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Aftermarket chips allow for stock O2 correction, there really isn't much they can do VE wise. Stock bins have have total timing at 30* to 28* SA depending on the injection system, and once you see CTS temps reach over 150 degrees nearing Closed Loop enable, there is an additional amount of timing taken out at wide open throttle dependent on IAT and CTS data. Bottom line, you can advance your distributor by hand a few degrees and run your stock chip at a cold temperature, say 80 degrees. Then compare it to the Hypertech at fully warmed up. No difference whatsoever. That's what those chips do, more spark advance, and less timing pull, at normal operating temperature. If you're a tuner, you can burn a chip to do the exact same thing...
As for Ray Jr, I just caught your response from what Fast355 quoted. Here's a tip. In reference to your hero, any fool can slap a turbo onto an engine, or tune an engine, what matters is that the engine lives and can still be used as an example as viable proof. Where is it? As for your engine, well, lets just say I don't blame the setup. All the best...
- Rob
The issue I have always seen atleast with the Hypertech and Superchips stuff is that both of those companies test near sea level and only adjust the 80-100KPA areas of the chip. When you get to 5,000 ft or above and get down to the 65-70 KPA range they aftermarket chips do NOTHING. The tuning is all factory in those areas. I have seen VE, spark advance, PE air/fuel ratio and TCC changes on everything I have read and compared to factory. That is TBI, TPI and Vortec applications. Hypertech also had a line of chips they made designed for cooler thermostats, to use with aftermarket intakes and exhausts that had numerous changes to support cooler running, more timing, preminum fuel and help provide additional fuel for the increased airflow.
Aftermarket chips allow for stock O2 correction, there really isn't much they can do VE wise. Stock bins have have total timing at 30* to 28* SA depending on the injection system, and once you see CTS temps reach over 150 degrees nearing Closed Loop enable, there is an additional amount of timing taken out at wide open throttle dependent on IAT and CTS data. Bottom line, you can advance your distributor by hand a few degrees and run your stock chip at a cold temperature, say 80 degrees. Then compare it to the Hypertech at fully warmed up. No difference whatsoever. That's what those chips do, more spark advance, and less timing pull, at normal operating temperature. If you're a tuner, you can burn a chip to do the exact same thing...
As for Ray Jr, I just caught your response from what Fast355 quoted. Here's a tip. In reference to your hero, any fool can slap a turbo onto an engine, or tune an engine, what matters is that the engine lives and can still be used as an example as viable proof. Where is it? As for your engine, well, lets just say I don't blame the setup. All the best...
- Rob
And that's why the Stage 2 Hypertech required a 160* t-stat? Or, IOW, bump your initial timing and run a cooler t-stat and get the same benefit from your stock chip.
And that's why the Stage 2 Hypertech required a 160* t-stat?
That is correct! The Stage 2 had more timing and the primary fan was designed to turn on at the matching cooler temperature. Finally they also suggested a low temperature fan switch for the secondary fan. Octane requirements linearly increase with coolant temperature for the same timing advance and same compression ratio. By increasing timing and not lowering the operating temperature, the Stage 2 would show horrible timing retard.
That is correct! The Stage 2 had more timing and the primary fan was designed to turn on at the matching cooler temperature. Finally they also suggested a low temperature fan switch for the secondary fan. Octane requirements linearly increase with coolant temperature for the same timing advance and same compression ratio. By increasing timing and not lowering the operating temperature, the Stage 2 would show horrible timing retard.
So there some actual ignition timing changes in that one, it does more than simply turn on the fans sooner. What about the Stage 1 which required no t-stat changes?
So there some actual ignition timing changes in that one, it does more than simply turn on the fans sooner. What about the Stage 1 which required no t-stat changes?
It still had timing changes, mostly in the lower engine speeds at WOT as well as VE and PE air/fuel ratio changes. That being said the Stage 1 had noticeably less timing increases than the Stage 2.
It still had timing changes, mostly in the lower engine speeds at WOT as well as VE and PE air/fuel ratio changes. That being said the Stage 1 had noticeably less timing increases than the Stage 2.
That's good. I'm considering a Stage 2 Hypertech chip for my '85, just so the fan comes on sooner. If there are ignition and air/fuel improvements, even better.
That's good. I'm considering a Stage 2 Hypertech chip for my '85, just so the fan comes on sooner. If there are ignition and air/fuel improvements, even better.
