*UPDATE*What happens if the cam is 180 out?*UPDATE*

[porkchop]

Well I put in the summit cam today. When I took out the old one I put the summit cam back in in the same way. Well when I went to go put on the timing chain it would not go on. There are two notches on the gear. One is a clear notch for the guide on the cam and the other is a groove (does that make since). Well the guide on the cam will not slide into the groove. I look at the old timing gear and it looks like who ever put the timing gear on last time forced it on there past the stop on the gear. I don't know if I explained that well enough so here is a picture. The red arrow shows the correst notch. The blue arrow shows the cut out or groove that was forced onto the guide on the cam shaft.

http://www.jasonthomasfrance.com/jeeping/timing%20gear.JPG

So may question remains, what happens if it is 180 out? I was driving the wag for some time but could never ger a lot of vacuum from the engine. Could this be the reason?

[ July 03, 2002, 05:10 PM: Message edited by: porkchop ]

[Midnightwagon]

awesome i figured there had to be something else wrong well you gonnakeep the rv cam? and stab it correctly?

[OBX-AUTOMOTIVE]

I THINK THAT THE EX WOULD BE IN AND THE IN WOULD BE EX... :confused: GEE I HAVE TO THINK ABOUT IT :confused:

[OBX-AUTOMOTIVE]

WHEN YOUR DAMPER IS AT TDC..YOU WOULD BEEEEE ON THE EX STROKE

[Jerk]

yeah, your engine will run backwards and suck air in the exhaust and fart out the carb. no, if your cam is 180 off, it won't run at all! the spark will be at the wrong time and will not have the fuel air in the chamber at the time.

[OBX-AUTOMOTIVE]

:confused: :confused: I ALSO DON'T THINK THAT IT WOULD RUN AT 180 OUT AS FAR AS THE CAM GOES!!! :confused:

[OBX-AUTOMOTIVE]

YA!!!!!WHAT MATT W SAID!!! :D smile.gif

[jasonthomasfrance]

Yep, wouldn't work. Remember my posts from Jan/Feb timeframe with the Summit cam? It was because the cam was put in right, but the timing gear was installed wrong. Sorry I can't be too helpful. All I know is I played with it for about two weeks before I got it setup right... There's a guide (image) in the Hayes/Chiltons that shows you how to check if the timing is set right, without puttin the timing chain cover on...

Good luck!!

[Dan]

Not sure if I can help, but the square notch should be for the guide on the cam and the other half-circle notch should be a hole for oil to go through. I couldn't tell you why it's not fitting. Are you having problems when trying to put everything on at the same time (crank gear, cam gear, and chain)? If so, what happens if you just try putting the cam gear on? Does it go? If so, maybe you have to adjust the cam or crank ever so slightly to get just the right slack in the chain.

[porkchop]

Well the cam was in there 180 out and I was driving it around so it must start and drive that way. If you line up the timing marks the way they should be then the timing is set. I checked the timing marks to make sure it is right. If you take off the #1 plug and check TDC then put the dizzy back in so it is pointing at #1 then it would be firing but it would just be slightly off. Right? All I can say is that the cam was 180 out and someone put the gear on wrong.

[Tad]

Holy Ghost.
I did not think that was possible unless you had the plug wires off by 180 too.

[ June 30, 2002, 09:49 PM: Message edited by: tadsal ]

[mdill]

Well lets think about this, if the cam is 180 out, that means the crank is
360 degrees out with respect to the cam, hmm, does that not mean
the cam can not be 180 out as that is the same as being 0 degrees out
with respect to the crank. My best guess is that the wrong notch is not
exactly 180 out and that it you were running with the the cam timing
slighty retarded, hence the lack of vacume but it ran, most likely run
better as the RPM's got higher was just a little doggie on the bottom end.
The correct notch should give your vacume back and make it pull better
off the line. (Best guess from info given) If the above assesment is
correct.

Mike D.

[Stolen76]

I'll second mcdill's post, been there done that with an adjustable timing set. Next time I'll save my money and get the standard set. I see that yours is not adjustable but I would bet that those grooves aren't exactly 180 apart.

[porchpiggy]

But a cam /crank turn at a two to one ratio meaning 360 degrees on the cam is 720 degrees on the crank. So...couldn't you be out 360 degrees on the crank? Also, remember the cam is not symetrical, you don't have all the cylinders exhausting at one crank turn, and all intaking at the other turn. Different things are going on at different times. :confused:

[mdill]

The crank, does not know the differance between 0, 360, 720 ..
it is all the same to it. The cam is what sets the differance between
compresion stroke and exhast stroke, so having the cam set "180" out
is the same as having it set "0" out. All the rest follows from there
you install the distributor the same, TDC (+/-) on the compresion
stroke, wire the plugs the same ...
The big differance here is the the key way (oil slot) used is not what
the cam was indexed to when ground so it is only about 180 out not
exactly 180 out. From his statment that he could not get decent vacume
I would assume that the slot is slightly retarted from 180.

