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1988 S10 2.8 5-speed
107 Posts
Discussion Starter · #1 ·
I am building a 2.8 for my '88 Cameo prototype- yes, it is an '88 and the earliest known one in existence. It is said that its very likely the first one built. The original engine threw a rod, and I will eventually rebuild it if I can. I have an engine from a '93 that I have stripped it down to the bare block. The block, crank, and heads are currently at my machine shop. I am going .030 over with new pistons, Hastings moly rings, Clevite bearings- seems the "77's" are NLA for our engines. I am keeping it TBI but want to run a bigger cam and use Comp Cams 1412-12 Magnum 1.52 Roller Rockers since I don't want to change valve covers, etc. I have read a lot on here about them running lean, getting different chips, 4.3 injectors and boring the intakes. My question is if I get the Comp Cams 16-233-4 cam, what exactly do I need to do? It looks like if I go with the 16-232-4 cam, it is drop in without any modifications if I am understanding correctly. My attitude is go for the gold and go with the 16-233-4 cam set with springs, lifters, etc. My other question is I have read about the elusive Cloyes double roller timing chain set for the 2.8. Is this also a drop in replacement? More importantly, what is the part number for it and where can I find it? I am either looking in the wrong places for one or something because I cannot find it. Lastly, what are the thoughts on a high volume oil pump? I have seen mixed messages on it. Should I just go stock? Thanks for the help.

· time to get cereal
7,603 Posts
I would contact Ben at wot-tech.com, he is the most knowledgeable person I'm aware of when it comes to 60degreev6's.

· Registered
84 Posts
Mike, I found a double-roller timing set at ARI Racing Engines site, it says available on backorder. Probably the Cloyes set and you're right it seems pretty hard to find.

Note they say the timing damper needs to be ground down for clearance between the sprocket/chain assembly and also the timing cover may need to be clearanced. I saw postings at the Pennock Fiero site that confirm this.

The Comp Cams 16-233-4 "260" cam is a pretty "hot" one for a 2.8. This would be primarily a street runner with mostly hiway work, as you're gonna have a greatly enhanced top end and midrange but your low-end may suffer.

The 16-232-4 "252" cam is more of a "torquer" grind however in the 2.8 I'd imagine it'd still be considered fairly "hot".

With either cam, you need performance valve springs and caps (the stock springs will coil-bind from the extra lift). Those can be either Comp Cam's components in the kit, or early Z28 "beehive" springs and caps.

BTW I've run the Magnum 1.6:1 roller-tip rocker arms in my old Trooper 2.8, and have a generic set of SBC V8 1.6:1 roller-tip rockers in the built 3.4 that's in my current '90 Trooper. Used to have an '86 Jimmy 4WD 2-door SUV with a 2.5 Cast iron Duke. I always wished it had a V6, the 3.4 would have been great in there!

At any rate, both the 2.8 and 3.4 run stock cams and I never did change the valve springs, even though Comp Cams recommends it. I figured the stock cams just don't have enough lift to make it an issue. The aftermarket replacements definitely do. Or maybe I just got lucky!

I've never had any issues with stock valve cover clearance, either, using the higher-lift rockers. I think that if were to use full-roller custom rocker arms, they'd be considerably higher and might hit the valve covers. Maybe in that case a set of Fiero valve covers would work better. I'm sure the experts here know more about that than I would.

The "252" cam with 1.6 Magnum rockers would be a pretty snappy setup and you wouldn't have to worry about piston-to-valve clearances. One of the Trooper Dudes at the Planet Isuzoo is running the "252" cam, and 1.6 rockers in his "stroked" 2.8 (i.e. a 2.8 with 3.1 crankshaft and pistons, overbored) and he says it has excellent performance. And this is pulling around a 3800-lb "tank", the Troopers are quite a bit heaver than an S-series.

