Hello, I've decided to finally upgrade my vette. Im only expecting a new power output at the crank of around 280-300hp which is plenty for the street cruising I do. The engine is bone stock with iron heads and I'm on a tight budget, so the only things I'm planning on doing is the cam, roller rockets, full exhaust, and possibly a new intake set up. I'm thinking of going for a zz4 cam, comp cam 1.6 roller rockers with lt4 valve springs to suit. Will this set up be reliable with no additional mods? If this is a poor set up, can anyone recommend a better set up that will give me more bang for my buck?
Thanks in advance

 

Tuning will be a.problem with low budget. Better exhaust. Long tubes, lt1 dual exhaust 1.6 rockers should not require tuning. A cam change will.

 

I suggest an AFPR so you can tune A/F for best power at WOT. Also, cut the air filter lid and use a K&N filter. Install a 160deg. T-stat for a little "free" chp.

Since your base is ~230chp I estimate that you can get to over 280chp with the stock cam.

 

What is a tight budget? How much are you actually having to set as a limit? I'd do intake, headers and a dyno tune but again, it depends on how much you have to spend. Based on the odds of us having the exact same expenses and income and possessions, I'd say your definition of a "tight budget" is going to be different be it more or less in which direction. Personally, I'd say that if you are even on a tight budget as in under $3000, leave it alone and save your money. Free mods are pretty much "SOTP deep" and are limited by your imagination. Good headers you can build on later and intakes and a dyno tune to maximize it will definitely be over $3000 unless you can score used stuff. Dyno tune is about $600 and up, headers $1000 and up and intake probably north of $1000 and that is if you do all the work and have a few misc things you need to do.

 

I haven't planned out the budget completely yet but I'm expecting to pay $3000 total before a tune. Ive found some LT1 headers for $500, intake I'm expecting $1000 unless I stick with the stock intake and do the grate cut out mod with a k&n filter. Cam will cost less than $500, and roller rockers with springs roughly $350. That leaves me room for a few extras if needed. My $3000 budget isnt set in stone, it's some what flexible since I'm desperate for some decent power in my slow as a boat c4, lol.
Thanks for the reply
P.s i will be doing all labor myself, I'm a typical backyard mechanic but havent had a tonne of experience on cars, ive only rebuilt a few of my motorbikes engines and done simple things to my other cars.

 

Wow, you really think that much of a power gain from those few mods? I'll add those onto the "to do" list, but I am prepared to put a cam in for even more power, plus I'd rather a bit more of a grumpy idle so it really purs when I pull up at a set of lights.
Thanks for the reply

 

I'm prepared for a tune up and will adjust the budget to fit in a tune. My low budget is roughly $3000 but is reasonably flexible. Labor isn't a factor either since I'm a backyard mechanic and will do everything myself. Do you know if I would need to change the pushrods for the roller rockets? Or only the springs?
Thanks for the reply

 

My opinion is your plan is good. The only cange I would recommend is adding a set of used 1988 and up 113 alum heads. These will raise your compression, flow better, add power, reduce knock sensitivity, and cost almost nothing. One question, what year is your engine? If it is pre 1987 the zz4 roller cam will not work without adding retro fit lifters and those can get pricey.

 

Thanks mate, I'll keep an eye out for a set, although hard to come by here in Australia. I may have to ship a set of heads over from the states, in which case it will get pricey. Damn, that isn't good news, mine is an 86. Is there an alternative cam that will work?

 

On an 85-86E, a worry is the heads. You really need better heads than the '624s, preferably you can find the 88-91 '113 heads, then work those over.

The cam is going to warrant a custom tune, so plan $500 for the tune by itself. ZZ4 is fairly small so you might be able to get away with just some AFPR changes to help it, but if you're going to go that route, then I'd go slightly bigger than ZZ4, I'd go with something in the range of 210/215 or 210/220 intake/exhaust at 050". You can use roller cam but you must convert over for a roller, yours came with hyd flat tappet.

I do believe you can get to your CHP goals with just headers/1.6rr/ported plenum/TPiS base/AS&M or other larger Runners however.

 

Sounds like I might be opening up a can of worms here if I replace the cam. Maybe I'll plan around the mods you mentioned. As long as I get to 280-300CHP I'll be happy. Would building around a hyd flat tappet cam be more beneficial? Apologies if that's a stupid question. Once we get into the more technical stuff, I have no idea.

 

You just have more options from converting to roller cam than sticking with tappet, and most of us here have rollers so we'll be recommending cams that we use ourselves.

Just keep in mind that if you want to go higher, you will have to get rid of the 86E iron heads.

 

IIRC, people have used the LT1 manifold. Not sure if the LT1 Long Tube headers will work. TPIS makes a set for about $1000 and some change with the Y-pipe. I'd go with a Miniram or Superram if you can find one for an intake. After that, as far as the cam goes, get the tuner to recommend what he wants since he is doing the dynotune. For some reason, my tuner recommended 1.6 and 1.5 instead of 1.6 all round so ask him that. I'd also dump your old injectors while there since they are probably Multecs or in need of cleaning. FIC has a reman set that will work for under $200. Change fuel pressure regulator diaphragm and new gaskets and injectors should be about $250 total

Also, do you have a facility to do the tuning before we go there?