Mike D.

[OBX-AUTOMOTIVE]

BODYMAN GIVING ANS TO ENGINE QUESTIONS...IS ALL MESSED UP :confused: REMEMBER THIS GOES BY THE #1 PISTON FIRING...FIRST...HELL YOU COULD HAVE THE #1 PISTON SET AT BDC IF YOU WANTED TOOO!!!IF THAT ENGINE WAS 180.. ANT NO WAY THAT YOU WOULD NOT THINK THAT SOMETHING WAS WRONG!! !!!!!!...WE NEED MR.MAN!!!!!! HE KNOWS ALL!!! :cool: :cool:

[Lindel]

I'll agree that the crank doesn't know 720 from 360 from 0, but by the same token 0, 360 and 720 is the same thing for the camshaft, too. It is possible for the cam to be 180 out, in relation to the crank.

Technically, you shouldn't be able to put the camshaft sprocket on 180 out, but looking at the picture, the oil passage, and the keyway, are almost exactly the same size, probably a casting defect on that cam. PC, was that the timing set that was in the engine when you bought it?

Anyway, the engine will run that way, but very poorly, and will lack lots of power. If there's no internal damage to the engine (pushrods bent, and the like), then you should be able to reassemble correctly, and press on. Be sure that you use the same lifters on the same lobes, or replace the lifters, if you didn't keep them in order. Same with the rocker arms, and pushrods, it's very important, since they've got specific wear patterns now.

BTW, engines can run backwards, but it's not likely. Makes for an interesting day when you put it in gear and doesn't go the direction you think it should.

[porkchop]

Yes that was the timing gear set that was in the engine when I got it. The marks appear to be 180 of but then there could be a slight difference. The timing gear set I bought for the old engine would not go on either cam the way the one that was in there did. This is still pretty confussing.

If the #1 piston is compressing air, pushing your thumb out, then you took the cam and flipped it 180, then reassemblied the engine, what would happen?

[Lindel]

PC, here's an article I found, while researching your question. Cam Timing in a 4 stroke engine. (http://moparjimsgarage.virtualave.net/camvalve.html) Hopefully, it can answer your questions with the graphs, and text.

I'll keep looking, and as I find more info, I'll post that as well.

[mdill]

Lets say you had the engine a TDC compression stroke
(The finger in the spark plug hole just got pushed out
by the air) If at that point you somehow magically rotated
the cam 180 degrees The crank would still be at TDC, but
it would now be TDC on the exhast stroke. Since you magicaly
fliped or rotated the only cam without changing the distributor
timing the distributor would now still be pointing at #1, which is 180
degrees out. So to get everything back to "normal" all that is needed
is to pull the distibutor and rotate it 180 degees and slide it back in.
Everything would be exactly the same as before the magical 180 degree
cam rotation.

Mike D.

Mike D.

[porkchop]

Thanks, Lindel, that page will help. I need to sit down and read it all when I have time.

Mike D. that is what I figured and just wanted to be sure. But one question remains, is this the cause for my poor engine vacuum?

[mdill]

If the extra slot is not "exactly" 180 out, then the cam timing is going to be
off. From your vacume problem, I would take that as the cam timing is retarted
from where it is should be. Does the engine come alive as the RPM's come up ?
What are the specs on the cam to sart with ? Retarding the cam timing or a cam
with lots of over lap will have poor vacume at idle.
Unless you degree the cam (figure out what the cam timing is in relation to the
crank) you will not know for sure but it is a pretty safe bet that the cam timing is
off using the oil slot as a key way.

Mike D.

[gsmikie]

the cam will be retarded by 3 degrees (at 180) causing low vacum strong top end

[gsmikie]

and a motor that has this kind of stuff done to it should go to porkchop so he will have somthing to do i knew a sunday could not go by with out porkchop finding somthing new or broke........

[Jerk]

heres a stupid idea! tongue.gif look at the instructions that comed with the ****! hmmm too unmanly? :rolleyes:

[Stolen76]

just had to jump back in with my .02

I still think he could be 180 out minus the difference in the oil hole and the keyway. It doesn't take a long way around a circle to go from 170 to 180. You may not even see the difference.

however... been re-thinking the 180 out deal, here's my thoughts on that
the crank doesn't know any difference between 0, 360, 720 etc.. a complete turn is a complete turn. The cam turns at 1/2 the engine speed, if he is getting pressure in the hole on what he thinks is the TDC stroke, the cam could be 180 out. It would not produce compression if it has valves open. So if it is off by a too many degrees from its normal position there would be a valve open as lobe seperation is shorter. If it was off a few degrees and 180 out where the lobe seperation is greater, then he could have compression and still be out 180. I have seen an inline 4 banger on a non interference engine run 180 out. Totally undriveable could barely stay running, but it did run.

