It's not loss of torque, it's loss of torque - or more accurately having a balance of making the best torque - at low rpm while still having some mid range performance improvements. From everything I've read and experienced over quite a few years of building various brands of street performance engines from mild to wild, the 170 size runners in general are more likely to help build better torque in lower rpm ranges because of better flow velocity than larger runners.
And having read many articles of builds with Vortec heads shows they do build good low rpm torque and still will support a pretty decent hp level which, of course, is also dependent on the cam and intake manifold and the other parts of any combo. Being I'm on a budget, I therefore have concluded that Vortec style heads are a very good combination of relatively low cost and performance in my desired rpm range. I'm sure there are other heads that can more or less match their lower rpm, such as the RHS Vortec style heads, but all those I've looked at are at least $300 more.
It is my understanding that those particular EQ "BA" Vortecs do accept valve covers and intakes as you mention. Valve covers aren't a huge item as they can be had used from a salvage yard or individual at reasonable cost.
As I'm going to upgrade the intake manifold, anyway, the cost difference between Vortec and non-Vortec intakes isn't excessive and, there again, with a little shopping a used intake can possibly be found. If not, there are aftermarket units available with dual bolt patterns if a Vortec style would happen to be required.
I am going to also upgrade to roller style rockers, and there are basic guided tip rollers available at reasonable cost compared to conventional style by the time you add in guideplates and hardened pushrods. Not so much for increased high rpm horsepower as a reduction in friction and heat and more accurate ratios.
"1.9 Performers" are Edelbrock Performer heads in the 1.9 intake valve size. I built a Ford 351 Lightning (Windsor) motor a few years ago using mostly used parts in good shape at good prices that I gathered over nearly 3 years of shopping. I found a set of them for that engine at $600 which was a competitive price to oem GT40P heads (comparable to oem Vortecs for Chevy) and were a comparative performance upgrade. The 30k mile thing was that I freshened the shortblock (which reportedly had low miles but one can never be sure of a used motor without checking it and I wanted to closely inspect it before I put it in the vehicle anyway so replaced rings and bearings and thoroughly cleaned the block as it had been sitting open with no intake or heads for awhile) before I built the motor, and have put about 30k miles on it since without problem. Anyway, if I could find a similar deal for a set of 1.9 intake (valve size) Performer heads I'd consider them in lieu of the EQ heads. That's the best possibility of finding good used heads at a reasonable cost as they've been around a long time and there are a lot of them in use which increases the chances of finding a good used set at a competitive price.
About the pistons, etc. I plan on a compression and leakdown check before I pull the stock heads, and if I don't discover any problems there or in the cyl walls after I remove the heads, I will leave the shortblock alone other than a new stock oil pump as they're relatively inexpensive. The cost of replacing the pistons and rings along with the machine work would still not allow me to use 87 octane without staying close to the stock low compression ratio, esp with a short duration cam which wouldn't allow some of the compression pressure to bleed off to help avoid detonation, so would not justify the cost from a gas mileage perspective. If I can use the existing pistons/rings and avoid the machine work cost, it will go a long way to offsetting the cost of 91 octane over 87 or 89 octane over the probable max of 50k miles I'll be driving the car after I retire before I get too old to drive safely. If I'd go to flat top pistons which would be better for quench and for 87 or 89 octane, I'd have to go to larger comb chamber heads which are also more expensive. And I do want a head upgrade as one of the major improvements. I can achieve a low 9 compression ratio with the stock pistons and the 64cc Vortec style heads with .039 head gaskets. That should run fine on 91 octane while allowing a compression boost over stock and more advanced timing which will help torque production, and maybe a little better mileage as a side benefit.
