I have an 85 IROC that I plan on building on it a little bit. I'd like to make it run maybe a low 13. I just figured I'd give you an idea of what I plan on doing to it and you could give me some ideas. I'm only 19 and I could really use help of some people with some experience, and don't say go with a 350 or anything like that. I'm on a low budget. lol.

It's a stock 305 TPI with a stock rear end and transmission. As of right now it has a K&N air filter and a 40 series Flowmaster muffler. I have a set of 292 angle plug heads for it, just waiting to be put on. I plan on buying a set of Hedman long tube headers, a Lunati Voodoo 60102 cam. Duration: 262/268, Lift: .468/.489. Just shoot me some ideas of some stuff I could do to this car to make it fast for a reasonably low budget. If anybody has any used parts or anything just post on here. If you have anything I could use.

 

A 100HP increase to the engine's output can be done without changing heads. You will have to have machine work done to allow increased lift and some bowl work and clean up of the ports to provide a little better flow. I'm not as familiar with the early GM "high performance" cylinder heads as some members here but I can tell you that most likely the 202 heads you have are low compression pieces from the 70s and like most old technology, including the flat tappet cam you're looking at, they sound alot better in conversation than they work.

The stock TPI is capable of supporting 310HP from the 305. To do this, you need to maximize flow and combustion efficiency in the engine. Higher flowing heads, increased lift, and optimized valve timing can achieve this. However, the TPI is not friendly to huge amounts of overlap. Overlap creates reversion and this reversion kills the velocity in the runners. It is this velocity that makes TPI work. Kill the velocity with a big flat tappet cam and you end up with a cool sounding engine with a very narrow power band between where velocity finally picks up against the reversion and where the runners reach their stall point.

The solution to this is a roller cam that provides optimal lift and duration while keeping overlap under control. Yes, roller cams are expensive especially with retrofit lifters to fit your early block. But the difference in performance is worth every penny. So, unless they have 58cc chambers, scrap the 202 heads, and have your factory heads machined to allow .520 lift. Port the crap out of your manifold base and your plenum. Buy an adjustable fuel pressure regulator. And buy a hydraulic roller cam retro kit with about 220-230 duration at .050 and .500-.510 gross lift(lift with 1.5 rockers), with 112 degrees lobe separation angle(LSA). Of course install roller rockers(you'll need either Crane Gold Race or Comps Magnum narrow body rockers to fit the centerbolt heads) and tell the cylinder head shop that you will be running a roller cam and to set seat pressure at 125-135lbs.

This combination should be capable of a solid 300hp and will be very streetable.

Just one opinion of course.

 

So which heads should I use? and will putting that cam or heads or anything on it mess with the tuned port? i dont really know how to explain what i mean. lol.

 

I'd always heard that if you're gonna do stuff like that to stay away from the tuned port. how come?

 

Because the people who say that don't really know that much about engines. As I said, a 100HP increase can be had fairly easily from a factory tuned port motor. There are few carbureted engines ever made that this could be said about. The DZ302 in the '68 Z28 is one of them. You just have to know how to make tuned port work. I just told you how. And if you do it the way I explained, it will sound good at idle, it will be very drivable and it will make good power over a broad power band.

My extreme TPI makes just over 450HP and I can cruise it around town just fine. It pulls the car very nicely from a stop with light throttle using a 2,300stall converter, 700R4 with auto manual high performance build, and 3.23 rear gears. And it hits 100 MPH in about 11 seconds from a dead stop. I work on hot rods all day and none of them holds a candle to my extreme TPI Beasty.

The best heads today are probably AFR. For your application you need to stay with 58cc combustion chambers or you will kill your compression ratio. Otherwise, and you said not to mention this but, you could build a 355 and then you can use 64cc chambers. AFR makes either size chamber with a 195cc intake port, 2.02 intake valves, and centerbolt valve cover mounting so you can use your stock valve covers. Even if you use aftermarket covers, centerbolt is much better for sealing.

The AFRs will work very well with the combination I gave you. They will also put you right at 320HP. If you want to add some top end power to this combination, toss in a Big Mouth base and some large tube runners from TPIS(port the base runners as big as you can go without breaking through, and go to a cam with 230 degrees duration at .050 and 520-540 lift. The AFRs will like a single pattern cam since their intake/ exhaust flow is much better balanced than the stock heads. This will put you closer to 370hp with peak power coming at about 5,900. With a 355 and a bigger cam, ported AFR heads, you will be closer to where I'm at but I won't give you all my secrets. If you go to this point, you will want to replace injectors with some 24lb/hr, maybe 30lb/hr for the 355. I run 24 lb/hr in my 355 with a huge fuel pump making 70 psi but I'm a little touched.

A carb combination is cheaper to build but no carb combination will make this kind of power and run this well.

 

'85 would be the older style perimeter bolt valve covers, so swapping to centerbolt valve cover heads means getting a new intake manifold base too.

