainless steel. much the same as a race preped motorcycle, you get the power where you need it, dont worry about the low end cause you didnt design it for that purpose. as an avid race fan and driver, i would love to drive a car like this (i do) and have fun, but it is such a pain to get around in traffic with an ill mannered vehicle that draws attention (the wrong kind mostly) because you just cant drive it in its sweet spot on the public roads....
     
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  20. steve

    steve DSM Wiseman

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    Thanks, I edited the post to correct the mistake.

    Steve
     
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  21. Big Woo

    Big Woo DSM Wiseman

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    GTM Good idea with the protractor and cardboard. Makes more sence for the do it yourselfer. And yes it can all be done with a single dial indicator just more time consuming.

    Steve yes you can figure overlap with the opening and closing time numbers. I guess I overlooked that page in the book.

    It would be difficult to sugest a specific overlap duration, without alot of additional information. Idealy it should increase with RPM. If you have dataloging capibilites plumbing an additional 3-bar MAP sensor into the exhaust manifold will allow you to map exhaust manifold pressure, vs RPM, throttle posistion, and boost. I have a set up like this on my 93 and am using the AEM EMS for logging.

    I would suggest that one should check the cam posistions before moving them. I have found variences of up to 9 degrees on cam posistion, and yes all the timing marks were lined up correctly. This simply comes down to production tollerences. If you think about it there are many variables that can effect final cam posistion. Such as dowel pin posistion, woodruf key posistion, orientation of crank gear teeth to wooruf key groove, orientation of cam gear teeth to dowel pin posistion, ect, ect.. Anyway you get the idea, some typical production tollernces are +,-.005 on three place decimals, +,-.5 degrees on most angles. Then if you think about how many differnt parts make up the entire cam timing system it is easy to see why actual posistion will vary.

    Also there are some other tricks that can be used to move camshaft posistion. Offset keys on the crank gear (moves both intake and exhaust in same direction), Offset dowel pins can be made for the camshaft, and the Small block chevy offset bushings can be modified along with the cam gears to move the intake and exhaust cams seperatly up to + or -8 degrees. Just some more food for thought.
     
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  22. Silent2g

    Silent2g Proven Member

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    , Independence_Mo.
    so the general speaking of the cams is there isn't a difference in them in the turbo cars. m/t
    i knew there was a slight difference in the auto's

    so in theory if you have a 90-94. you all have the same stock cams {being they are all turbo cars}
     
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  23. GTM

    GTM Proven Member

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  24. Big Woo

    Big Woo DSM Wiseman

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    GTM don't know about the data logger, but the EMS will allow mapping of any auxiliary analog input so long as it is scaled correctly. 0-5v if memory serves.

    I think that the furthest I've seen a 4G63 off cam timing wise is 6 degrees. I believe the 9 degrees off was on a olds 2.3l quad4 back in 89 or 90, when I was involved in their showroom stock, and firehawk programs.

    Slient2g I think if you look closer you will find that the 93 and 94 turbo 5-speed cars had slightly more exhaust cam. 90-92 turbo 5-speeds were the same. Since all of the cams were ground on the same diameter base circle having a slightly larger lobe height sugests that at least the maximum lift is greater on these cams. When I get home I will look at the opening and closing times (I have to remember to read :) ) to see if there is a duration change as well.
     
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  25. hostile

    hostile Proven Member

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    For some reason my cams have a R8 number on them. I belive they came from a 1990 Galant j spec.

    The new exhuast cam I got in with my head say R8. I double checked them one is a b and one is an 8. Which one is better?
     
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