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Old 07-08-2007, 04:59 AM   #1
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I am no master mechanic but have rebuilt a few engines in my lifetime. My neighbor is a race car builder. So when my 84 454 P30 Itasca overheated and cracked a piston (discovered after driving it home after a slight "ping" developed and pulling the heads to check it out), I decided to rebuild the engine myself and with his assistance here in my driveway. A year later we had it running and sounding better than ever. However, it seems to have lost about 30% of its power when climbing.

During the rebuild, my friend/neighbor convinced me to add a "RV cam" We added a Crane PowerMax Cam and Lifter Kits
Cam and Lifters, Hydraulic Flat Tappet, Advertised Duration 260/ 272, Lift .484/ .515, Chevy, Big Block, Kit. This cam was suggested by the Crane tech support group from my supplying all my engine and drive train info. They said no distributor alteration would be necessary.

However, now when I head to Colorado the beast will barely make it up Rotan Pass. I had to turn around when I attempted Monarch (6% grade). When I last started up Monarch, it started skipping badly which got so bad 3/4 the way up, I had to turn around.

Back when I first bought this "slightly used vehicle" (fat dumb and happy with it unknown to be falling apart behind the hood with bad lines, a gas tank full of rust and a clogged radiator), yes back then it had no trouble climbing Slumgullion Pass (9% grade). (If I only knew then what I know now about what shape that old buggy was in, I would have never even tried that pass!!!)


P.S. My local mechanic rebuilt the carburetor at the same time as the overhaul. He also timed it but I remember he spent only a couple of minutes setting the timing. I have read where a lot more needs to go into testing the timing by restricting the springs, checking the angle, vacuum in and out angle, etc but this was not done.

Where should I begin :-(
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Old 07-08-2007, 07:55 AM   #2
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Sounds like you need to look in to the timing and carb adjustment. If your neighbor the mechanic he thinks he is, this should be no big deal for him. Do you have the QuadraJet carb? If so, these carbs can be a real pain to get set right. While not the easiest to work on, they work very well when set up correctly.

I always hated to work on them, but had a buddy that could make one sit up and salute him.

Good luck,

Ken
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Old 07-09-2007, 06:48 PM   #3
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I agree with TXiceman, I would get the timing set and the carb reset and if that doesn't do it get another carb! Mine was somewhat like your engine but went with the roller rockers and lifters too!
I got rid of the Q-jet and got a carter type spread bored Edilbrock. One of the best things I did. Good luck and let us know how it goes. Capt.Dan
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Old 07-10-2007, 01:04 PM   #4
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Before you start messing with carbs and timing... Check the basics... Did your race car guy set the cam up correctly. Check with Crane for the specs. Then pull the valve cover off #1 side, put a degree wheel on the crank and check the specs from Crane against the install. Depending on what is needed you may have to much cam advance or not enough. This can be change with offset degree bushings on the cam index pin.

Assuming te cam is installed correct.. I would pull the distributor and either replace it or have it rebuilt. I would suspect the is lots of slop in it.

Reinstall the distributor and with a good induction timing light set the timing. It can run anywhere fro 4 to 12 degrees BTC.

Next check for vacuum leaks. I use a propane can with a small hose attached to it. Just let out a very small amount of gas and run the hose around the intake manifold , carb and so on. If he engine speeds up you have found the vacuum leak.

Rebuilding carbs at home is not fun. You really need to tear them down to do it properly. Example - Throttle shaft bushings, welch plugs and other items that are not in a kit. Get a good Edelbrock or Carter.
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Old 07-10-2007, 01:35 PM   #5
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Don Juane

One thing you mentioned is that "it was skipping", I take that to mean that it was missing, is that correct? And if that is the case, does it miss all the time or just on a heavy pull? If it is missing I would find the cause of that first as it might fix the other symptoms. Low power could be caused by a lot of things but missing is something you can hang your hat on.
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Old 07-10-2007, 01:52 PM   #6
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I think I wore out my welcome with my neighbor, since I had him over every night for a month of Sundays. He hides now when he sees me :-). So no, he didn't do all the adjustments with the cam but I think I was on the economy package (free help). Basically the cam was slapped in on the same mark as the factory one came out.

