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TBI to carb swap

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MarineK5

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Need some help. I've got a 1989 k5 blazer with a tbi 5.7 in it and thinking about swapping over to a carb. Jus curious who out there has done it. I know all the obvious parts needed intake, carb, hei distributor, fuel pressure reg. Question is is the transmission going to operate correctly with just a throttle valve cable? It's a 700r4 trans. I've already got a cam ready to put in and getting vortec heads soon. I had thought about keeping the tbi but I jus think it would be a lot easier to do and tune if I swapped over to carb.
 
After converting a carb to a throttle body, I would question why anybody would go the other way :eek1:

look at the stuff from EagleMark, he understands the tuning process
 
You're about to join the long list of people who posted this questions and then were swayed away from doing it by 95% of members on here :waytogo: Just prepare yourself.

The 700r4 will operate w/o issue. Its mechanical, theres no ECM input to it.

Lets play a game, its called whats the real cost of things. Note I may quote some things high as I dont exactly check prices everyday...

Swap to carb:

$250 for a good intake manifold and gaskets, probably a little more for a vortec piece. You're stuck buying this either way with vortec heads though.

$100 for a fuel pressure regulator plus plumbing.

$400-$600 for a good carb

Another $100-$200 and a lot of time and effort to tune said carb in, lets not even put a price on the frustration you'll have with a carb off road.

$100 for the cheapest drop in HEI dizzy. $15 for a pigtail to hook her up because spade terminals wont stay on, especially offroad.

So you're into the swap for lets say $1000, to go carb and downgrade basically. Clearly you're allocating funds to your truck and aren't really on a budget given you're changing heads, intakes etc.

Normally this is the part where I rant and rave about downgrading you're truck, taking a step backwards, and ensuing frustration upon yourself for doing so down the road. But instead Im going to make a suggestion. Buy a FAST self learning throttle body kit... You never have to tune it, it supports north of 500hp and if you decide to change your cam again, or put long tubes on or change from 1.5 to 1.6 rockers its self learns!

Its a $1700 kit new, and yes you would still need that manifold but you need that manifold under any scenario here. The only other thing you would need is a higher flowing fuel pump (which you can get for about $60 that will direct replace yours) and the HEI dizzy. You win all the way around. I understand the frustrations with TBI, especially when you hold it next to LS port injection but seek your answers out else where my friend. Hell they just came out with the 2.0 version that supports 2000hp. Perhaps you can find a racer somewhere upgrading from 1.0 to 2.0 and grab a used setup even cheaper! I really believe this is the way to go for someone sticking with a small block that doesnt want to deal with the oldschool computer hassles of tuning.
 
Another mistake averted :-)

I feel like ck5 is the fuel injection to carb intervention capital of the net.
__________________

-Vinnie


^^THIS^^​
 
I have everything from an earlier truck. Not going to say why.





Ok, I will. EMP. But I am paranoid sometimes.
 
Well I initially wanted to keep the tbi. I was gonna go through Tbichips.com for my chip but I've read some things on other forums that don't sound too good though. And I know the vortec intakes for tbi are around 400 bucks, so I was thinking about getting an edelbrock spread bore intake and using a adapter plate to bolt on my tbi.
 
MarineK5 said:
Well I initially wanted to keep the tbi. I was gonna go through Tbichips.com for my chip but I've read some things on other forums that don't sound too good though. And I know the vortec intakes for tbi are around 400 bucks, so I was thinking about getting an edelbrock spread bore intake and using a adapter plate to bolt on my tbi.
Click to expand...

You can definitely do that. Ive never really read anything bad about Brian over at TBI chips. Every time Ive talked to him hes been helpful and reassuring that if a tune didnt come out right hed be willing to rework it. It seams most people who take issue with him simply take issue with the concept of mail order tuning in general. I know he was more than willing to have me data log my truck and tune it with the given info rather than take an educated guess off of specs.
 
Ok, as far as using like an edelbrock air gap vortec intake and using the adapter plate for the tbi. Has anyone on here done that?
 
I would expect the only issues with that intake would revolve around the TBI fuel lines, perhaps TV and throttle cable, but probably not as likley as the fuel lines.

IMO for a TBI motor as you are describing, you likely don't need anything other than an Edelbrock performer or whatever their bottom of the barrel intake is.
 
dyeager535 said:
I would expect the only issues with that intake would revolve around the TBI fuel lines, perhaps TV and throttle cable, but probably not as likley as the fuel lines.

IMO for a TBI motor as you are describing, you likely don't need anything other than an Edelbrock performer or whatever their bottom of the barrel intake is.
Click to expand...

This is true with stock TBI heads. But with vortecs he will have an RPM ranged well above that horrendous 4500 wall the TBI heads have so the air gap would be better suited. I would get a short air gap that ranges from idle to 5500 rather than the taller one that is 1500-6500.
 
Well thanks a lot for all the help. I may not be able to do the heads now, my torque converter is acting up now and my trans is a used jasper trans. So I ordered a new trans and converter from monster transmissions. I hope it gonna work right cause I've read some mixed reviews of them since ordering it.
 
I can add a couple things here for ya:

1) I am running an edelbrock performer vortec with an adapter and my throttle body and it works fine.

2) You may not even need a chip necessarily depending on how aggressive you go with your cam. If you do stay TBI, make sure you get a cam that's compatible cause TBI needs a strong vac signal.

3) You might want to invest in a nice data logging cable - http://www.aldlcable.com/

4) Good luck with Monster. My experience with them was terrible. They wanted me to pay for return shipping AND charge me a re-stocking fee for a part THEY recommended that was wrong and some other stuff I don't need to rant about.
 
Pretty sure the TBI throttle body is done right around 4500RPM anyway, intake or no.

I'd have to check the flow specs, but isn't it something like 525CFM? What's a 350 with normal VE need at 4500RPM?
 
I mean my best bet if I was gonna do the head swap would be a new multi-point fuel injection setup but their stupid expensive. If I was gonna spend that much id be better off to jus throw a 5.3 in it.
 
A bored tb ($180), better fuel pressure spring and tune would get you where you need to be with your setup if you even need mods. All depends on your cam really.
 
I'm also using carb manifold (I think edelbrock air gap) with an adaptor, but I don't have TBI heads. Been working fine. I converted over from a carb.
 
Agreed, multi-point with Vortecs gets pricey quick. LS starts to look much better at that point.
 
mega squirt or some other stand alone ecu will negate the need for a tbi friendly cam.. you can convert it to run speed density instead of map..
 
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