The only MAF car I have played with was a 1985. I repinned and rewired the harness to run a 1989 165' ecm and eliminated the MAF burnoff module. Doing this also allow me to remove the cold start injector and sensor. Then later when the MAF went bad, I removed it, replaced the boot with a SD intake boot, mounted a MAP sensor to the firewall on a TBI MAP sensor bracket and hooked up the MAP sensor to the intake. Repinned the ECM harness to match a Holden 808 ECM and ran the SD V8 808 ECM Holden code in the 165' ECM. IIRC it is $12P code
The only MAF car I have played with was a 1985. I repinned and rewired the harness to run a 1989 165' ecm and eliminated the MAF burnoff module. Doing this also allow me to remove the cold start injector and sensor. Then later when the MAF went bad, I removed it, replaced the boot with a SD intake boot, mounted a MAP sensor to the firewall on a TBI MAP sensor bracket and hooked up the MAP sensor to the intake. Repinned the ECM harness to match a Holden 808 ECM and ran the SD V8 808 ECM Holden code in the 165' ECM. IIRC it is $12P code
Impressive, however I'm more of a "just replace the PROM" guy.
Same here.. I used to run that Hypertech Thermomaster chip with a 160 thermostat back in the 90s..
Not sure if it did much.. I think the fan came on sooner.. Maybe you’d notice more with an automatic.
That car did run way cooler than my bone stock 88..
I've had one in my black '89 since...around '89. I got tired of having it run at 220* all the time. Between the chip and the 160* thermostat, it's hard to get it over 180*. Also apropos to this thread, my '89 has most of the free/cheap mods of the era and it runs much stronger than it did bone stock.
I never did a before and after Dyno or track run with my 87, but when stock I’d race an L98 and my nose would be at his rear wheel. After I did some of these hacks with exhaust and a hollowed cat he’d consistently be at my rear wheel. Once I spent some more money I pulled ahead more, but the stupid hacks seemed to work. I never started going to the track until the car was pretty fast and people would say to bring it and see what it does so I couldn’t compare the difference each stage of mods would make.
I dont know know that I could feel the difference but it was nice to edge out an L98. It took a little more money to feel a real difference.
I had a friend with a white G92 and he would do all kinds of stuff to his car and tell me what he’d run after doing heads, cam, injectors, ignition, plug gaps, wires, etc.. I would just pick and choose what was working for him.. He got a little crazy with taking seats out and stuff, but I drew the line..
I wouldn’t do most of the stuff I did to my 87 to my 88.. I do want a cooler Thermostat and replacing a PROM chip wouldn’t be bad.
Back then I always heard get the air in faster, exhaust out quicker, and keep the engine cooler, get good tires and performance will improve..
A lot of my crazy tuner friends had cars that never ran right so I was always wary of getting in too deep over my head..
A lot of my crazy tuner friends had cars that never ran right so I was always wary of getting in too deep over my head..
I hear you. Me too. That's why I like small, incremental changes/improvements. I remember experimenting with the initial timing back then. I kept bumping it 1 or 2 degrees to see how it'd run. In the end, I had to pull back 2 or 3 degrees, because of, believe it or not, wheel hop.
The Stealth Ram Graph is the first picture. 1991Z28
Just going to Stealth Ram without changing anything else. Look at where the peak power had changed. This is a Dyno with a Stock powered Super Ram with a TPIS ZZ9 Cam, AFR 180’s Heads, 358cu, T5 Trans and 3.42 gears.
Valve events play a key factor as well. You can install an HSR on an otherwise bone stock L98 and see the RPM band rise because of the increased plenum volume, but then you can also run the correct valve events on an otherwise stock TPI L98 and get similar results, with overlap and rough idle being the byproduct of course, but that is just the way it is. It was mentioned above that although my TPI 305 may rev to 6000-RPM, that the RPM isn't that usable, but this is being said without knowing my valve events, nor my injector size, it was just being based on Tuned Port Injection. My lift is relatively low, but my duration is very wide. Stuffing in a roller camshaft with increased lift is more than doable, and will gain more usable RPM up to 6000, but I chose my camshaft for a reason. RPM was never the point because I am running a turbo, but the TPI will rev as high as I need it to, and if you think (not you Vince, I'm speaking in General), if you think boosted pressure at 6000-RPM isn't "usable" with TPI, then, well, it's kinda moot on my part to even argue...
what Fast355 quoted. Here's a tip. In reference to your hero, any fool can slap a turbo onto an engine, or tune an engine, what matters is that the engine lives and can still be used as an example as viable proof. Where is it? As for your engine, well, lets just say I don't blame the setup. All the best...
