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TBI improvements...?

Mad-Dog

Mad-Dog

1/2 ton status
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Mar 20, 2005
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Location
Ocklawaha,Fl
I have a question about hot rodding the TBI but never tried techniques such as using the spacer under the throttle body or raising the injectors or unshrouding or increasing the fuel pressure.
If any of you have had any success with this or horror stories to tell please share them with me before i start working on the wifes rig: 305/700r4/TBI
Thanx
 
horror stories... none. Wonderful? eh. I've never felt a bit improvement from throttle body spacer or spacing out the injector pod. I always cut the "lip" off the top of the throttle body and blend it into the throttle bores. I always die grind the throttle shaft to get a little more wide open air. Does this stuff do anything? I really don't know. It sounds like it sucks more air, but sound means nothing. Its never hurt my performance, I can only guess its gained me like 1 hp, and no gas mileage.
 
They work. No horror stories. I have gained a good ammount of power for $$$ spent modding my TB
As far as TB spacers go, dont get the 2 hole kind they dont really make more power.They just increase low RPM air speed velocity and give better throttle response.
The open plentium kind will make more power on the top end. 1/2" is pleny of spacer.
When you put on any spacer you MUST re adjust your TV cable!
The spacer alone wont do much but when added with injector spacer, Velocity stack(Power Charger), Adjustable FP regulator, Combined with good exhaust. you will feel a nice improvement in power and may pick up a little better fuel milage.
Get your stuff from either;
turbocity.com

cfm-tech.com Click on the TBI tuneing button on that page. Lotta good info there.
Both companies have good tech dpts to help you.
 
I have stick so no TV adjustment, but I did have to adjust my throttle bracket(duh). My throttle was really sticky before I adjusted the bracket(bent it back at an angle).

Personally I wouldn't spend the change for most spacers. I bought one off of Ebay for something like $30 and modified it with a die grinder and a hack saw so that it had an opening between the 2 throttle bores(the best way to actually find an improvement). Saved me like $30.
 
As thunder said, there is a good amount of power to be had out of modifying your tbi. I recommend that you go to www.cfm-tech.com and purchase their "tbi power package." It comes with an injector spacer, a velocity stack, throttle body spacer, adjustable fuel pressure regulator, and fuel pressure guage. The parts are easy to install, and they offer a noticeable power gain. They also gives you a ton more throttle response and torque. I did this stuff and noticed a nice power gain. I also gained appx. 2-3 mpg over stock.
-Harrison
 
The following post is just my opinion.... i don't want to start arguing.

265 bucks is alot to spend on spacers, a regulator, and a gauge IMHO. I've heard of spacers doing jack and i've heard they work so i don't know which to believe but a holley 670 cfm tbi can be had off ebay for 150 bucks if not cheaper and will add a good 15-20 hp. I haven't looked for the holley manifolds but im sure those can be had for 130 or so. those two will give you 40 hp + for the same price as the cfm tech package which is said to give you 40 hp but i have a little trouble beleiving claims of 40 hp simply by adding spacers and an adjustable regulator. The holley manifold and tbi and an adjustable pressure regulator WILL give you more power... something along the lines of 50+ and will only cost you a little more than the power pack. I bought the holley tbi, manifold, used a high psi pump, and headers and i've never had so much response or power on tap. the motor has 10:1 comp and a bunch of other bells and whistles like a cam, prominator(in the mail), etc but the holley stuff made a huge difference.

If somebody can show me a dyno chart from the spacer and regulators gains then it might be worthwhile but until they do its just numbers on the screen to me.
 
I wont argue about the holley stuff making power. But I preferr to sitck with proven GM FI stuff. I have never had much good luck with Holley products. Holley is notorious for having injector problems with their TBI units. I had a Holley Projection system (same 670 cfm TB) that blew the injectors in less than 2 years of use.
Holley has susposed to have fixed the problem. But I dont know. I have never been impressed with the Quality of Holley FI. I know there are a few people who are running the Holley 670 TB on CK5. Some have said good things about it and some have had problems with it after they have ran it for a while.
I wunder if you wil be talking so good about your Holley TB 2 years from now?

I know the products from CFM and turbocity work and are dependable. I have been using their stuff on many TBI engines I have built up both for my self and other people for many years. Everyone, including me has been satisfied with the performance gains from those products. I do not build these engines to make a lot of horse power. Fuel mileage and high torque are my goals in a TBI truck. My K5 gets 18 MPG no problem at 70 MPH on the freeway. Has plenty of power for towing and can do well over 100 MPH if I so desire. Thats good enough for me. I dont need no stinking dyno chart :grin:
 
Only reason i said that is because the power gains they claim come from spacers and a regulator... thats it. I never said anything about torque because on their site it says 40hp for under $265. I know your not looking for hp but has anybody really tested they're stuff on a dyno? spacers are very controversial in the world of making power and that is why i want to see the dyno chart. Hell i will probably end up with a couple of their spacers down the road when i have enough money to do it but 265 seems steep for spacers and a regulator. I never said they won't make power i was implying they haven't been proved to make power just testimonials. throttle response can seem like power sometimes.

