72 Olds Project

Okay so again I am still working with my 455 trying to sort all the issues out. Going to have to play with timing and other things as it lags bad on acceleration. My question is I bought my Mondello camshaft BEFORE I found out the deal with them. I also got my lifters from them as well. Could they be giving me issues with a crazy idle? I swear at times it feels like my motor wants to jump out of the engine bay and will vibrate like crazy. When you rev it then it sounds great and smooths out. The engine was all balanced, but it sure doesnt feel like it. I have the JM-18-20 cam, headers, Edelbrock Performer, stock valvetrain, C Heads and Holley 750 carb.
Thanks

JM-18-20 0.488 0.496 260°/266° 216° 226° 112° 1000-5000
Street HL-230
555-H
555-HCR SK-247-SP SK-245-D TR-252
TR-499 ARK
SAR 110-140 290-340

Beob

Sounds like similar problems I had. I also have Mondello cam/lifters(jm25-28), but yours is a bit milder. Advancing timing seems to help my problem. I advanced timing til I heard pinging when accelerating, then back off on throtttle immediatly, then backed off on timing a hair til pinging is gone.
Did you get you vac adv in the right spot? Also mixture screws on carb adj right?

72 Olds Project

That is what I find strange Beob. I figured I got the mild cam because I did not want to get too crazy. My 455 sounds like the Chevy 350 that I put one of those Thumpr Cams in. I moved my vacuum to the bottom of the carb. Still needing to dial in the correct timing. Using HEI so I messed around and moved from a "35" gap to a "44" . Funny thing is I have a driveway that is raised a little and it struggled to get into my garage. It feels like it has LESS power than my Pontiac 350 had in a 68 Lemans

72 w29 all green

What's the actual compression ratio?

Was the cam degreed when installed?

What do you have for a vacuum reading?

72 Olds Project

Compression was 9.5:1 pistons....but you know with the new gaskets probably about 9?

The cam was not degreed but it was lined up correctly.

Not sure on the vacuum front as I need to get my hands on a gauge The Power Brakes do work fine though.

Lee_A

That is a LITTLE cam for a 455, it should have more off idle power than you can possibly use.

Hook up a vacuum gauge. If it has a distinct "tick" that corresponds to the idle speed, then you probably have lost a cam lobe.

Only a few reasons for a 455 with that cam to NOT have a smooth idle and GOBS of lowend:

- Cam was NOT installed properly
- Cam lobe(s) worn
- Carb tune WAY off
- Something screwy with the ignition system
- Mechanical issues with the motor itself

I have the 22-25 cam in my 455 (bought it direct from Engle, though, and put it on a tighter LSA), and it idles decently and has great low-end (I do have some stall speed, though). Your cam should idle even better, and have much more low-end.

Lee

72 Olds Project

Yeah I would not even be able to break the tires lose because of the bogging of the car on take off. This engine should have tons of torque, but not feeling it. Again..when its in Park and you rev the motor it sounds great! You get in the car and put it in gear and it feels like it has been neutered. I am hoping that it is more carb not being set right. My mechanic buddy has not had time to come out and mess with it again. This engine has a MAJOR lope to it and just does not seem right. It to me should be very smooth. Thanks!

cutlassefi

For everyone, this is not an acceptable way of setting the timing. you're asking for trouble.

Check carb tune and overall timing, idle thru to full throttle.

I'm on record as not liking those cams, even before I became an Erson dealer. I had that exact one, didn't perform well.

72 Olds Project

Yeah I just started thinking about the issues and was hoping that maybe the cam is not at fault. I have read bad things and should have known when my cam came in with no specs on the cam at all. Find things out after the fact.

Lee_A

I'm new to this site, but have been hot rodding since the early 80's. I'm a little confused about the problems you are alluding to, with the Mondello cams?

The double-digit cams (16-18, 18-20, 20-22, 22-25, etc.) have been around since the 70's. They were all made by Engle, and in the 80's were state of the art. I ran a 16-18 in my old 350 for years, and it was a great cam and had no problems. As I mentioned earlier, I got my 22-25 direct from Engle, as the LSA provided by Mondello was not what I wanted - but it has been in my car since the mid-90's and still works fine.

