Don't forget when you're looking at the miniram to factor in the cost of a rebuild on the bottom end, if it needs it, and more for upgraded valvetrain as it will become a high rpm engine. Plus you will definitely need a tune with it, but most of the other intakes mentioned can be run on the stock chip from what I've learned.

There is a TON of information to be learned on this site. It just takes time and lots of reading. From everything I've read/learned here, I feel like I can do anything with my car.

P.S. I'm all for moding what you already got, instead of buying something stock but better, because you know that vehicle isn't gona stay that way for long either.

 

ive been trying to find a ballpark hp limit for the factory bottom end.. my motor is pretty fresh at 45k so i dont think ill need a rebuild... i would imagine she should take at least 400hp? whats the weak link in these? rods? pistons? crank?

also trying to find out a reasonable rpm limit for stock valve train and TQ limit for factory clutch

 

I bought the TPIS ceramic-coated headers for mine.

It has been 10 years now since they were installed, and they are JUST now ready to come off and send in for a re-coat @ JetHot.

Don't ever let anyone tell you different..."You get what you pay for". There IS a reason that some things are "cheap"...because they are.

The TPIS Headers fit like a glove, zero modifications needed. Once they get a re-coat they will be good for another 10+ years.

 

oh i don't disagree with that... but sometimes for me anyway its worth it to sacrifice a little of the niceness for cheapness as long as the functionality is still there....

 

The CAST crank is gonna be your limiting factor on the bottom end...unless it had a forged crank put in during the rebuild. It'll limit your RPM's and the amount of HP it can handle.

Stock valve train limit is gonna be around 5700-6000 RPM. Full roller rockers, new springs (mine have double springs) and titanium keepers will bump the RPM limit to 6500-7000 easy.

 

its never been rebuilt its got 45k original miles so its def on the original crank.


whats the HP limit on that thing? and if it were replaced what then is the factory pistons and connecting rods good for?

thanks a ton for the info man

 

BDP is located in Lakewood NJ (exit 88 on the GSP). The Hedman Elite's have been on my car for years (they were my first mod) with no problems. If I had to complain about something, it would be that some of the plugs are a bitch to get to. I don't remember them being really expensive either. Hope this helps.

 

thanks, lakewood is not very far from me so ill def remember them when tuning time comes

 

I have the stock rods in mine...just upgraded the fasteners to ARP. I'm pushing 430 FWHP, and have done so for 10+ years.

The stock pistons are hypereutectic, so they are really only good to about 350 HP (reliably). I upgraded mine to forged units. The stock cast crank will be about the same...I wouldn't turn more than 6000 RPM's on it...

Here's a good article on Crank Tech to read...

 

wow thats terrible! i would of expected it to be a little more stout then that

 

350hp is pretty stout in these cars, but of course with horsepower more is ALWAYS better!

 

A good rule of thumb is the engineers build a 50% margin into the design for reliability. A stock 1991 L98 was rated @ 245 HP, 50% of that would be 122.5, so a total of 367.5 HP is the "engineered" design max.

Remember, these were the days when a 405 HP engine was considered Supercar territory, ala the LT5. The bean counters saw no point in totally over engineering the components like they did in the C3's, which saw completely forged bottom ends installed until the mid-70's.

Will the cast crank and stock pistons hold 450 HP? Yes. The question is, HOW long? It could be 3 runs, 3 months or 3 years. You can't know for sure...it's a crap shoot. It's why you upgrade components in the first place.

I left my stock motor completely stock. I bought a second L98 complete, and used it as my core to build the current motor. When it was done, I swapped it out, and still have the numbers matching L98 unmolested...hell, the valve covers never came off the car in the first 9 years and 48k miles. It's wrapped in plastic in the shed...waiting to be reunited with the car whenever I get done playing around (NOT likely to happen anytime soon ).

It's all a gamble...upgrade bits & pieces and run the risk of totally destroying the block, crank and possibly heads, or do it right the first time. Upgrade it to handle 50% past YOUR maximum anticipated HP. That's what I did. The only hiccup to it was being an idiot and sticking the stock oil pan on it. The "new" motor lasted 4 months...tops. I spun 3 rod bearings and cracked the crank in 2 places because I didn't think I'd put those kind of loads on it.

Needless to say, it has a Canton Road-Race pan on it now...and has been bullet-proof for 10+ years. I get in it and race...still no wrenching required beyond the regular wear & tear maintenance items like wheel bearings, clutches & universals.

 

still thats very disheartening... even the 2 valve 4.6 mustangs can take 400 without much issue...

my truck came from the factory with 310chw and it now has 550whp and ts holding strong....

 

This is the sum of the story

 

Your truck is 22 years old?

 

no, but what should that have to do with anything really? as was said early the c3's had forged bottom end and their on average 10 years older or better...

can anyone speculate as to what a big mouth, spl runners, ported plenum, 52mm TB, headers and full exhaust, tune, and a small cam with stock heads would give me at the wheel?

 

Not very much improvement...honestly. The choke point will be the heads then. You HAVE to do it all to really gain any benefits.

You have to look at it from this perspective...with your scenario above you just took a 4" bar straw and made it 1/4" long to breath through. You opened everything else, but still made the heads the choke point for air coming into the cylinder. From throttle-body to cylinder, it is a complete system working together. You can't open up the front and not the heads and expect great gains...you'll spend a lot of money and be HUGELY disappointed when you run it going that route.

Your best bet (IMHO) is to get everything from the heads up over time...do it all together and get it tuned. You'll see 5 hp here, 7 hp there when you do it piecemeal. You'll see 150+ when you look at it as a complete package and do everything matched up.

Read the "Recipe for a 400HP L98" I posted on my web site. Page 2 gives you a detailed breakdown of the costs I had in building it...including parts. The TPI is a complicated system...designed to work in harmony. Unless you plan to put a blower on it your limitations will be the flow of the runners. Once you have that number, then everything else needs to be built to handle that flow. Heads need to flow that, base manifold AND the throttle-body...as a unit.

Until you do that, you'll be pissing in the wind.

 

gotcha, so i would never really see 300hp with the stock heads?

 

Maybe at the flywheel, but certainly not at the wheels.

 

ok... thanks


anyone have an approx cost to have the head ported?