 

The thriftest way to make it quick is to change rear gear. L98 isn't a high revver but it has a far amount of torque. Base automatic gear was a 2.73 and performance option and manuals used 3.07. Manuals and automatic use different rear carriers M d44 A4 d36. Replacing the 2.73 with a 3.07 will make a noticeable difference.

 

3.45 can be fun, too. Yes you can get your goal with a simple flat tappet cam...google Wongs Performance hes a member here. Had good luck with mail order tunes from him, even passed Ca smog
10:1 $850 cheapie shortblock
Edelbrock heads with some bowl & shortturn work
Ported TPI, shorty headers..it was in an IROC with that lousy 2.59 ? gear, it pulled no different than a 383 in 2nd, fried them all through first. Passing gear got tire smoke
All with a little flat tappet "256" type cam.

 

The suggestion of using an aftermarket intake is a good one to follow. The original EFI system for the L98 was designed for a 305 engine not the 350. The long runners are designed for low and mid range torque, this a huge problem for making High RPM power. Unless you get a lot more air into the engine the headers are not going to give you the results you might be expecting.

Changing the rear ratio might be the cheapest bang for the buck, you will have a car that accelerates strongly but it will all be gone by 4500 rpm. This will also have a serious effect on your fuel mileage.

What are you all paying for fuel in Australia? How much octane is available? By the time you consider using the 1988 up aluminum heads it might be better to just buy a new set of aftermarket heads that flow even better. I rebuilt two iron cylinder heads that I got a "good deal" on and ended up spending over $1000 just to make them perfect again.

A friend who has two used LS3's offered me one for the 1988 C4, I hesitated at the swap even though the power would have been nice. On my C4 I can get 30 mpg driving at 60 mph with A/C running, it is a nice comfortable fun to drive car.

There is an automatic transmission in our 1988 Coupe and it does take off nicely and accelerates hard up to roughly 4,000 rpm and then starts petering out. The C4 still has enough power to get one into trouble with the law in a big hurry.

My other Corvette is a 1968 L-71 C3 convertible with the 427 and 4 speed. Now that car will cleanly run up to 6500 rpm without missing a beat, the only place I can do it legally is on a race track. For a while I used a local airport's runway as it was 2600 feet long and had room to slow down from 135 mph runs. I love the big block in the C3, it "fits" the car well. The sound of the high compression 427 at 5000 rpm is a beautiful kind of noise.

Best regards!

 

Two comments ...

1. I'm not a big fan of the ZZ4 valve springs. Two people I know have had a ZZ4 valve spring fail. Now - to be fair - both of those were on cars that were subjected to track use - and both had the 1.6:1 rocker arms, but both spring failures caused significant engine damage - so If I were you - I'd go with a somewhat better valve spring from a company that is more concerned with material quality than with cost.

2. The HP numbers you describe will be pretty darn tough to attain with stock heads - even if you do make significant improvements in the intake (which is not the easiest thing to do on an L98). I have absolutely NO Idea what the emissions rules are in your neck of the woods - but I would suggest doing a good set of long tube headers first. Most people will agree that headers are probably worth 15 - 20 HP on an L98 motor. While a cam swap WILL move the torque band - you may be shooting yourself in the foot - the fact is that if you move the torque band up the RPM range - you need a intake system and heads that will flow the additional air required. Simply put - you don't have that. So - consider doing the long tubes first - and see how you like them. If you still want more - think about moving to a better flowing set of heads and a better intake and a mild cam together. Needless to say - significant tuning WILL be required.

 

Those are some good suggestions, thanks for the advice. Emissions rules aren't a problem in Australia, they don't check cars for that yet. Ill keep an eye out for a good set of heads in these upcoming weeks and start from there

 

I would like to try and keep some top end power and not change the rear ratio to go for all torque, simply because I'm on the highway a lot, and fuel costs enough to send you broke in Australia.
​​​​​​We have 91 octane as our lowest, then go up to 95, then our highest fuel is 98 octane, although ive been told our fuel is different to yours and our 98 octane is equivalent to your 89 octane. I'm not sure how that can be though or if its true.

Ive converted our prices from $ per liter to $ per gallon for you, lol. For 98 we pay $6.2 per gallon. and for 91 we pay $5.2 per gallon. I'm not sure if that's considered expensive to you guys compared to your prices but it is what it is.

I was trying to avoid going all out with mods because I know once I start replacing the heads then it will just snow ball and I'll soon have $5000 or more put into the engine. Plus it is ridiculously expensive in Oz to have any sort of engine machine work done, so while you guys might pay $250 to get a set of heads Ported (I dont know if that's how much you pay) we would be paying $1000

 

Not related to you build did Holden use tpi or mpfi there? I read years ago OZ had better metallurgy in their engine parts then here in the U.S.