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How much power from bolt ons for TBI 350

trailblazr81

trailblazr81

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Hey guys Im used to running older solid axle carbed 4x4's but want the convenience of overdrive, fuel injection, and ride of IFS. Im looking at getting a IFS Blazer or Silverado extended cab. Gonna go TBI because of budget. Ive read that the TBI motors put out 200-210HP and 300-310 torque at LOW RPM's. Ive done alot of reading on TBI mods, injector spacers, fuel pressure regulaters, TBI spacers, Air intake mods, chips, and the standard headers, mandrel bent pipes and high flow cat backs. Now without tearing into the motor how much power can I honestly get a TBI 350 to make? From what Ive read supposedly you can add 50HP+ but I find this hard to believe. If I could make 250HP and 330 lbs/ft torque I would be happy. I plan to build my current 383 into a TBI torque monster, but want to get a little more pep out of the OE motor til then. So does anyone have any dyno numbers or can honestly say they added 50 HP to their TBI without changing heads, intake, or cam? I also plan a 3" BL and crank the torsion bars an inch to run my nearly new 35x12.5's Thanks guys
 
BL and cranking the torsion bars for 35s is a BAD idea. especially so if you're looking for the "cooshy ride" with an IFS truck. you'll need to crank at least 3" for 35s to clear, and that will cause the truck to ride like crap. also, regearing the IFS front is pretty involved being that you have to completely remove the diff to regear it. without regearing it, your hope of the "convenience of overdrive" is gone. honestly, if you want something reasonably big, and a decent driver, find an 87+ K5 or Burb, sling a set of 4.10 gears 3/4 tons under it, a GOOD quality set of springs up front (TC EZ Rides or BDS) and properly located/length shackles, along with a shackle flip out back, and you should have everything you want and then some.
 
Theres alot of people with IFS trucks running 35's with just a BL and some trimming. Theres a IFS Blazer where I work that has a 33" tall tire on it and its stock. Im not afraid of the :hack: or :grind: and my cousin had a Z71 with 36's and stock gearing. HE would even pull a boat with it. But even if I went with a 87-91 K5 Im still looking for info on real HP numbers on TBI bolt ons. And if I went with a SFA model I would just swap the axles from my 73 K20 and only lift it 3" and hack fenders. Ive had a 81 and 86 K5 both with 6" lift and 35's and there was plenty of room.
 
there are in fact alot of people running 35" tires on an IFS truck. however, when you crank the torsion bars you're not only gaining ride height, but you're also eliminating what little drop exists in the suspension. this will cause a poor ride. also, with cranking the torsion bars that much, suspension geometry gets a little tricky to realign.

your cousin may have sucessfully pulled off 36s with stock gearing, and had the truck survive, however his fuel economy isnt where it could be with proper gearing. if it is, he's not figuring it correctly, because he hasnt recalibrated his speedometer.

50hp should be pretty easy with some fine tuning and TBI mods and exhaust though. hell, making 300hp shouldnt be too hard with a little blueprinting inside the engine, using all the stock parts.
 
beater_k20 said:
50hp should be pretty easy with some fine tuning and TBI mods and exhaust though. hell, making 300hp shouldnt be too hard with a little blueprinting inside the engine, using all the stock parts.
Click to expand...

Thanks this is what I wanted to know. :bow:

Also I know cranking bars alot kills wheel travel which is why I would only go up one inch.

Heres my poor riding, worse fuel mileage ride... http://s84.photobucket.com/albums/k8/trailblazr81/?action=view&current=truck.flv A cam swap, different intake, and maybe Holley throttle body to swap in next truck.
 
dont mess with the Holley throttle body...

www.cfm-tech.com

good place to get your injector spacers too. as for an intake, skip the actual TBI intake, and get a carbed intake and run an adapter.
 
Good exhaust and tbi mods will get you 50 hp easy enough...
 
www.TBIChips.com

That's the guy to talk to. TBI guru.:bow:

I've been down this road man...it's a dark and scary place lemme tell you. My second truck, and the one that I had when I first started on the internet and CK5 here, was a '92 Blazer Sport K1500. Beautiful truck, sounds exactly like what you want. However that front end was the devil. Gave me all kinds of issues and I never went bigger than 285/75R16's (33x11.25R16). It did some rock crawling and trail work fine for me but when I sold it there was a bit more play in that front end then there should have been.:crazy:
Honestly I don't think the ride was that great. People talk like GM torsion bar IFS rides like a Cadillac but hell, my coil sprung TTB Ranger, coil sprung SFA Ram, and my MacPherson strut coil IFS Suzuki all ride just as good if not better and honestly, I think Big Ugly's 20 years old 1 ton springs ride pretty good. I won't go back to GM IFS for the ride, that's for sure.

On a 88-98(00) GM IFS K rig you can fit 285/75R16's, 255/85R16's (tallish 33x10.5R16), or 305/70R16's (33x12.5ishR16's) stock if you put them on the stock rims or rims with the same dimensions as the stock 16x7 rims. Backspacing is critical. I put 285's on some 16x8's with about 1.5" less backspacing than stock and I had BAD rubbing. Then I got the Rancho 3" lift...MISTAKE...it was a nightmare. I should have sold the thing and gotten a diesel or TBI SFA truck and been done with it.

As far as 35's I've seen it done two ways with a 3" body lift. One was to put some 315/75R16's on the stock wheels (or again, aftermarket with the same dimensions) and they fit pretty well with minor trimming of the air damn and I think maybe the bumper. The other was regular ol' 35x12.5R15's on 15x8's with as much backspacing as you can find (typically around 4") and then trimming the fenders, bumper, air damn, etc.
 
Ya, Ive talked to the guy from TBI chips and looked at cfm-tech and just wanted to see if the power gains they claim are legit. Alot of people claim big power gains when you really get nada or loose some. My only reason for looking at IFS is Ive been in IFS trucks, coil spring solid axle trucks and Jeeps, and Ferd Rangers and ben able to go down dirt roads, 2 tracks, and open fields with GO pedal mashed. You may loose traction but the soak up the bumps without beating you to death. All my leaf sprung front end trucks (81 and 86 K5, now 73 K20) if its not pavement, sand dunes, or a mud bog I have to take er slow and easy or I'll rattle my fillings loose, or break something on the truck. I'd love to hit an old dirt road and be able to move at a decent pace without a custom design 4 link coil over front on a K5. I guess its just the nature of the beast. Of course Rough Country springs dont help...:haha:
 
Yeah, that's what I was thinking...

Rough Country springs, from what I've heard...actually on several different vehicle boards...are very rough with high spring rates. Find some leaf springs with low(er) spring rates and you'll be amazed at the difference in ride, flex, and capability. Off the shelf Tough Country and BDS springs have good reputations.

Several years ago when I was stationed in San Diego, CA I rode in a 80-something GM half ton that had custom National Spring packs front and rear. I'll swear up and down that thing rode better than my Blazer and some cars I've been in. That thing was cool.
 
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