My overall build plan is this. As I plan on taking a number of extended road trips around the country, I'm planning the engine for good gas mileage. Low highway rpm is a recognized way of achieving this. But to improve 1st gear throttle response, a deeper overall first gear ratio would be of great help. Therefore the stock 3 speed TH 350 with it's high internal 1st gear ratio and no overdrive, along with the oem 2.87 gears, can be considerably improved upon both in 1st gear and on the highway. I'm therefore planning on a relatively low cost but internally improved 200-4R to get a lower internal 1st gear and an overdrive. The Level 1 at Bowtie Overdrives has a number of internal improvements that help avoid the common problems of those units and will support my intended engine horsepower while still being relatively inexpensive as far as performance transmissions go. Same for their Level 1 lockup converter in the lower 2k stall range which will also help response off-idle in 1st gear. With the gearing in the 200-4R, I'll switch to 3.31 differential gears which will further help 1st gear - I have to rebuild the diff anyway. (I do all my own work) That will get me about a 25% overall ratio reduction in first gear. With the .67 OD in the 200-4R I still reduce my highway rpm about 400 with the 3.31 gears. So significant improvements in 1st gear and in highway rpm. That combo will result in 1600 rpm at 58 mph for two lane roads, and 2200 at 78 for freeways. Low highway rpm is a major factor in new performance cars with very high horsepower getting surprisingly good highway mileage, the new Vette's being a great example. Of course all the sophisticated electronic engine management and efi make those engines perform well in a very wide rpm range and allow them to cruise at low rpm and still run smoothly and efficiently.
So that rpm range establishes the torque curve goal for my engine, which I am trying to build as part of the overall powertrain combination at the most cost effective price point. Also, I would prefer to avoid taking the max effective rpm over the low 5k range to minimize stress on the stock shortblock and hopefully make it last. And I won't be doing much hard driving anyway, so don't figure on needing a lot of horsepower at higher rpm.
That is what has lead me to try to optimize the torque curve in the low rpm ranges as a first priority, while still getting improved torque and throttle response from off-idle up into the mid rpm ranges, up to around or slightly over the 5k rpm point. And I feel the 170 intake port size will best meet those goals. The EQ Vortec heads should meet those parameters with a low comparative cost. I don't want an engine that will not have good throttle response and run smoothly at those rpm ranges becaue it's focusing on high horsepower and built for too high of an effective rpm range.
I definitely plan on efi having experienced the improvement in lower rpm throttle response, driveability, and fuel economy of efi. I've worked with efi to a fair degree having successfully modified the eec-iv system in my 89 Lincoln Mark VII LSC to work with the modified 351 Windsor I built and installed. And a number of years ago, I had bought a Holley 670 cfm 2bbl TB setup I used on a small block 3/4 ton conversion van. I was amazed at the improved throttle response and mileage over the 4bbl carb it replaced, and (a budget consideration) I still have that system so plan to use it. I have found thru researching it that Holley now has a closed loop kit for it with an 02 sensor which will automatically maintain a good air/fuel ratio for highway driving, and I have an Innovate wide band which will help in tuning idle and WOT. The Pro Jection has a small control box in the passenger compartment with knobs (dashpots) for adjusting air/fuel ratio on cold start, idle, WOT, and cruise. I found I had to tweak it occasionally to keep a good tune with weather changes so the wide band should be a great help to optimize the idle and WOT tune and to keep an eye on that and the closed loop cruise setting on a daily basis. In stock form it supports 275 hp, but I have found that larger 85 lb injectors (80 stock) are still available at reasonable cost and that I can use the built in pressure regulator to increase fuel pressure from the stock 15 to 18 psi. That should increase the horsepower it will support to around 325 and the 670cfm airfow is sufficient for that too, so that is one of the basic criteria I will use in selecting my engine build parameters and goal.
As far as exhaust goes, I'll likely leave the existing small tube factory headers as small primary tubes are better for low rpm torque. If I happen to find a better performing (probly used) set but still with small tubes that's an option, but don't feel with a low rpm torque curve that new ones would be as cost effective of an upgrade as the other items. I'll replace the single pipe portion of the exhaust with a larger diameter section of pipe, and use a single high flow true 3" in/out performance cat which can be had new for well under $100. A larger diameter single generally works better for low and mid range torque than duals, and those minor mods would be the least expensive way to improve exhaust flow in my desired rpm range.
