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Old 06-02-2013, 06:58 PM
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holly 670TBI

Is the fuel regulator adj in these TBIS and if so how do I do it. Its set at 11 pounds. I did a vortec head swap on a 1995 gmc truck and it hesatates when I give it the gas

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Old 06-03-2013, 10:21 AM
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Originally Posted by lowhirod View Post
Is the fuel regulator adj in these TBIS and if so how do I do it. Its set at 11 pounds. I did a vortec head swap on a 1995 gmc truck and it hesatates when I give it the gas
Yes it's adjustable from atop the body with a 5/32 allen.

With a 670 and Vortec heads, what else did you do?

You need to check the injector part number in the 670. The original Swirl Port TBI only flowed 60 pounds per hour. The 670 can have a larger injector (upwards of 90 punds per hour) which without a chip change and or substantial changes to fuel pressure can flow too much fuel.

Bogie
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Old 06-03-2013, 11:43 AM
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What ECU/tuning are you using to run it? 11 pounds is a little low but adequate for TBI, your hesitation is probably from your tuning or perhaps a sensor fault?
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Old 06-03-2013, 09:35 PM
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Originally Posted by oldbogie View Post
Yes it's adjustable from atop the body with a 5/32 allen.

With a 670 and Vortec heads, what else did you do?

You need to check the injector part number in the 670. The original Swirl Port TBI only flowed 60 pounds per hour. The 670 can have a larger injector (upwards of 90 punds per hour) which without a chip change and or substantial changes to fuel pressure can flow too much fuel.

Bogie
1249682 GM TBI intake vortec 60979 E-tec 170 Edelbrock heads 3702 edelbrock cam with lifters 398/442 lift 244/264 adv duration 7800 edelbrock timing chain and gears scorpion 1.5 self aligning roller rockers gipson headers magnaflow cats and complete exhast kit MSD coil airaid 1 inch TBI spacer
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Old 06-03-2013, 09:47 PM
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stock ecm unit
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Old 06-03-2013, 09:49 PM
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edelbroc Tech told me this cam will work with stock ecm
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Old 06-04-2013, 05:12 AM
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Originally Posted by lowhirod View Post
1249682 GM TBI intake vortec 60979 E-tec 170 Edelbrock heads 3702 edelbrock cam with lifters 398/442 lift 244/264 adv duration 7800 edelbrock timing chain and gears scorpion 1.5 self aligning roller rockers gipson headers magnaflow cats and complete exhast kit MSD coil airaid 1 inch TBI spacer
Egr is also hooked up
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Old 06-04-2013, 05:34 AM
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Originally Posted by lowhirod View Post
stock ecm unit
What year and model is the ecm and wiring from and what is the ecm part number?
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Old 06-04-2013, 08:00 AM
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Originally Posted by lowhirod View Post
edelbroc Tech told me this cam will work with stock ecm
It sure will if you mess with it enough, by the time you get done "tuning" it though you'd be ahead to just buy an aftermarket ECU.

It will NOT do a good job of running the engine without it being retuned and could lead to failure, at the very least you'll be down a very significant amount of power and see increased wear.

I would have chosen a better cam, as that one really chokes your heads, but to each their own.
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Old 06-04-2013, 10:34 AM
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Originally Posted by lowhirod View Post
1249682 GM TBI intake vortec 60979 E-tec 170 Edelbrock heads 3702 edelbrock cam with lifters 398/442 lift 244/264 adv duration 7800 edelbrock timing chain and gears scorpion 1.5 self aligning roller rockers gipson headers magnaflow cats and complete exhast kit MSD coil airaid 1 inch TBI spacer
Edlebrock used to offer a chip with this cam, depending on how much of your computers "learn" function has been used up to compensate for pushing production variation and aging true functions back to the nominal a chip may or may not be required. Given you've changed the TBI, heads added a spacer, headers and I guess duals with cats the air flow through the engine has substantially increased and the computer chip is probably metering a bit lean.

I'd start by removing the spacer to see if it gets better. These little things can be quite disruptive, inspite of the advertising, they mess things up as many times as they make improvements. Then play with the injection pressure. You may want to try changing the thermostat, a cold one that keep the running temp under 170 will cause the cold start enruchment to stay on. A hotter thermostat of 195-to 210 increases the burn efficiency of aluminum heads which pull combustion heat out really fast, this is a place where changing pistons to run the compression up a ratio would have helped a lot, otherwise running the engine hotter often compensates for the low compresson and aluminum heads. If you engine had 193 Swirl Ports on it, the compresson with the E-Tecs didn't change, where aluminum can take a ratio higher just to stay even with the hotter running iron head. If these simple things can't dial it in then you'll need to look at a chip.

Bogie
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Old 06-04-2013, 10:39 AM
How fast is fast enough?
 
