haack52

Hello everyone. Well I'm trying to finally get my engine running, but I'm having problems with the Mondello JM-20-22 cam.
Hope someone can give me the answer.
I have a 455 with this cam, turbo 400, and Carter carb. I can't seem to get the engine to idle less than 1100 RPM and not die when I put it in drive.
I have heard of others using this cam and are very happy with it.
Is this too much cam for the street?
any suggestions would be appreciated!!

My442

I run that cam.

Need more information:

1. Timing?

2. Jetting?

I had my engine on the dyno, and had to do quite a bit of carb and distributor work to get it dialed in.

haack52

Hi My442
Well the carb is a 750 carter, I don't know what jets it currently has. The engine was in a 4 speed. So I'm sure the idle wasn't an issue before.
As for the timing I've gone as low as 20 to as high as 38 advance. It idles best at around 32 but still can't take being put in gear

gearheads78

What converter? Probably not all your problem but if you still have a stock stall you are adding fuel to the fire so to speak.

My442

The first thing is to be sure your timing is correct.

The best power on the engine dyno was with 16 initial, and 36 total mechanical. All in by 3000 RPM. I have the vacuum advance limited to 10 degrees.

***Did you degree the cam?***

You need to access a A/F meter. My bet is that the carb is way too lean.

How do the spark plugs look? If they are white, then you are too lean.

Report back with your findings.

PS - be sure you don't have any vacuum leaks.

haack52

Thanks Gearheads78 & My442
Yes I do have a stock converter, I expected some issues with that, but didn't expect the engine to just die when I put it in gear, not with an idle of 1000.
The first thing I thought was that it was too lean, but it didn't change anything even when I richened it up.
This is probibly just too much cam for the street and a stock auto trans. This engine was in a GTO for about 1000 miles, but with a standard trans. I'm sure it's a great cam, just not for my applacation. I was just hoping to be able to make it work, (I'm just being cheap)!

My442

I have run that cam in a 70 442 with an automatic trans and a near stock converter. It ran well after I dialed in the carb and distributor.

haack52

My442
Well ...........mabe I shouldn't give up yet. It's just that right now there isn't and "dialing in"... It just plane won't run.
How much lope did you have in your 442? I can get it to idle with a mild lope at 1000 rpm but just dies right out in gear.

tim72

tim72

I had the same cam in mine and it seemed to be ok not very radical at all. The cam did take a crap due either to poor break in or a bad cam. Personally I would not buy a thing from Mondello in CA as there customer service is very poor as well as there waranties and return policies. Just my opinion which I have heard from many different folks.

I does not sound as though your issue is the cam. I would look some where else for the problem.

Tim

Tim

haack52

Thanks Tim
I'll keep working on it. I'm just running out of ideas.

tim72

Just started mine up with the stock converter and it stalled. I am changing the converter as the original is to tight. I went with a 2600 to 2900 stall made up by Transmission specialties with baloon plates. They had a 28 to 32 but I am not racing at the strip every day. Remember your motor will make about 460 ftlbs of torque from 2000 rpm till 5000 rpm. The torque spike is at about 4500 rpm. There you wil be at about 500 ftlbs torque or better depending on whats been done to the motor. I was really upset having to pay $400 for the new converter and having to climb under there again and remove the converter.

Tim

Tim

haack52

I wasn't planning on racing, just wanted it for the street, and thought the standard converter would work for now.

88 coupe

That grind is not the source of your problems. More likely it is a vacuum leak.

Disconnect the vacuum advance.

Unless their combination (all engine components, car weight, trans, stall, rear gears, suspension, etc) and driving habits (and philosophical outlook) are identical to yours, that information is pretty much useless.

Not for a 455. What is your compression ratio? What fuel are you using? How old is it?

With no vacuum advance? When you assembled the engine (or degreed the cam) did you verify the the timing marks lined up at #1 TDC?

Disconnect the vacuum advance. Then ignore how it idles and pay attention to what your timing light tells you.

If it dies, it must not be getting enough fuel?

Did you change jets or did you adjust the idle mixture?

Turn the mixture screws in, until they lightly bottom out, then back them out 1 full turn.

Check the firing order.

It is a relatively mild street cam. It will be fine, once you fix what is broke and stop fixing things that are not broke.

Remove the distributor cap and verify that the mechanical (centrifugal) advance is working properly. Set the initial at 12° BTDC @ 800 RPM in Neutral/Park.

Norm

haack52

Thanks 88coupe
Most of what you suggest I have looked into. Vacuum leaks, not using the vacuum advance, adjusting the carb (it's at about 2.5 turns out now,) Compression is 9.75:1
It idles at 1000 but no lower, and dies in gear. it has a stock converter but I thought if I could idle at 1000 I would be ok.
The cam is at 0 advance.
I haven't checked the mechanical advance, (That's an excelent idea).
I appreciate the help. I'll keep plugging away at it

jhfries

my guess would be not enough carb for the cam. if i'm not mistaken the stock rochester pushes 780 + cfm.

john

svnt442

That would have no bearing on the idle. The Carter has larger primaries than any Q-Jet.

haack52

Well I'm out of ideas, dist. checke out fine, swaped out carb with an Edelbrock from another 455, and checked for any vacuum leaks.
This week end I'll dig into the cam, may be that who ever built it has the cam way advanced. I see it does have a split front timing chain cover plate. In any case I have another cam to go in.
Thanks for all your help guys I do appreciate it!!

cutlassefi

My guess is you have a vacuum leak. With it idling, put your hand lightly over the carb. Does it raise the idle, lower it and stumble or stay the same? Then go from there.

Also check to see just how loose your mechanical advance is. It's a long shot but if it's real loose it could be retarding enough when you put it in gear (lower rpm) to cause it to stall. I've seen it happen. Chased it myself once many many years ago on my dads Datsun 2000. Check it out.

haack52

Thanks cutlassefi
I

haack52

I did find 1/2 the problem...The cam was dialed in way advanced. So I set it streight up, and WOW! I have idle. smooth and runing great at 600 rpm. Now the second half of the problem has to be transmission. If I put it in drive even at 600 rpm the transmission trys to pull hard and stalls the engine. This is a stock converter but it shouldn't pull this hard at 600.
Is

haack52

Anyone have a suggestion?
Thanks I do realy appreciate all the ideas I've gotten.

nonhog

I hope you get it working right. I'm no diagnostic tech or even a good mechanic for that matter "Just enough skill to be dangerous"
read the post that Norm was kind enough to add about what the cam card says......
Oh and thanks for all the input I just got reading your thread re: jm20/22



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