92 Formula

iTrader: (2)

Okay, this is long, but I wanted to put in all the information I thought you would need.

I am converting from 305 TBI to a '86 Corvette L98 in my '92 Formula. I figured that while making the conversion I should
probably put in a better cam.

I did a thorough research using "cam" as the search under the TPI and came up with 200+ messages. I then looked over the one's that would concern me, pre roller motor cams. There were a few, but naturally they were with the 305 TPI, as F-bodies were not available with 350 prior to '87. So, I did
not know how to compare the 305 suggestions with my situation.

Here is what my setup will be:

1992 Formula
3.42 posi
stock converter/700R4
1 3/4 SUM/SLP headers
3" Cat
Edelbrock cat back exhaust
stock '86 L98 heads
all stock TPI

The heads will be the stock '86 L98 heads, because, frankly I will have no more money. But, when I do have the money I'll probably get AFR's. The TPI will be a TPIS base plate, LTR's, and ported plenum (I'm converting from MAF '86 350 to SD, too). So, too, next winter will come a Vigilante converter. Presently my area of Virginia does not have emissions, but might one day...so a slight concern, but not major.

I want the car to be streetable, but strong.

I was looking at one cam, but I have no idea how it would relate to TPI:

GM part # 12353918

Duration. 050 214/224
Lift .442/.465
Lobe Centerline 112

What do you think? Any and all suggestions wanted and welcomed. Pros/cons. Everything.

I want to thank you sincerely for taking the time to read this, and if you can provide any help I thank you in advance for that, too.

FlashGTA

Do you want to build for now or build for later. In other words do you want a cam optimized for the proposed combo or the future one with AFR heads? Do you want to convert to a roller cam? What stall Vigilante are you planning on? It's just not a simple question.

92 Formula

iTrader: (2)

Hi FlashGTA,

Thanks for the quick response. I'm sorry I didn't make it very clear...I want the cam to match the setup that will be coming now (headers and all) but also one that will respond with the stock TPI, but keeping in mind I will also be adding better flowing TPI parts I propose before the winter is over. I only added about the heads and the converter so that people would know I'd like to do those mods now, but can't now (out of money).

Thanks.

dgoodhue

I was going to use a lingenfelter 74213 in my car before I ended up getting a great deal on a Retro lifters, LPE 74219 cam, pushrods & cam button.(This stuff cost ~$750 new)

http://secure.techservices.net/fwist...ID=101&CATID=3

In your case, I would go for a 74212, you might need to change the spring though. I know the Vette springs will be fine for .443 but I am not sure about .465

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Dave
86 Vette Conv.

92 Formula

iTrader: (2)

Thanks for the advice. Yeah, I definitely can't convert to roller now. I will be checking out the LPE cam, what are your thoughts of the above GMPP cam I listed, though? See, I don't really understand how the cams will work with TPI. I've always done cams with carbs, never with TPI.

FlashGTA

The cam you listed should work well with a TPI setup. The problem is you probably won't be real happy with it after your other mods including heads. It all depends on what you want. If you want tell me what kind of heads you plan on putting on it and I'll punch it into Dyno 2000 and see what you get.

FlashGTA

With your current set-up you should end up with about,
330 HP @ 5000 rpm. 390 Ft-Lb Torque at 3500
Also I didn't check but that cam sounds like the exact same grind as one that Summit sells dirt cheap.

92 Formula

iTrader: (2)

Hi FlashGTA,

That's more horsepower than I was expecting. Thanks for the info. I will have to check the Summit catalog for that cam, too. GMPARTSDIRECT has the above cam for $127.51, does that sound comparable with the Summit one to the best of your recollection?

The heads will remain the L98 Corvette heads from '86 (are they the same cc's as the '87 up?), but will look into the best AFR application when next fall comes around. I want to get the car strong now, even if the cam won't be used in the future it must give the best benefit for now.

Thanks, too, for giving me an idea of what cam will work with the TPI, for that is truely virgin territory for me. Any other thoughts and advice are welcome and needed.

dgoodhue

I just noticed the specs of the LPE cam is almost the same. I guess I would save the $35 and go for the GM cam.

I really don't know what works best with a TPI either, but I have seen guys at the track use the carb cam with little success, so like to use a proven combo.

As for the CC's, if you have the aluminum heads they are the same CC (and same part number) as the 87 58cc aluminum corvette heads, compression should be 9.5:1
If not they not aluminum, they are 68cc iron heads, the compression is 9.0:1.



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Dave
86 Vette Conv.

