Author Topic: How many horses ?  (Read 2557 times)

Offline Snag

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How many horses ?
« on: November 27, 2021, 06:01:23 PM »
  I've been a member here for a couple (or more) years , but since my son had my truck ... Rojo Grande is an '86 GMC 1500 , 305 with a TH700R4 . The problems started when I let my son "borrow" it ... but that's another story for another day .
   Today , the story is that it ran out of oil and nearly seized - not his fault , broken oil pressure sensor dumped the oil . I've got the motor stripped some but still in the truck , and piston #1 is bumping the head  but that's also not what I wanted to ask .
   This is the "H" motor , supposed to be 9:1 compression with the 1.840 intake/1.5 exhaust valves and closed chambers . The Chilton manual sez this motor makes 165 Hp @ 4400 ... stock . I'm planning on an .030 overbore with stock .110 dished pistons , an Elgin E-922-P CAM (.444"/288° intake, .465"/298° ex) with an Edelbrock Performer or Torker intake , 1.25" diameter long tube headers and the stock Quadrajet . I'm also stripping most of what's left of the emissions plumbing and running some fairly quiet mufflers .
  My real question is how much can I reasonably expect to gain horsepower-wise from these mods ? Am I too optimistic to expect around 220 or so ? I'll also be swapping the original 2.73 rear axle gears for a set of 3.42's , which I expect will also add a little snap off the line without hurting mileage much - I'll be turning around 1750 at 60 MPH .   

Offline JohnnyPopper

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Re: How many horses ?
« Reply #1 on: November 29, 2021, 09:52:26 PM »
There will be some brainiac here that will help you do the math. It won't be me though 8)

Curious if you know the stroke specs of a 305 vs a 350. Longer strokes get their torque/HP at lower RPM's which it looks like your going to be at 60.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline VileZambonie

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Re: How many horses ?
« Reply #2 on: November 30, 2021, 05:53:07 PM »
Do not use a Torker II intake. Why bother with the 305 though, especially if it is in the condition you describe? Find a 350 and be happy.
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline Stewart G Griffin

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Re: How many horses ?
« Reply #3 on: June 12, 2022, 03:10:45 PM »
i think the  E-922-P cam would be a good choice-----won't give up too much bottom end while should get you over 200hp on the top end.  Might still be able to use the stock converter here?

i would use an edlebrock performer rpm if you're going to continue using the q-jet.

But really, switching to 3.42 from 2.73 alone, i think, will make a big enough difference.

Now, remember, i'm not an engine  person and my "advice" is free.......

Offline Mr Diesel

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Re: How many horses ?
« Reply #4 on: June 13, 2022, 09:41:13 AM »
As already stated above, get a 350 and dump the 305. I have an H 305 in my Camaro. I rebuilt it .030 over, better cam, edelbrock intake and carb and put together a good tune. Basically what you are considering. I'm certain it is less than 200hp. I had good reasons for it at the time (trying to keep car original). I later regretted it and now I'm trying to wear it out so I can justify building a 350 for it.

Edit: I just realized this thread started in November of last year. Hope the OP got things worked out.
1976 C20 Crewcab, 6.2L/SM465
1982 K30 Crewcab , 427TD/TH400
1983 C30, 6.2L/TH400
1983 K30 Crewcab 454/700R4
1986 K10 350/400. 1989 K30 cab/chassis 454/SM465

Offline peewee0413

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Re: How many horses ?
« Reply #5 on: July 14, 2022, 07:24:51 PM »
I don't know about a stock converter....

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