quote:Originally posted by mike the snake:
Stickt throttle is due to either needing a new or lubed cable, or something within the linkage as the engine heats up.
There's a bridge across the two banks of the injector banks (these are Tall Yates Heads) that I assume keep them from moving when the engine heats up.
There's a custom center galley cover because each injector bank is separate, they're not joined into a manifold.
I put some more miles on the car today, it runs sweet. Except for having to blip the gas every once in a while to get the idle down, it runs great.
I have yet to really go full throttle, the motor is kinda scary powerful, so I want to take things in stages. So far it's been a little bit of freeway and mostly in traffic, but the car runs well, so I'm not touching anything for a while.
I'm just going to drive it, put a hundred or so miles on her and then check the plugs.
#1 was black and caked moreso than any of the others, so I suspect a low hole on #1, just a gut feeling.
It could also be the way the old air cleaners were fitted. For me it's drive it, enjoy it, and read the plugs in about 50 miles.
My guess is it's hard to get all 8 butterfly valves to open exactly, so my idle, and Juuust off idle "miss" i'm feeling, may be just due to that, because once above idle everything runs smoothly and runs sweet.
You've learned quite a bit. Way to go!
I think you are very close to a problem free car?
You've remembered virtually everything that I've pointed out on some of the very obscure and weird "shortcoming issues" of the set up being basically a race engine on the street. Very excellent.
I suspect ultimately there is going to be one area of "concern" that no one has much experience here at all with?
That is the steel bridge from head to head?
I would be very, very surprised if Roger put thousands of miles on the engine with that "fix" installed?
What I am thinking on it is as follows. Theses engines with iron blocks and aluminum heads were developed literally, like it or not out of the big 3 race programs of the '60s.
Initially it was impossible to offer them as street cars because they would just develop leaks in competition EVERYWHERE.
Eventually what enabled them to be now commonplace was the development of the silicone coated head gaskets. "Felpro blue" etc.
What's important about that is now the aluminum head "floats" on top of those gaskets. That is the device that permits two such dissimilar metals, cast iron and cast aluminum to be compatible.
What Roger has done in dealing with the throttle issue is reduced that expansion with the steel bridge, he has not eliminated it entirely though.
He is reducing the amount of expansion the aluminum heads are permitted into the center valley direction, and making them expand in the other direction?
So that means they have to "float" twice as far towards the outside of the engine, AND apparently doesn't eliminate completely the change in the throttle settings from expansion, just reduces it?
That COULD mean these head gaskets are going to wear out faster than normal and at some point they are just going to blow compression? Maybe yes, maybe no?
Keep an eye out for phantom oil leaks coming from the front or rear of the heads.
If you look at SOME OF these types of head gaskets, SOME incorporate a drain in them. It's really for excessive coolant pressure build up, but there is one in front and one in the rear.
When the head gasket is loosing it's ability to seal caused by too many duty cycles, you will get oil from the oil drain back holes in the cylinder head, weeping through the head gaskets and appearing usually in the front or real of the heads.
If you see that, change the head gaskets.
Other than that, you are good to go. Remember what I said about having to modify the throttle cable itself on the carb end. There are few here that will agree with that simply because they haven't discovered that yet. Simple.
When you get to that, check for kinks in the inner steel reinforcing tube. It's very, very common and few realize the implications of those kinks on hanging the throttle up.
That tube is VERY easy to remove and once you do that you will have an Epiphany. The cable itself within the sheathing needs absolutely NO lubrication itself. It's the cable being pinched by the tube that is causing the havoc.
LOTS of Pantera owners have put in "race" cables needlessly. The stock Pantera cable is fine once you deal with this issue.
As far as an oiled plug, put some miles on this engine and see if it dries up.
As long as that plug isn't fouling from the oil you are ok.
Lots of modern engines run lots of oil through the intake manifolds from the internal pcv systems and it causes little harm and they need to deal with oil fouling of the cats which for them is expensive under warranty.
A little oil through the intake is alright and MAYBE a good thing, as long as you aren't caking dried, cooked oil on the stem side of the valves. That stuff can come loose and get sucked into the combustion chambers and will act as "carbon grit" like we use in sandblasters now. You don't want that.
You are also correct about the throttle shafts in individual throttle bodies twisting. Excellent observation. This is why you HAVE to have the throttle actuated in the center of those AND use as little return spring pressures as possible.
A little out of sync as a result though isn't as big of an issue as you think. It isn't the end of the world. Lots of cars with similar setups are running with them UNKNOWINGLY with little issue.
You just need to verify that at WOT the butterflies are equal and that at idle they are all equally closed. Unequal WOT will make it feel like the engine is misfiring there.
Sometimes a twisted throttle shaft can cause idling problems like you have. You would be surprised how many mechanics never even look for it.
That's a school of hard knocks thing. You have to discover that usually for yourself. No one tells you. You already are aware of the possibility so you are FAR ahead in the game.
Now go drive this thing on some open roads where you can do WOT and see how it returns to normal. That's what you need to do now.
You may find that there is less to do on this car than you currently think.
Once it is set, it should not be a daily maintenance thing at all. These throttles rarely change once you have them right where they should be.
Good luck or if you prefer "break a leg" (not a breastbone
)