BlackZee

I just upgraded from a 305 TPI to a 358 TPI in my '86 Z28 (Auto) and had the same questions you have concerning flat tappet cams. After a lot of research, I ended up installing a Comp Cams Extreme Energy 262* cam. I also have World Products S/R Torquer heads, 1.6 rockers, and SLP headers and full exhaust. This cam's powerband is from 1300 to 5000 rpm, making for a good street engine. As of this writing, my car isn't idling good in park. I have to replace the IAC valve. If that doesn't take care of the idle, I will have a custom prom installed. The cam from Summit that has the spec's you are thinking about purchasing goes for $79.95. The XE 262 cam comes on smooth and strong compared to the original cam!

FlashGTA

I would recommend going with the Extreme Energy cam as well. The cam you are considering is an old grind and is old technology. The extreme energy cam is more bucks but it's a better cam. The guy I sold my old TA to put in a similar Extreme Energy cam and is very pleased with it. He is running a carb motor so he has a little more duration.

92 Formula

iTrader: (2)

O.k., I'm looking at the Xtreme cam...but how will it work with the setup, realizing I will still be using the stock '86 L98 heads, and stock converter.

Believe me guys, I'm listening to all of your suggestions and am taking this all very seriously.

cp87GTA

I'm running a Comp Cam xe268 in my GTA. Don't have very many miles on it yet. I've drove it down the road a few times. I'm also starting to burn my own prom. So far my hypertech stage3 chip performs the best. Hoping to get it on the street full time in the next month. It has a rough idle in open loop but closed loop is a OK with the stock 350 chip.


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87 GTA 355/700r4
ported&polished 083 heads
xe268h comp cam
1 5/8 blackjack alumicote
homebuilt y pipe,pasesetter 3in mandrel cat back.
ported/manifold,upper plentum, tpis maf.
airfoil, 24# svo injectors, home programed chip, underdrive pulleys, erson roller rockers, chromemolley pushrods,2100 stall, shiftkit, 373 10 bolt.

92 Formula

iTrader: (2)

My friend just put in a xe268 CompCam in his '79 Malibu, but it's a carb car. I never thought it would be a good choice for a TPI car, but as I said I don't really know what works well with TPI.

When you say it has a rough idle in open loop, is it like an almost stall idle? Do you think you will be able to smoothe it out with your custom chip? I intend to burn my own chips too, so this is interesting.

Does anyone think this cam is a bit much for my current heads/converter?

This is getting really good.

[This message has been edited by 92 Formula (edited August 30, 2001).]

cp87GTA

Depends on what chip you have in it. Like I said it runs good with a hypertech stage 3 chip.I've tried several differant burns, so far the stage 3 is the best. The car will just lite the tires and pull 5500 or more. I originaly was going to pull the tpi in favor of a street dominator and holly 780 but my buddy talked me out of it. I've also got a 77 T/A with a 400 Pontiac with the same specs on the engine, with 323 gears and the GTA is by far quicker.

cp87GTA

I'm also running a maf, that mite make a big differance.

JakeJr

test



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1986 Corvette Coupe, 415 CID, Edelbrock 6073s, ZZ9

JakeJr

I've got an 86 Vette with a TPI engine and did the mods you're considering a couple of years ago when I had a .030 over 350 in the car. I used a CompCams Xtreme Energy hydraulic flat tappet cam.

Are your heads cast iron or aluminum? Iron heads cause special concerns.

What do you need to know?

Jake



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1986 Corvette Coupe, 415 CID, Edelbrock 6073s, ZZ9

92 Formula

iTrader: (2)

JakeJr., glad you came in here. I read with great interest your posts a while back on the ZZ9 cam and the differences between the advertised and what it checked out to be. Call me a fan.

O.k., I don't know that much about modding a TPI. The engine is a 350 from an '86 coupe Vette. That should make it an iron head? Right? I haven't seen the engine yet (it's been shipped). Basically, from the above set up I laid out (first post) and remembering I will be keeping stock heads and converter till Fall of 2002, what do you suggest?

92 Formula

iTrader: (2)

Perhaps I should add that I'll be converting it from the MAF to SD, too. Don't know if it makes a difference in your suggestions, but I just wanted to add it.

super83Z

I am not sure but I thought all 350 vettes got aluminum heads.