I have heard the same about the holley stuff... I'm ALMOST paustive that was the earlier tbi that was rated at 325 hp... this one is 275 without tuning.
I'm sure there are gains to be had with those products, i however need further convincing i.e. dyno chart. :grin: :D

I really don't want to piss on this thread.... most of these arguments get started because i get misunderstood.
 
heres their dyno for a carb spacer

http://www.cfm-tech.com/HVHdominatorspacersdynotest-1.htm

pretty funny how the king of "adding up all the little h.p claims for aftermarket manufacturers" is now questioning a h.p claim... :confused: :haha:

me thinks its a reaction to you running the Holley stuff... which btw, i tend to agree with previous statements on Holley... i remember hearing horror stories about the Projection... hopefully they've ironed it out...

i run the full CFM package except i'm running stock injectors at this point.... definitely a seat of the pants power gain... its really helped on the bottom end, much snappier.. top end is hard to tell at this point with stock exhaust.... i expect to see more gains from it once i open the exhaust...

at this point, i just want to figure out how to run one of the free Mercruiser MPFI systems i have at work for when i go 383... ;)

13480tbi31.jpg
 
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Ok, i appreciate all the info.....and i definately understand you about the being misunderstood part..!
 
you see any Holley parts on my motor...... :confused:
neither do i.....!

b4 i built this motor (for the 3rd time) i spent countless hours researching proven dyno combinations and dozens of different recipes and bore/stroke combinations before settling down on a 357 cid motor.
all the parts are designed when installed and tuned correctly to work in conjunction with each other to produce maximum power within a given rpm range.
This engine is built to begin making power at 1800 rpm with a very strong midrange grunt around 3000 rpm and pull to 6500 rpm.
i have also noticed that some engines built using the dominator manifold enjoy a spacer whether it be a open,4-hole or 4-hole tapered design while other engine combinations using the same manifold don't.....it depends on the heads, camshaft and bore/stroke ratio used for that particular application.
i have never used a Dominator manifold because the rpm range (3500-7500) does not match up with my requirements.
The spacer i use is designed to work in harmony with the Edelbrock performer rpm air-gap which has a small window cut into the plenum, this window technology is very similar to some TBi spacers which allow the intake runners to draw air/fuel from both sides of the fuel metering device.
Imagine combining the benefits of a dual-plane, divided-plenum high-rise with a single-plane, open-plenum high-rise.....(now we got chocolate in our peanut butter).
It's the best of both worlds my friend.....have a blessed day :cool1:
 
Mad-Dog said:
you see any Holley parts on my motor...... :confused:
neither do i.....!
Click to expand...

ummm, my reply was to DW.. not sure what your confused about...

best of luck with the project!
 
Mad-Dog said:
I have a question about hot rodding the TBI but never tried techniques such as using the spacer under the throttle body or raising the injectors or unshrouding or increasing the fuel pressure.
If any of you have had any success with this or horror stories to tell please share them with me before i start working on the wifes rig: 305/700r4/TBI
Thanx
Click to expand...

I am currently running a 350 TBI on my 390 stroker engine. I had to make a custom adapter for the spreadbore edel intake, I goofed the adapter too, I cannot get WOT completely because of the offset. Its works for now and i don't have the time or money to get another.

I had to install 454 TBI injectors (available for me free), or my other option was to increase the fuel pressure. There are bolt ons available on the internet for these TBI units. CFM tech

If you do have a performance engine I would recommend putting a 454 TBI unit on, it has much bigger bores for better flow. You would just need an adjustable fuel pressure guage and an adapter for the TPS. To determine your A/F ratio I would recommend an A/F guage to tune it, just remember at WOT it should be rich.
 
Ryoken...

I know what you are talking about with the holley stuff... my dads friend built a 383 and put one of the older holley tbis on it and the injector kept falling out. that was a different model... they changed it a couple years ago and i hear nothing but good things about the one rated at 275 which i am running...the one your talking about was rated at 325. the master mechanic that did the 383 ( my dads friend) couldn't even tell it was a holley until he saw the emblem because those two holley tbis are a lot different. I can't say nothing will go wrong but from what i've heard they've fixed the problem. Seems real hard for the injector to pop out now becuase the air filter stud would have to either strip out or come loose.

my praise for holley may be a biproduct of running holley stuff... just like your praise for cfm tech is a biproduct of you running it. I am happy with the performance of the dual plane manifold and the tbi and this subject is on hot rodding a tbi.(which i am in the middle of trying to support up to 400 hp with a 2bbl tbi) also because holley is a big name with a well known reputation for performance... first time i heard of cfm tech was on here but then agian first time i heard of a prominator was on here.

The dyno chart starts at 5400 rpm? got anything lower? the gains people claim tend to be that it has more tq and throttle resposne not more top end on a 650 hp motor!!!! And the dyno chart is from cfm tech!!! :rotfl: :shame: i meant somebody on this forum who bought one and found a gain on the dyno.

Actually the final numbers that were added up were rjfs... i posted my estimates and he corrected them about 2 months ago. first i said it was 375 but the final result was more like 340-350.
 
ive run the 670 holley tbi on my truck for the last two years. i havent had any big problems with it, but didnt really make a difference in power. i've decided to put the old stock unit back on and add the cfm upgrades to it.

i think the holley 670 is just too big for a stock motor. runs too rich. might work better with the holley manifold tho. i havent heard many people who actually drive thier trucks say that the holley made a difference in power, but ive heard almost everyone say that the cfmtech stuff did.

btw he said he this is for a 305, not a 350... so i think the holley tbi would be even more mismatched than my stock 350
 
Fuel pressure makes a big difference. you are right about the stock motor tho... the tbi has bigger bore but the stock manifold doesn't. That is why i suggested the manifold and tbi. a 305 may be a little too small for this tbi.... don't know tho.

I guess for a stock motor the cfm tech stuff would be the better way to go.


good luck.
 
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