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06-08-2006, 11:22 PM
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#1 |
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Registered User
Join Date: Apr 2006
Location: Hockinson, Washington
Posts: 114
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250 Inline 6 Question
Hey guys, got a motor question about timing a 250 straight 6. I have a 1968 Chevy truck that had a early 250 straight 6 in it, but a 1977 250 straight 6 was dropped in a day before I bought it since the other motor went belly up. I drove it home and it ran like crap, so I did a little looking around. The distributor was bolted down enought to keep it in place but it was sliding all around when I was on the road. I am freshening things up and figured that timing it would be in my best interests. Here is my dilemma. Apparently in 1977 there were two applications of the 250, heavy and light duty. I would imagine that the heavy means truck, and the light means car....The heavy needs to be set at 12 degrees before TDC, and the light at 6 degrees before TDC. I have no idea what this motor came out of, what can I do to find out? Thanks,
Josh
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1968 Chevrolet C-10, 2WD, Longbox, Vortec 350, Monster Transmission 700R4, 3.73 gears Good judgment comes from experience, and experience, well......that comes from bad judgment. 1968 Chevy C-10 "Longshot": Bought used from my Uncle George in 1994 and proceeding to beat the hell out of it for 4 years. Sold it. Bought it back, dumped an ungodly amount of money into it since then. |
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06-08-2006, 11:39 PM
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#2 |
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I'm back with 2nd truck!
Join Date: Feb 2002
Location: Texas
Posts: 3,775
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Re: 250 Inline 6 Question
Best thing is to find a engine cating block number on there to find out what kind it is. Really the TDC is a guideline to where it should be from factory. Best thing is to take a timing gun and see where it runs the best with the carb tuned as well.
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1979 Chevrolet Bonanza Big10 "Tootsie Roll" 1985 Chevrolet Silverado (wife's) Member of the Southern Bowties Club "Don't underestimate how sexy a fat man who drinks to excess can be." Homer Simpson |
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06-11-2006, 03:47 PM
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#3 |
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Registered User
Join Date: Jun 2006
Location: SC
Posts: 47
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Re: 250 Inline 6 Question
i have a 250 in my 79 and when i replaced the lifters i had to pull the distributor.i made marks to line it back up for a quick drop in after i finished, but i had to turn the motor over to get some of the lifters up enough to get them out. so i just found top dead in no.1 and dropped it in so the rotor was pointing towards the no. 1 on the cap, cranked it up and advanced the timing a bit till motor ran the strongest and smoothest without detonation. the motor runs like a fresh 305 and cranks easy and idles smooth. All without a timing light. It did take a while to get it right tho. Hope this helps
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06-12-2006, 10:06 AM
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#4 |
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Registered User
Join Date: Jun 2006
Location: SC
Posts: 47
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Re: 250 Inline 6 Question
i guess no one cares about straight sixes anymore... no one is posting on this thread or mine
sob sob.....
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71 chevy longhorn 1 ton 79 chevy straight 6 79 burb 454 91 silverado 350 TBI and a few others that my brand loyalty wont permit me to post. Eureka Boys!!!! 
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06-12-2006, 10:16 AM
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#5 |
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Registered User
Join Date: Jun 2006
Location: SC
Posts: 47
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Re: 250 Inline 6 Question
testing...
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71 chevy longhorn 1 ton 79 chevy straight 6 79 burb 454 91 silverado 350 TBI and a few others that my brand loyalty wont permit me to post. Eureka Boys!!!!
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06-12-2006, 05:00 PM
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#6 |
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www.73-87chevytrucks.com
 
Join Date: Dec 1999
Location: Birmingham, AL
Posts: 6,935
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Re: 250 Inline 6 Question
No one is posting here possibly because they are not really sure of what the question is...
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Chris Lucas 1973 Chevy C-10 1978 GMC Jimmy (2WD) - SOLD 1987 R10 twin turbo LS 1991 R3500 SRW CrewCab 1985 K5 diesel swapped project 1989 K5 2WD conversion w/ Vette susp Project Captkaos Customs 73-87chevytrucks.com |
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06-13-2006, 09:53 AM
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#7 |
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Professional Beer Tester
Join Date: Aug 2004
Location: Louisiana
Posts: 453
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Re: 250 Inline 6 Question
I still like strait sixes; I've had alot of them and still have a couple left. As far as the timing goes, with the crap we have for fuel now the specs are pretty much useless. Like 79BIG10 said, just set it where it starts and runs best without a lot of clatter and go with it.
60-66 Nut
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60 Ford F100 Custom Cab 61 Apache Short Fleetside 64 C10 Short Stepside 65 C80 409 V8 5spd(X-Firetruck) 83 GMC 350 Olds Diesel 85 GMC Short Bed 86 GMC Short Bed 90 GMC R3500 Crew Cab 92 GMC 1500 |
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06-13-2006, 11:17 AM
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#8 |
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7000 #'s of american IRON
Join Date: Dec 2004
Location: north tx
Posts: 883
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Re: 250 Inline 6 Question
yea, i looked into it, this ethanol blend isn't helping when it comes to fuel mileage or horsepower (both do down). So as said, eyeball it.
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06-16-2006, 01:02 AM
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#9 |
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A little east of nowhere
Join Date: Feb 2006
Location: LaBroquerie,Manitoba Canada
Posts: 168
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Re: 250 Inline 6 Question
Use a vacuum gauge and advance timing until you reach the highest reading, then retard it so it drops 1 inch of vacuum. I find this is close to the "sweet spot". You can also use this to adjust idle mixture on carb. I haven't used timing marks or light in 2 decades using this method.
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68 C10 250 4spd 69 C20 327 4spd 69 910 250 3spd 80 K10 350 4spd 76 C60 366 5spd school bus "THERE'S NOTHING YOU CAN BREAK THAT SOMEONE CAN'T BE PAID TO REPAIR" |
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