70 LT1 carb help

[Dennis D.]

Re: 70 LT1 carb help

Had some time to check a few things today. Confirmed the port below the choke has no vacuum at idle.(previous pic)
Also pulled the distributor cap to check the advance can....


Finally, hooked up a dial back timing light and found initial timing to be 6*. Idle is also low, hovering between 7-800.
Before i replace the vac advance can, I'm thinking to put all the hoses back to the stock configuration, bump the timing up 2*, reset idle to 900 and see if there's an improvement.

Everything's there for that change, while I wait for a 28B can.

[Patrick H.]

Re: 70 LT1 carb help

What spark plugs are you running?

[Terry M.]

Re: 70 LT1 carb help

What spark plugs are you running?

Patrick
Now there is a loaded question. LoL. I am tired of the chisel mark story.

[Dennis D.]

Re: 70 LT1 carb help

Patrick
Now there is a loaded question. LoL. I am tired of the chisel mark story.

My L46 is setup from the chisel mark. Dont know if the lt1 distributor is original

[Patrick H.]

Re: 70 LT1 carb help

Patrick
Now there is a loaded question. LoL. I am tired of the chisel mark story.

I could tell you to find a bush then.
Sorry Dennis, we have new stories from Bloomington this past week.

I ask which plugs because I found them to be the cause of a hot running problem one of my cars was having.

Oh, and if the distributor is not original to the manifold, the chisel mark means nothing.

[Terry M.]

Re: 70 LT1 carb help

My L46 is setup from the chisel mark. Dont know if the lt1 distributor is original

Doesn't work if they are not mated original, but then you knew thatt.

BTW: I did a story about 1970 LT1 timing for The Restorer many moons ago. There are two different emissions labels for 1970 LT1s and they show different timing settings. Mine was set at 14* from the factory, but then I still have the original distributor with original weights and vac with TCS still functional. I doubt setting by the chisel mark will work if the distributor has been "tuned."

[Terry M.]

Re: 70 LT1 carb help

I could tell you to find a bush then.
Sorry Dennis, we have new stories from Bloomington this past week.

We could carry this on about people who can't hold the wine, and others who can't sit on a chair without injury, but this is not fair to the innocent who have not had the bonding experiences we have.

Let's leave it with "It is all about the people."

BTW: For those who were not at Bloomington Gold the last few days. The Special Collection this year featured 1968 to 1972 Corvettes with two Owens Corning Race cars (Yes, the real ones) and the 1965 Manta Ray along with someplace close to 50 of the most unusual 1968 to 1972 Corvettes around. It was one of those "You had to be there times."

Enough off topic banter.

[Duke W.]

Re: 70 LT1 carb help

That 360 12 VAC starts at 6" and 12 @ 12". I thought the 70 LT-1 had a 201 15 VAC, but that might be later years. The 360 12 was also OE on L-72.

8 initial may not be enough, but I don't recall how much total centrifugal the '70 LT- 1 has. You want the sum of full centrifugal and initial to be in the 36-40 range, as high as the engine will tolerate without detonation.

While you're at it you should get a Mr. Gasket 928G spring kit and install the black springs, which should be the lightest, then silver, and gold. If it doesn't detonate with the black springs and 38-39 WOT advance, you're good to go.

Idle should be about 900 @ 12", with somewhere near 30 degrees total idle advance. It can be difficult to set initial timing since centrifugal may start below the speed that the engine will idle stably long enough to set timing. The better way to set timing is to rev it up a few hundred revs above the point of max centrifugal with the VAC disconnected and plugged in the above range.

Due to the added idle advance both hot and cold idle speed will be higher, so go through the idle speed/mixture adjustment procedure, and it you don't have to be field emission tested you can use the pre-emission procedure which is to adjust the idle screws for maximum vacuum at your target idle speed. Once that's done, adjust fast idle speed to spec,'


Duke

[Dennis D.]

Re: 70 LT1 carb help

Thanks Duke. Will sort of your info out. First order of bussiness is getting those old wet r45's replaced with a new set.

[Larry E.]

Re: 70 LT1 carb help

I would change your fuel for a try. Use 100LL straight Av-Gas. I bet is cures your problem>worth a try-Larry

[Dennis D.]

Re: 70 LT1 carb help

I would change your fuel for a try. Use 110LL straight Av-Gas. I bet is cures your problem>worth a try-Larry

Used to use 100LL av in my 70 l46. Car ran great on it.

I was told the fuel in the tank is 100 octane mixed with pump, and an ethanol additive. I dont understand why ethanol additive, but theres still ln a 1/4 tank. Plan on putting 110 leaded to run through.

[Patrick H.]

Re: 70 LT1 carb help

Thanks Duke. Will sort of your info out. First order of bussiness is getting those old wet r45's replaced with a new set.

I would not be surprised if you find that R45s will still give you pinging or run-on.
Unfortunately R44s are no longer made, so I had to swap for a similar Champion, which helped immensely.

[Dennis D.]

Re: 70 LT1 carb help

I would not be surprised if you find that R45s will still give you pinging or run-on.
Unfortunately R44s are no longer made, so I had to swap for a similar Champion, which helped immensely.

I still have a few sets of r44s. Ran them in my L46 for years. Think I have 45's in it now.

I pulled 2 plugs from the LT1. Really fouled and old. Its no wonder the car runs like crap

[Ron G.]

[James G.]

Re: 70 LT1 carb help

I was having a heat soak problem on my LT1 - boiling the fuel in the carb and it went away after having my fan clutch rebuilt(spun freely at engine op tempt) and changing the heat riser... heat riser was not opening more than a crack at full engine temp. - forcing hot air under the carb constantly.