Any one else done this tbi mod

[jbristo67]

I read an article the other night where you put a set of votec heads and a mild cam on your stock short block and it was capable of producing between 400-425 hp. Been thinking about doing this on my 91 k5 and I was curious how it worked out for yall
Posted via Mobile Device

[bigwheel15]

I find it a little hard to believe a set of vortecs and a small cam with no other mods making that kind of power. What cam were they running in the article?
Posted via Mobile Device

[rs74]

I was just talking about this with my engine builder. He builds motors for dirt track cars as well as for many other applications. I was asking about the vortec heads for one of my engines. He said that with regular flat top pistons at about 9:1 putting vortec heads on would be pushing 10:1 - 10 1/2:1 compression ratio. Which I have heard this in the past about putting on vortecs and bumping compression.

If pushing that much compression with vortecs then it probably won't be good on pump gas and might burn up a pistion or two. Maybe put on a set of 72cc chambered heads if you want a little more but still be able to run on pump gas. Just my thoughts.

[rs74]

Of course I was talking about carburetors too. Shouldn't be any difference in TBI.

[mongoose]

its boarderline impossible to make that kind of power with tbi..

[mrhino]

Yep that would be a tough one.

[jbristo67]

You have to run bigger injectors. I don't know why it would be impossible. With the vortec heads on my motor compression will be 9.5:1 I want to say they were running a 228 cam with an edlebrock tbi intake for vortec heads. I'm going to Dyno it after I do it and ill let you know.
Posted via Mobile Device

[mongoose]

you'll need bigger injectors a bigger TB, a new tune.. bigger fuel pump?

not trying to knock ya.. but there was a reason why i threw out all my TBI stuff in favour of a carb.

[jbristo67]

It's still not a high pressure fuel system. I'm sending my throttle body out to be reworked. There is no way on the planet I will ever run a carb. If I did anything other than tbi i would run a tpi.
Posted via Mobile Device

[meatwagon83]

and what is this magical camshaft?

[LEEVON]

Sorry to be a downer, but it's not going to happen with just heads/cam. 300-325 hp might be more realistic, and that is with extensive fuel delivery, bolt-ons, and tuning mods. Remember these things make a dismal 200hp stock, more like 120-140 at the rear wheels!

[Firebirdjones]

Leevon is right. A mild cam and vortec heads on a 350 with a bottle neck TBI setup on top is going to make in the 300hp range, maybe 325ish depending on the camshaft choice,,,,and that's at the flywheel. Might be pretty decent on torque but it's not going to be a HP queen. And even as mild as it sounds, it's still going to need tuning to optimize it.

If you went TPI things don't get much better unless you spend some dough on a mini ram

If you want an honest 400-425 HP the cheapest and easiest route would be a carb. If you insist on fuel injection, you'll be spending some money either on the mini ram mentioned above, or get yourself a nice Edelbrock or FAST multiport setup.

Frankly, if you want fuel injection and HP, (since the good aftermarket fuel injection systems for a gen 1 are expensive) I'd just shove an LS engine in there and call it done

[jbristo67]

I'd love to have an ls motor but I don't really want to go that far. I've got a good tpi set up already with a vortec intake and an over size throttle body. I'm just not sure i want to get that in depth.
Posted via Mobile Device

[MalibuSSwagon]

I don't believe that there are big enough injectors available for a TBI, and airflow is limited due to the injectors being in the way.

If you want that kind of power out of your 350, you may want to use that TPI setup you have.

[Firebirdjones]

Originally Posted by jbristo67

I'd love to have an ls motor but I don't really want to go that far. I've got a good tpi set up already with a vortec intake and an over size throttle body. I'm just not sure i want to get that in depth.
Posted via Mobile Device

TPI would be a better direction than a TBI, since you'll have multiport fuel injection (even better if it's a 91-92 unit). But it's still a batchfire system and the design is limited in making power. You still won't reach your 400hp goal with stock parts. Larger runners probably still won't get you there. You'll need to invest in a mini ram as I mentioned, and then you may as well update the computer system for easier more in depth tuning (better software) and gain sequential fire injectors.