Cam. I've worked a lot with cams in various performance builds at various rpm ranges and done a lot of research on the topic in general. I went into the Comp Cams website and used their online CamQuest program with the embedded dyno program as a good starting point. Before I finalize my cam choice, I will run it thru Desktop Dyno for the closest possible engine parameter input. However, using my basic engine combo info in that Comp program, including Vortec style heads (they have the 1.94 valve size as an option in the head category so am assuming that's for Vortec style heads), and the other major factors such as a basic level dual plane performance intake (a Performer style for rpms up to 5500), 9-1 compression, small tube headers, and efi, CamQuest came up with several suggested options for cams. Running those thru the dyno portion of the program narrowed it down to 3 choices that maximize torque between 1500 and 3000 and are efi and computer compatible (the "computer" being the Pro Jection closed loop control with 02 sensor). Going flat tappet to avoid the cost of a roller setup, I started out looking at the XE262 cam having read several builds highly recommending that for a moderate street engine even over the 268 which was regarded as generally producing less torque in the lower rpm ranges altho it is an excellent cam for a little bit higher rpm engine. Then studying the cam specs on those 3, I set up a spreadsheet listing the specs incl 050 duration, valve timing events, LSA, etc. I then looked at comparable cams from other mfgs such as Lunati and Crane and added them into the spreadsheet, altho of course only with hp & torque results from the Comp cams from their Camquest & dyno program.
The 3 Comp Cams best matched to my goals so far are:
XE 256 with 212-218 @ 050, 112 LSA, 108 Int CL, intake close at 36 ABC, tq peak at 3500, hp peak at 5000. Similar peak torque to the other 2, 15 hp more at peak than the other 2, 10 lbs less torque at 1500 compared to the other 2. Effective rpm range of 1200 to 5200.
252 XFI with 208-217 @ 050, 113 LSA, 109 Int CL, intake close at 33 ABC, tq peak at 3500, hp peak at 4500. Similar peak torque to the other 2, 15 hp less at peak than the 256 but same as the 249, 10 lbs more torque at 1500 compared to the XE 256 and similar to the 249. Effective rpm range of 1300 to 5300.
XE 249 with 206-212 @ 050, 112 LSA, 108 Int CL, intake close at 33.5 ABC, tq peak at 3500, hp peak at 4500. Similar peak torque, 15 hp less at peak than the 256 but same as the 252, 10 to 15 lbs more torque at 1500 than the 262 and similar to the 252. Effective rpm range of 1000 to 5000.
Pretty much a toss up at this point, will try them later in Desktop Dyno to see if the results stay about the same. So far, the 252 XFI has the lower rpm torque peak like the 249, comparable torque at 1500 to the 249 which is marginally better than the 262, and a little better effective rpm range like the 262.
I hope that adequately explains my overall goal and how I hope to achieve it. I'll be 68 or so by the time I get all this put together, and am looking for a nice cruiser with good mileage and still a little exitement but not too intense for an old man. And I've got my 1150 BMW bike for a little fun. I've had my fun with hot cars over the years with things like a 426 hemi which eventually was quite thoroughly modified, a moderately warmed up 375 hp 396 SS Camaro and 440 six pack Challenger RT, and several other more moderate but still fun rides.
Budget concerns for the engine stem from the fact that many of the major systems on this old of a car need upgrade to make it more than just a weekend toy, so don't want to spend all my available resources just on the engine and ignore the other
upgrades that need to be made to make it a well balanced overall good driving and decently performing car. I also hope to upgrade to stainless O ring brakes (the rear calipers are shot anyway) maybe with a hydro boost, a 6 link for the rear along with a new composite 330 or 360 lb spring, new shocks, rack and pinion steering making my own brackets and using the typical 82 Grand Am rack, either rebuilding the front suspension or going to a monoleaf depending on the ride quality, and of course new tires. So have plenty of places to spend my available money besides the engine.
That's a big part of the fun of doing a project, and I've found thru experience the more I know and consider the options the happier I am with it when I "get 'er done".