iroc192

I've just aquired a 1985 Corvette with an 85 MAF TPI and I understand that it's a flat tappet cam. What cam can I run with freemods, no computer tune, and mods to exhaust?

I know nothing about flat tappet cams D:

Mr Froman

A flat tappet means that your hydraulic lifters are not rollers...basically:


http://www.myrideisme.com/Blog/wp-co.../figure1-1.gif


Roller on the left, flat tappet on the right.

It is recommended to add a zinc additive each oil change with the flat tappet cam. Going from flat to roller really shouldn't have any effect on your computer's operation/control over fuel system unless you put a performance cam in. And if you do put a cam in, you should definitely replace the hydraulic lifters anyway. Rollers are the way to go. I'd imagine they'd come together.

I can not answer your question on which cam to run with your given mods, but hopefully my brief description helped some.

iroc192

I believe 85-86 all TPI vettes were hydraulic flat tappet, so it is what it is... :/

Jim85IROC

iTrader: (2)

How far you can go without a tune is a subjective matter. Some can live with more "issues" than others. Generally a MAF car can tolerate a fair amount of variation, but you have an 85. The 85 used a one-year-specific computer that had about as much processing capability as a Timex. I have my doubts that the 85 ECM will do as well adjusting to a cam change as an 86+ ECM. One thing that will help is to select a cam with a fairly wide lobe separation angle (114 or wider). This will help keep the computer happy. When I swapped my 350 into my IROC, it ran awful with the stock computer. However, that computer was tuned for the stock 305, not a 350, so it did have "farther to go" than yours would, but swapping to an 86-89 ECM was a huge improvement. My cam is a 214/224 .442/.465 112lsa cam.

The best 1/4 mile time I could get out of the car with the stock ECM was a 16.1. With the new computer and a much better tune, along with a 700R4 to T5 swap, and just a couple minor mods (Accel base, SLP runners), I've gotten the car down to a 13.6. Most of the difference was in the computer & tune.

manifoldsrme

iTrader: (3)

I just swapped a 1988 L98 350 into my 85 IROC. I used ALL the stock computer system, stock exhaust and all factory emissions equipment. I used an aftermarket maf that uses a chip instead of the factory wire and had a chip custom burned that mimics the 85 Corvette factory setup with a few "add ons" for driveability and a little more power. I am VERY happy with the swap. Runs fantastic, plenty of power.

I took my 85 IROC to the strip when it was bone stock and ran a 15.18. Not sure why yours was in the 16's. Something must have been off........

Jim85IROC

iTrader: (2)

Yes, something was off. The tune. The stock tune was way, way way too far from what the new motor needed. From the sound of it, your 350 build is pretty mild, and you had a chip burned that should get it a lot closer to what it needs than mine had.

That said, I'm sure that your setup still isn't optimized and could be improved upon. The 85 Corvette ran a lower fuel pressure than all other TPI setups (35lbs vs. 43lbs), so having a stock 85 Corvette BIN isn't going to be ideal unless the injector constant has been modified to compensate for the difference in pressure. Either way, any time you deviate much from the stock setup, a custom tune is always best.

manifoldsrme

iTrader: (3)

I now see where your time was after the 350 swap. My 15.18 was with the bone stock 305. I should be way deep in the 14's now if not 13's. I think it is FULLY optimized for what it is. I had a custom tune made based on the 85 Vette chip, I did not use the stock Vette bin. I bought new injectors and the chip was customized to them. You may be right about 85 not being ideal, but my car runs VERY hard, does not stutter or hesitate or miss. From a dead stop I can just nail it and send the car sideways. I am very happy. I thought out my combination, made sure everything worked together, and the results are fantastic. It is a bone stock 1988 350 TPI engine but as I said, I run a Micro-Tech MAF and I think that is 90% of the gains in the way the car runs. Once I installed that, the idle smoothed out, the power went up and the gas mileage improved.

Jim85IROC

iTrader: (2)

All that MAF does is send "fudged" airflow data to the computer to fool it. A properly tuned car will maximize power, rendering a custom MAF obsolete.

