360 Crate motor vacuum ?

[dakman1]

On a 380hp 360. Manifold vacuum at idle is about 9lbs. This seems kinda low.
I was thinking more like 12. Any opinions welcome.

[cudabob496]

Originally Posted by dakman1

On a 380hp 360. Manifold vacuum at idle is about 9lbs. This seems kinda low.
I was thinking more like 12. Any opinions welcome.

auto tranny? is reading while in gear and stopped?
what is idle rpm?

[dakman1]

Reading is in neutral. In gear at 700rpm reading is about 7lbs.

[dakman1]

Auto trans.

[chirorod]

how are you checking vacuum? should read in mmHg. If you're using a combination fuel pressure/vacuum gauge, the needle is dual function. you may be noting the pressure scale. if so, read the other end of the needle on the other scale.

[cudabob496]

I'd up your idle.
Vacuum seems low. In gear, stopped, my 496 is at 10 inches, and it has a solid roller 254/258 @.050 with .625 lift.

I would suspect your reading is not accurate.

[rampage_82]

when Mopar Muscle did their test on the 380 crate, they reported 6.5" to 7" of vaccum at 850rpm... Here is the article... http://www.moparmusclemagazine.com/t...dup/index.html

[cudabob496]

Originally Posted by rampage_82

when Mopar Muscle did their test on the 380 crate, they reported 6.5" to 7" of vaccum at 850rpm... Here is the article... http://www.moparmusclemagazine.com/t...dup/index.html

kiss your power brakes goodbye!

[rampage_82]

Originally Posted by cudabob496

I'd up your idle.
Vacuum seems low. In gear, stopped, my 496 is at 10 inches, and it has a solid roller 254/258 @.050 with .625 lift.

Yeah that is the funny thing about vacuum though, cubic inches and or stroke has a huge effect on vacuum readings. first take your combo for instance, beings that it is a mechanical roller then you can take what the Hyd equivalent would be which would be around 244/248 @ .050". Then factor in the stroker kit, and some small port aluminum heads (I'm guessing Indy SR's). It stands to reason why you get good vacuum. Take this into consideration. I had fully ported 906 heads and a Lunati Bracket master II cam in a 440. That combo would pull 15" @1,000 rpm easily. I put those parts on a 383, it only pulls 8 to 9" @ 1,000 rpm and that is pulling every trick I can think of to get it higher.

[cudabob496]

Originally Posted by rampage_82

Yeah that is the funny thing about vacuum though, cubic inches and or stroke has a huge effect on vacuum readings. first take your combo for instance, beings that it is a mechanical roller then you can take what the Hyd equivalent would be which would be around 244/248 @ .050". Then factor in the stroker kit, and some small port aluminum heads (I'm guessing Indy SR's). It stands to reason why you get good vacuum. Take this into consideration. I had fully ported 906 heads and a Lunati Bracket master II cam in a 440. That combo would pull 15" @1,000 rpm easily. I put those parts on a 383, it only pulls 8 to 9" @ 1,000 rpm and that is pulling every trick I can think of to get it higher.

I guess it makes sense, in that big blocks are always known to be able to handle longer duration cams (have a more decent idle), than small blocks. Must be due to the
cylinder not bleeding off as much pressure due to having a larger volume.

[dgc333]

What's your initial timing? With that cam you should be up around 20. Adjust the initial timing for peak manifold vacuum.

[dakman1]

Thanks rampage 82, I feel better after reading that article.
dgc 333 I did use vacuum gage to set timing. Engine response is crisp but I don't have a dial back timing light to say for sure where initial is at.
Thanks to all for your feedback.

[cudabob496]

Originally Posted by dgc333

What's your initial timing? With that cam you should be up around 20. Adjust the initial timing for peak manifold vacuum.

may not crank over at startup with an initial timing of 20. May need some kinda timing retard. I solved that by having a switch in the power lead to my MS6 Box. I get the motor cranking then cut in the ignition, and pop, she starts right up. Saves wear and tear on your starter and electrical system, and you don't have to pay for timing retard. Its also a great theft deterent, as they don't know about the switch.

[rampage_82]

Haha funny story... my buddy had a 13.5.1 BBC, and he decided he wanted to lock out his timing. I kept on telling him that he needed to get a timing retard for starting, and he didn't listen, and decided on the flipping the switch trick. Anyways he set it at 28 degrees to be safe, and the first time he tried to crank er up, kerblamo his brand new MSD starter broke in half... So there he was on the phone ordering a new starter and retard box... All he said after he hung up was.... "Shut the F up Guy"

[cudabob496]

Originally Posted by rampage_82

Haha funny story... my buddy had a 13.5.1 BBC, and he decided he wanted to lock out his timing. I kept on telling him that he needed to get a timing retard for starting, and he didn't listen, and decided on the flipping the switch trick. Anyways he set it at 28 degrees to be safe, and the first time he tried to crank er up, kerblamo his brand new MSD starter broke in half... So there he was on the phone ordering a new starter and retard box... All he said after he hung up was.... "Shut the F up Guy"

28 degrees BTDC seems extreme, and I would think that may have caused the starter failure.
I think my initial timing is about 17 degrees BTDC. My system of flipping on the MSD box after hitting the starter has worked fine for the last 8 years. If I have the MSD box on while hitting the starter, the engine can be harder to start, especially when it is warmed up, and due to my battery being in the trunk (which causes a larger current draw at startup).

