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Old 11-29-2002, 12:51 AM   #1
soala70
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Pros And Cons Of 402bb?

I am planning to buy a 72 gmc sierra Swb loaded w/402bb. 2nd owner doesnt use oil smokes a little when first cranked but thats all.owner not for sure if original owner had been into motor being he pasted.Anything I should look for and IF it turns out to need a rebuild being (if Im correct) a 396 bored .030over from the factory what are my best options? Also being in good condition no dents or rust whats a fair offer hes wanting $5500?
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Old 11-29-2002, 01:00 AM   #2
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the 402 was bored out for company reasons. Chevy cmae out with the 400 sb and they didnt want their smal block to out displace the 396. Voila 402. I have no problems wit 402's torquy and fun. But of course being a big block they are hard on gas. The smoke thing is just valve guides. Maybe just a head job. dont run under 91 octane unless necessary. Ive found big blocks like higher octane gas
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Old 11-29-2002, 01:32 AM   #3
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If it needs work

Sounds like the price is high, seeing it needs work. How many miles on it? Whats the rest of it like? Driveable as is? What else does it need? The thing it has going for it is: SWB and Big Block. They say there is an a$$ for every seat, sounds like about worth half of what hes asking IMO.
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Old 11-29-2002, 11:45 AM   #4
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I paid $500 for a loaded 68 anniversary special CST with the 396 that needed paint and interior work. 6 months later the engine is rebuilt ( not the same engine . I went with a small block although it would have been cheaper to rebuild the big block ) , the paint is new and it has a new interior and new trim. Drives like a new truck. I dont have close to $5500 total in it.

IMHO his price is too high.
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Old 11-29-2002, 11:50 AM   #5
Bill72BB
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soala70

Out here that would be a good price for a SWB ,BB .With ps,Pdb air ,tilt , auto .
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Old 11-29-2002, 12:03 PM   #6
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Up in these parts, a short/fleet big block with no rust would get that even if it didn't run.
Depressing huh?
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Old 11-29-2002, 12:11 PM   #7
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Quote:
Originally posted by longhornmail
Up in these parts, a short/fleet big block with no rust would get that even if it didn't run.
Depressing huh?
Andy there was a 67 swb in the next town restored for 16,000 ,they are just getting out of sight.
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" If I knew I was going to live this long I would have taken better care of myself "
Marriage changes passion...suddenly you're in bed with a relative. A GUY'S PRAYER....

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Old 11-29-2002, 02:40 PM   #8
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I think the 402's are just fine. I've had two. You can safely bore the 402 another .030 and if you have to go .060 get it sonic checked for cylinder wall thickness. They make tons of torque and tow like a beast. I had a 69 camper special 402/th400 dana 3.54 and towed a 68 3/4 4x4 with the box full of stuff. Total weight was 13,700 lbs when we crossed the ( closed for the night ) scale. We hauled this over a small mountain pass and it maintained 50 mph no problem. It averaged 9 mpg. Unloaded it gets 15 mpg. I'm considering building another for my truck now and putting the Throttle body injection unit on it.
The price seems good to me considering you said it had no rust or dents and it's a short box with a BB.
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Old 11-29-2002, 03:17 PM   #9
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Terry... Let me get this straight. Your 3.54 geared big block 1969 truck gets 15 mpg unloaded. Is that downhill with a good back wind? I'm not saying your full of it but mine got 9.6 mpg when I was REALLY trying to see what kind of mileage I could get out of it. same rig . Long bed 1968 C20 396 with 3.54 gears 4 speed tranny , stock q jet in excellent condition , excellent compression etc. weighed in at 4550
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Old 11-29-2002, 04:34 PM   #10
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mikep, I'm not kidding. I drove this thing back and forth to work for a long time. approx. 40 miles per day, and I checked the gas mileage often. I also had a 8' camper I used to haul it and I got 12-13 mpg all the time.
Actually my buddy just bought the truck from me and he is here right now. He did two trips lately. One with a camper,trailer and race car and got 9mpg with a scaled weight of 12100 lbs. The last trip was unloaded and he went 14.5 mpg driving at 60-65 mph. Maybe the difference is this engine has a 600 holley with 64 primary jets. Also our gallon is 4.54 litres and your is 3.78 litres. This will make a bit of difference.
Terry.
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Old 11-29-2002, 06:21 PM   #11
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Hahaha .... I guess using imperial gallons would make a wee bit of a difference.
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Old 11-29-2002, 10:45 PM   #12
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Everything works cold ac,auto trans,wipers,etc. He still drives it about three time a week to work has approx. 80k on it bed is in good shape as far as rust but used alot. Im going to offer 4k it doesnt hurt to try heh?
On the engine a 402 is already bored .030 over .030 more is all you can go isnt it?Im asking cause I have no idea just what Ive read.Are there .040 over slugs for a 396 or would you say .010 slugs for a 402?If needed at all
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Old 11-29-2002, 11:23 PM   #13
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.040" is possible on a 402 but not real likely . Sonic testing is the best way to go. Different area have different expectations of what a sonic test will cost but in this area its about $150 for a mapped test. Ive had a few done and its saved me from boring at least one block to the point it was unusable. Its difficult to go from .030" to .040" without problem on an engine thats been run for a while. Sometimes it wont get cleaned up all the way. It might not even be necessary to rebore anyway. If the cylinder walls are within spec you might just be looking at a hone and re-ring. Still sounds like too much money. Good 396 blocks are getting harder to find although you might find a standard bore block in the $400 range if your'e lucky. Desert rat seems to have some good pricing on 396 blocks if you dont mind paying the shipping.
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Old 11-30-2002, 12:43 AM   #14
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mikep i had purchased a 396, when i went to rebuilt it i was suprised it was still origanal bore.calling around for machine work,britco in chehalis wanted it pretty bad because it hadn't been touched yet, offered $200 cash for bare block or a 454 block aready done for 550 fully prepped.i stuck with it though now i have 396 .030 overbore{402} now it runs pretty strong now with the forged pistons and tradeing the truck heads that were on it for a set of $200 rebuilt swap meet 4290 heads that i pocket ported and polished.
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Old 11-30-2002, 02:31 AM   #15
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Good old Brittco. Back in the day when I lived in Longview I used to be good drinking buddies with half the guys who worked there. Remember when their shop was under 8 feet of water during the flood of '96 ? I had a brand new siamesed bow tie block submerged with it. Had to have it overbored after that as the cylinders got all pitted. Pissed me off as I had to get different pistons. Some jerkoff swapped my nodular caps out for standard 4 bolt caps too. Last work I ever had them do.
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