 

I would take about everything that "ASE" doc said and ignore it. Why?......Because aside from 1/2 of that last post being a bunch of BULL, he hasn't helped your original question one bit! I believe you asked for something like "some ideas of some stuff I could do to this car to make it fast for a reasonably low budget". The bold items in ASE's post above total up to well over $3500.00 in parts and machine shop work (not including acquiring a 350 block), and SHOULD be a 400+hp engine, but won't be b/c of the TPI type intake. I don't think that a $3500+ new engine is what you were asking for.


Now for some budget oriented advice. You're on the right track; shorty headers and aftermarket "Y", flat tappet cam is the BEST BFTB you can find in car mods (sans nitrous), and if you have the ability you could port your own heads/intake. Then tune it w/fp and base timing to get it "good enough" and I think you'll see a marked improvement. I'd expect that to get you into the low 14's high 13's depending on driving. I don't think you'll see low 13's on a TPI 305 on the kind of budget that I interpret that you're working with.

What gear is in that stock rear?

 

And then some people are just ignorant. Reread my first post. The flat tappet "voodoo" cam will run like snot in your TPI engine. And if you doubt that TPI can make 450HP, come by my way some time and let me show you how a little 355TPI eats 430HP Chrysler Hemis for lunch. Or I guess Tom actually believes you can build a hot motor for cheap. LOL

 

To recap. My original advice was to have your factory heads machined, port your manifold base and plenum, and install a roller cam and retro kit. The only expensive part of that is the cam kit at about $750 the head work should run about $400. The rest is free but for your time. I only added the later mods because you asked for advice on what heads you should buy. As far as HP estimates are concerned, mine are proven from years of experience. Of course run your shorty headers. This combo will put into low 13s or high 12s. The 350 Formula would do corrected high 13s with timing changes and a little underhood cooling. But then I guess you have to do some reading to know that.

I forgot, the 85 does use perimeter bolt valve covers. Center bolt wasn't til 87. So stay with perimeter bolt heads, if you decide to go that far. The perimeter bolt valve covers can seal okay when you use cast covers and rubber embossed steel gaskets like Felpro offers.

 

Well dude, nice to see you can call names, when you're called out. Nice one.

Where did I say TPI can't make 450 hp? You'll have to quote where I said that.

Your "little" TPI beats Hemi's for lunch because every car the Hemi comes in is a 4000lb turd. And yes, you can build a hot motor for cheap. May not last long, but depending on your criteria, you can do it. A GOOD ASE tech would know that.

 

So you're recommending $1k in mods to a guy looking for free parts? That's cool. You can't beat the BFTB of a flat tappet cam, and you won't need to machine the heads with one either, due to less lift.

Which combo is going to put him in the "high 13's"? The $1000+ combo or the $3500+ dollar one? We still don't even know what gear he has. He isn't going 13's with a 2.73 gear, that is for sure. But then I guess you'd have to spend some time at the track to know that.

 

Tom, by the way sorry for the ignorant remark. I don't sometimes take criticism well and you kinda started it. The 85 TPI didn't come with 2.73s. Only 3.23s or 3.73s with the G92 option. Even the 3.23s with the 700R4's 3.06 1st gear is plenty of gear to get quickly into the engine's torque curve with even 2,300 stall. I know because I do it in my Beasty.

The $1,000 setup will get him into the high 13s fairly easily with some practice on launches. When this combo is done right, getting the tires to plant becomes a big issue. He will need to do a good job of porting on the base and the plenum and gasket port match the parts together.

The $3,500 route(heads, cam and high flow intake parts) will put him in the low 13s all day long. He may need to run drag radials with this setup to control tire spin. But since this motor will make most of its power between 3,000 and 6,000 rpm, it should still pull pretty handy mid 13s even on street tires.

The 355 that I eluded to would be a beast, even without my special little tricks this motor will make 410HP and could pull high 12s.

 

Copy that. Sorry if I offended you in my first post. Thanks.

My '85 TPI came with a 3.07...so that is odd. I guess?

I agree with you about the $1 combo (with porting) hitting high 13's on good driving, and the other combo too. In fact, I feel that your other combo with good suspension/converter, etc could do mid 12's. That is a long way off though, for the OP.

 

Okay, I call a truce. Sorry again for my remark. You need to be careful calling my statements "BULL". I will prove you wrong. BTW, those 4,000 turds are no slouches. I used to tune them for Chrysler and the 430HP SRT8 will scare the pee out of you. And nice one about a "good ASE tech". The people who work with me would laugh their butts off at that. I didn't mean to say that you can't build a cheap high performance motor, just that, unless you like doing engine swaps, it's kind of silly.

Unfortunately, most beginners don't follow my advice on the roller cam vs. flat tappet. They go the cheap route because it's just too tempting. Then They end up eating cam lobes or even if the flat tappet survives, they never know what they could have had if they just spent the extra money in the first place.

 

How you gonna tune all that once its put together? need to factor in tuning equipment which will run 200-250 bucks and then have to deal with the old school 85 ecm which apparently is a bit of a bear to play with. I havent used it but I'd upgrade to an 86-89 MAF system if you can find a used setup. Those are MUCH better from what I read on the 85

A properly spec'd thirdgen doesnt need alot of power to run low 13's if in good weather/DA. 240's whp and 300lbft torque across the rpm range will do it with good suspension, right converter and gear. 240hp isnt asking too much from a 305 but it still gonna need some air intake parts. Likely ported stock base and some kind of runner mods.

