Although a larger throttle body was never high up on my list of upgrades to do on my L98, trouble with my stock throttle body recently gave me no other choice but to buy a new one.
After installing my new runners/intake a few weeks back, I noticed that the throttle would sometimes remain "open" after letting off the gas. Other times it would close, but close REALLY slowly. I took it off and gave it a thorough cleaning and sprayed some WD-40 in some key areas hoping it would clear up the sticking problem but it never really went away.
The final straw which lead me to buy a new one, was when I was driving home after work and had to slow down for upcoming traffic on the free-way. The throttle once again stuck open and the engine was spinning at nearly 4000pm. Unfortunately, my brakes just weren't strong enough to bring the car to a complete stop with the engine spinning that high and I was approaching the stopped cars up ahead real fast. I shifted the tranny to neutral, and slammed the breaks.
I could see I wasn't going to make it in time so I veered onto the shoulder and finally was able to bring the car to a complete stop right beside the car that would have been directly in front of me. It was one of those tiny little "smart cars" and the old bag driving it looked over at me and gave me this real dirty look and shook her head at me. WTF?
She must not have had any idea just how close she came to getting run over, had I not pulled off onto the shoulder as soon as I did....
Anyways, I popped the hood and manually pushed the throttle closed and carefully drove home as slow as I possibly could.
I wasn't going to take the chance of having the same thing happen again and wind up in a serious accident so as soon as I got home, I placed an order for a new throttle body. Since I was about to spend the money anyway, I figured I'd get something nice to go along with my new intake and runners so I ended up going with Holley's billet aluminum throttle body.
When I ported out my plenum originally for my bigger runners, I increased the size of the entry ports behind the throttle body to roughly 52mm thinking that if I ever decided to go with a larger throttle body in the future, the plenum would support the extra flow. It's a good thing I did as it ended up coming in handy after all.
I just finished installing this a few minutes ago. I still have to hook up a scanner to adjust the TPS sensor but so far, the car runs fine. It's obvious that the intake is sucking in a lot more air then before 'cause you can literally hear the air going into the plenum through the larger throttle body. A quick spin around the block revealed that throttle response (thankfully) remained crisp and instantaneous. I was originally a bit concerned that the larger throttle body would have a negative effect on throttle response since that's a very common "side effect" of using larger than stock throttle bodies but I guess porting out the plenum to match the the new TB payed off after all.
The final results?
The car pulls noticeably harder from 3500 and up which was a nice surprise. Not like it gave me an extra 50hp or anything but enough to feel a definite improvement over the factory 48mm. The Holley is a really nice piece for sure. It really cleaned up the engine compartment nicely and it's silver finish matches my AS&M runners perfectly. Very sharp looking if I do say so myself.
All in all, I'm happy with the purchase.
Here are a few pic's I snapped off of the throttle body on its own and once I installed it on the motor. I give Holley's TB two thumbs up as far as build quality and over-all "eye-candy" is concerned. The red throttle blades look so nice it's a shame they can't be seen once the air intake is installed. If only the intake tubing was made of clear plastic, you could see everything. (Hmmm....I think I just came up with my next project idea....)
Finally, although I did get an improvement in performance, it's only because I have an intake set-up that takes advantage of a larger throttle body's increased air flow. I wouldn't recommend one for a stock intake car 'cause there'd be no need for one but if you (like me) have an intake designed/modified to take advantage of the increased air flow, go for it.
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__________________ Follow the links below to get information and see some picture's of the parts I've purchased so far. The car by they way, is an '88 Iroc-Z powered by L98
that had to run u a pretty penny! id say like 400$ and u never really specified the size? u said u ported to 52mm so im guessing its a 52mm TB.
i got a really nice performance products 58mm TB altho it isnt as nice looking as yours?shinny i only paid 210$ u coulda saved urself sum dough, unless u wanted the looks which i can understand bc its pretty
wow thats awsome! Great post. Maybe i'll save for one now.
__________________ 305 TPI, Elelbrock hi flow intake, Edelbrock hi flow runners, ported & polished plenum, holley AFPR, 24# LT1 injectors, air foil, SLP cold air induction system, Crane roller Cam#104224, Crane springs #11308-1, Summit # SUM-G6601 Roller timing gear set with polished aluminum timing chain cover. Richmond 3.73 posi rear end, Ceramic coated headers, and matching Y-pipe, Flow through exhaust with Flowmaster muffler, Torque Thrust 17" rims, Sportline springs (lowering almost 2 inches all around), Custom made box in the rear that holds 2- 12" subs, Updated speakers all the way around. CD player, A/C deleted. Custome tuned and dynoed.
Yes, it's a 52mm throttle body. That was just about as large as I could go when I was porting the plenum's opening's. Trying to open it up to 58mm would have been too large and I'd end up grinding through the plenum's walls. A 52 will flow roughly 900cfm which is more than I'd even need with my TPI set-up, so I'm happy with it. Other's may want or need something bigger (58mm), but the 52 works just fine with what I'm running.
Again, the only reason I went with Holley's is because it was, in my opinion, the nicest looking of the bunch. Performance wise, I can't see it performing any better than any other other brand like Edelbrock/BBK, TPIS, AS&M or Professional Products.