Ok...i had enough
street lethal... i got 100$ says your car put on the dyno doesnt make power you think it does and doesnt hold power to 6000.
Put up or stfu. You run your dumb mouth for years with no results. I try to be helpful and tolerant of your ignorance but its clear to me that you dont know what you are doing. Finish your car for once. Put up the results like i have. How many slips or vids do i gotta post to be considered proof??? How many dyno sheets do i need to show you? All the while you have jack shyt.
didnt know about timing being pulled at high coolant temps and iat’s??? Man thats tuning 101, how you not realize that. No wonder you aint gonna put a turbo on it, it will never run. Pop the bottom end in first hit. Hit me up if you wanf it tuned to work
as for ray’s build, it still runs and runs well. Idk what more proof you want
I beg to differ in opinon. I have run stock runners, ASM oversize and Siamese ported SLPs on multiple setups on the dyno. On a Vortec 305 with ported heads that had 1.94/1.60 valves installed, a factory 203/210 @ .050 LT4 cam and 1.6 rockers the stock runners will level off in the 5,600 rpm range but the HP will stay completely flat all the way to 6,500+. On a 350 the stock runners will stay flat until 5,800-6,000 rpm. The ASM runners will move the peak upward from 4,800-5,000 up to about 5,200-5,400 and the power will stay flat until 6,200 rpm. The Siamese runners will trade some low-end torque and the peak moved up to 5,600-5,800 rpm and the power stayed flat until past fuel cut-off. I had a ported 3817 base, Siamese ported SLPs, fully ported plenum on a 10.5:1 vortec head 383 with a small 214/218 @ .050 on a 114 LSA roller cam that made peak HP at 5,600 and had a flat HP peak from 5,600-6,200 rpm. 380 RWHP AND 450 RWTQ OUT OF THAT ONE
I have a 1987 Firebird I recently setup with a 10:1 355, LT4 Hotcam, Stock SD TPI system, LT1 injectors, tuned by me with my Autoprom, 1 3/4" primary shorty headers, dual 2.5" exhaust with a X-pipe, custom CAI, 4th gen cooling fans, and 170*F thermostat. The engine is backed to a TH400 with 2,800 rpm stall 9.5" converter and a 9-bolt limited slip 2.77 rear end. The car launches hard and the engine has ZERO difficulty pulling to the 5,800 rpm shift points. The car has run a best pass at full weight of 8.20 @ 85 mph in the 1/8th in 2,800 DA NO LESS with the stock intake base, stock runners and a plenum with the egr diffusers ported out.. The power in this car peaks at 5,200 and stays completely flat up until the ecm fuel kill at 5,800. From what I remember while tuning the car runs 2,500 rpm @ 75 mph on the highway, the owner is getting about 26 mpg with lean cruise enabled @ 16.5:1 air/fuel ratio and 52* of timing. This car on a conservative street tune made 280 RWHP through the TH400 with its loose converter on 91 octane at 12:1 air/fuel ratio and 32* total timing. I have since retuned the car to bring it up to about 13.2:1 air/fuel ratio and 34* total timing which it responded noticeably too. Even before the retune based on the previous track times and my track experience with cooler weather, in good weather this car would run 7.90s @ 88+ mph in good weather and that is good for a mid 12s 1/4 mile run.
all i can say is i wish i had your dyno lol. I have yet to see a tpi pull that high that was not boosted
Have either of you had the opportunity to read a "performance chip" of the day, like a Hypertech Stage 1 vs Hypertech Stage 2 vs the factory PROM? If so, I'd like your take.
The only “back in the day” experience I had with chips was back in 1986 - my 85SS was used in Hypertech’s R&D of their 1985 up chip for the Monte Carlo SS. Long story short, my stock chip with the base timing set at 10-degrees ran the same as the best time with their chip once we brought the base timing back down to 6-degrees. I asked the guy riding along during the testing if they were doing anything other than bumping up the timing. He reluctantly said, “No, but don’t let Mark (Heffington – the owner) know I said that”. He did go on to say that they could do a little more with the EFI cars (he wouldn’t say what) but had to keep things rather generic due to the one-fit-all approach they had to take.