[rampage_82]

I think you missed the part of my story about the "locked out" timing

[dgc333]

Originally Posted by cudabob496

may not crank over at startup with an initial timing of 20. May need some kinda timing retard. I solved that by having a switch in the power lead to my MS6 Box. I get the motor cranking then cut in the ignition, and pop, she starts right up. Saves wear and tear on your starter and electrical system, and you don't have to pay for timing retard. Its also a great theft deterent, as they don't know about the switch.

I am running my 10.6:1 360 (190-200 psi cranking pressure) at 18 and have had it as high as 22 and the starter spins it over just as easily as it does at 12.

[cudabob496]

Originally Posted by dgc333

I am running my 10.6:1 360 (190-200 psi cranking pressure) at 18 and have had it as high as 22 and the starter spins it over just as easily as it does at 12.

Are you saying that more initial timing does not make it harder on the starter, or the electrical system, to start a motor?

[pishta]

Originally Posted by cudabob496

28 degrees BTDC seems extreme, and I would think that may have caused the starter failure.
I think my initial timing is about 17 degrees BTDC. My system of flipping on the MSD box after hitting the starter has worked fine for the last 8 years. If I have the MSD box on while hitting the starter, the engine can be harder to start, especially when it is warmed up, and due to my battery being in the trunk (which causes a larger current draw at startup).

Ditto, friend turned me onto that years ago too. Never tried it, never had to but I heard him do it. Pretty cool. ditty-ditty-ditty-diity-vwoom! like clockwork. says it saves wear as the free spinning no load RPM's are enough to start the oil pressure before starting. He looks at the oil pressure guage and as soon as it registers he lights it off. Some how Wire an oil pressure idiot light sender to the white wire or relay that kicks the MSD on when oil pressure builds..?

[cudabob496]

Originally Posted by pishta

Ditto, friend turned me onto that years ago too. Never tried it, never had to but I heard him do it. Pretty cool. ditty-ditty-ditty-diity-vwoom! like clockwork. says it saves wear as the free spinning no load RPM's are enough to start the oil pressure before starting. He looks at the oil pressure guage and as soon as it registers he lights it off. Some how Wire an oil pressure idiot light sender to the white wire or relay that kicks the MSD on when oil pressure builds..?

Ya, a $5 switch is better than a $100 timing retard module!

I didn't think about the oil pressue coming up quicker too! Thats another plus!!

I'm all for the engine lasting longer. Getting too old for engine rebuilds!!

[dgc333]

Originally Posted by cudabob496

Are you saying that more initial timing does not make it harder on the starter, or the electrical system, to start a motor?

On my engine there is no noticeable difference in the way the engine turns over between 12 BTDC and 18 BTDC or even 22 BTDC. I am quite sure it puts more load on the starter and battery but the engine does not kick back against the starter and the engine starts instantly cold or hot.

The starter is a parts store rebuilt mini starter and has been on the engine for just shy of 36,000 miles (5 years).

[cudabob496]

Originally Posted by dgc333

On my engine there is no noticeable difference in the way the engine turns over between 12 BTDC and 18 BTDC or even 22 BTDC. I am quite sure it puts more load on the starter and battery but the engine does not kick back against the starter and the engine starts instantly cold or hot.

The starter is a parts store rebuilt mini starter and has been on the engine for just shy of 36,000 miles (5 years).

No doubt it will work, but may shorten the life of some components. How much? Who knows? Also, the fact that oil pressure starts building earlier with no load on engine is a big plus.

[cudabob496]

Originally Posted by dgc333

On my engine there is no noticeable difference in the way the engine turns over between 12 BTDC and 18 BTDC or even 22 BTDC. I am quite sure it puts more load on the starter and battery but the engine does not kick back against the starter and the engine starts instantly cold or hot.

The starter is a parts store rebuilt mini starter and has been on the engine for just shy of 36,000 miles (5 years).

The real bummer, is when you have a lot of advance in at starting, and your battery is a little weak, and you just fill up at the gas station, and then the car won't turn over. I've been stuck there once because of that. Had to turn the distriutor to remove some of the advance so it would start.

[RacerHog]

Originally Posted by dakman1

On a 380hp 360. Manifold vacuum at idle is about 9lbs. This seems kinda low.
I was thinking more like 12. Any opinions welcome.

Sounds like its got the large chamber iron smog heads on it with a 300 Duration (Purple)cam in it...???

And it pings its azz off....Dont it?

[dgc333]

I can't see the sense in compromising timing which impacts how the engine runs all the time because it might shorten the life of the starter or if you have a weak battery it might not start.

[cudabob496]

Originally Posted by dgc333

I can't see the sense in compromising timing which impacts how the engine runs all the time because it might shorten the life of the starter or if you have a weak battery it might not start.

I agree! I try not to compromise performance for anything. But it makes sense to me to initially spin the engine with the ignition off, which takes stress off the battery (especially if its in the trunk) and starter, and helps build oil pressure quicker (most all engine wear occurs at startup), then flip a switch to cut in the ignition. Like was mentioned, a $5 switch, which is also a great theft deterent. May be the best $5 ever spent!

Also, before the engine ignites, you are drawing in more gas fumes to make the start easier as well. On my single plane, when its cold out, that helps quite a bit.

If an engine fires immediately, then it is under load with oil not present in all areas, like the valve train!!