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Average jet size used on a LM 110 and
Posted by: OttawaCorvairGuy ()
Date: January 14, 2018 05:44AM

What is the average jet size used on a LM 110? My guess is 48
(FYI - I can't recall 100%. But we either use a 51 or 53 with a LM in an Ultravan)


Carburetor gurus - What jet size should I start with or be used on a LM when it has a single carb for each cylinder?

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Re: Average jet size used on a LM 110 and
Posted by: RobertC ()
Date: January 14, 2018 09:05AM

Don't you have Bob Helt's book on Rochester carbs?

The info is also in the Shop Manuals / Shop Manual Supplements.

The stock jet depends on the carb you have - LM power Valve or "smog" carb.

Your guess is wrong - 65 - 66 power valve carbs were 50 / 51.

I would start with 52 - with ethanol gas.

I am sure there are many other opinions.

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Re: Average jet size used on a LM 110 and
Posted by: OttawaCorvairGuy ()
Date: January 14, 2018 09:26AM

RobertC Wrote:
-------------------------------------------------------
> Don't you have Bob Helt's book on Rochester
> carbs?
>
> The info is also in the Shop Manuals / Shop Manual
> Supplements.
>
> The stock jet depends on the carb you have - LM
> power Valve or "smog" carb.
>
> Your guess is wrong - 65 - 66 power valve carbs
> were 50 / 51.
>
> I would start with 52 - with ethanol gas.
>
> I am sure there are many other opinions.


Thank you Robert

I have Bob's book and a lot of others books. I even have old shop and labor manuals (back to the 40's) for when I ran my own auto biz..

However, until we are fully settled - with only the one house and I'm finally am able to build my garage = I have no clue where most of it is. Grin


I'm not saying 52 to start is wrong. I honestly don't have a clue and it's why I'm asking. But 52's sound high to me to be running on 6 carb setup = one for each cylinder.

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Re: Average jet size used on a LM 110 and
Posted by: RobertC ()
Date: January 14, 2018 10:00AM

OttawaCorvairGuy Wrote:
-------------------------------------------------------
>
> I'm not saying 52 to start is wrong. I honestly
> don't have a clue and it's why I'm asking. But
> 52's sound high to me to be running on 6 carb
> setup = one for each cylinder.

Missed the each cylinder...

Peronally think 1 Rochester carb per cylinder is way too much "air" for a Corvair engine.

Though I think Roger Parent did something like that - posted in a thread here.

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Re: Average jet size used on a LM 110 and
Posted by: OttawaCorvairGuy ()
Date: January 14, 2018 10:32AM

RobertC Wrote:
-------------------------------------------------------
> OttawaCorvairGuy Wrote:
> --------------------------------------------------
> -----
> >
> > I'm not saying 52 to start is wrong. I honestly
> > don't have a clue and it's why I'm asking. But
> > 52's sound high to me to be running on 6 carb
> > setup = one for each cylinder.
>
> Missed the each cylinder...
>
> Peronally think 1 Rochester carb per cylinder is
> way too much "air" for a Corvair engine.
>
> Though I think Roger Parent did something like
> that - posted in a thread here.


They might be too big.
If so - I thought I could have spacers made like the ones Dave got done.
However, I would have them trapper so they get smaller as they get closer to the intake and reduced the size of the opening.
I could then make the opening larger - IF needed - after each test or DYNO run.

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Re: Average jet size used on a LM 110 and
Posted by: American Mel ()
Date: January 14, 2018 10:32PM

OttawaCorvairGuy Wrote:
-------------------------------------------------------

> They might be too big.
> If so - I thought I could have spacers made like
> the ones Dave got done.
> However, I would have them trapper so they get
> smaller as they get closer to the intake and
> reduced the size of the opening.
> I could then make the opening larger - IF needed -
> after each test or DYNO run.


Okay, please have some mercy on me here as I must admit that I know nothing about the topic which I am going to address, but I have a theoretical idea based on the limited knowledge that I do possess.

I would not think that a tapered spacer would be the answer, because in my little mind, that would be the same as adding a second venturi!
My thinking is that six carbs would just look absolutely AWESOME ! ! !
BUT, if that is too much air, then my thinking is, can't you just adjust the throttle linkage to limit how far the throttle plates open ? ? ?

One more thing,
Is this going to be a real performer, or a show stopping cruise-in car?
Several years ago I attended one of the big car shows in PDX.
They had a few of the George Barris TV cars on display.
two of them were the "Munster Coach" and the Monkeymobile".
When you look closely, neither of these cars were what they appeared to be!
Both of them in reality only ran a naturally aspirated 4-barrel carburetor!
The Monkeymobile's carb was hidden beneath the empty shell of a great big herkin Jimmy 6-71 blower.
Why do you think you never see the actually blower belt?
Because there ain't one !
The carburetor on the Munster Coach was buried down between/below 10, (yes TEN!) one-barrel carburetors ! ! !
Depending on which of the prop cars you were looking at, the 4-barrel was under or between those multi-carbs.

So you see, anything is possible!!!
How creative do you want to get?

.
-----------------------------------------------
WA. state, 1 mile south of the Canadian border,
I am not at the end of the world, but you can see it from here.
'66 Monza Coupe - 4spd, 140 Daily driver beater
'67 Monza Vert. - PG, 140 Daily driver beater

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Re: Average jet size used on a LM 110 and
Posted by: OttawaCorvairGuy ()
Date: January 15, 2018 05:58AM

Mel,

I don't have all the answers. That is why I am bouncing this around with those who have built Corvair engine of all kinds.

IF I'm able to do the idea I have had in my mind for many years I will have to figure a lot of things on the fly as they pop up.
But it is helpful to get a starting point (some feed back) with as much of them as possible.

As for the tapered spacer. Let's say the opening on the bottom of the carb was 1.5" and I reduced (choke down) the opening on the spacer to 1.25" on the top and 1" or even .75" on the bottom to start with. Maybe I also had to do that in combo with the throttle linkage so that it could never go wide open. I hope that is not the case. As I would like this to preform well and be fun to drive.

Anyways, I'm going to run big valves and cam. Not sure what combo yet. At some point I will also want to get feed back from those who have run other cams than stock. But that is another time and another thread.

Thank you for your thoughts.

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Re: Average jet size used on a LM 110 and
Posted by: American Mel ()
Date: January 15, 2018 05:05PM

Well, what-ever you do, Good Luck with it!
Sounds like it is going to be a fun project.
Keep us posted on it as it comes together.

.
-----------------------------------------------
WA. state, 1 mile south of the Canadian border,
I am not at the end of the world, but you can see it from here.
'66 Monza Coupe - 4spd, 140 Daily driver beater
'67 Monza Vert. - PG, 140 Daily driver beater

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