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Originally Posted by oldbogie View Post
Edlebrock used to offer a chip with this cam, depending on how much of your computers "learn" function has been used up to compensate for pushing production variation and aging true functions back to the nominal a chip may or may not be required. Given you've changed the TBI, heads added a spacer, headers and I guess duals with cats the air flow through the engine has substantially increased and the computer chip is probably metering a bit lean.

I'd start by removing the spacer to see if it gets better. These little things can be quite disruptive, inspite of the advertising, they mess things up as many times as they make improvements. Then play with the injection pressure. You may want to try changing the thermostat, a cold one that keep the running temp under 170 will cause the cold start enruchment to stay on. A hotter thermostat of 195-to 210 increases the burn efficiency of aluminum heads which pull combustion heat out really fast, this is a place where changing pistons to run the compression up a ratio would have helped a lot, otherwise running the engine hotter often compensates for the low compresson and aluminum heads. If you engine had 193 Swirl Ports on it, the compresson with the E-Tecs didn't change, where aluminum can take a ratio higher just to stay even with the hotter running iron head. If these simple things can't dial it in then you'll need to look at a chip.

Bogie

a 1995 TBI computer doesn't "learn" anything. And while you can fuss and fiddle with sensors and pressure you'll never get fueling to be quite right and your timing will be way off too.

Getting this thing "chipped" or better yet replaced is the only option that will give you even close to good results. "chipping" will likely cost more than replacing the ECU as you're not going to get it perfect on the first try.
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Old 06-04-2013, 01:50 PM
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a 1995 TBI computer doesn't "learn" anything. And while you can fuss and fiddle with sensors and pressure you'll never get fueling to be quite right and your timing will be way off too.

Getting this thing "chipped" or better yet replaced is the only option that will give you even close to good results. "chipping" will likely cost more than replacing the ECU as you're not going to get it perfect on the first try.
TBI computer has about a 10% margin of leaning where it can adjust fuel mixture to keep O2 levels withing legal compliance, or at least try to do so. If this set up is outside that boundry then a chip with corrections will be necessary.

When Edlebrock sells that cam as a compliant replacement, the certification with CARB was done with an otherwise stock Swirl Port TBI engine. This has been substantially modified beyond that with heads, headers, a much larger CFM TBI which most likely has much greater capacity injectors. So this doesn't fit Edlebrock's advertised no reprogramming required definition. The closest ECU that would fit what he has done would be from the TBI cop cars which use a similar cam to the Edlebrock with heads that are more related to the L98 than the Vortec which the E-Street is an aluminum copy of.

But from the way he describes it running it doesn't sound too far off so I don't think that jumping into either chip or ECU changes at this point are justified till he plays with the set up a little. Afterall, chips and ECUs are expensive often taking more than one attempt to be a sucessful improvement.

Bogie
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Old 06-04-2013, 02:04 PM
How fast is fast enough?
 
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But from the way he describes it running it doesn't sound too far off so I don't think that jumping into either chip or ECU changes at this point are justified till he plays with the set up a little. Afterall, chips and ECUs are expensive often taking more than one attempt to be a sucessful improvement.
$200 to see probably upwards of a 50hp improvement, better fuel consumption and lower wear- seems like he should have started with an ECU.

It'll make more of a difference than those $1,000 heads.
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Old 06-04-2013, 02:46 PM
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$200 to see probably upwards of a 50hp improvement, better fuel consumption and lower wear- seems like he should have started with an ECU.

It'll make more of a difference than those $1,000 heads.
But we're all having to guess this from his description that it runs pretty well but has a hesitation when the throttle dumps in. I wouldn't necessarily argue against your point, I guessing that if it's so close maybe this dog can be potty trained without a big expenditure so I'm suggesting a few tuning games before diving head long into the computer. If that can't solve it then it's time to whip out the old Visa card and get medieval on the computer.

Bogie
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Old 06-04-2013, 10:10 PM
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I HAVE NOT HAD TIME TO REMOVE SPACER YET BUT I DID PUT A 160 thermostat in. IT now surgs a bit at idol about 200 rpm up and down. I had a 195 in it. Not sure if it runs better with 160. WITH 195 I can drive it moderately and it will actelarate nicely I love it!!! but if I get down a little harder or abruptly or stomp it thats a NO GO .I took a spark plug out to look a it .IT is black around the edges and the wire tip is tan in color qnd the ceramic is white like new. I am runing stock air box. I have a new airaid cold air sys. at hand. IT just came today. The truck had a single exhast system with 1 oxygen sensor. I PUT a 1996 Magnaflow system with dual CATS and dual exhast . IT has provisions for 4 oxgen sensors. I pluged 3 of the holes and put my oxgen sensor on the up stream side of the cat passenger side. I am trying better let you know what I have done and how it runs . IF I need a chip or if BETTER anew ECU Where can I get one at a good price?
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