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motor problems still...UPDATED...HORRIBLE MPG

01maroonz71

01maroonz71

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well, my motor when i got it i was told it was a 383stroker motor...but i am not positive...would there be a way to find out for sure w/o pulling the motor apart???? when i got the truck, it had half a tank of feul in it...i then filled it up with cheapo(87) and drove home...no biggie, it wasn't till the next tank(100% 87 octane) that it began to diesel, and run funny...well, today at the speed shop i asked the guy what he thought and said, you may need to run premium feul, so i just put 20bucks in her(from empty) and ill see how it runs. another thing is that i bumped the timing 2 degrees(to 10 DTDC) last night to see what would happen...should i back it back down????

basically, how do i know if i need premium...should i check the compression???? any help is appreciated.



oh yeah, it also idles funny...if i tap the gas, it will idle down to around 500(where i have it set) but i have to hit the gas pedal once or twice to get it down there if im going from drive to reverse/vice versa or if i just started it. sometimes it will get as high as 8 or 900RPM's....would that have to do with this?????
THANKS!!!!
 
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A 383 has to be externally balanced. If you have a 383, your harmonic balancer will have a few holes drilled into the surface of it
 
alright...ill check that out....if it's not a 383, then it's a 350 w/ alot done to her...he's got a holley double pumper/mild cam(not sure on specs)/ mallory igntion, and everything looks like it was built right...he didn't have the vacc. advance hooked up, so that makes me think it's a high HP motor...it's very very torquey...but if it's just a 350 w/ cam, rebuilt,etc...could it have enough compression to need premium fuel????

thanks!!!! im gonna go look at the balancer now.
 
well, ididn't see any holes, but i left my keys in my apartment...so i didn't turn the motor over at all...are they pretty obvious??? and would there be more than one???? im pretty sure it's just a built up 350...not a stroker.
 
The balancing holes on mine are on the front and very visible.

As far as timing, if your motor isn't knocking (preignition) than you are fine. 10 degrees BTDC doesn't mean anything to anyone. You would have to know how much mechanical advance is in the distributor and how fast it comes on, compression ratio and which cylinder heads you are running.
 
i do know that if i rev the motor just about like 500-1000RPM while im watching the timing mark, with the vacc. advance unplugged, the mechanical advance will advance the motor quite a bit, like 10-15degrees, but i didn't have anyone to watch the tach, i was by myself....i will get a timing light with an adjustable advance light tomm and check it out...is advance changing as simple as pulling the cap of the dizzy and changing some springs??
 
You should have gone the other way with the timing. Retard it some, and see how that works. I bet it will run better.
 
well, it appears to run better the way i have it, but i will try that tomm. for sure. thanks alot man. if i might ask...what makes you think it will run better????? im sure your right, but just wondering

also, should i unhook the vacc. advance???, maybe the guy had it unhooked for a reason.

********
i should also add that im lucky to get 100miles out of a tank the way it's running now...im pretty desperate to figure this out.
*******
 
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maybe if i back the timing down about 4 or 6 degrees and increase the idle a bit...it seemed like it was going to die when i backed the timing down(just messing with it)
 
500 is too low an idle to begin with.. And I'm hoping you mean in gear... idle should be 600, 650 in gear... especially if it's got a nasty cam...
 
Hi there,

My 383 from Mr. Janke is rated at 550 HP/550 Ft/lbs Torque. She is set at 38* advance timing, has a monster cam, 850 CFM Holley 4 Barrel, MSD HEI Pro Billet Distributor, Doug Thorley Headers, and will require the use of a minimum 92 octane at all times. From my understanding the 383 is a H.O. Engine and needs the higher octane to sustain the firing for the compression rate. Mine is 11:1.

I'll have more info on Friday when I pick up my truck!

Manny
 
hmmm...how would i determine if i have a 383???? can it be bored to 383 w/o being a stroker motor??? maybe that's what i have.

don't kill me if im asking "dumb" questions ya'll....b/c i am learning as i go along....thanks again!
 
