2012FLHX

I purchased a really nice 1987 IROC 5.7

Unfortunately, I discovered a cracked block due to freezing that someone smeared JB weld on to fix.

I want to keep the stock look, keep the TPI, but get the most HP I can get. Would love a little cam sound of course if possible.

I have posted on another forum and was bombarded with LS swap recommendations but don't want to do that.

I want it to look stock but have a little more punch. I reached out to ATK and Blueprint for their recommendations but never heard back from them.

Surely someone has done this in the past.

Thanks!

aliceempire

iTrader: (14)

Keeping a tpi and replacing the long block is sort of a conundrum. There are plenty of options but all have some caveat. You can get a vortec long block from GM (I believe they're still avail) but then you need the vortec replacement base intake manifold to make it work. You can get a short block (even still from GM if you like), have your heads rebuilt or find 083 casting replacements. Most other factory heads except for vortecs are likely to cost you power. Regardless you're looking at rebuilds. Not the biggest deal but you have to find what you need. Going to aftermarket heads or long block is fine but the tpi manifold is automatically restricting you unless you modify it. That calls for porting, maybe a different base, different runners, in which case it's easier to replace it to something like an HSR or a carbed manifold(which dismisses the look you wanted to keep). Then at the end of it all it'll need to be tuned and that is getting harder and harder to do with factory ecms, especially if you can't do it yourself. Point being, what seems simple isn't. Usually why people suggest and go LSx. On a tpi car, it's about as much work, about as much money(if using a JY motor/drivetrain for ls compared to a rebuild sbc) and you end up with more power and available future power. All you really lose is the look.

My suggestion, get a quality replacement short block, reuse your cam, rebuild your heads. Small mods like gears and exhaust. Put emphasis on maintaining and driving. Don't worry about more power, it ain't gonna matter.

2012FLHX

Thank you for the response! For sure something to think about. If I have to I will just go with stock and keep enjoying it! The car has all documents back to when it was sold new (except the JB weld Repair lol) and body and interior are near perfect. I would love a little more power but want to keep the stock appearance for sure. The crack is external and barely leaking at all. No water in oil or oil in coolant. Some of my friends are telling me just to drive it and have fun.

sofakingdom

iTrader: (1)

First off:

If your block is cracked, you need a BLOCK. Now obviously at some point you'll need the internal goodies as well; butt, FIRST THING FIRST. Concentrate on the BLOCK. That's what you REALLY need.

A "long block" is a fully built-up motor, to the point of heads and valve train, but minus tin except maybe with the timing cover and crank damper, intake manifold, and exhaust.

If you don't need heads, you don't need a "long block".

Your TPI heads (should be casting number 083) are arguably among the best factory heads ever made for the traditional SBC until the introduction of Vortec heads in 1996. (in production vehicles, that is... not comparing them to racing parts) The thing here is, people COVET those heads, and will do ALMOST ANYTHING to get you to give them up as cores, while supplying you with GARBAGE like TBI heads (casting number 193 most commonly) or 70s smogger crap such as 882 or 624. You DON'T want to let this happen. Therefore, you DO NOT WANT a "long block", unless your heads were also damaged by the freezing. Sometimes they are, but not usually. Most common way they get destroyed by freezing is cracks between water jackets and intake ports, or cracks down the outside along the exhaust ports. If yours don't have such damage, you DO NOT need a "long block".

A "short block" is a block fitted with the basic internal parts: crank, rods, pistons, rings & bearings. It does not include heads or valve train (cam). This is probably the level you need to be working at. You can refresh your existing heads - again, DO NOT let somebody take them in as "cores" and give you something inferior - perhaps with some improvements such as better valves and CERTAINLY better valve springs.

Forget about cam "sound". The properties of TPI require a specific match of valve timing to the intake system's ACOUSTIC characteristics. Which sounds kinda stooopid, butt, that's what the "T" in "TPI" means. The length of the runners is chosen such that the pulse of positive pressure that happens (think of it as a popping noise) resulting from an intake valve closing while air is rushing into one cylinder, travels BACK UP the runner, into the plenum, and ADDS TO the pressure driving air into THE NEXT cylinder drawing in air. It provides constructive reinforcement by way of this pressure wave. TPI's runners are designed to maximize this effect at 3600 RPM, give or take. Above that RPM, the acoustic effect begins to work AGAINST itself, reaching peak NEGATVIVE reinforcement at around 5400 RPM. This is why TPI has a torque peak that feels like Mount Everest: it has good torque at low RPMs due to the typical stock cam, then as the RPMs pass 2800 or so the reinforcement effect begins to have its effect, then it peaks at 3600, then the "boost" effect disappears between 4200 and 4800, then the torque CRATERS above that. To make TPI work then, you need a cam that supports this specific behavior i n this particular RPM range. You CANNOT do like a typical carbed engine, where if you want it to have its torque peak at some other RPM, you just jam in more cam. TPI doesn't work like that. The very property that causes "cam sound" works AGAINST the effect of TPI; you end up with LESS THAN STOCK performance. Don't make that screwup.

A typical "rebuilt" short block will have lower quality pistons than stock, they will often be dished, and they won't come as far up in the bore. This all leads to MUCH lower compression than stock, therefore MUCH less power. The less you try to pay, the worse this whole deal becomes. DO NOT buy the cheeeeepest thing you can find that somebody calls "350", because that's what you'll get: the foundation of a gutless 70s smogger turd, NOT anything "performance". Look for flat-top pistons, and veerify that they come up to within .025" of the deck. Typical "rebuilder" pistons, even if they're flat-tops, will be around .045" or more below the deck at TDC. That extra .020" of deck clearance will drop the compression from around 9.6 to 9.2, all by itself. (.030" overbore, .025" deck clearance, .041" gasket, 6cc valve reliefs, 64cc heads) With a typical "rebuilder" long block (.030" overbore, .045" deck clearance, .041" gasket, 15cc dish, 76cc heads) the compression will be below 8:1 and you'll have one of those magnificent 160 HP snails from the 70s.

