Hey All,

My 90 Formula is a 305 TBI with 130k on it. She uses a little oil and runs 16 flat in the quarter.

I am looking for the cheapest way to drop a 350 in, so I figure my best bet to start would be to keep the factory TBI.

I have a friend getting ready to put a new motor in his 92 Z71 and he is willing to sell me his 350 for $400. It is a 92 motor, doesn't use any oil, runs strong, and I believe its a roller motor. It has nearly 160k on the odomerter, however I know the motors history and it was well taken care of. (not to mention he is gonna help me drop in the motor, and he has a cherry picker and all the tools I don't have!)

My plan is to drop this motor in with new main bearings, an LT1 cam, 350 injectors, and a set of hedman 1 5/8 headers. Looking for 250-275 horse. I am also going to install the S10 torque converter and a trans go shift kit at the same time. I already have a beefy Haden cooler for th trans, and it has 50k on a rebuild, so I am confident it will hold up.

On top of this I plan on adding Spoon SFC's, rear control arms and a pan hard bar, along with an SLP take off posi, 3.73 gears and 28 spline axles.

I'm trying to hit high 13s or low 14s. Is this realistic?

Also am I a fool for keeping the stock intake or can I get away with this, as I do not want to spend the money on an intake since I plan on buying vortec heads/intake down the road.

Anyone see any serious holes in the plan? Am I pretty close on my HP estimate?

 

More likely than not it isn't a roller cam. Not 100% sure on the year, but trucks didn't come with roller cams until the "LS1" version was released in '99.

I have a block out of a 1990 3/4 ton (350 4 bolt main casting #638) and it has all the provisions for a roller cam, but just didn't come with one.

I've heard of a few people on here say they got a block out of a mid '90s truck that DIDN'T have any of the provisions for a roller cam so the only way you'll know for sure is to rip off the intake.

If you have the casting #, you can go to www.mortec.com and look. More than likely it's a #638 block also (BTW, 638 is the last 3 digits of the casting #). It's a pretty common casting from '87-'95.

You won't be able to do the LT1 cam for very cheap if it didn't come with the provisions for one. Frankly, unless you're going to go radical, or looking to get 200K miles out of the engine, then you don't "need" a roller cam. A complete flat tappet cam w/ lifters, springs, retainers, and timing chain can be had for what it costs just to buy an aftermarket roller cam (using the "K" kit from Comp Cams as an example).

With the LT1 cam in the factory heads, I would expect ~275 HP at the flywheel. Those heads are gonna restrict the ability of the LT1 cam something terrible, but it'll get you by for now. You more than likely have either #191 or #193 heads which have a swirl port under the intake valve. It's OK for mixing up the A/F mixture in a truck with a whimpy cam, but it'll interfere with any large amount of air that the cam's trying to get to flow.

For a starter motor, it sounds like a good deal. I don't know if I'd jump the gun on replacing the bearings, rings, and gaskets if you don't have to. I've seen a fair amount of blocks that have +150K miles on them that showed VERY little bearing wear. Maybe ~.005" of wear at the most. Although it would hurt to go through the block and change all those anyway.

It would all depend on how anxious you are, and how much cash you want to lay out to start. IMO, there's no need to rip it apart unless you're going to do it all, like have the block bored out, have it checked for cracks, check the deck surface for levelness (<--- is that a word???), and AT LEAST change the rod bolts to ARPs. Of course you're going to be looking at about $300-$500 for the machining and another $500 for everything to rebuild it, and that's using the stock heads.

I'd say do a compression and a leak down test BEFORE you pull it out of the truck (it's easier that way ). Those two tests (actually I prefer the leak down test) will give you a great idea on how well the rings, valves, seals, gaskets, and guides are gonna hold up.

Other than that..... GO FOR IT!!!!!!!

There are a lot of other things you're going to have to change since you're gonna use a 350. Like the knock sensor, chip, etc., but I'm sure the guys that actually know about that stuff will be here soon.

AJ

 

I just did this exact swap, except mine was out of a 92 Buick Roadmaster. I am disappointed in the cam and heads as far as performance go. Don't get me wrong, it is a LOT stronger than my ragged out 305 was, but it still lacks the punch I realised I wanted after I got it put together.

I went through the engine when I pulled it out, punched it .030, new ARP bolts all the way through, same headers you are gonna use, Holley 670 with a bored out Edelbrock aluminum intake. I bought a chip from www.tbichips.com, which was good to get me started. But it is only a starting point. I started burning my own chips about 3 weeks after I got the engine broken in. I am still learning to tune these chips, but it is a necessity.

My opinion, if I were to do it again, do not tare into it unless you want to do it right the first time. It is a pain to clean the gasket material off the block and keep debris out of your journals when you replace the heads later on down the road. The cam swap is pretty easy, but you might as well do the heads at the same time. If you go with larger than a .480 lift cam, you will need new valve train components anyway.

I also wouldn't go with the Vortec heads, for a little bit more, you can get a good set of aluminum heads that will give you better flow and more choices on your intake.

Just my .02

 

All 350 Vortec engines from 1996 onward were roller cam equipped. Use a 1996-98 block with an LT1 cam and you are gonna have a sweet powerplant. Am planning on having mine finished and installed by mid January, but mine is gonna be a 383. The guy who is doing my machine work redid his engine after I talked to him, he said the LT1 cam and the TBI computer love one another, didn't have to do any chip burning. Of course, without a doubt I think he could see some gains in power if he DID have a custom chip made, but that is another topic...........

 

I wouldnt even mess with the stock truck heads they are absolutely horrible. Personally i dont think you'll see 275 hp with the stock heads and an lt-1 cam. In 96 they went to roller in the vortec motors. I have a 94 and it had provisions for roller cam. Ive heard that from 91 on they all have provisions for roller cam.

 

Since the LT1 cars only made 275hp at the flywheel, your not going to make that with just a cam change. Stock 92 L05 truck engine is rated 210hp so I would say around 240hp with the cam. You can gain some more with the headers, exhaust, and intake replacement. That may yield the 275hp at the flywheel. But to get over 300hp is going to require a head replacement.

 

There's one thing you're forgetting. :nono:

The 275 at the flywheel on an LT1 was SAE rating. They usually knock off 15%-20% after you add all the accessories. So a 'naked' LT1 makes ~320 GROSS HP using 15%.

I'm talking about 275HP 'naked' with the POS swirl heads. That's about 235HP if you knock off the 15% used for SAE ratings.

AJ

 

ok thinking a little deeper into this 275 hp is not very likely.. but that doesn't matter anyhow because I will see a nice torque curve....


So the new plan is going to be either drop it in bone stock with headers OR get the vortec heads and possibly the Comp XE 274 cam....

now this may entitle a rebuild, since the old motor may be a bit tired...

Is 400 too much to pay for a motor to rebuild it anyhow?

 

for 400 you could buy a nice carb 350 not needing anything, i dont think id give 400 for a later engine needing work just cuz it has FI

hmmm..

although id like to find an 87-up caprice 350 TBI roller common, ill find one eventually

 

But he said the engine doesn't need any work.

AJ

 

If you search on www.car-part.com you can find a decent mileage 96+ Vortec 350 for $700-800. Then you get the much better Vortec heads and roller cam that can be easily swapped for a LT1 cam and put out over 300hp with much less trouble than trying to get that much HP out of an L05.

 

i would be sketchy dropping something in with 160k+ miles. it might run good, but for how long. it doesnt have a roller cam, although it might have the provisions

 

my 350 block that came out of a 89 3/4 ton truck has all the roller cam provisions 4 bolt block just the bosses for the spider plate in the lifter vally werent taped
ryan