01maroonz71 said:
hmmm...how would i determine if i have a 383???? can it be bored to 383 w/o being a stroker motor??? maybe that's what i have.

don't kill me if im asking "dumb" questions ya'll....b/c i am learning as i go along....thanks again!
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Only stupid question is a question not asked. A 383 Stroker is a 350 block, bored .060 over. A 383 and a stroker are one in the same. I have heard of other stroker motors, but again, that specific displacement number can only mean one thing: STROKER.

The only way I know how to measure if it's a stroker is to tear it down and measure the thickness of the cylinder walls. That will tell you if it's stock, .030 over, or the stroker .060. I'm not an engine expert, so I hope the others will chime in and give their .03 cents worth at the current rate of inflation.

Manny
 
awesome man...thanks alot...i know the motor was rebuilt for sure...but whether or not it's bored at all...i don't know. i wish i could get ahold of the damn guy who owned it before me. damnit.
 
a 383 stroker motor is a 350 bored .030" with a 3.75" stroke crank. a stock 350 has a 3.48" stroke crank. I dont think that you could bore a 350 out enough to make it a 383 without a longer stroke crank. I know that if you just bore the block .030" it will make it a 355 and I think .060" will make it a 360.
 
big dan said:
a 383 stroker motor is a 350 bored .030" with a 3.75" stroke crank. a stock 350 has a 3.48" stroke crank. I dont think that you could bore a 350 out enough to make it a 383 without a longer stroke crank. I know that if you just bore the block .030" it will make it a 355 and I think .060" will make it a 360.
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Hey BigDan,

Thanks for the clarification. I didn't want to mislead Maroon. Thanks for the correction!

Manny
 
i always thought that a 383 was a 350 block witha 400 crank...and was bored like 15 over...:confused:

the dieseling could be too far advanced timing, fuel still leaking into the carb, intake manif leak. try shutting it off in gear that *should* make it not diesel...
 
broncoman6524 said:
i always thought that a 383 was a 350 block witha 400 crank...and was bored like 15 over...:confused:
quote]

actually it is a 400 crank. the stroke on a 400 is 3.75". I only mentioned the stroke on it cause there are quite a few companies that make cranks just for 383s but in reality thats what it is.

and no problem Manny. sharing knowledge is what its all about.:wink1:
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01maroonz71 said:
what makes you think it will run better????? im sure your right, but just wondering

also, should i unhook the vacc. advance???, maybe the guy had it unhooked for a reason.
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It will run better because the stock timing is around 2*-0* BDTC. Stock motors idled really smooth. Also I know this from experience that you might have too much timing on that thing.

Also whenever adjusting timing unhook the vac advance. 500 is also even a little too low for even stock motors. I like my idle right around 750rpm or so. Its a very good spot to set it at.

I say raise your idle a bit, then retard the timing a little. Also I am more than sure you are going to have to tune that carb too.

My 305 is currently set at about 8* advance with the stock cam and I use 93 octane.

Also, Manny you said you have like 40* timing, that is total timing, we are just talking initial timing. Glad to clarify ;)
 
Chevy305 said:
It will run better because the stock timing is around 2*-0* BDTC. Stock motors idled really smooth. Also I know this from experience that you might have too much timing on that thing.

Also whenever adjusting timing unhook the vac advance. 500 is also even a little too low for even stock motors. I like my idle right around 750rpm or so. Its a very good spot to set it at.

I say raise your idle a bit, then retard the timing a little. Also I am more than sure you are going to have to tune that carb too.

My 305 is currently set at about 8* advance with the stock cam and I use 93 octane.

Also, Manny you said you have like 40* timing, that is total timing, we are just talking initial timing. Glad to clarify ;)
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Okay,

Here's a noob question if I ever smelled one. What is the difference between total timing and initial timing?

Manny
 
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