Hi All,

I'm hoping to get some advice on which direction I should go with my build. I should hopefully be starting to mock things up here in the near future, and I'd like to decide on and order my exhaust components for that purpose.

First, I suppose I should itemize my build a bit.

The shell is from a 1990 Forumula, since my 84 Trans Am had turned into a Flinstone-mobile. Everything else (except for the Engine\Transmission) is from the 84 Trans Am or aftermarket.

Engine:
CID: 350 (Honed rather than bored)
Compression: Approximately 9.5:1
Crank: Stock, polished
Rods: Stock, new bolts
Pistons: Stock 12-13cc dish, re-ringed (I might toss in some Sealed Power flat tops instead if I can figure out which part number is actually the 1.560 compression height)
Roller Cam:
280/280 Advertised
224/224 @ .050
.560/.560 Lift with 1.6 rockers
108 LSA
104 ISA
IVO is 36.0° BTDC
IVC is 64.0° ABDC
EVO is 72.0° BBDC
EVC is 28.0° ATDC
Overlap is 64°
Heads: ProTopline 906 Vortec Replacements w/minor cleanup, new valves, guideplates, 1.6 roller rockers, springs, etc
Intake: Vortec Crosswind
Carb: Edelbrock 1407 750CFM
Mounts: Energy Suspension Poly

Transmission:
Stock 700R4 from a 1990 Caprice, ES Poly Mount, Stock Torque Arm, Circle D 2600 Lockup Converter
Will likely add a Trans-Go Shift Kit

Rear Axle:
84 10-bolt, DM Disk Brakes, Torsen LSD from a 4th gen, 3.73 gears, 28-spline axles

Front Chassis:
Stock K-Member, Stock A-Arms with Poly Bushings, new Moog 5662 springs, new KYB GR-2 shocks, Founders Camber/Caster plates, all new Moog steering components

Frame:
Spohn Wonder Bar, Spohn Subframe Connectors

Rear Chassis:
Founders Poly\Rod Single Adjustable LCAs, Founders Poly\Rod Single Adjustable Panhard Bar, stock upper Panhard brace, Moog CC635 Springs, KYB Gas-A-Just Shocks


Sorry for the wall of text, but it helps if we know what we have to route around.

As you can see, it's not an all-out effort build with some of the the lesser expense components, but it should be a fun street car with a couple trips to the track for kicks. I suspect I'll be around the 400-450FWHP mark at around 5800-6000 RPM with proper tuning, judging from other similar builds.

Essentially, what I'm looking for is a set of long tubes and an idea of what I'm going to need to support the motor. I have a welder, so needing to piece some of it together is no problem. Obviously I don't mind trading some elbow grease for cash, but laying on my back on the cold concrete with not much clearance doesn't excite me much, so the easier the better (as far as exhaust routing goes).

Obviously, a 3" catback would be easiest, but I'm not sure if it'd be the most efficient. Do you feel that a 3" exhaust would be enough for my build? If it does hurt, it probably wouldn't hurt *too* much... But I don't want to leave power on the table if I can avoid it, which is why I'm here.

I've seen a couple of dual exhaust setups that looked like the clearance was really good. Lack of clearance wouldn't bother me since I'm in Minnesota, and there's not a whole lot of speed bumps around where I live, but my driveway is steep as hell and I don't really want to grind every time I go up and down.

As far as sound goes, I don't want to be that obnoxious neighbor nor the guy that the cops pull over all the time. I don't see any reason to call extra attention to myself. Suffice it to say that I would like it to be quiet under most circumstances (ie, leisure driving around town under 2K RPM) but I don't mind it being louder if I open it up. So basically, as quiet as I can get it without restricting flow.

So, that's the jist of it. If anyone has any advice or recommendations, I'd love to hear it!

Thanks!
Mike

 

I'm not seeing anything in there that looks like a single 3" would be inadequate.

Just get the Hooker cat-back system, and once you get whatever headers, some 3" pipe and mandrel bends and some ball flanges and all such as that, to make the hookup to it.

And some LCARBs.

A better cam, better matched to the rest of the motor by being more suited to the int/exh imbalance of the Vortec head design by having a longer duration exh lobe (but not necessarily higher lift), wouldn't hurt either.

 

Hi Sofa,

Thanks for the advice. I just wanted to verify that a 3" would be sufficient.

Sort of off topic from the original question, but how much more duration do you think the cam should have on the exhaust? This is basically a copy of a build from David Vizard's newer edition of How to Build Max-Performance Chevy Small-Blocks on a Budget.

Thanks!
Mike

 

Something in the 8 - 10 degree kind of neighborhood for the duration split, seems to fit those heads well.

Remember, what makes them special, is all that BIG INTAKE FLOW, resulting from raising the intake runners and STRAIGHTENING OUT the path to the valve. Problem is, the exhaust ports aren't any different from any other SBC heads. Meaning, the heads become severely "unbalanced"; it doesn't do any good to improve how easy it is to get more intake charge INTO the cyl, if you can't also get the spent exhaust OUT first.

