pressure in the intake

[180shabah]

Re: pressure in the intake

150* is not hot, and a swing to 175*(if the gauge is accurate) is not exactly cause for alarm. Do the vacuum test mentioned above, it will probably answer alot of questions.

 

[Quadruplecccc]

Re: pressure in the intake

Plumbed correctly she will run @185* to 190* with a 140* thermostat. What really gets my attn. is I can't hold my hand on the manifolds when hot. It's been said many times over that this is not good and I'm not willing to ignore this.

 

[jtybt]

Re: pressure in the intake

ABSOLUTELY!

If your cam was installed a tooth or two advanced, that would advance all the lobes of the cam and make the intake, which is already opening when the exhaust is still open at the top of the exhaust stroke, to start opening earlier in the exhaust stroke and force exhaust into the combustion chamber and out the carb.

 

[Quadruplecccc]

Re: pressure in the intake

looks lke i'm going in to check cam to crank timing. I hope this gives some answers. Thanks everyone for your help. If anyone has more to add , please feel free!

 

[bruceb58]

Re: pressure in the intake

If your manifolds are getting hot, it is not an engine problem but a water flow problem. Check your waterflow. Have you changed you impellor lately? Ever run the engine without water...even for a few seconds?

You also better make sure you have your firing order correct. Check this again.

 

[Quadruplecccc]

Re: pressure in the intake

Unless I've overlooked something , I've replace and checked all the normal stuff. New Thermostat (140*) , new water pump, I pulled the hose off the manifold that is hotter than it should be and had lots of flow. Just got done pulling the timing cover off to see if the cam to crank timing is off. Marks are right on the money.
Next step is to pull the intake and heads and poke around . Looks like I may have to have the heads done. Seems like a valve is sticking. Or, maybe even a bad head gasket.

 

[bruceb58]

Re: pressure in the intake

Have you pulled the risers to see if the riser manifold junction is not clogged? Has this boat been used in salt water? If so, how old are the manifolds/risers?

 

[180shabah]

Re: pressure in the intake

Unless I've overlooked something , I've replace and checked all the normal stuff. New Thermostat (140*) , new water pump, I pulled the hose off the manifold that is hotter than it should be and had lots of flow. Just got done pulling the timing cover off to see if the cam to crank timing is off. Marks are right on the money.
Next step is to pull the intake and heads and poke around . Looks like I may have to have the heads done. Seems like a valve is sticking. Or, maybe even a bad head gasket.

You still have not verified waterflow THROUGH the manifolds and elbows/risers. If the water can't get back out, then you will not have FLOW.

How did you determine "sticking valve or maybe head gasket"? Have you hooked up a vacuum gauge yet?

 

[Quadruplecccc]

Re: pressure in the intake

verified water flow in the first post. Pulled the hoses off while running and had lots of flow. Alsso replaced water pump. Don't know how to do a vac. test. Was told I need special equip. that I don't have.

 

[180shabah]

Re: pressure in the intake

Which hoses did you remove while running the engine? 1/2" or 4" ?

The only equipment you need for a vacuum gauge is the gauge and some rubber tubing, maybe an adapter or two. The gauges are cheap and most are marked right on the face with the most common "readings".
"late timing" "sticking valves" "improper mixture" etc.

 

[Quadruplecccc]

Re: pressure in the intake

pulled the 1" hoses off the manifolds where water exits manifolds.

 

[180shabah]

Re: pressure in the intake

Where does the other end go? Should be to the elbow/riser, the last place that the water is contained before being mixed with exhaust and "dumped" overboard. Elbows have very small passages and are prone to clogging with rust and scale from the rest of the system.

 

[Don S]

Re: pressure in the intake

1. If the manifolds and/or the risers are plugged up, you don't have water flow through them. Nor does the water any longer flow through the engine as much. Thus the overheat. The flow to the manifold from the 1" hose stops or slows way down when you hook it back up to the plugged or partially plugged manifold.

2. Don't Ford vibration dampners have timing marks for both BTCD and ATDC? or was that just on the 460's? If it is on the 351's, are you sure you have the idle timing set on the BTDC and not the ATDC side of TDC. That makes a big difference in how they run under load.

3. Check the firing order of the plug wires. I had a 302 with 2 wires crossed. The engine idled fine for about 1 to 2 minutes. Smooth as silk, then it would just pop and die. Start right back up and idle perfect for 1 -2 more minutes and just kept repeating that. Till I finally found the crossed wires I installed.
Took me 3 tries to find it for some reason.

 

[Quadruplecccc]

Re: pressure in the intake

It's a 351 and does have the marks on the h-balancer. I have it set at about 8* btdc and runs fine but too hot. Here is something that I wouldn't have thought of without seeing it first hand . I did more reading and found site that was auto related but same kind of symtom. On that car which happened to have a 289 , they found that someone installed one of the head gaskets backwards. They went on to describe what would happen if both are in backwards. In short they described imediate temp spike but does not boil over. Also the right bank will run extremely hot. This is what I've been dealing with. Reason it doesn't boil over is that the front half of motor is keeping just cool enough to prevent this from happening. Long term use is FAILURE. Head gaskets can and will fit on motor backwards but will block off water flow to the heads. This is why I have good water flow comoing out of the hoses but I don't have water going to all the right places. Unless someone disagrees wiith this possibility, I'll be spending some time having a looksee. What do you think? I'm hoping I'm on to something here!

 

[bruceb58]

Re: pressure in the intake

Your manifolds are getting hot...is that correct? You have a flow problem if that is the case. We keep going back to this but you seem to be ignoring it.

Read #1 in Don's previous post...again!