I'm screwing together a motor for someone who supplied me all the parts they want to use. Including a used, fully prepped set of 23* GM high port aluminum race heads (basically, NASCAR heads). It was obvious at first glace that it required offset rocker arms (intake pushrod is way over to the side). I've got limited expereince with offset rockers but I tried out a set of typical .15" offset rockers. Close but no guitar. Tip of the rocker is still about 1/2 way off the side of the valve tip. Looks like it needs a .20 or maybe .25 offset to center up the roller tip on the valve tip.

I took off the guideplates just to see if the pushrod could be moved closer to the intake port to work with a .15 offset rocker. Again, no way. It's already almost rubbing on the outside wall of the intake port.

What do I need to make this work? Are there rockers with more than a .15" offset? Is there some kind of funky shaft-mount rocker arm system that we're missing?

 

I think I found the answer. "These heads require the use of shaft-mounted rockers." So says lord GM. That woulda been nice to know before I started on this. Why do I always end up doing the research for other people? I need to start charging people for my RESEARCH time instead of labor. Turning wrenches is easy. Making sure everything's going to work together BEFORE wrench turning begins takes the real time.

 

hehe

you need .180 offset Lifters AND the shaft rockers

 

What particular head casting number or part number is that? I don't recall any 23* heads that required shaft-mounts. I thought the first, or most popular, were the 18* Bowtie heads (P/N 10134363 and 4364).

The reason I mentioned it is that those heads aren't exactly bolt-ons. Manifold flange angles head stud lengths, etc. will all add to your misery.

Good luck.

 

Well, they're actually 4.3L V6 race heads. 23* valve angle, tall port. I have the matching single-plane high rise intake, although the intake face angle appears to be the same as a stock head. These were apparently an earlier design race head, since superseded by the 18* heads. I think it was used on ARCA cars or something like that that used V6 motors.

I don't have the casting numbers but I'll be working on it later today. I'll post back.

 

Ok, V6/90. The casting number should be 14044883. They had 2.10/1.60 valves on a 1.91 centerline spacing. That makes them basically Phase 6 Bowtie. Do pushrod guide plates have "05" stamped on them?

Is it the 2-piece cross-ram manifold? Off hand I don't know of another manifold that fits the raised port V6 heads. Any numbers on it?

 

Head casting number is 14044883. The guide plates are Manley units that have been obviously had a "cut & weld" job done to them to make them fit (but they DO line up the pushrods correctly). They are a raised-style guide with the guide part set up elevated about 1/4" over the rocker stud mounting flange pads.

The intake is a Pontiac/Brodix 10093314. It's a high rise single plane 4150 carb flange style intake. I doubt it was designed to fit these heads since the original bolt holes were welded-in and I had planned on redrilling them myself manually once I got everything lined up correctly. The intake flanges and ports on the Pontiac intake are in the right spot and are the right height top-to-bottom but ever so slightly wider then the ports on the heads. I am aware that the crossram was the only intake DESIGNED to work with these heads from day one, but sourcing one is difficult and $$$$. As you can imagine, $$$$ is something we don't have after buying all this stuff.

 

I curious as to the final use for this engine. Street car? circle track car? drag car? or ? Why all the trouble to use the V6 in the first place?

What displacement? I think you can get to 305 with a 4.155 x 3.75 in a Bowtie block.

Odd-fire, right?

My favorite version was the NA 550 hp or so 305 that ran in the GMC Syclone Bonneville truck about '91 or so. Over 200 mph with that brick.

Good luck and keep us informed.

 

Application: Import killer. NOPI Comp 6 naturally aspirated drag race class. We wanna kill the dual overhead cam boys with old fashioned pushrod technology (plus more displacement than the typical 6 hole motors from the land of the rising sun.) Basically, rules limited stuff. No way I'd put money into a V6 otherwise. This is my brother's project car for the year.

It's going in the a$$ end of a Fiero that's getting stripped down to about 2100 lbs. race weight but still has to be "street legal" with inspection, wipers, lights, something resembling a stock interior, etc.

