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Old 07-23-2019, 11:23 AM   #1
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90 Suburban questions

So, last night I sold my very well loved 84 K30 Dually service truck. It had only 19K original miles on it and was fantastic.
However I sold it because it just did not fit my needs. I have a 30ft travel trailer and like to take my wife and oldest daughter (26) camping. With 3 dogs, 3 people, the single cab of the K30 just did not cut it.
I found a 90 2500 Suburban. I had the dealer send me the RPO (photo) and I went through all 88 codes. It is exactly what I am looking for.
3/4 ton, 4:10 with LSD, 4x4, tow package, HD rad, HD trans cooler, HD alternator, front and rear A/C, etc...
My only concern about the truck is power. It has the 5.7L F.I. engine rated at 192HP.
Because it is a SBC, there is a ton of things I can do to get more power, but what can be done keeping the F.I.? I am not looking for anything radical, I want a good tow rig for my trailer and a fun light off roading back woods rig. I work from home so I don't have a daily driver, I don't go anywhere.
Can I bump it up to a mild cam and better intake and keep the F.I.?
What would you suggest.
Oh, and according to the original info from GM the same 5.7L in the 2wd trucks had 210HP and in the 4x4 it was 190HP. Why, and what is the difference?
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Old 07-23-2019, 11:46 AM   #2
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Re: 90 Suburban questions

I don't know I'd be too concerned about the horsepower number. That number is only relevant at 4000 RPM. That engine does make 300 ft/lb at 2800 RPM.
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Old 07-23-2019, 11:48 AM   #3
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Re: 90 Suburban questions

Originally Posted by Old65C10 View Post
90 Suburban Questions
That's a lot of questions...

...sorry. I always have to make the same comment whenever anyone mentions anything having to do with a "Brazilian" as well.

Originally Posted by Old65C10 View Post
Oh, and according to the original info from GM the same 5.7L in the 2wd trucks had 210HP and in the 4x4 it was 190HP. Why, and what is the difference?
A lot of times there are differences between platforms either because of exhaust/engine air induction differences, or intentionally detuned for marketing reasons.

The 2008 Hummer 6.2L engine was rated at 398HP (net) in the Hummer, but the same engine in the Escalade was 403HP.

For a 1990 Suburban: I don't see a distinction in the literature between 2wd and 4wd.

In this case it seems to be GVW rated (below 8600 vs above 8600). That happens to be the breakpoint between LD and HD emissions packages.

In the truck world "HD" does not equal "high performance". Heavy Duty equates to increased durability, which is usually attained through 4 bolt mains and lower compression ratio, which also results in lower peak power output.

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Last edited by Keith Seymore; 07-23-2019 at 12:03 PM.
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Old 07-23-2019, 12:07 PM   #4
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Re: 90 Suburban questions

Personally, you're not going to win a ton of races with it....that's just the nature of these trucks in this era. Yes, you can add a few things but at the end of the day, it's not going to be any substantial hot rod.

With that said, I do like what you've done and spec'd. Depending on the tire size, the 4:10 will be decent. The tranny will be the 3 speed instead of the rare, 4 speed found in 1991 only. Also, just because it's on the RPO list doesn't mean it's been swapped out. Check that out when you test drive it.

I run 35's with the TBI 350 and 4.10's on the K5. It's nice and decent movement. 4.56's would be better for me but don't want to do the cost. I also have a 4 speed OD.

I had a 91' 1500 suburban.....great truck! Actually bought it in Bellevue, WA.
- Jeff

89' K5 Blazer, 2.5" lift, 35" tires
04' GMC Yukon XL, 3/4 ton, 8.1L
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Old 07-23-2019, 01:04 PM   #5
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Re: 90 Suburban questions

I don't want a hot rod. As long as it tows my trailer the few times a year that I need it to, I am fine.
Other than that it will be used to do some camping in, exploring the Back Country Discovery Routes and forest service roads.
Mileage will be low. I sold my K30 almost 2 years after I got it, and I put under 2500 miles on it. I hope to do more with the Sub, but if I do 5,000 a year I will be surprised.
rpmerf, thanks for the link, I have read it and it gives me some ideas of what to get, and not get. If I can get another 50-70HP out of it I will be thrilled. It will take time, but no big deal.

One more question, is there a place I can look on the web, or here that would give me the dimensions needed to figure out what size lift this truck has? Like center of the axle to fender lip? I think it may be a 4in, but I will not know without something to measure it by. I would have preferred a stock height, but this is the only one I could find that had the spec's I wanted in a decent condition.
First thing I need to do is a full inspection and make sure it is all good, then I need to get rid of the stupid wheels it has on it. Someone put some big 20-22in rims on it and it looks, well, wrong. Just not right for a 50 year old white guy from farm country.
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Old 07-23-2019, 03:16 PM   #6
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Re: 90 Suburban questions

I pulled a smaller trailer with our 1991 Suburban and never felt any great lack of power. It has the 350 TBI with 700R4. Never use OD when towing, and I did find that it works better to manually shift down to "2" when you start losing speed on a hill. Otherwise it slows down to about 30 mph in Drive and then shifts to 2 and runs up to about 50 and shifts back into Drive and starts slowing down again. Put it in 2 and it lopes up the hill at about 45-50 without any strain.

Unless you just absolutely have to top every hill at 70 mph, mountain roads are usually curvy enough to make that too fast anyway. That's what the slow lane is for

One time we rescued our friends in their mini-van up in the mountains. We rented a u-haul dolly and towed their van full of camping gear along with the five of them in the Suburban. Of course, my wife and kids had to go along so we were plum full with four adults and five kids along with four dogs, and their loaded van on the dolly behind. There's a pretty good little hill down by Columbus where I-90 leaves the river for a while and we cruised right over at 70 mph with the AC on
Current/past Chevy/GMC trucks:
1958 Chevy C-60; 1965 GMC C-50; 1965 Chevy C-10; 1971 Chevy K-10; 1973 Chevy K-20; 1976 GMC C-20; 1977 Chevy C-10 Suburban; 1980 Chevy K-10; 1989 Chevy K1500; 1991 GMC V1500 Suburban; 2016 Chevy K2500 HD

Other vehicles: 1988 Jeep XJ; 2011 Toyota 4Runner
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