Sparkytfl

I'm running the Lunati Voodoo 60101 in my 88 vette. (Using a flat tappet because I replaced the block with one I had just rebuilt for the firebird, this cam in particular because it was the biggest that worked with the vortec heads I was using at the time. But thats not important, what is is how it's working with my tpi)

Lunati claims "Best mild performance cam. Works excellent in TPI fuel injection applications." It really does work well. Tons of torque. Gas mileage is about 20/24. Sounds great. Though my car also has slightly higher compression because of the flat pistons from my rebuild. No problems with my computer, but it's an 88, and jim has a good point about your computer handling it differently than mine does.

Sparkytfl

Keep in mind that the tpi intake runs out of breath at a fairly low rpm (4500ish is what I usually hear) so you want a cam with a lower power band unless you get a new intake.

manifoldsrme

iTrader: (3)

Honestly, I do not care how it handles it. It runs amazing. Starts right up after a half crank, idles perfect. I have owned over 50 sbc's in every form and this one may just be the smoothest , best running one I have ever owned. So I really could care less that it is "inferior" in some way to a different years. My combination works VERY well. That's the botom line.

My god, you must just think carbs are the most HORRIBLE invention ever. Talk about old technology, no computer to control ANYTHING. Just a very slightly controled fuel leak really. How can they possibly work efficiently without at least a timex running them.............

Actually, I do HATE carbs. And even the 85's fuel delivery is LIGHT YEARS ahead of a carb. You can bad mouth the 85's computer all you want. It does not change the fact that my car runs EXTREMELY well and goes through emissions SQUEAKY clean.

What a POS................

manifoldsrme

iTrader: (3)

I can't let this go. I have to disagree. My 3 factory maf's were all junk. They all failed because of age I assume. These original GM parts are aging and failing. After buying my aftermarket maf the car was a COMPLETELY different animal. Seems the car was MUCH MUCH better "tuned" after ditching the GM piece. So I am assuming the stock GM tune was junk in accordance with your statement? Because I would agree. Seems the new maf made the gm one obsolete. And if GM doesn't have them properly tuned.......... they never will be I guess.

Jim85IROC

iTrader: (2)

Product failure and "adjustability" are two entirely different subjects. I'm only referring to the adjustability aspect, not the OEM reliability. Having an adjustable MAF is nothing more than a way to "fool" the factory tune into changing the air/fuel ratio for better performance. With a custom tune, your air/fuel ratio is optimally tuned anyway, thus making any adjustability from the MAF irrelevant. If the new MAF is more reliable, then great. That's certainly a benefit.

DAVEY420

My 85 Iroc has the old L82 cam from the vettes in its crate motor. its specs are 222/222, .450/.460 114LSA. We put it in the car ran fine didn't feel tip top but was ok. Then I got a mail order tune from LSracing chips cause no one has equip to dyno tune an 85. Now it feels a lot better but still is rich at idle. But I do get plenty of comments that the idle sounds good. Its a little choppy but no codes so im happy.

BlackenedBird

iTrader: (5)

What is required to do that? Plug-n-play? Just swap PROMs, not the complete ECM?

Jim85IROC

iTrader: (2)

The ECM is different... That's the whole point of the swap! The 85 ecm is a very basic ECM with a very slow communication speed. The newer ECM is much more powerful and has a much faster communication speed so it can read inputs and adjust it's output many more times per second. This makes it react to changes much more rapidly. Plus, a lot of guys are tuning these ECMs, so there is a lot more information and help out there when it's time to do a custom tune.

The swap is mostly plug & play. You need the computer and harness from the newer car. Although the MAF was unique to the 85 cars, it will work with the newer computer (but newer MAFs won't work with the 85 ECM). There are some minor differences between years, such as single/dual fans, different distributer, alternator & a/c compressor locarion, etc. Those issues will vary depending on what year ECM & harness you get. The 86 harness is the easiest to swap, but the 87 only requires a couple small changes. The 88-89 will require repositioning the alternator & a/c connections in addition to the other minor changes required for the 87 harness.
The only other "mod" involves enlarging the hole in the kick panel where the harness bulkhead passes through.

BlackenedBird

iTrader: (5)

Thanks. I'm fixing to put a 1985 F-body TPI into a 1968 so I have the option so easily change out the ECM and harness anyways. Just looking to see what would be required to do that. MAY go SD for appearances (no MAF) but I like the semi-self/more forgiving to mild changes tuning aspect of MAF.

tbroherd

I just got an 85 corvette 350 tpi. Can I use it in my 91 z28. Just use a 9th injector block off plate and a different distributor gear?