On a side note, on my way to work early this morning, the car ran like a honda. It was embarrassingly slow and I had a really difficult time taking it past 2500rpm 'cause it kept cutting out on me. I thought for sure it was an ignition problem. It rained all night the night before and was cold and damp outside so I figured maybe a little dampness somehow found it's way into the distributor's cap and rotor. I figured it would clear up and evaporate once the engine warmed up after a few minutes of driving. Unfortunately it never did. I got to work and parked it.At the end of the day, I got back to my car and started it up. Same thing. Car kept cutting out as if there was no spark past 2500rpm.
I looked at the wires to see if any of them had burned through (a common side-effect of running SLP headers), checked the cap and rotor for moisture and even disconnected the MSD ignition I just installed thinking maybe it was malfunctioning. Nothing worked.
It occurred to me afterwards that I never did get a chance to adjust my TPS sensor when I switched it over to the new throttle body. Since my test drive with the car after installing it went so well (and I had no problems with it the next day either) I figured it was set up pretty close to where it should be.
Boy was I wrong. The TPS sensor was so far off, I can only assume the reason why it ran so badly this morning was because the car went into "limp-home" mode. It was that far off. I hooked up the scanner and set it to exactly .54 and the car ran mint. In fact, now that the TPS has been set properly, the new throttle body's performance improvement is even more noticeable than before. The car absolutely screams from 3500 and up. Night and day difference. Wow. Hard to believe it's still TPI
Moral of the story?
When adding a larger throttle body, ALWAYS remember to set your TPS sensor or your car will never run properly. It may sound like a no-brainer to some, but as you can see from my experience, a simple 'over-look" can lead to some major headache's.
Never underestimate the importance of a properly set TPS sensor and just how much it effects a car's performance...
__________________ Follow the links below to get information and see some picture's of the parts I've purchased so far. The car by they way, is an '88 Iroc-Z powered by L98
I'm glad you had a good experience with the Holley TB. I did not, but it was an older unit and, I believe a non-billet piece.
Let me as you a question about that TB.... does it have a positive stop to prevent the throttle plates from opening beyond 90*? My unit did not and it loved to knock the TPS out of whack becuase of that. One of about 3 things I hated about my Holley TB and made me swear to never buy one again. Stuff just so idiotic that it was obvious nobody at Holley had ever actually tried to use it on a real car before they put the product on the market.
i love the professional products TB, i go the 58mm for 210$ and its a nice piece. its a good looking piece, i didnt get the polished one since im not all about looks for me, but the non polished one goes with the non polished HSR very well. comes with all new linkage but not TPS sensor and u have to swap over the IAC assembly. it doesnt look as good as that HOlley one but for less than 1/2 the price i cant complain. im all about performance the looks arent bad tho. i can post sum pics if u want
i love the professional products TB, i go the 58mm for 210$ and its a nice piece. its a good looking piece, i didnt get the polished one since im not all about looks for me, but the non polished one goes with the non polished HSR very well. comes with all new linkage but not TPS sensor and u have to swap over the IAC assembly. it doesnt look as good as that HOlley one but for less than 1/2 the price i cant complain. im all about performance the looks arent bad tho. i can post sum pics if u want
please post a pic I might buy one also do they
have a web sight
I just recived Professinal products 58mm throttle body(85-92 tpi)I bought it from cnc motorsports.It supplied with two throttle levers,one for 85-88 and another 89-92.At 85-88 throttlelever was missing mounting tap where throttle cable should mount,and I have 85 tpi,so I must firgure there some solution.I mailed to cnc motorsports at that defective throttle lever,and they answered:"i don't have single parts, they are purcahsed as u recieved the product".Not very good customer service.
i got mine from performanceparts.com
they only sell through distributers.
as far as the part thats missing with yours.... um from what im looking at i dont see any prob with mine. im not totally sure i know which part im talkin about if u could show a pic or soemthing i could tell u.
__________________ 87 Firebird formula 350tpi
poly everything
headman longtubes true 3" duals with xpipe
upgrades 700r4, kevlar bands, billet servos, boost valves, transgo shift kit, raptor fluid, deep pan, kickdown valve, 13 vein pump,trans cooler, b&M mega shifter
ported plenum matched to SLP runners, ADJ FPR, TB air foil, and spiral spacer
march pullies, smog deleted, AC removed
motorvation strip chip
160 thermostat, 166 on fan switch
sterwart warner gauges and triple pillar pod
UMI LCA relocation brackets, UMI adjustable panhard rod, hand made tubular LCA's, custom thru floor subframes, TDS wonderbar, KYB struts and shocks, sportlines, moog suspension tierods etc
SSBC force 10 front calliper upgrade kit, slotted and dirlled rotors, stainless braided lines all over car, rebuilt master, SSBC proportioning valve, rebuilt booster
SLP 17x8's wrapped in Nitto 555 ZR rubber
but enough to feel a definite improvement over the factory 48mm. The Holley is a really nice piece for sure. It really cleaned up the engine compartment nicely and it's silver finish matches my AS&M runners perfectly. Very sharp looking if I do say so myself.
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