OK, back to what I am calling skipping. At 50% up Monarch pass, the engine acts as if someone is turning the key off for 1-2 seconds and turning it back on. If I pump the gas while driving it seems to help. I thought it was vapor lock but the last time before trying the climb I had installed a rear Holley Blue fuel pump next to the gas tank and installed the companion fuel regulator next to the quadrajet. I did get further up the pass that time but still had the skipping.

Further info regarding the fuel setup .... On a prior trip I had installed a dash mounted pressure gauge and noticed the stock holly blue pump regulator was breaking the seat. The regulator set at its lowest point was 5 PSI and kept jumping up to 15 PSI (carb would flood) so I ordered the low pressure spring kit and now have it setting at 3 PSI and this pressure stays constant now on all climbs.

As a side point, of course this setup caused all my neoprene hoses to fail with the new higher pressure of the Holley Blue fuel pusher, which called for some better hoses. I elected using the high temp & high pressure stainless steel mesh encased teflon I found at a local shop called Stuart Hose. Only $5 a foot - WOW! But the good news is that I am done replacing fuel lines every year.
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Old 07-10-2007, 02:34 PM   #7
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It looks like your Crane cam is a 133901 and at the 0.50 duration it is 204 intake & 216 exhaust and that ~should give e'nuf low/mid range grunt to pull it along.
Now if the cam is dialed in correctly you can go on from that point.
The ignition will be a PITA to straighten out, What is your initial base timing set at?
With the vacuum advance disconnected what is the mechanical advance at 3000 RPM?
I setup the HEIs at 10º base and modify the mechanical advance with 41 weights and a 375 center and that combo will hand you a 22º mechanical advance soooo 10º base + 22º =32 without the vacuum advance hooked up.
Most mechanical advance (stock) I've seen is around 16º and thats why Chebby installs a 25º vacuum advance unit which drops out once your engine drops below 5" of vacuum.
This is a good place to start then on to the fuel section.
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Old 07-10-2007, 03:29 PM   #8
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The timing light was borrowed. I need to buy one and learn how to do this, so which one do your recommend?

Last time I timed an engine was my 64 chevy and it ran very well (could smoke the tires with the 327 2 barrel carter and 2 speed turboglide). :-)
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Old 07-10-2007, 05:23 PM   #9
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My opionion is timing lights are a personal preference.....Sears sells a decent unit with a dial back knob and induction (wire) clip on.
Now you can double the price with an "Equus" and that has a tach on it, Summit racing has two types $109.00 and $199.00 (grump)
If you happen to have the timing tab at the 4:30 (or so) drivers side just hook the unit to #5 cylinder and have fun.

Jim
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Old 07-10-2007, 05:58 PM   #10
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I'd say the cutting out is due to the float in the carb set too low since it did better after adding the fuel pump and the effect you describe is exactly like running out of fuel or the float too low.

I'll second the Sears timing light, works great and has the advance knob on the back of it.

Keep in mind that since you've changed some things the stock timing setting may not work. In most situations I set the timing at about where it is supposed to be, then play with it from there, I advance it until the engine pings under load or is hard to crank when hot, then back it off to where the pinging stops, thats usually where the engine wants the timing. However, if you are not experienced with things like this you might be better off to take the MH to a shop that has a wheel dyno and pay them to tune it up. They can set it on the dyno and put a load on it and set everything up right the first time, from timing to mixture, the whole nine yards. The plus side to this is if something is breaking down or failing they can see it and fix it whether it be carb, ign or whatever. Good luck.
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Old 07-10-2007, 07:00 PM   #11
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Yep! Tom is right I do beleave! Keep going like that and you will burn the pistons!
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Old 07-10-2007, 07:42 PM   #12
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Tom, Thats pretty much right on and that new cam will need some better tune times....
I'm pretty sure a stock Chebby cam is around 193/I & 203/E and his new cam is 204/216 (both at 0.50) and that will bleed off some (but not much) compression.
The ignition will need a sharp tune but once it's set properly lock it down and forget it.
I only touch ONE thing at a time just so the issues don't get confused.

Jim
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Old 07-11-2007, 09:16 AM   #13
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Looks like I am on my own with this one. The local Chevy dealer doesn't want if it its not stock cam and all the local speed shops don't want to mess with it.

Anyone near Lewisville, TX a good mechanic and bored :-)?
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Old 07-11-2007, 09:34 AM   #14
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P.S. No one I called in the DFW area has a wheel dyno that will accomodate the 28' motor home.
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