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gm 502 in the 70's ???????

4K views 23 replies 17 participants last post by  LOGANSTANFORTH 
#1 · (Edited)
was looking around and saw (The 502-cubic-inch (8.2 L) (501.3cuin) was offered in various fleet and service vehicles in the late '70s and early '90s) is this tru and if so what were thay in?
 
#9 ·
The largest post war gas job mass produced was the 500 cube caddy motor avail. around early 70's. These are interesting motors have a buick olds pontiac (bop) bellhousing. There is couple of companies making aftermarket stuff for these motors and can be built to be quite an animal.
 
#13 ·
I do believe the gas 502 came about as a result of Mercury Marine asking GM for more HP and more TQ than they were getting from the 454, in a package that would mount, attach and connect like the 454, and retain the manifolding from the 454.
The later 8.1L production pickup truck engine wasn't, and in fact couldn't be, the 502 because of emissions issues. Bigger bore diameters increase the difficulty of getting clean emissions, partly due to surface area, partly due to crevice volume, partly due to flame propagation / travel, and partly other details.
If you're starting with an aftermarket block, it is possible to build 605 CI without resorting to the tall deck, and still have a better R/S ratio and piston crown height than the somewhat common 632 / 638. This probably isn't a concern for anyone on here, but matters for some Camaro ( and some Corvette ) swaps where the tall-deck is a serious problem if not an outright deal-breaker.
The 454, bored and stroked to 496, offers better breathing and thus more power than the 500 Cadillac, plus forged parts are cheaper for the BBC to survive the power. Aftermarket heads for even more power still favor the Chev. The Cad is great for cheap torque from the salvage yard, if you want a TH400, but the cheap torque, the dare-to-be-different aspect, and the novelty ( which wears off rather quickly ) are it's only ( and minor ) advantages.
Good luck with the GMC 702 as it's rare, huge, heavy and costly, and while it can do torque, it's never going to be about amazing HP.
The IH offerings are news to me, and I'm thankful to have something new to learn about.
 
#20 ·
i have read that before about the 502 chevrolet gas v8 being put in certain trucks but i kinda doubt it. the mercury marine thing makes more sense to me. you just never hear of someone pulling a 502 out of a jy, EVER.

one thing that sort of surprised me was at work, we have a gmc C6500 flatbed, it has a 454 tbi. I thought all the mdt's got the 366 or 427. pretty sure it isn't a tall deck either, looks like a regular 454 tbi and it is listed on the truck's spid sticker.
 
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#22 ·
they made 454t as well, not very common but they are out there.
Got any evidence?

Tall-deck truck 427s are great for extreme builds, with extra thick cylinder walls, extra thick decks, and even extra-thick pan rails. It adds quite a lot of weight, at least 60 pounds. But boring them to 4.375" without sonic testing is still safe past 700 HP.
Trying to do a low-budget tall-deck 454/467/476 ( 4" stroke ) or 496/505/511 isn't as cost-effective as just starting with a 454, because the 6.535" rods aren't cheap.
You can easily run 4.5" of stroke, and have 541 cubes, at less cost than a 4.25" stroke in a real 502 block, but doing it this way doesn't un-shroud the valves as well as starting with a 502 block, which hurts the power potential.
 
#24 ·
427 Tall Decks were used alot in 2wd pulling trucks in the 80's and early 90's, they were cheap and like stated above, very strong. They were great starting points for 500 cube naturally aspirated pulling engines. Ford also had a 530+ cube big block industrial motor from what I understand. My brother claims to have had one in a box truck of some sort several years ago...
 
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