Technical big block 429 Mercury sat 12 years, no power but runs-HELP

I bought me a Mercury, and hope to cruz it up and down the road. New plugs, points condenser, fuel filter. Will start but no power, about 2500 rpm max. Any suggestions from any Ford/Merc folks. I know it is new as it is a 1973, big ol boat but in such mint condition. Interior is a 9.75. So my plan is a little low in back, has fender skirts, bullets on the stock full hubcaps, bellflower tips out the backside. Drive and enjoy the comfort. Her name is Elisabeth, Liz after you have met her. I will post some pix of my little mods when she is able to run down the road. Any help about my lack o power would be appreciated. It is a 429 4barrel motor which has been down powered by FOMOCO. HELP

 

What is the ignition base timing/advance timing set at?

Jim

 

Get after market timing set to get rid of factory built in retard of cam timing. Check dist for proper operation, is vac can working, what is the timing set at. Is vac sec carb working properly...sounds like carb and timing are off

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I had a '73 Marquis with a 429 way back then. Normally it ran great, but once in a while the choke pull-off failed and then it hardly ran at all. Happened a few times before I got around to fixing it. Ran great thereafter.

 

What kind of carburetor is on it?

 

Stock Autolite carb is a POS and a real pain to rebuild. From '72 up, ford built the 429 and 460 with the cam retarded 8° for emission purposes. Earlier '68-71 Cloyes and Comp Cams sets are machined "straight up" and make a lot more power. If it hasn't been run in a long time the valves could be tight in the guides because of the oil drying out. Try running some Marvel Mystery Oil in it for a while.

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Just thinking....could the pipes/mufflers have some issues like a little mouse put some rags in there ? Just saying...I had a clogged up pipe on one of my earliest rides....

 

Just read it again. Sounds like no power enrichment circuit in the carb. Did you even have the top off it?

 

I'd follow stillrunners advice FIRST. You can just drop the head pipes and see if it revs. If the studs are long just back nut off till you can get an open gap. Costs no money to try and a good chance varmits have set up house keeping.

 

I would go with a plugged exhaust. When I worked for the park service at the Grand Canyon we had a constant battle with squirrels storing pine nuts in the tailpipes of seldom used vehicles. We ended up welding crossed wires on the tips to keep the varmits out. I have also seen the two layers of pipe in the head pipes have the inner layer collapse and restrict flow.
The 429 cobra jet timing chain and gears makes a big difference in the throttle response. Check the distributor to make sure you are getting advance.

 

Southcross. I remember when I put the new exhaust system on my 56 Buick station wagon. After putting the muffler on 1 mouse ran up my shorts pant leg causing to scare me and bang my head on the frame. LOL. Then when I had my step son fire her up with the new exhaust system a whole mouse nest came flying out the tail pipe with a few more mice. LOL. It ran a lot better after that.Bruce.

 

Jim, we have not checked timing yet. I am probably premature in my plea. I have been told that the vacuum advance is a thing to check, not sure how that even works. All the stuff under the hood has me a little nervous. Will check the timing.

 

Yes it could be blocked exhaust. Equal chances that it is the carb. Less chances that it has to do with timing as it should rev higher than 2500rpm with timing off. Choke pull offs were very common problem in that era.

 

I'll try one more time to narrow this down, then I'll leave you with 5 pages of guessing, which will be all over the map.
No offense to anyone, but we don't have enough info yet.
Okay, I guess you don't know what carb. it has and haven't looked at it yet.
So, when you say 2500 limit, I'm figuring you don't have a factory tach, or a tach and dwell?
Then, is the 2500 guess in low gear, foot on the floor? Is it 2500 (approx) in neutral at the carb , with the air filter off?
Is the 2500 WFO? No? What happens with the carb. wide open in neutral? Does it shut off? Backfire? Just bog down?
We'll go from there.
These cars are relatively simple to diagnose, compared to the new stuff.
Not so easy over the internet, but we need all the help you can get here.

 

I would suggest the timing advance isn't working in the distributor, maybe stuck from sitting.

 

I am re-stating what others have already posted, but with a purpose. New gas is crap, and if the engine hasn't run in a long time, I would be suspicious of clogging of one or more circuits in the carb. It will probably mean that you have to pull the carb, but sometimes you can get lucky by warming the engine as much as possible, and then emptying a can of carb cleaner into every orifice of the carb, then letting it sit overnight.
This next step is a cheap and dirty trick that will sometimes help clear the carb.
Next day, rev it has much as possible and have a friend cover the inlet with a large clean rag, to create as much of a vacuum as you can. Repeat if there is an improvement. This will sometimes clean the crud enough to make the carb useable.
I would also check the exhaust for blockage, but in my experience, the symptom of this problem is, that it will normally start well and then gradually lose rpm as the pressure builds up in the exhaust.
'A complete blockage is always possible, but then I don't believe you would get it running.

Bob

 

I'll bet the vacuum advance doesn't work either and that would definitely kill the power but you really think it was shut the motor off at 2500? ( response to s w a d e)

 

All these are things as earlier me tioned that will keep it from accelerating....stuck choke, stuck advance or diaphram on advance rotted, carb plugged, timing way off, exhaust plugged.....check all these and eliminste one at a time and see.....fuel filter, fuel pump.....????

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Does the throttle linkage move all the way at the carb?. Fixed a few that didn't

 

If the Strait forward stuff (vacuum advance, linkages, exhaust. etc.) fails to work, a carb rebuild kit will just cost you $50, you could try to disassemble/clean your carb yourself and see if that helps. You probably have an Autolite 4300. Probably not a bad idea either way, a carb sitting with ethanol fuel for a long time will almost always have some clogged passages.

I would be weary of soaking the entire carb in chemicals, (if it's an Autolite) these carbs have plugs that are supposed to be permanently installed that can pop out after a carb soak and dump gas on your engine. Brass wire and aerosol cans of cleaner are easier on the carb and effective at freeing up passages.

I love the boats, good luck.


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Please post the cure when you find it.

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After sitting that long i,m sure there are half a dozen basic things that arent working.

 

I'm thinkin' the secondaries is stuck closed....
I could be wrong....

 

Can somebody explain how the vacuum advance not working will kill power? It is strictly for fuel mileage, do a little research on when the vacuum advance comes into play, it sure as hell isn't wide open throttle when we want power.....


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Good point but first and foremost, how could it cause an engine to not be able to rev over 2500?

 

Ok I'll bite....


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I have no idea LOL

 

Ya, toss out the vac advance and frozen weights ....no reason to go into "why"...but that's not he OP's issue here...yes, they may have a problem, but certainly not the cause of the engine running to only 2500 rpms.

Majority of the other suggestions were spot on...would be where I would concentrate my efforts.

 

Ok! I read your last post as you had a reason!! Lol! Thought I had missed something. Definitely not the cause of low power.


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