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Discussion Starter #1
i got a used 5.7 vortec from a 96 tahoe and i got a nice intake from summit and a edelbrock 600cfm carb. iam running the mallory unilite marine dist. anyway i got it started up it run great. but going down the lake it would bog out when i nailed it in the secondaries.so after a couple burn runs up and down the lake adjustment after adjustment still no change.primaries everything fine seconds not so good.
so here is what i have done. changed the carb,checked timing,new plugs, compression test which all cyl's look good,checked dist which is brand new,so iam stumped:)st.so to give you a better insight here is what i've got..

5.7 vortec totally stock bottom end and stock vortec heads.
weiand dual plane intake
edelbrock 600 cfm
mallory marine dist
carter elect. fuel pump
stock roller cam ?????
this motor is in a 88' miller 21' open bow with a omc cobra outdrive.

any help with this would be greatly appreciated
 

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you've gotta tdc the motor, if you're goin by the frt stock marks, they're not right, that's for initial crankshaft variation;) put a dial indicator thru the #1 plug hole and get the motor to tdc with it, then mark the balancer and retime it. those efi cams on carbs only like about 34* total timing.
 

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My suggestion is to ck Edelbrock's website for the tuning
on a Marine Carb. What carb do you have? Both the 1405
& 1406 Edelbrock's are way leaner on the secondary side
than the marine version's. Get the spec's from the website
& re-jet your carb........
 

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My suggestion is to ck Edelbrock's website for the tuning
on a Marine Carb. What carb do you have? Both the 1405
& 1406 Edelbrock's are way leaner on the secondary side
than the marine version's. Get the spec's from the website
& re-jet your carb........
his timing is too slow, everytime someone uses the frt marks on the vortec 350's, that's gonna happen;) its to retarded now to hit on the secondaries:)sphss
 

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Discussion Starter #5 (Edited)
when i was running it up and down the lake i did advance the time a little each time slowly to the point of pinging then back it off a couple deg. could it be the stock cam. i was looking into getting a marine can befor summer
 

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when i was running it up and down the lake i did advance the time a little each time slowly to the point of pinging then back it off a couple deg. could it be the stock cam. i was looking into getting a marine can befor summer
that's not timing it:)bulb you either know it right, or not;) if the carb is a fresh 600cfm edelbrock and getting plenty of fuel pressure at wot, it should work just fine on a stock vortec 350, without any jet changes.
 

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Discussion Starter #7
i agree on the timing thing, but it wouldn't get WOT. as soon as it started the sec.it bogged and sputtered.
 

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Discussion Starter #8
what are some other possablitys. i did try a 800 cfm carb just to try it but it was the same thing.iam going to try the timing like you suggested. thank you very much for all yout input.
 

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you've gotta tdc the motor, if you're goin by the frt stock marks, they're not right, that's for initial crankshaft variation;) put a dial indicator thru the #1 plug hole and get the motor to tdc with it, then mark the balancer and retime it. those efi cams on carbs only like about 34* total timing.
What the.....

Tom, really??? why in the world would you say such a ridiculous thing?


AP
 

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mo balls than $cents$
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What the.....

Tom, really??? why in the world would you say such a ridiculous thing?


AP
because the cam timing is slighty advanced in those motors;) i know them very well:D hyd roller with alot of advance already in the camtiming won't appreciate much timing from a dizzy unless the cam and timing chain has been changed. seems like the last time i tdc'd 1 of those on the stand the balancer was off almost 15* from tdc, that's why i was sayin to double check it.kinda like the ole bbf's how they'd jack with cam timing for emmission, same deal
 

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just do a checklist while its runnin sick:

look at the fuel pressure gauge while its sick, make sure it has at least 6-7psi

put your timing lite on the balancer while its sick, make sure its not in the ignition system

then i'd start lookin at the carb tune, but personally i've never seen a 600 edelbrock run lean on a vortec 350, generally to fat if anything.
 

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what intake gaskets did you guys use? composite or the plastic replacement style?
 

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By the way

What altitude are we talking about? Where is this Vortec motor being asked to run? Generally, high altitude would affect both primary and secondary runability, but Impatient1 bringing up being too fat jogged my memory about N/A motors and altitude.
 

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Discussion Starter #15
the last time i ran it i was at naciamento lake, i did check fuel psi and it was at 5.5 . so sould i get a new marine cam? and i dbl roller chain? and can i put just a flat hyd. tappet cam and lifters or should i stay with the roller set up. the price diff is like 2 to 3 hondo.and if i do get a cam what kind and what grind. thanks you guy for all this info.
 

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the last time i ran it i was at naciamento lake, i did check fuel psi and it was at 5.5 . so sould i get a new marine cam? and i dbl roller chain? and can i put just a flat hyd. tappet cam and lifters or should i stay with the roller set up. the price diff is like 2 to 3 hondo.and if i do get a cam what kind and what grind. thanks you guy for all this info.
As long as the carb wasn't set up for high altitude (lean), you should be OK for a base carb tune.

Sure, you can change cams, BUT DON'T GO BACKWARDS TO A FLAT-TAPPET. You've got the extra hp ability with the roller setup. IF you decide to change cams, you would only need a new CAM only and timing chain. You would re-use your roller lifters and valley spider.
 

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i got a used 5.7 vortec from a 96 tahoe and i got a nice intake from summit and a edelbrock 600cfm carb. iam running the mallory unilite marine dist. anyway i got it started up it run great. but going down the lake it would bog out when i nailed it in the secondaries.so after a couple burn runs up and down the lake adjustment after adjustment still no change.primaries everything fine seconds not so good.
so here is what i have done. changed the carb,checked timing,new plugs, compression test which all cyl's look good,checked dist which is brand new,so iam stumped:)st.so to give you a better insight here is what i've got..

5.7 vortec totally stock bottom end and stock vortec heads.
weiand dual plane intake
edelbrock 600 cfm
mallory marine dist
carter elect. fuel pump
stock roller cam ?????
this motor is in a 88' miller 21' open bow with a omc cobra outdrive.

any help with this would be greatly appreciated
I have the same motor and had the same problem. Dumped the Edelbrock and went to Holly.........problem was solved. Beats the sh*t outa me.
 

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Um. get into secondaries and it stumbles and lays down. LEAN STUMBLE !!!!!! Out of the box edelbrock for marine apps is to lean especially on a boat. Due what LUMPY did and lose the edelbrock get a holley and be done.
 

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Discussion Starter #19 (Edited)
adding infoso i took all of your guys advise and made some changes and checked some stuff. here is what i did..

fuel pressure gauge . running 6-7 psi
changed the coil to a pro comp hi energy
set timing at 8* init. and 30 total
changed to a holley carb 3310 with 70 jets and a 6.5 power valve
gaped the new plugs at 35
checked all plug wires and cap and rotor
compression test. all cyls at 160-165 psi

now it seems to run a little better but it still has that high rpm stumble and pop. i would through a high rev and you could hear it like pop a little though the carb. iam almost ready to through it away and start over.
does anyone have a clue because iam stumped

it does have a mallory marine unilite dizzy, and i heard there is alot of probs with it. maybe just maybe that is my nightmare. any help with this would be much appreiciated. there is nothing worse then taking your family out to the lake and have your boat not perform.
 

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Discussion Starter #20
ok i have some ????s

what makes a dist. a marine dist. and can i turn a auto dist. into a marine one?

what is a good dist. to run on a 5.7 marine eng.?

i heard that a k&n filter qualifies and a spark arrester, is that true.?

thank you to all you good people for your help.....
 
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