1972 351C runs crap

[Odmark]

Okay so the engine is now pretty much assembled, everything is moving smoothly as it should.

Now im going to drop the intake on, but now i need some advice.

I bought a valley pan, wich also included regular gaskets as well ass rubber seals for the edges and a tube of rtv silicone.

How do i do this? Just valley pan with rtv or valley pan+gaskets?

Rubber edge seals or just rtv?

Remember doing the olds engine i used just the valley pan with the rtv, no rubber seals either just rtv there as well.

 

[Don C]

I'm assuming you're installing an aftermarket aluminum intake. From experience, the bare turkey pan (with gasket on the head side, only) will eventually wear grooves in the surface of the manifold, due to the different expansion coefficients of the aluminum and steel/iron. This is the way the previous owner of my car did it and the Shelby/Blue Thunder manifold has slight grooving from the ridges on the turkey pan.

Plus, I believe that it is more difficult to achieve and maintain the proper seal with the turkey pan.

 

[Odmark]

Yes indeed, edelbrock aluminium intake.

So you are saying i should go for no valley pan at all?

 

[Don C]

The turkey pans are desirable because they keep the hot oil from splashing on the bottom of the intake manifold. People have used them with two gaskets, one on the head side and one on the manifold side, with some success. However, that may set the intake too high and cause a port mis-match.

A popular modification is to trim the manifold surfaces from the turkey pan, drill a couple of drain holes in it and use it as a splash shield and with a regular set of gaskets.

Another way to insulate it some is to paint the bottom of the manifold with ceramic engine paint.

And, yes, use silicon instead of the rubber end pieces. I prefer The Right Stuff.

 

[Odmark]

Hello again.

Engine is in the car and almost everything is attached, starting it up on saturday with help from my neighbour.

In the meantime, i have a problem with the kickdown rod. As you can see the rod is faar off from the linkage. I hear there is some sort of adapter kit for this? Anyone have the part number?

 

[Don C]

That's pretty common when changing intake manifolds. Sometimes they can be re-bent, but yours looks too far off. I have added in a piece of tubing, to lengthen them, or have found one that is close enough to be used at the junk yard. The easiest and cleanest way would be to get a Lokar kick-down cable.

 

[Odmark]

Thanks for the reply Don C, I think ill go for a lokar kit. But for now i will shift myself and skip the kickdown.

The car is now started and the cam is broken in, everything went fine.

So now its a little bit of tuning in to do, i think i have a vacuum leak because it runs pretty rough below 1500rpm, so im going to check that.

Also the radiator is leaking, so the fan covered the engine bay in coolant... Think im going for a aluminium radiator.

 

[Vicus]

Hello again.

Engine is in the car and almost everything is attached, starting it up on saturday with help from my neighbour.

In the meantime, i have a problem with the kickdown rod. As you can see the rod is faar off from the linkage. I hear there is some sort of adapter kit for this? Anyone have the part number?

At my last project I have had much problems with this kind of air filter. At first it worked fine but within weeks the filter element gets clogged and the engine did not get enough fresh air. Effect: gas consumption increased and the engine runs crap.

First I changed to an big open round air filter; it went better, then I reassembled the original air filter box and it kept at it's best.

Just my 2 cents

Cheers

Frank

 

[Odmark]

My air filter is brand new, so that is not the problem. Good to know though for the future, i need a small air filter because the distributor is so big.

But there are smaller versions of the normal round filters as well.

I checked the vacuum at idle and it wandered from about 3-8. It should be around 18 right?

Pulled and plugged some vacuum hoses but no difference.

Also it sometimes rises in rpm by itself.

Havent troubleshooted any further, going to buy some starting gas tomorrow and spray away.

 

[basstrix]

You can use wd-40 to get a similar result. Our shop used to use a small bottle with gasoline and the red tube off of a wd-40 nozzle to accurately squirt gasoline in various places looking for vacuum leaks. There are many inherent risks to the gasoline method, so proceed at your own risk if you choose that route.