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I WOULD RATHER PUSH A CAMARO THAN DRIVE AN IMPORT

1983Z28 350w/ edelbrock performer RPM power package , dynomax shorty headers, 700R-4 with shift kit, 750cfm carb, edelbrock 3" exhaust system, 16" IROC rims and ASCD SS hood.

future mods:
SLP headers, completely done over suspension, black paint with flames, NEW PLAN IN THE MAKING:
BUILD A WILD CHEVY 302 JUST LIKE THE ORIGINAL Z28 HAD

FlashGTA

Changing from MAF to SD is going to make a difference. A SD engine is much more sensitive to any changes and almost always requires a new PROM to run right after a major change like a cam swap. I would call Comp Cams prior to selecting the Extreme Energy cam and talk to them and get their input, it's free.

dgoodhue

No only half of them receive aluminum heads. If the engine is out of a convertible (production started mid year) is definately an aluminum headed motor.



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Dave
86 Vette Conv.

92 Formula

iTrader: (2)

I'm just curious dgoodhue, as I said above I haven't seen the engine yet, it's being sent directly to the shop. If I gave you the vin number would that help tell you if it is an iron head or aluminum? I have the title of the donor car.

FlashGTA yes, you are right...once I have a good idea of what everyone says here I shall then move forward to the tech people and listen to them. Hopefully my late next week the cam will be ordered.

Everyone of your opinions, advice and knowledge are greatly appreciated and are very helpfull.

JakeJr

If you have an iron head engine then you've got to have the shop mill the stud bosses and tap them for screw-in studs and guide plates. The pushrod slots must be elongated too, especially if you plan to run 1.6 rockers.

If you don't, you'll end up with a lot of bend pushrods like I did. A cam with more than about .490 lift (maybe less) moves the pushrods too close to the slots in the head; they bind and then bend.

I went through exactly that problem before I found out the cause. Needless to say there was a lot of extra work involved to have to pull the heads to have a shop do the necessary work. At the time I was running a CompCams Xtreme Energy 252 flat tappet hydraulic cam, which is really mild.

BTW, TPIS mentions this interference problem in their 'Hints' book. Too bad I didn't read about it before I had the problem.

Trouble is that checking the clearances during the engine build didn't give any sign that I'd have a problem.

Hope this helps.

Jake

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1986 Corvette Coupe, 415 CID, Edelbrock 6073s, ZZ9

[This message has been edited by JakeJr (edited September 04, 2001).]

92 Formula

iTrader: (2)

I know now that I have iron heads, at least I was told that perimeter bolt valve covers means iron heads.

Can somebody give me the horsepower/torque figures on the '86 L98, as well as the compression ratio? I assume 9.8?

JakeJr thanks for the info on the cam, that was a true horror story!

I bought a bunch of parts today for the swap, so I'm including my sig with them.

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1992 Pontiac Firebird Formula (original 305 TBI) The project has begun:
just purchased 1986 Corvette 350 TPI, Summit SLP 1 3/4" Headers, Dual Catco Cats, Flowmaster American Thunder 3" Exhaust, Dual fan setup, OEM Posi, GM 3.42 gears and JEGS Ultimate Support Cover for 7.5 rear.

1997 Chevrolet Camaro SS # 379 (1 of 371 Black, T-Top, 6-speed)
1973 Chevrolet Camaro RS/Z28
1969 Chevrolet Camaro SS 350

RIP Dale Earnhardt.

Mista

Simple to tell if the heads are iron or metal...take a magnet out to the car and check!

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86 T/A 5.0 A4 & 2.77 gear
15.62 @ 86 mph
93 Civic 1.6L
13.5 @ 100 mph

dgoodhue

The iron heads are rated at 9.0:1 from the factory.


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Dave
86 Vette Conv.

JakeJr

Should have mentioned it earlier, but FLASH is dead right. SD are really not forgiving to changes in the engine.

A MAF system has a lot more adaptability and you can make lots of 'not too radical' changes that the MAF can adapt to. Not so with Speed Density; at least that's what all the Big Boys tell me.

Seems like modding engine components on a SD system requires a re-programing of the computer since the engine runs off fuel and spark tables differently than a MAF system.

There are guys who are SD gurus and can make them work wonders, but for someone without their expertise, MAF is by far the best way to go.

Just my thoughts on an often discussed topic.

Jake

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1986 Corvette Coupe, 415 CID, Edelbrock 6073s, ZZ9

[This message has been edited by JakeJr (edited September 13, 2001).]

JakeJr

Somewhere around mid year of 86 GM switched from cast iron to aluminum on the Vette. That's why there's confusion as to which set he's got.

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1986 Corvette Coupe, 415 CID, Edelbrock 6073s, ZZ9

[This message has been edited by JakeJr (edited September 09, 2001).]