Fast forwarding to 2000, I read a “custom” $400 chip from Jet that the guy I bought my old IROC from was running. While ultimately his fault, Jet had not even changed the “stock” 18# injector constant for the 26# injectors and he kept running it until it washed the cylinder walls down. The only things that were changed were the on/off temps for the fans and the timing had been bumped little. According to other’s I’ve spoken to with much more experience in programming chips than me (including what Fast355 has said), that seems about par for most of the name brand chips and some have told me they’ve even seen some cheap rip-offs that were totally blank..
Anyway, since the hack and equipment is available now to burn your own (along with the support from this and other boards),,, you are MUCH better off investing that money to burn your own chips. I know it can seem a little intimidating at first but once you take the plunge, it’s not that bad at all – just a little time consuming.
thats totally different. Claims being made of stock base runner setups doing it. Allens example is an engineered system of correct length, diameter and cross sectional area and camshaft to make those rpms. Tons of work into that system. Stock stuff will not do it
The only “back in the day” experience I had with chips was back in 1986 - my 85SS was used in Hypertech’s R&D of their 1985 up chip for the Monte Carlo SS. Long story short, my stock chip with the base timing set at 10-degrees ran the same as the best time with their chip once we brought the base timing back down to 6-degrees. I asked the guy riding along during the testing if they were doing anything other than bumping up the timing. He reluctantly said, “No, but don’t let Mark (Heffington – the owner) know I said that”. He did go on to say that they could do a little more with the EFI cars (he wouldn’t say what) but had to keep things rather generic due to the one-fit-all approach they had to take.
Fast forwarding to 2000, I read a “custom” $400 chip from Jet that the guy I bought my old IROC from was running. While ultimately his fault, Jet had not even changed the “stock” 18# injector constant for the 26# injectors and he kept running it until it washed the cylinder walls down. The only things that were changed were the on/off temps for the fans and the timing had been bumped little. According to other’s I’ve spoken to with much more experience in programming chips than me (including what Fast355 has said), that seems about par for most of the name brand chips and some have told me they’ve even seen some cheap rip-offs that were totally blank..
Anyway, since the hack and equipment is available now to burn your own (along with the support from this and other boards),,, you are MUCH better off investing that money to burn your own chips. I know it can seem a little intimidating at first but once you take the plunge, it’s not that bad at all – just a little time consuming.
Thanks! I'm just very curious at what the tuning changes actually are. Like I said, I put a Hypertech Stage 2 chip in simply for earlier fan temp and if there were any ignition/fuel improvements, I considered that a bonus. But with the Stage 2 chip, my base timing is at, IIRC, 11 degrees. I had it as advanced at about 14 degrees, but as I mentioned earlier, got wheel hop and backed it off and the wheel hop went away. I did most of the free/cheap mods back in the day on my '89, and except for one G92 L98 and one '92 1LE B4C, I can't remember a stockish 3rd gen which felt faster to me - and I've driven many dozens.
Thanks! I'm just very curious at what the tuning changes actually are. Like I said, I put a Hypertech Stage 2 chip in simply for earlier fan temp and if there were any ignition/fuel improvements, I considered that a bonus. But with the Stage 2 chip, my base timing is at, IIRC, 11 degrees. I had it as advanced at about 14 degrees, but as I mentioned earlier, got wheel hop and backed it off and the wheel hop went away. I did most of the free/cheap mods back in the day on my '89, and except for one G92 L98 and one '92 1LE B4C, I can't remember a stockish 3rd gen which felt faster to me - and I've driven many dozens.
You’re right! What you may not know is that TPI base is a First Manifold Base. It flows over 300cfm stock compared to the factory TPI base in which it flows 210cfm. He modified the SLP runners to fit the First Base. It has a Mike Jones Custom Grind Cam(232/232-585-585 lift), AFR195 Competition Eliminators, Dyno Don Headers, 3 1/2in cat-back Magnaflow Muffler, dual cats, 4L60E Trans and 9bolt 3.70 gears.
The main problem with the TPI is the base. Even the after market base doesn’t flow much better even though it flows 240cfms. That’s why the HP stops around 45-4700rpms. A long time ago I had my Big Mouth Base Extrude Honed and flowed 260cfms which allowed maximum HP to move up to 5200. Then with a few more tricks to the base, got it to flow 290cfms. Here are the results.
Interesting Vincent, but I'm not sure I understand how your post relates to mine.