If they don't outlaw us (they probably will) we figure we got the field covered by at least a half second at this point. And that's just with the Vortec V6 heads and intake we're using currently just to get it up and running. These aluminum heads and intake are "phase II" if we can ever get all the details ironed out.

 

I'm sorry, did I jsut say "NOPI"???? Let's just say it's an import killer and leave it at that, OK. Just saying the word makes me feel like I've gotta take a shower or something. I'm not sure I can wrap my mind completely around the thought of racing in that organization. Heck, I can't wrap my mind around the 4 letter acronym right now, quite frankly. I just build engines. What people do with them is their own business.

Remember this is my BROTHER'S car, not mine. Direct nasty comments appropriately.

 

I think that car/engine is a great idea! The Fiero driveline strength would bother me. It's possible to adapt a 4T80E, the Cad Northstar FWD automatic transaxle. It's very strong, dry sumped and has internals approachind THM 400 for strength.

http://www.detnews.com/2003/autoscon...g02-297998.htm

http://www.design1systems.com/download/nrthstar.pdf

Adapting the engine to the trans isn't hard.

Old Timer's story: when GM was developing 4T80 prior to early 90's introduction, they needed to durability dyno test it at something like 150% of the design 300 hp of the Northstar at 6500 or so rpm. The had a race shop build a couple of 355 SBCs for them, but they could only get something like 10 hours of WOT 6500 rpm out of them before they went toes up.

They went to a Cup race shop (maybe Roush, but I'm not sure), and ponied up the big bucks for engines that would do over 100 hours at WOT 6500.

OEM engines are run for more like 800-1000 hours @ WOT hp peak rpm for durability. That's like 100,000 miles at full power. During the I6 4200 Vortec testing, I think they ran 5 or 6 to 300,000 miles (maybe 2500+ hours at 6000 WOT). They did shut them down occasionally to change oil.

 

My brother is the Fiero guy. He's dropped in V8s, 3800 blower motors out of late model Grand Prix, Grand National turbo motors and even a Quad 4. He's also considered putting in the Northstar V8 and the "Shortstar" V6 version, but hasn't ever done it yet.

Our Fiero has to run a 6 cyliner N/A engine to compete in the class. Otherwise we'd just shove a GN motor or a high winding 350 V8 in the tail and be done with it.

The tranny he is using is a race-prepped TH-125 3 speed automatic (like the FWD cars use). My brother found a bunch of ex-GM tranny engineers who are building these things for racing. High quality guts, converter stall built to your spec. We're stalling around 4000 with this combo. With sticky tires and all the weight naturally over the rear end, 11s should be very do-able.

 

Cool! THM 125 is a strong box. I had a few of them in FWD, RWD(Fiero) and AWD (STE) configurations.

Some of my best friends were/are HMD (now aka Powertrain) engineers. Sounds like your bro has it covered.

How many cubes in the 6? Who's doing the cam?

 

Stock cubes, plus a 30-over on the block. That's about 266ci. Crank is stock throw.

Cam is an off-the-shelf Lunati Oval Track flat tappet mechanical cam with too much duration. 255/259 @ .050 on a 106 LSA. It doesn't "wake up" until about 4000 RPMs and isn't going to breathe very well through a muffled exhaust (required under the rules) and stock Vortec heads. It's what we could lay our hands on in a short period of time so we're using it for now.

I could probably make just as much HP but with more torque if I could get a Comp Cams 282 solid flat tappet Xtreme Energy cam for a 4.3 V6. Which I can't. At least, not without waiting for a while, which we can't afford to do. Rollers are out of the question at this point, although I could certainly stretch the "bandwidth" of the torque curve quite a bit if we used one. Just a $$$$ consideration right now, plus nobody stocks the roller cams either.

We're putting a self-imnposed shift limit of 6500 on the motor since it's an all stock bottom end with the exception of pistons. Everything is properly prepped, machined and outfitted with ARP bolts, though. The stock offset journal crank is a known weak point, as are the stock rods with their larger big end diameter and less beefy rod bolt heads. We're nervous about taking it any higher, unless something really important is on the line.

Should make around 350 REAL horsepower @ 6000. Torque around 315 or so @ 5500.