I haven't seen the book in question, therefore of course not the combo either. While I respect Vizard's opinions experience knowledge etc., simply copying something he wrote, isn't always going to be the best choice for any given setup. Especially not if it's an "almost" copy. Instead of copying something, use what he teaches to LEARN and UNDERSTAND and APPLY to what you're doing, so you can make your own judgments and decisions.

 

Thanks, Sofa.

Fair enough. I'm leaning on others' experience to try and avoid mismatch mistakes, since this is my first time building anything other than stock rebuilds\replacements. Unfortunately, reading often isn't a replacement for real world experience.

But back to the main topic. Would you recommend 1.625" primaries or 1.75" primaries for this application? They will most likely be longtubes, and I'll fab up my own Y-Pipe.

Thanks!
Mike

 

If it were mine, I'd go with the 1.75".

Again, tip the balance between intake and exhaust a bit toward the exhaust, since the intake has already been gifted somewhat in the form of the improved ports.

 

That's what I had thought as well.

Thanks again!
Mike

 

If it were my build I would seriously consider a 383 kit. I personally think you cam looks good but I'm not an expert on vortec heads. My cam is a 236/242 on 112 with .600 lift and it's a little trick to tune in the 1800 range.

As far as exhaust long tubes are good but I don't think they're necessary and will make your install a little more difficult. With my 350 build I really liked my Edelbroc TES short tubes and y pipe. It was good quality and didn't leak. Plug access ok- ground clearance good.

My current build is a 414CI Dart/AFR street build. I used Hookers basic short tube 1 5/8 headers and fabbed my own 2 1/2 head pipes past the tranny and 3 1/2 single over the axel and out the drivers side. I think you'll be fine with a 3" system of any decent design. I'm a fan of straight through mufflers since I have a single rear pipe. I used a pair of 2 1/2 Ultraflow's in the head pipes near the trans and a 3 1/2 Ultraflow in the stock location with a resonator near the outlet. Sound and performance is great, not too loud at all. With your 3.73 gears and OD you probably won't drone too much. Seems ~1600 ish with a little load is where the drone is most prevalent.

 

Hi Antman,

I've mulled the 383 idea over and over in my head, and I keep getting stuck on it. It's essentially $1000 for the crank, rods, and pistons on the lower end. With the increased torque, comes increased concern about the longevity of the 700R4 and 10-bolt. By the time you're done, you're 3K into it with an extra 40lbs or so, unless I were to upgrade the heads, too, so there's another 1K.

Or maybe I'm over analyzing.

In any event, I might pick up some OBX longtubes. It seems that the 4th gen and LSX swap guys are pretty happy with theirs. If I were to go with shorties I'd probably do Don's, but I'm having a hard time justifying the price to myself.

Thanks,
Mike

 

Yes, there are added expenses. But by the time you clean and polish the crank, add rod bolts, clean and resize them and then if you add pistons as indicated you'll be all most there. If the block is a 2-piece rear kits are pretty cheap if you aren't getting the top end stuff. It'll be worth a lot more than long tube headers. Trans and rear will be fine at the power level you are planning.

Regardless I understand your plan. Basically a refreshed stock bottom end. Nothing wrong with that.

 

With a 1-piece rear main seal on this beast, I've found the cost to be a little higher unless you go with bargain-bin, questionable parts.

I agree with you, though. I'm just on the fence with it all. I just have a feeling that by the time I'm done, there will be a lot of extra costs with little to show for it, but who knows.

On the other hand, I do have a spare 1-piece RMS flat tappet block that I could build up in case this motor doesn't do everything I want it to.

Mike

 

Hey Mike, I am in no way trying to talk you into something out of your original plan. There are always extra costs and with a stroker kit there are additional components like balancer, flexplate, block clearancing etc. IT really depends on what you are trying to achieve. I always go a little overboard and honestly built a motor way more powerful than I use on a daily basis and drivability suffers a little. Your plan appears to be a good one. I wouldn't worry too much about the long vs short tube headers. Use a good quality, cost effective header. I think I paid less than $200 for the Hooker shorty headers I'm running. Sand blasted them and painted with VHT silver and they look new after a year of running. BTW the one piece, roller blocks are actually a very good block regardless of what type cam/lifter you run.

One thing I noticed, you mention the caprice trans, are you having the tail housing swapped out or running some other torque arm mount? I ask because I don't think the caprice trans will fit the stock mount. Having adjustable torque arm is nice if you happen to need to change the pinion angle but otherwise the stock arm and rear suspension is fine for the power you are looking for and all that stuff could wait til later. Spend the money to build your power train right the first time. I'm running stock lower control arms that I boxed in and added urethane bushings and a stock panhard bar. I made an adjustable torque arm but the stock one would have probably been just fine. When you are making good power having adjustable lower control arm brackets becomes a good option. Again, I made my own but they're only a bill or so.

 

Hey man,

No problem! I didn't think you were trying to talk me into anything.

I have the 700R4 from my 84 TA that I was planning on using for parts, since I'll need to swap it over to a gear driven speedo anyways... Which reminds me... I broke off the speed sensor when I pulled the motor and transmission out since I was in a hurry and forgot to disconnect it. I'll have to find a replacement somehow.