Well Guys I'll be done modding my GTP in the next month or so. But modding is in my veins now and I'll need to mod something. So I'm thinking of buying an modding L-98 or Lt1 with a t-56 to put in a 91 convertible firebird?

What do I need to build an engine besides the engine, stand, and the parts?

I want to have it be emissions legal and have A/C and minimal tuning problems. I know TPI's are notorious for sensor mishaps, I know my 85 was.
Would an Lt1 cam in an L98 cause computer problems? I will read up on my TPI books, but I need your guys imput/info. Any ideas are more than welcome.

Thanks, Kevin

 

....So I'm thinking of buying an modding L-98 or Lt1 with a t-56 to put in a 91 convertible firebird?

Sure. Why not? With time, patience and $$$, anything can be done.


What do I need to build an engine besides the engine, stand, and the parts?

Knowledge.


I want to have it be emissions legal and have A/C and minimal tuning problems.

Take your time, do it right the first time and you'll achieve this goal. Example: My car.


I know TPI's are notorious for sensor mishaps, I know my 85 was.

Have to disagree here. Use all new sensors, make sure that all new wiring is soldered and heat shrunk (no winding of the wires or electrical tape), and you should be good for years! Example: My car.


Would an Lt1 cam in an L98 cause computer problems?

No, it won't. But why settle for a factory cam with relatively lame specs? As far as performance is concerned, the LT1 cam doesn't have much duration and only moderate lift. And because it's a factory piece, its intensity is low. You can do much better with an aftermarket piece (off the shelf or custom made), still be able to drive it daily AND pass emissions. Example: My car.

 

I think it sounds great, except for the Convertible part. I know, Firebird 'verts aren't all that desireable right now, but with less than 600 made... There seems to be plenty of older 'birds and Camaros that would be far easier to get into initially and would hold the stress/torque better.

I've wanted a 91-92 Trans Am 'vert since I saw them new, and haven't given up hope on owning one. I just think that modding something other than a 'vert would be more prudent.

My $.02

 

go for it. i may have a tpimotor from a 91z28 pretty soon as im gettin the 91z28 tomorrow and then gettin a 95 lt1 that was wrecked in the rear next week and i may use the lt1 as the 91's new motor,and im taking its 6spd also...go for a convertible firebird in my opinion, you dont see alot of them.

 

why wouldnt a lt1 cam work? it works in 305's? which many on the boards have done..

why would you put a lt1 in a 350 i have no idea... in my opinion to small..
Shawn

 

LT4 Hot Cam. 'nuff said.

(And burn your own PROM for it.)

 

why wouldnt a lt1 cam work? it works in 305's? which many on the boards have done..

Of course it will work, but why bother changing a cam if its specs are only slightly better than the one you're replacing? Never replace a cam with another stock piece, although your perception is that it has "better" specs. Factory cams all have low ramp speeds. Also, the published specs do not tell the entire story. Other variables include:

Intensity (delta between advertised and 0.050" duration figures),
Valve timing, &
Symmetric vs. Asymmetric lobe design.

With an aftermarket cam (shelf or custom), these specs are obtainable. Unfortunately, GM does not publish many specs with their cams, nor do they include a cam card (with these specs) with their cams. This is why I will not use a GM cam, including the Hot Cam -- you don't know what you're buying -- unless you plan on running it on a cam doctor. If the Hot Cam (or any factory cam for that matter) is what you're looking for, my approach would be to have an aftermarket manufacturer grind one with the known GM specs. The advantage here is that you can choose (and know) all the other important specs as I listed above. Guys who choose a stock cam (albeit for another engine, i.e. LT1) don't know much about cam theory and design, and don't want to spend the time researching it.

That being said, the choice is completely yours. I chose to have a custom grind made by Cam Motion, the leader in custom cam design.

Willie

 

LT4 Hot Cam: 218/228 duration & .525" lift.

 

LT4 Hot Cam: 218/228 duration & .525" lift.

It just reinforces what I've said.
What is the LSA? (This is probably published, but not sure.)
Cam timing? Not published.
Advertised duration? Not published.
Intensity? Not published.

This information is vital when selecting the best cam. You get what you pay for.

Willie

 

It is all published for that cam. In the GM Performance Parts catalog. I'd post it here but ChrisFormula stole my copy. That info I got from the paceparts.com web site.

 

It is all published for that cam.

Not quite. Look at the attachment below. I took the liberty of going to the website you mentioned. It lists advertised duration at lashpoint, which cannot be used to compare it to other manufacturers. Most aftermarket manufacturers use either duration at 0.004" or 0.006". No one I know of (except GM) uses lash point. Without this info, one cannot calculate intensity. Speculation: GM does this so you cannot make a true comparison of their cams to other aftermarket manufacturers.

We also need to know centerline angles of both intake and exhaust OR valve timing events. All that's given is LSA which yields the delta between the intake and exhaust centerlines. It does not tell you what the angles are. Where do I find this info?

To determine if the lobe is symmetric or asymmetric, one needs to know the 0.050" lift centerline and its relationship to the lobe centerline. Where do I find this info?

I also checked in the 2003 GM Performance Parts catalog and it has even fewer specs than the website.

Willie

 

Bottom line: I don't expect everyone to learn about camshaft theory and design. Maybe I'm taking it a couple of steps further than most, but I am an engineer who tends to analyze this sort of thing as much as I can. So if you're content on saving a few bucks buying stuff with specs you don't know, that's your business. I, on the other hand, must know everything there is to know. I'm at the point with my car that every minute difference does matter >> It was easy to improve from 15.5 to 15.4. Conversely, it's very difficult to go from 12.4 to 12.3.... every little bit does matter for me. That's why I studied this subject, asked questions, then designed my own cam and had Cam Motion make it.

http://www.cammotion.com

My 305 will be back at the track with my "new" setup (including cam) this fall. Hoping to see 11's. And yes guys, it's still driven daily and emissions compliant AND has A/C!

Willie

 

Whoa!!! I didn't want to start a whole argument on better cams.

Let me clarify, how about what cam is the best, that doesn't need a custom tuned chip and all that stuff. Just a nice plug-n-play deal? I thought an Lt1/Lt4 cam seemed like a good substitute. That's all.

I think a converitible Black 91 Firebird with some Firehawk/Ronal wheels and an 83 Trans Am hood, and 85 Tail lights. would look pretty cool. Then have a nice powerful engine and of course I'd need to stiffen the chassis quite a bit.

Would one of those Checker Auto engine stands be fine to get?

 

It has the duration @ .050" right in what you quoted.

Of course, I dunno what I"m talking about really.... the cams I work with only have 4 lobes. (VW)

 

Hey Willie, I know I'm just jumping in on this argument.............but HONESTLY, all the specs you mentioned besides duration .050, valve lift, LSA and installed centerline are pretty much a moot point when you are picking a cam based off a somewhat normal engine setup. Why bash the LT4 hotcam?? Even though some people may not know exact specs on the unlisted parts, it is a proven performer shown to make over 400HP in both carbed and tuned port applications with vortec or similar heads on a 350. You really do not need to be a master of cam theory to build a quick car, in fact I believe that knowing only the basics will prevent you from believing "old timers" myths on the subject and spend time learning about other important aspects of the engine. I'm not an expert on cam theory, but I'm willing to bet my new motor will be easily in the 11's (as proven on my friends identicaly setup HEAVIER chevelle that went 11.40@119) and I used an off the shelf mechanical cam and a stock, but solid upgraded short block. Point is.............you don't need to be an expert to go fast, you just need to get the "right" idea going.