 

[Vicus]

Havent troubleshooted any further, going to buy some starting gas tomorrow and spray away.

Bromsrengöringsmedel will work fine too!

Cheers

Frank

 

[barnett468]

i use flammable brake cleaner with the long nozzle and spray it gently . if anything drifts into the carb, it will give a false reading.

 

[Odmark]

I have sprayed EVERYWHERE with no luck, cant find a leak.

If i mist gently over the air filter it runs very smooth though so it is running extremely lean.

Im starting to think the carb is faulty in some way, it does not respond at all when turning the idle mixture screws, not even with both of them turned all the way in.

Sometimes it still goes up in rpm by itself, like its sucking air... Wierd and extremely annoying, im so close now.

 

[basstrix]

Have you disconnected and plugged the PCV valve and vacuum to brake booster? You said EVERYWHERE, so I assume you sprayed the base of carb too?

 

[Odmark]

Have you disconnected and plugged the PCV valve and vacuum to brake booster? You said EVERYWHERE, so I assume you sprayed the base of carb too?

Yes i have, neither made any difference whatsoever.

And yes on the second question as well :-/

 

[rcadd1ct]

You may have the pleasure of learning to rebuild the carb, too.

Fuel fresh?

 

[Odmark]

You may have the pleasure of learning to rebuild the carb, too.

Fuel fresh?

Yes it appears so rather buy a new carb, i was going to swap for a holley later on anyway.

But still not sure thats the problem, luckily my neighbor had a holley 650 on the shelf so im going to put that on and see.

Still he was unsure about wether it was functional or not.

Otherwise a colleague of mine had a brand new 650 double pumper i could try this weekend.

Well the fuel is over 1 year old, didnt even think of that.:chin:

Edit: Picked up the holley from my neighbour, seems complete except for one thing (see attached picture). Not a lot of experience with holley, but shouldnt there be a plug in this hole (big threaded one)?

And also, wich one of these are timed and manifold vacuum? I guess the big one is the PVC port.

 

[barnett468]

I have sprayed EVERYWHERE with no luck, cant find a leak.

If i mist gently over the air filter it runs very smooth though so it is running extremely lean.

Im starting to think the carb is faulty in some way, it does not respond at all when turning the idle mixture screws, not even with both of them turned all the way in.

idle circuit air bleeds are probably plugged.

 

[Odmark]

I have sprayed EVERYWHERE with no luck, cant find a leak.

If i mist gently over the air filter it runs very smooth though so it is running extremely lean.

Im starting to think the carb is faulty in some way, it does not respond at all when turning the idle mixture screws, not even with both of them turned all the way in.

idle circuit air bleeds are probably plugged.

I did a lot of reading on this subject just now, and since the holley is not complete i will pull my edel and thoroughly clean it.

Also mentionable is that the passenger side cylinder banks exhausts are way colder then the drivers side at idle, so they are probably the ones not getting the fuel.

 

[Stanglover]

I have not read ALL the threads/posts on this, so forgive me if I'm repeating something. I can only relate to a small problem I just encountered with my new re-rebuilt '71 351C 4V. I too had a rough idle when I started up the motor after installing it. Turned out that I had a dead plug and although on 7 cylinders it didn't sound that rough, the exhaust was considerably cooler on that side because of it. A new set of plugs and wires fixed that issue. There is a simple tester you can likely buy at your parts store that lights up on good wires/plugs and does not on bad ones.

As for the Holley carb, I run an 80670, 670cfm, which I put on a couple of years ago, It ran very well right out of the box and needed only minor tweaks. It gives me good mileage and near perfect plug read, BUT if I were to replace it, I would definitely go for a Quick Fuel as they are a better design and more tunable. Locally, they are cheaper than the equivalent Holley, another reason to buy one. Anyway, I really hope you get this sorted soon, sounds like you've been plagued with issues far too long.

All the best.