Your block is probably casting number 638. That's the earlier (86 - 90something) 1-pc rear main seal 350 block. Later ones are casting 880. Either is fine. Others are not.

I would suggest either a used short block from a 96 - 2000 truck (the ones that come with Vortec heads, except without the heads since you can't use those without considerable extra expense); or, buy one from Summit or Jeg's or the like, looking for one without the extra "rebuilder" deck clearance.

Rework YOUR heads if they're still the 083s; maybe add better valves such as Manley Street Flo; LS6 valve springs with the Comp "adapter" retainers; and a cam SPECIFICALLY designed for TPI, such as the Comp "501" grind if you don't want to deal with tuning or the "502" if you're willing to do some of that; and good quality ceramic-coated stainless-steel headers. Clean up and re-use your existing intake system and tin.

2012FLHX

Thanks for the reply, Thanks makes a lot of sense. I talked to an engine shop right beside my office, he suggested just ordering a long block for the easy factor. He actually told me I could buy a complete engine cheaper than he could build me one. I'll take your suggestions and go visit with him this morning.
I don't "need" more power but thought if I was replacing anyway that it would be nice. At the end of the day though I want it just for cruising around with the wife and remembering my high school days. Since I have a CDL and Private Pilot Lic I probably don't need anything that will get me in trouble anyway. lol

sofakingdom

iTrader: (1)

Problem is, to get a long block that's the same as the engine you have now, is next to impossible. Practically anything you get will be markedly inferior.

It's true that it's "cheaper", as well as less expensive, to buy a mass-produced replacement, than to build the one you have. No question of that. THIMK for a minute about what you'd have to do to "rebuild" THIS engine exactly as-is: you'd have to disassemble it, keep each of its parts & pieces separate from ALL THE OTHERS that might be similar and happen to be in your shop at the same time, label them indestructibly, clean them separately, reassemble THOSE EXACT parts, replace THE part that you happen to come across that's bad, account for THOSE EXACT hours and minutes and materials and whatnot to be able to bill you legally and accurately, ... nightmare. As opposed to a "rebuild" factory: you have a bunch of goons tearing cores down, they put all the blocks on this pallet and the heads on this one and the rods in this barrel and ... you grab up a PALLET of whatever part, clean it without paying the least attention to which one is which, prep them all exactly the same (like, bore the blocks all out to the absolute max), inspect them and throw away the ones that don't make it (maybe at acoupla stages in the process), then have more goons grab one of these, one of those, 8 of those, open a box of these and a box of those, grab ahandfulla bolts outta the bin you keep, and slap it together. VERY DIFFERENT processes, as well as costs.

TPI will largely keep you out of trouble anyway. As long as you don't behave like I did when I first started driving. Just don't try to race any minivans, they'll probably humiliate you.

Wouldn't hurt to positively identify the heads you have now. If they're not 083, odds are you're already screwed in that area, and preserving a stock TPI motor is no longer an issue. Clearly that would figure heavily into deciding what to preserve, if anything, or just replace it outright.

Komet

L31s are still available in the yards for cheap. You can get a quality casting, factory roller 1pc rear main block that way. If you built it up with your still-good L98 stuff, I think the only practical difference is the lack of an internal bypass in the block which can be accomodated by tapping an additional port into the intake. Or you could keep the vortec heads and use the SDPC vortec lower to glue it all together, they're not always in stock but are right now:

https://sdparts.com/i-23896057-sdpc-...baseplate.html

That $450 might make the difference between just finding another L98 pullout and having exactly what you need, though.

But if you're changing cams, you'll probably want to modify the intake for more flow, which is a whole subject in itself and then also getting it tuned. It all depends on how much money you want to spend and where you want to make your power. Staying with stock components will give you the least hassle and shortest downtime.

Fred SS

iTrader: (3)

Chevy Performance Parts has a ZZ short block, 19433053. But it is pricey at about $4400. Your best bet I think is to go with a L31 used or new and get the SDPC Vortec intake. Of course, if you change the cam you will have to do the mod that allows Vortec heads to accept higher lift cams.

Fred

ULTM8Z

There's also engine tuning to think about... i.e....do you want to re-tune the chip? A MAF car (87-89) can tolerate a mild upgrade w/o too much trouble.

What I would do to achieve your goal would be to (as some have suggested) get a 350 short block (L31 Vortec is a good budget level choice, as stated). Rebuild your heads, then get say a ZZ4 cam (208 @.050 on the intake). See if they can convert them to screw-in studs and get good valve springs to run the ZZ4 cam reliably.

The cam will add the extra "punch" w/o running afoul of smog. In a 350, it'll sound and idle stock, run cleanly and efficiently, and the good thing is it's power band is well within the TPI, so it'll still be a well matched combination.

BTW, while the engine is out... if your car is an automatic, do yourself a favor and get a ~2000-2200 rpm converter. That'll REALLY give you some more punch.

Also, with the engine, you can always get some smog legal TPI parts like runners and base. People are selling them used quite often here and on Corvetteforum.

With all of that you should have a solid 300hp engine with a lot of really good power and easily pass smog.