I'll add these tidbits, though. GM states that an L98 cammed, N10, LB9, doesn't even hit peak horsepower until 4600 RPM. That's 200 RPM higher than an L98 cammed single cat LB9 or any L98,( with single or dual cats), and a whopping 600 RPM higher than a peanut cammed, single cat LB9.
So a dual cat, L98 cammed, LB9 is a bit more "revvy" than any of the other TPI combos and I'd go so far to say, has a different personality.
Interesting Vincent, but I'm not sure I understand how your post relates to mine.
I'll add these tidbits, though. GM states that an L98 cammed, N10, LB9, doesn't even hit peak horsepower until 4600 RPM. That's 200 RPM higher than an L98 cammed single cat LB9 or any L98,( with single or dual cats), and a whopping 600 RPM higher than a peanut cammed, single cat LB9.
So a dual cat, L98 cammed, LB9 is a bit more "revvy" than any of the other TPI combos and I'd go so far to say, has a different personality.
I’m going to keep saying it, the power is in the manifold of the TPI. The next power upgrade is removing the factory merging pipe for a smooth flowing pipe.
I’m going to keep saying it, the power is in the manifold of the TPI. The next power upgrade is removing the factory merging pipe for a smooth flowing pipe.
You can point to restrictions everywhere in the system, I'm still not sure if we are talking about the same topic, though.
Bingo! He would completely be wasting his time, as well as devaluing his third gen. I just don't understand what some of our members are thinking when they mention mods like that, it does absolutely nothing. I have taken my GTA down the track with no hood at all, and the ET and trap speed remained the same, so guys looking to cut their hoods to draw in more air are just wasting their time. If people want results,I mean real results, then put your money where it counts. Stall speed converter if it's an automatic w/TPI and around 2400 stall (stock couples at 1500-RPM), gears, camshaft, and tune. You will feel one hell of a difference without the need of ruining your F-Body with little gimmicks that..... do..... not.... work. Here's a tip guys, the reason why "cold" is good is because of the bin, timing get's retarded when increased temps are detected when feedback is being looped, this is why Open Loop drives so much better than Closed Loop, it's in the tune. It's amusing when members can drive to the store on a hot day, shut the engine off for a minute or two to grab something, come back in, start it up and she pulls very good, gets to nearest stop light a few minutes later, someone pulls up wanting to play, light turns green, your F-Body feels like it is running slower, and they immediately tell themselves it's because it is hot. It's not that. It's the bin. The difference in Injector Duty Cycle between ambient temperature and an IAT reading of 125 degrees is not as much as you may think, and if IAT temps bother you, then simply invest in a bird caged IAT sensor from a V6 and relocate it before the throttle body. Or, just change it in the tune and keep your stock heat soaked CTS posing as an IAT, makes no damn difference.
- Rob.
Can you give me more info on this "bird caged" IAT? Do you have a pic of it? It is from a V6 third gen? any specific year? Is it Plug and Play? Can it be located in the air box below the filters?
I have a Hypertech 121342 chip, 180 t stat, TB bypass, Cut air box w/ K&n filters, stock exhaust minus cat with a Flowmaster muffler.. The car runs @ 180 on the button. The temp will increase to 210=220 with the A/C on running in traffic in the hot Florida summer. When this happens the **** dyno really feels the power loss.
Vinny, yes from a 3.1 V6. You'll need to extend the stock harness to reach it if you relocate it properly in the intake pre-throttle body, which I highly recommend doing...
Maybe, but we haven't even gotten into "Lucas oil additives", and their RWHP gains yet.
I'll tell you about a buddy that picked up 65RWHP with Lucas products some other time......
HAHAHAHA!
I use synthetics for durability in my stuff. From engine oil, trans fluid, differential oil, wheel bearing grease, etc. Cannot say that I gained any noticeable power but you can easily tell the before and after difference in parasitic loss from the increased MPG and just from the fact the vehicle rolls more easily at speed. Acceleration times at speed were noticeably reduced and the engine works much less at highway speed. I also had a dragging caliper once from the slide pins being rusty and seizing. The calipers were old and the pistons were sticky in them. I replaced the calipers with GM low-drag calipers and the master cylinder with a quick take up style from a later model in addition I used synthetic caliper grease on the slide pins, swapped in new rotors that were not warped and new pads. The new calipers/master cylinder allow the pads to withdraw from the rotors eliminating constant frictional drag.
Point I am making is maintenance issues on a vehicle this old can drastically effect how the vehicle runs and performs. How many 3 ton brick shaped vehicles do you know that still get 18-19 mpg running 70+ mph?
