Vacuum with Lunati 60303

Posted By: Chilort

Vacuum with Lunati 60303 - 02/27/10 12:14 AM

Just wondering what you all are getting for engine vacuum with the Lunati 60303 cam. I just got the truck started up. I must have a vacuum leak since I'm only getting about 10psi. Now I need to track that down.

Posted By: Dougsmopars

Re: Vacuum with Lunati 60303 - 02/27/10 12:23 AM

Vac is in inches. You need to see if you have a vac leak and readjust your carb for max vac. Depending on other factors with your setup that 603 should give you around 15 in of vac

Posted By: Chilort

Re: Vacuum with Lunati 60303 - 02/27/10 01:49 AM

Yeah, sorry, 10 in hg. I drive a '86 Daytona Turbo Z CS as my daily and forget the vacuum side is in "in hg." And it has been a long week with little sleep.

I get lots of vacuum at higher rpm and unloaded (20 in hg at 2000rpm during break in).

I'll start sorting it out tomorrow. Maybe after I get the exhaust on it so I can maybe hear it.

Posted By: DaytonaTurbo

Re: Vacuum with Lunati 60303 - 02/27/10 06:48 AM

My vacuum gauge is a piece of junk, but I get somewhere in the 10-15 at idle(gauge is not too accurate, got a new one going in).

Posted By: Chilort

Re: Vacuum with Lunati 60303 - 02/27/10 04:10 PM

I used to get a solid 18 in hg with a stock cam. My guess is that I have a vacuum leak since various changes I was making to the carb weren't doing anything at all.

Thanks for the extra data point.

Posted By: Pacnorthcuda

Re: Vacuum with Lunati 60303 - 02/27/10 04:24 PM

I run the 60303 in a 440. I get 12-13 at 750 idle.

Posted By: Chilort

Re: Vacuum with Lunati 60303 - 02/27/10 05:06 PM

I had the idle speed set at 600rpm. I checked my '70 B-body book last night and with a factory 4160 carb (I'm using a very basic Holley 750 - pn: 80508) they recommend a curb idle of 650rpm in a 40. So it looks like I need to bump that up a hair.

Posted By: Chilort

Re: Vacuum with Lunati 60303 - 03/01/10 01:06 AM

Worked with a number of things and got the vacuum up to about 13 in hg. I have the Park/Neutral engine speed sent to around 750rpm. It drops quite a bit when in gear. Played with the idle mix screws a bunch. Seems to run really nice. Thanks for the help.

Posted By: patrick

Re: Vacuum with Lunati 60303 - 03/01/10 05:18 PM

Quote:

Worked with a number of things and got the vacuum up to about 13 in hg. I have the Park/Neutral engine speed sent to around 750rpm. It drops quite a bit when in gear. Played with the idle mix screws a bunch. Seems to run really nice. Thanks for the help.

dropping a lot in gear means your distributor is starting to advance the timing below your 750RPM idle. put it in gear, idle drops, which pulls timing, which drops the idle further. you need to recurve your distributor with a slightly stiffer spring so your mechanical advance doesn't start advancing until ~900 RPM....

also, I'd run that cam with about 14-16 degrees initial advance and ~38 total. you may need to reduce the amount of mechanical advance in your distributor to get the 22-24 degrees of mechanical advance. you do that by welding up the slots in the advance place. if you weld to the inside of the slots, that'll increase the spring preload, which will raise the start RPM of your mechanical advance

Posted By: DaytonaTurbo

Re: Vacuum with Lunati 60303 - 03/01/10 05:26 PM

Well a tight converter will drop your rpm more too.

Posted By: Chilort

Re: Vacuum with Lunati 60303 - 03/01/10 09:11 PM

Converter is 17501 from Turbo Action.

I am actually running 16* advance initial (IIRC) but need to double check it. I was trying to set it to get max vacuum at idle and I think it was 16*. I may have backed it off some so that I would run less risk of going over 36* total but didn't back it off too far from 16*

I am using a Mopar Performance distributor that supposedly has 24* mechanical advance as setup at the factory and I have not verified those numbers (though I've never seen anyone contest the factory setup). If that is true then I need to adjust the total mechanical advance but I have never done that before. Also, I think I can adjust when the advance starts with this dizzy too but haven't done that either. The dizzy came with zero instructions, which isn't very helpful.

Posted By: Anonymous

Re: Vacuum with Lunati 60303 - 03/01/10 09:46 PM

Cubic inches, compression, where the camshaft is degrees at, AND how much initial timing you have, all effect vacuum at idle..........My video goes into detail to help you get the most out of your combo

Here's a link to the highlight reel on YouTube........

Wayne

Posted By: Chilort

Re: Vacuum with Lunati 60303 - 03/01/10 09:49 PM

Cubic inches -- 440, 0.040 over
Compression -- about 9.2:1 with little quench (milled Eddy heads to get compression up)
Where the camshaft is degreed -- suggested retail price, 106* IIRC
How much initial timing you have -- around 16*

I'll watch the video when I'm not at work.

Posted By: Chilort

Re: Vacuum with Lunati 60303 - 03/03/10 11:49 PM

I had the initial timing at 14* BTDC. Bumped it up to 16* and it seemed to like that the most of other things I tried. I've go the idle rpm set around 730-750. I played with the mixture screws some and it seems to like the factory settings (or there about) the best. Went for another 15min break in run and now I get a solid 13 in hg whereas it had been 11-12 in hg before. So two of about 4 short break in runs for the engine now in the books. Maybe do another Thursday and the final one Saturday before putting it out on the interstate.

So far, I love this thing. The power is unreal and quite a bit more than anything I've ever driven. This is the first engine I've ever built. Kind of nerve wracking but still a lot of fun.