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Discussion Starter · #1 ·
I am really getting pissed. Here is my problem.
I have a fresh (1200 mi) 302 in my 69 EB, mild motor, 30 over, reused RV cam from before rebuild (and lifters) And I have a set of 66 289 heads on it that have oversized valves (Indy cyl head)with screw in studs and roller rockers.

I have had 3 carbs on it trying to get a smooth consistent idle. Started with a Holly universial 4bbl, Idle just went away and I dont speak holly so I took it and the alum intake off and shelved it.

Installed a stock 2bbl intake and a 2100 2bbl carb, ran so so but had really poor mpg, it felt sluggish and had a bad run on. Turns out it was from a 390.

I robbed a 302 carb from a 74 rancharo, rebuilt it, still get 7.5 mpg and a crappy inconsistent Idle, and more run on, some days it holds a steady RPM others I need to raise it to keep it going at a light. I did get rid of the flat spot I had with the bigger 2bbl tho.

The truck has;
stock automatic tranny
stock (? duno) gears
31' tires.
Mallory unilite breakerless ignition with no vacume advance


I have checked for vaccum leaks till I am blue in the face and have a buzz from ether and various other cans of combustable fluid.

My question is without knowing excatly what size cam is, (all I rember is it was an erson RV grind, lost the sheet) should I consider changing it out and installing new lifters? Do you think that the over sized valves and runners could be effecting me?

I just want it to run about like a stock 5.0, with no run on.I need no serious power! I want smooth damit!

Sorry for the long post, I am willing to take a weekend and redo the top end with other parts to get a bronco that runs like a station wagon! I just wana drive it!
 

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Still sounds like you have a vacuum leak. It could be manifold gaskets leaking under the manifold (possibly the wrong gaskets? Did you make sure they fit the ports before installing the manifold?) Disconnect vacuum lines to see if you get any difference. Make sure you don't have a leaky EGR port under the carb.

I assume you adjusted the timing? Are you sure the balancer is good? On the last 302 I did, the balancer ring had slipped almost 20 degrees, which would make the timing 20 drgrees retarded from where you set it. This would definitely cause rough idle, poor power, and run on. Another gotcha is a sticky advance mechanism in the distributor. It may be stuck advanced when you check it, then retard after the engine speed has been changed a couple times. This could cause the problem to come and go.

An RV cam won't cause any problems on its own. They generally run smoother than the stock cam.
 

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Discussion Starter · #3 ·
Ya, I thought about the intake leak last go around, So i changed the gaskets, no difference. Then I changed the intake and carb. I just have piss poor idle/ off idle. I used to run a 289/302 in an old mustang, ran better than a EFI 5.0. I just dont get it.

I checked the balancer against the #1 being at tdc, it looked on to me.

Now the distributor, thats another story. If i had a stock ford electronic from the 80's I would change it! I hate being stuck with mechanical advance only.

I think the heads in combination with that cam makes for poor low end airflow.
 

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Is this the first time you have run these heads? Larger valves will decrese the air flow velocity going into the cylinder, hurting low end torque and idle quality. Mabey the RV cam and big valves are a bad combo.

I know it is a lot of work to go through, but if it were me I would put a set of stock heads on and see what happens. I have a set of ARP studs in my motor not for the superior clamping power of studs, but rather cause in the first 200 miles of running my engine I had the heads off 3 times.

JYS
 

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Discussion Starter · #5 ·
I really think that may be the case. I may buy a new cam and lifters first, if that does not do any good I need to find a good set of rebuildable heads. Only reason I may do the cam first is the $$, it is cheaper.

Of course I still think it could be a distributor problem.
 

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Well, what size valves are in the head anyways? Unless they're huge I wouldn't think it'd be a problem.. I'd look vacuum leaks, ignition.. then heads unless they're ungodly huge valves. Might wanna check the lift of the cam too, so you actually have some idea. Just take a valve cover off and use a dial indicator, twis her around a couple times, and you'll get acutal lift. (position over pushrod) put it over the valve and you'll get total lift (with the rocker ratio)
 

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How used is the cam? Unless it's a roller cam and lifter, it isn't a good idea to reuse them. The spec on the cam, however, seem to be fine, nothing to extreme.

I'm stumped.
 
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