The L98 will do 250-260whp with just the bolt ons so a 305 is down 45 cubes which is gonna be close to 30 hp or so. Make that up with cam swap for sure. 305 wont have the 350 torque to move off the line, so you may need more gear/more stall. 2800 worked great on the L98's, maybe 3000-3200 for a 305 depending on the intake mods and where peak torque ends up

I've run them down in my bolt on LS1 which is only likely 330whp or around 400 crank. I'm lighter tho but still far from 450hp I've seen those hemi's trap 109-110 mph in stock form which is where I trapped, 110-111 with some weight out the car

 

Yeah, I forget that the 85 EFI system was a problem child. The MAF itself is a mess. He may able to pull off a notable improvement with cam, headers and some head and port work work and still get away with the stock ECM tune. I've gotten pretty good results with stock ECM tune on 87-89 cars with only timing adjustment and raised fuel pressure. It's mainly cruisability that suffers. But the kids I was building these for didn't seem to mind. I don't think using tuner pro on the 85 is even possible. Would have to swap in a newer ECM and harness.

 

Well man, just so we have our fact straight;
I can beat any stock or stockish SRT8 at a drag track with my box stock LT1. So "Scare the wee out of you" doesn't impress me. Track times do, and when you get 'em on a track, they suck 'cause they're overweight pigs.

You can build cheap motors that meet certain criteria. I've put many -a junkyard motor together that have met performance, economy, and longevity goals for DIRT. If you were a great mechanic, you'd know that, 'cause you'd have done it at least once. Considering some people are budget limited, doing a budget motor (thoughtfully) isn't "silly".

Roller vs. flat. Now we're talking stock or stockish 305's here, 'cause that's what this post is about. I put a $80 Summit cam & lifters in an '83 305 and dropped a second off my ET. Show me a better BFTB. A roller cam may have shown me 1.5 seconds (at best) and would have cost $500+. So although the roller cam is hands down the BEST, it is NOT the best, when considering money/hp. Or even more so (and the OP needs to comment on this) when considering that you could have a flat tappet cam...or NO cam. Not everyone can just run out and buy AFR's, Roller cams, SS Long tubes, etc. and certainly, this thread is an example of that. L
Lastly, as a "Good ASE Tech" you ought to know that a properly broken in flat tappet should last. And last and last. 150k easy. I know that you already know that though. :Thumbsup:

 

^This^ I totally agree with, but remember that the OP is looking for free parts; he's on a tight budget. The ASE mechanic wants him to spend a grand on head work and roller cams. Where is the money for gears/converter/suspension? I totally agree that a converter/gear/suspension bolt-ons 305 could go low 13's....I don't think the OP can put all that together. He was asking for low 13's for who knows what, but I took away, basically nothing. That isn't gonna happen, unless he does it all on a pick'n pull 400 and home-built parts.

 

Hey Tom, I don't want to continue arguing with you and you make some good points. However, and I want to make this a clear statement for those who don't know this. The EPA has mandated that zinc content in engine oils be basically eliminated because zinc damages catalytic converters. The oils sold today, right now, have almost no zinc in them. Zinc, and you most likely know this, is the key high pressure lubricant in engine oil. Without zinc, flat tappet lobes don't stand much of a chance. Especially when we start increasing spring pressure to prevent valve float at high revs. That is why flat tappet cams make no real sense. Save a few hundred up front to lose performance and then end up either replacing the cam after a few 1000 miles or spend more than you saved on the cam over 5 years of expensive oil changes. Of course as I said in the beginning. This is all one man's opinion. A very opinionated opinion, but still just an opinion.

EDIT: And yeah, I've thrown together a few grenades for local dirt track tangos. Knock, knock knock, Bang! LOL. I've also put together some beautiful V8s for NASCAR NW that lasted an entire season. The difference was doing it right the first time.

 

Your right that I am well aware if reduced zinc in todays oils.

However, we can still all rest, assured that a flat tappet cam will go longer than "a few 1000 miles". In fact they will last well over 100,000 miles.

Again, in the context of this thread, we aren't going to have to worry about big lifts, fast ramps, or crazy profiles. The OP will be ok with either style.

BTW, admitting that you built a grenade for a racing environment proves nothing other than that you posess the skills to build a grenade. That in no way "proves" that you can't build a great motor for the street, for cheap. Again; context of tbe thread...different criteria.

 

True, he is on a budget....but theres a point where you need to have a certain mod to hit your goals and those mods cost some money. Roller cam is nice but for this build probably unnecessary. Car is gonna need gear/trans/suspension work, sticky tire and preferably drag wheels to get some weight off the car, and then still need a cam and intake parts IMO. You'll have to cam it up abit since its on stock 305 heads, hopefully it wont pull rocker studs out. low 13's in a 305 is pretty impressive deal...especially a TPI 305 car. Thats something you dont see.