On your TBI, bore the 2 intake holes out to 1-11/16". This is the bore size of a 4.3 TBI. That'll get a lot more airflow into the engine. You could use your 2.8 injectors but you'll need to increase fuel pressure until the engine is "hap;y". Changing the spring in the fuel pressure regulator is one way to do that. A 14 psi spring is a good performance upgrade and inexpensive.

You can also install an adjustable F.P.R. which will greatly aid your tuning. Add to that a fuel inlet adapter that has a 1/8"-NPT fitting for a gauge, and you'll know exactly how much fuel pressure you're running.

This site carries those parts and isn't horribly expensive:

On the high-volume oil pump, I have the "How to Rebuild Your GM V6 60 Degree Engine" "bible" Tom Currao, and he doesn't recommend using a racing-style hi-volume pump. Probably good for a track engine, where you would have larger bearing clearances, but unnecessary for the street.

One huge improvement you can make is to use an oil pump meant for a '93-'95 Camaro or Firebird (F-Body) 3.4. This pump has taller gears and will pump more oil than the older pump. And at a "stock" price, no penalty for a "performance" part. The '93 engine you're rebuilding may already have the upgraded pump, as I understand GM made the change sometime around the '91 models. You can tell by the pickup, or by the height of the pump if you have new/old to compare. The upgraded pump uses a 3/4" diameter pickup tube vice older-style's 5/8" tube.

Here's the Melling upgraded pump at Rockauto:

The only issue is to make sure you have the correct pickup tube/screen for the vehicle application. A 4WD like my Trooper takes the same tube as a 4WD Blazer/Jimmy (or S10) that used the tall pump. If you're 2WD you'll have a shallower pump and maybe the pickup that's on the 2.8 you're rebuilding will have the right pickup already.

This is the oil pickup specified for the Camaro and it appears to cross over to the S-series 2WD models:

Your stock ECM should handle the performance upgrades pretty well. Jacking up the fuel pressure will solve a lot of running issues, such as a lean-surge on cold starts, etc. I did the 3.4 swap back in 2002 and the engine is still running great. It has a Holley Big-Bore TBI (Unobtanium now) (same as a GM 4.3 TBI) and I've never touched the fuel pressure regulator (it's adjustable).

I installed a larger exhaust (2-1/2" out the back) and got rid of the Wye. IDK if the S10's have the same setup, but the wye with the O2 sensor sticking in it, very restrictive. You can eliminate the wye and use a cat that has dual inlets. Or a custom-built wye. Magnaflow among others carries those.

The new exhaust with a good turbo muffler made a huge difference in performance. It'll pull hard well over 5000 and gets considerably better mpg than with the old wheezy stock exhaust. The larger exhaust did cause a loss of low-end, it doesn't really come on the pipe until 2200-2500. I should put the 252 cam in there but that's a lot of work, eh!!

You probably want to stick with a 2-1/4" exhaust back of the cat. With a 2.8 that's more than adequate, 2.5 or 3" would be overkill.

My old 2.8 Trooper with Comp Cams Magnum 1.6:1 roller-tip rockers, a cheap 2" exhaust with generic turbo muffler, bored intake with the Holley Big-Bore, and a flipped air cleaner lid was pretty snappy (I thought), until I did the 3.4 swap in my other Trooper. That one would pull hills 1 gear taller than the 2.8 and still be gaining speed! But the 2.8's a good little engine and does respond well to old-fashioned hot-rodding techniques.

Some TBI tips for ya, just flipping over the air cleaner lid will make a huge improvement in airflow. Will be a bit noisier, though. I built my own dual-snorkel air cleaner by grafting an S10 air horn onto the stock air cleaner housing. Breathes great and just lets the faintest intake growl come thru. Just right! A cold air intake using a Cadillac TBI top hat (if you can find one) would also work and be lower-profile. I've seen a lot of aftermarket top hats that would work as well.

Use this injector pod spacer to get the pods up out of the throats of the TBI, it'll improve airflow and is a pretty cheap performance mod:

Well, I guess that's long enough for my first post here! Just wanted to share the knowledge.

Hope that helps and Good Luck with your project.............ed
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