[porkchop]

Originally posted by Matt W:
heres a stupid idea! tongue.gif look at the instructions that comed with the ****! hmmm too unmanly? :rolleyes: I did read the instructions that's how I found the problem. I always read instructions. I am a Helicopter mechanic by trade so you have to read the manuals all the time because things are changing. So it is a habit, and a good one at that.

So true Mike so true :D . If I had my non-valley pan intake gaskets the thing would have been back together and tested on sunday. I may find things broke, or brake them, but I do fix them quickly :D . Or you going to bring the carb down when you come?

[gsmikie]

yea ill bring it down i will be down tuesday or wednesday

[Lindel]

PC, on a good note, check with a local parts house about Mr. Gasket, they have an intake set listed that's not a valley pan, but a real set of intake gaskets.

Jeg's lists the part no. as 720-800G, for a 290-401, 1967-79, and the price is $11.99. It's in their latest catalog on page 61-L.

[OBX-AUTOMOTIVE]

YOU HAVE THE TIMING MARK ON THE CRANK GEAR...RIGHT AND YOU HAVE THE TIMING MARK ON THE CAM GEAR...RIGHT! !!!YOU PUT THE CAM GEAR ON WITH THE MARK ON THE CAM GEAR FACING DOWN.... ..TO THE CRANK GEAR..MARK AT 12:OO RIGHT!!!!..KO!!!! WHAT THE HELL AM'I MISSING......???? THIS IS DRIVING ME CRAZY....

[OBX-AUTOMOTIVE]

AND ONE OTHER THING!!! MR.CHOP....IN A FEW MONTHS I HAVE TO PUT MY...3.4 DOHC BACK TOGETHER....TALK ABOUT TIMING...I WILL HAVE 4 CAMS TO TIME. ...WHAT FUN...AND GUESS WHAT!!!! I'M ASKING YOU FOR HELP!!! SAY WHAT WAS YOU PHONE NUMBER AGAIN!!! :D :D I'LL BE A CALLING... :eek: :eek:

[porkchop]

Thanks Mike I will be here both days. I am helping the nieghbor's boyfriend put on some bal joints on his cheby truck.

Lindel, I already ordered the gaskets from my local speed shop. They are taking awhile to get here. If they are not here today I am going to just get the valley pan, wasting time. Mr Gaskets makes two different ones. The MRG-800 is the older ones with the silicone bead and the MRG-5844 are the newer and thicker ones. I went with the 800. You can get them from MotorHead (http://www.motorhead.com). they seem to be the only place that has them in stock.

Gary, I just changed my telephone number :D .

[mtn goat]

Ok, Porkchop

I think now the question should change from what would happen...to..DOES IT RUN BETTER NOW!!! I hope that was your problem.

[gsmikie]

(IN A FEW MONTHS I HAVE TO PUT MY...3.4 DOHC BACK TOGETHER....TALK ABOUT TIMING...I WILL HAVE 4 CAMS TO TIME. ...WHAT FUN..)cool what a dream let me know when you need info i have all the trick stuff for that if you want to go gear drive i think i still have one or two set ups left from when we used to run them in the off shore boats are you running serrpintine or cog ????

[OBX-AUTOMOTIVE]

...GSMIKIE...SERRPINTINE...IT'S IN MY 1991 OLDS CUTTY CP...I HAVE TO REPLACE RT AND LF HEADS..I HAVE THE TWO FACTORY MANUALS FOR IT!!! I'VE READ SOME ON IT!!!...NOT TO MANY AFTERMARKET PARTS FOR IT...BUT THE GEAR DRIVE IS NEWS TO ME!! :cool: I KNOW WHEN GM TESTED IT AT FIRST IT WAS PUMPING OUT 285 HP...BUT THEY DE-TUNED IT...DO TO THE TRANS "AUTO" WOULD NOT HOLD UP!!!DOWN TO 215 HP.. ..I'LL KEEP YOU IN MIND!!! THANKS!! :cool: :cool: smile.gif

[gsmikie]

the gm power books offered a posi /and a spool fot that trans and severe duty clutch drums a couple of gm techs showed up at corporate with one of them pumping out 710 hp at the front wheels car craft did the story on it along a zr-1 in a camero and a quad four twin turbo (680) hp with a auto also most of the parts can be had through the gm power books i think they were numbers 6 through 9

[porkchop]

Ok it is all back together and running! Thanks, Mike. I put on the the non-valley gaskets and that helped alot. I still need to get the carb tuned in but I didn't want to mess with it anymore today, it is hot about 115* :eek: :eek: . So I will play with it more this weekend and hopefully get it tuned in just right(LOL)! I can not tune a carb to save my life. So I am hoping to get it good enough to drive it to a shop to have them do the carb for me. No more playing must make Ouray.