Now, ANY flat-tappet cam will need some zinc added to the oil to keep from wearing out prematurely. When you run the proper valve springs for a performance cam (more pressure) you'll be in even MORE need for the zinc.

I just noticed in the opening post that "original valvetrain" is mentioned. If you still have the stock springs, your problem MAY be right there. The stock springs are wimpy when new, and get worse with age. Install a cam with much more lift, and old stock springs are going to have a REALLY difficult time controlling the valves!

Depending upon coil bind and retainer-to-guide clearances, some stock springs will destroy an aftermarket cam immediately. The cam OPENS the valves, the springs CLOSE the valves - no performance improvement unless you have the whole team working together.

Lee

56oldssuper88

It really sounds like a carb issue to me. Had a truck that acted like this. Try setting the idle mixture screws using a vacuum guage on the intake manifold.

TripDeuces

This doesn't sound like the cam at all. I'd be looking at a vacuum leak, carb issue, ignition, etc. I had a slightly bigger cam than that in a 70 Cutlass that ran 12's (same lift and 10* more duration). Even a wiped lobe would still produce gobs of low end in that engine.
I'd go back to basics and start there. Crossed wire, bad wires, faulty carb, bad vacuum leak, bent push rod. You can check for a bad lobe by just taking a valve cover off and watching the action of the rockers depending how severe it is. My gut is telling me carb but there's not a lot of info to go on here.

72 Olds Project

Thanks for all the info. I just put the gas tank back in with new sender. Wanted to dump all the year + old gas out. I put some 93 Octane in it just in case any impurities were left over. Yeah I have to agree 56 and Trip....most likely my carb is not set correctly and again my timing could still not be right. Though again when you turn the key the car fires right up. Just that little run on when the car is hot and I shut it off. My buddy that knows much more than I do is opening his own shop and has been busy with that. I have been flying solo pretty much and not sure that is a good thing. haha

72 Olds Project

Okay so I picked up a vacuum gauge from Harbor Freight today and going to see what I am getting after work. What should be a good reading for vacuum? Will it be close to 0 if I have a leak? Thanks!

TripDeuces

http://www.secondchancegarage.com/public/186.cfm

Nice little graphics depicting the different vacuum readings.

72 Olds Project

Thanks Trip! I just recorded from my phone what is going on. I will get it up on YouTube and hopefully you all can figure it out. It is all over the place

72 Olds Project

Okay here is the Youtube link. Hopefully you will be able to see it. First time doing this
http://youtu.be/gjDIkjYsrEU

72 Olds Project

Or try this one if that doesn't work. Thanks!

http://www.youtube.com/watch?v=gjDIk...t=HL1314742439

72 Olds Project

Looking at that page you sent Trip, it looks like I have scenario 11 with the changing idle perhaps. It just worries me though that when revving it can drop to ZERO. Is that a normal thing to do? Again...brand new rebuild on this engine.

TripDeuces

To me it looks like scenario 3 and 10. A little bit of overlap from a non stock cam (needle wiggle) and a vacuum leak/late valve timing. I would start by spraying starting fluid around all the sealing surfaces and checking hoses and connections. Since you didn't degree the cam but state it's installed properly I'll leave the late valve timing alone. Engle cams are typically ground 4 degrees advanced when 'straight up' so hopefully that's not the problem. I'm thinking vacuum leak which would be less noticeable at higher rpm like you stated.

TripDeuces

Yes it's normal for the needle to go to or near zero when revved. The bigger concern is why you have 10 inches of vacuum out of a cam that is not that big to start with. I would have expected between 15-20 inches at least.

72 Olds Project

Thanks Trip. I will give that a shot and see what happens. I mean is my cam really considered a performance cam? I just figured it would have more stock characteristics. You can hear the lobe the engine has which to me it does not seem right. Again it revs fine just sitting and sounds like it should go. Put it in gear and it drives like a Geo Metro It is very odd.

72 Olds Project

Oh forgot to add too when I pulled the vacuum line off the running to the distributor, I saw practically no change in pressure. Would that be right? Now when I pulled the full ported off the carb I could hear a change. I was using the Full Ported on the carb to do this test.