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Old 09-30-2007, 02:25 PM   #1
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How to tell if i have a 350 or 305

Is there any way i can tell the 2 apart besides taking it apart? I got this car used and i was told the 305 was replaced with a 350 but how can i be sure he is not lying?
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Old 09-30-2007, 02:52 PM   #2
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Re: How to tell if i have a 350 or 305

Find the Engine RPO Code that will tell you the year and engine size.
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Old 09-30-2007, 03:19 PM   #3
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Re: How to tell if i have a 350 or 305

The RPO will only tell what was in it originally. Check the casting numbers on the block to find out what it is now.
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Old 09-30-2007, 04:43 PM   #4
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Re: How to tell if i have a 350 or 305

Suffix number on the pad in front of the passenger side head or the casting number behind the driver side head. The suffix number is usually hard to read. If the block was ever decked, the suffix number will be gone.

Since the 305 and 350 use different bores, a casting number can easily tell if the block is for a 305 or 350.
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Old 09-30-2007, 05:50 PM   #5
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Re: How to tell if i have a 350 or 305

all i can make out on the pad behind the drivers side head is the GM logo and 5G does that tell me anything? I was told that it was replaced with a 350ci gm goodwrench truck engine.
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Old 09-30-2007, 06:18 PM   #6
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Re: How to tell if i have a 350 or 305

In that case I would just pull the valvecovers and look at the casting number on the heads.
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Old 09-30-2007, 07:33 PM   #7
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Re: How to tell if i have a 350 or 305

i would be willing to bet that the 5G you are seeing is really 5.0... the thing with casting numbers is that you really have to have them super clean and even then some digits can take some creative guessing... but on a relativly new engine it should be pretty clean back there so you should look for a string of numbers further outboard of the 5G you saw
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Old 09-30-2007, 08:15 PM   #8
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Re: How to tell if i have a 350 or 305

Quote:
Originally Posted by SpitotRs305 View Post
i would be willing to bet that the 5G you are seeing is really 5.0... the thing with casting numbers is that you really have to have them super clean and even then some digits can take some creative guessing... but on a relativly new engine it should be pretty clean back there so you should look for a string of numbers further outboard of the 5G you saw
i agree. youprobably looked on the driverside. the casting should be on the passenger side. you may have to use a rag+mirror to get a good look. as it is stamped in. it should contain 8-10 numbers. that way if it is a 305 (5.0) you will know what it is model wise.
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Old 10-01-2007, 01:32 PM   #9
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Re: How to tell if i have a 350 or 305

Refer to this link for casting number location.. http://www.mortec.com/location.htm
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Old 10-01-2007, 09:23 PM   #10
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Re: How to tell if i have a 350 or 305

Ok its confirmed it IS a 5.7L. I found that out behind the drivers side head next to the big GM stamp it said 5.7L. The 5g i saw before was actually SGI. so what would the date be? I read the link that 89rspower gave me but there is no way i will be able to see them numbers. Im just looking for a general idea what year it could be. This engine does have centerbolt valve covers so its a newer block. Also, I was told that the computer and tbi unit was not replaced with 350 stuff how does this run using a 305 computer and throttle body? i know it really doesnt have the power it should but should it be running with a 305 computer and throttle body? Also what would i have to change? Could i just change the fuel injectors and prom in the computer or should i replace the whole throttle body and computer? One more thing is there anything else i should replace?

Last edited by berlincam86; 10-01-2007 at 09:41 PM.
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Old 10-01-2007, 10:03 PM   #11
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Re: How to tell if i have a 350 or 305

If it has the 5.7 cast on it, then it's a roller block.
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Old 10-01-2007, 10:05 PM   #12
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Re: How to tell if i have a 350 or 305

what year did they start making the 350 a roller block?
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Old 10-01-2007, 10:06 PM   #13
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1987.
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Old 10-01-2007, 10:06 PM   #14
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Re: How to tell if i have a 350 or 305

1986
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Old 10-01-2007, 10:07 PM   #15
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Model year 1987 (which began production in 1986).
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Old 10-02-2007, 12:56 AM   #16
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Re: How to tell if i have a 350 or 305

I was told the same, when I bought my Z28 that it was a 350 engine but I don't know. I think it is just stock 305. It is an 87....
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Old 10-02-2007, 01:27 AM   #17
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350's were all TPI from the factory.
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Old 10-02-2007, 01:35 AM   #18
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Re: How to tell if i have a 350 or 305

Mine is carbureted. So I'm assuming it is the LG4...at least, that is what I gathered by the VIN#
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Old 10-02-2007, 07:04 AM   #19
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Re: How to tell if i have a 350 or 305

This is a GM truck replacement motor and i cant find one that has a roller cam.
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Old 10-02-2007, 12:31 PM   #20
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Re: How to tell if i have a 350 or 305

Doesn't mean it's not a roller block, though.
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Old 10-02-2007, 03:34 PM   #21
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Re: How to tell if i have a 350 or 305

Well you've found the casting numbers but just to make sure I'd try mashing the skinny petal on the right. If the car fishtails... it's a 350.
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Old 10-02-2007, 05:15 PM   #22
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Re: How to tell if i have a 350 or 305

its definetly not fast as it should be and im pretty sure its because of the 305 throttle body and computer. I still havent gotten an answer from that post.
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Old 10-02-2007, 05:20 PM   #23
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Re: How to tell if i have a 350 or 305

on second thought it is a carb... i thought those could pretty much adapt
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Old 10-02-2007, 05:25 PM   #24
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Re: How to tell if i have a 350 or 305

im just thinking the computer is not giving it enough gas as it should be for a 350.
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Old 10-03-2007, 10:26 PM   #25
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Re: How to tell if i have a 350 or 305

Did both the 305 and 350 come with the TPI?
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Old 10-03-2007, 10:30 PM   #26
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Re: How to tell if i have a 350 or 305

Yes, the 305 LB9 and 350 L98 are both TPI.
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Old 10-03-2007, 10:46 PM   #27
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Re: How to tell if i have a 350 or 305

Easy way to tell if you have a 305 or a 350 from that year.

Hit the gas...

I can attest to this because I actually did the motor swap. 350s really have more power, especailly above the 3000 RPM mark. Mine Dyno'd at 330 HP.
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Old 10-04-2007, 10:27 PM   #28
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Re: How to tell if i have a 350 or 305

Ok guys thanks for your help but i actually sold the car that i was having problems with not because of the problem but because i wanted another car. Thanks alot for all the help i learned alot.
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Old 10-04-2007, 10:27 PM
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