See how it just steam rolls and your wallet gets thinner?

You can see why carbs are still popular. They make power, get the job done, easy to tune, cheap to buy, cheap to maintain, easier to package, etc....
But I also see the attraction to fuel injection, I've been on both sides of the fence for a long time.

[bigbeardedbastard]

i did this swap into my 89 k5..... stock motor with 90k....i did pick up some significant power increase but i doubt it was near 400hp... brand new vortec heads, full roller rockers, flat tappet cam......yes you need to run a bigger TB...i pulled one from a tbi big block. i will tell you the only reason i did this swap was to try and keep the fuel injection. even with the power gains i noticed, it didnt offset the cost of it. the tbi manifolds arent cheap nor easy to find anymore. i think shipped i had 600 just in the manifold. the vortec heads are a great stock head..they flow much better than the stock heads that came on your truck. dialing in the larger throttle body helped however it still had hiccups from time to time coming off idle and at highway speeds. my $.02 is...if you wanna swap out to vortec heads, do it with a carb set up.....easier to dial in!

[jbristo67]

I've got large runners I want to say I was running 28# injectors. I also think its a 54 mm throttle body. I was trying to stay away from using it because I don't want to bite off a 500 harness. My ECM is out of a 91 vette
Posted via Mobile Device

[FritzA]

The vortec heads are without a doubt better than the tbi heads in terms of hp. Even with a mild cam you can get a big bump but not sure I'd be claiming 400 hp.

The vortec heads are cheap. The expensive part is the manifold. The GM manifold which keeps the tbi injection with the vortec heads is over $300 last time I checked. All other aftermarket manifolds for vortec heads work with tpi or carbs. You can use a carb manifold with a tbi bracket. Cheaper but the mounts for linkage are all unique then.

[jbristo67]

Originally Posted by FritzA

The vortec heads are without a doubt better than the tbi heads in terms of hp. Even with a mild cam you can get a big bump but not sure I'd be claiming 400 hp.

The vortec heads are cheap. The expensive part is the manifold. The GM manifold which keeps the tbi injection with the vortec heads is over $300 last time I checked. All other aftermarket manifolds for vortec heads work with tpi or carbs. You can use a carb manifold with a tbi bracket. Cheaper but the mounts for linkage are all unique then.

I found a harness and reprogrammed ECM for 425. Some place called Larry's electric. I think that's the route I'm going to go. Heads 265 + ECM harness 425 + 65 vette fuel pump. So that puts me at 755 plus cam. I can live with that. I won't count the 1k in intake plenum and tubes in injectors I have because I paid for that years ago and it's been a paper weight for 5 years lol
Posted via Mobile Device
Posted via Mobile Device

[jbristo67]

If all that I get out of it is that it runs like a brand new 98 model chevrolet pickup it will be worth it to me. I suspect it will be a bit better than that though
Posted via Mobile Device

[mrhino]

I built a bad 305 Tuned port a while ago and I bought a TPI harness from this guy several years ago. http://www.ebay.com/itm/TPI-Speed-De...item1e7641f661

you might wanna take a look. He has MAP and MAF harnesses. You'll probably want to get a adjustable fuel pressure regulator too.

[rfmaster]

Originally Posted by jbristo67

I read an article the other night where you put a set of votec heads and a mild cam on your stock short block and it was capable of producing between 400-425 hp. Been thinking about doing this on my 91 k5 and I was curious how it worked out for yall
Posted via Mobile Device

Basic fuel calculations required to support 400 to 425 HP level with two stock BBC injectors indicate that it is not possible. With four injectors and aftermarket TB it is possible. (Look at FAST fuel injection system)

//RF

[texasbigbear_wink]

Go to tbichips.com he has a list as well as the power gains from the doing the tbi mods.