I use synthetics for durability in my stuff. From engine oil, trans fluid, differential oil, wheel bearing grease, etc. Cannot say that I gained any noticeable power but you can easily tell the before and after difference in parasitic loss from the increased MPG and just from the fact the vehicle rolls more easily at speed. Acceleration times at speed were noticeably reduced and the engine works much less at highway speed. I also had a dragging caliper once from the slide pins being rusty and seizing. The calipers were old and the pistons were sticky in them. I replaced the calipers with GM low-drag calipers and the master cylinder with a quick take up style from a later model in addition I used synthetic caliper grease on the slide pins, swapped in new rotors that were not warped and new pads. The new calipers/master cylinder allow the pads to withdraw from the rotors eliminating constant frictional drag.
Point I am making is maintenance issues on a vehicle this old can drastically effect how the vehicle runs and performs. How many 3 ton brick shaped vehicles do you know that still get 18-19 mpg running 70+ mph?
18-19? Not many. 46-60 is what my buddy gets in his stock L98 (not really modded much, TB bypass and air foil, so he is only going mid 11s at a fuzz under 151).
I think if you add Lucas products to your maintenance schedule, you can pick up 36-41MPG, and at least 65-100RWHP. Definitely worth a look!
street lethal... i got 100$ says your car put on the dyno doesnt make power you think it does and doesnt hold power to 6000.
Put up or stfu. You run your dumb mouth for years with no results. I try to be helpful and tolerant of your ignorance but its clear to me that you dont know what you are doing. Finish your car for once. Put up the results like i have. How many slips or vids do i gotta post to be considered proof??? How many dyno sheets do i need to show you? All the while you have jack shyt.
didnt know about timing being pulled at high coolant temps and iat’s??? Man thats tuning 101, how you not realize that. No wonder you aint gonna put a turbo on it, it will never run. Pop the bottom end in first hit. Hit me up if you wanf it tuned to work
as for ray’s build, it still runs and runs well. Idk what more proof you want
took the iroc out for a drive today and man its running good .. might take it to the local test and tune in a few weeks to see what it does in the quarter .. again , good job !!!
This may be quite trivial for you guys but when we were doing the major tune up after purchase it was recommended that I put 21lb Bosch injectors in..... so I did. Is this a bad thing with having everything stock except no egr, A.I.R system, cats, and a 3 Inch magnaflow from the Ypipe? All plugs, wires, cap n rotor are O.E.M, thanks!
1990 l98 g92 n10 car 13.6 with sh!ty edelbrock headers lol, K&N's hacksawed air filter base even more lol, 3 inch single in single out super deltaflow muffler good tune up and gas, no runners no base no porting no cam no converter, and no suspension with crappy goodyears, yeah it was a nice cool day and the track was plenty sticky, oh yeah and I can drive, my buddy's mustang had every bolt on and a 100 shot and they thought I was spraying..
Last edited by Rocnation81; Sep 15, 2018 at 03:44 PM.
13.6 at 101mph usually consistent, fastest ever was 13.57 with pulley change. I beat a slow ls1 by default before and can be ahead of most of them until a lil past the1/8
13.6 at 101mph usually consistent, fastest ever was 13.57 with pulley change. I beat a slow ls1 by default before and can be ahead of most of them until a lil past the1/8
91-92’s L98’s are quicker than the 87-90 it seems lol cam aint as big but i believe they have flat top pistons for more compression
You mean the 90-92 L98’s are quicker than the 87-89 L98. But I think some 89’s L98 G92 N10 had flat top pistons as well. The 90 IROC was the platform for the 91-92 Z28 as far as Horsepower, performances and interior changes. The same goes for the T/A.
Not sure when the changeover was. My 89 had dish. Always heard 91-92 had flat. The 90 was kind of a transition year i thought. Regardless the later cars seem to post better times than what i hear from earlier ones
I know the later 92 TPIs that have the newer oil pan (indentation for lt1 oil level sensor but not punched), black valve covers, textured runners and blank tb plate have powdered metal rods and the lighter LT1 pistons. Not sure if they are true flattops or not tho.
Not sure when the changeover was. My 89 had dish. Always heard 91-92 had flat. The 90 was kind of a transition year i thought. Regardless the later cars seem to post better times than what i hear from earlier ones
My '91 does in fact have flat tops.....made by Mahle no less!
Last edited by auto_god; Sep 17, 2018 at 06:21 AM.
