Hey,

I'm in school for Automotive Technology and I bought an '86 Trans Am to learn off and fix while I'm attending college. In December I have the opportunity to repair or replace my engine. It currently has 180k miles and leaks from nearly every gasket. It also has an intermittent misfire (Plugs are getting oil fouled and the exhaust smokes on start up. I think valve seals may be leaking down rather than up behind the piston).

Here is the big question: Do I rebuild my 305 or upgrade to a larger engine?

If I rebuild I'll be putting a few upgrades in it because we all know the 305's are a little puny.

If rebuilding it is not worth the money, what are some options I have for replacements that are fairly easy. (Its my first overhaul.) I know people do 350's or 383's, but I've also seen some pretty affordable used 5.7L Vortecs that seem like a pretty good option.

I know the basics of everything and I'll learn more come December, but keep in mind I'm a student, haha.

I appreciate any and all the help!

 

Probably depends on your budget, and what it will let you do. Cost wise, finding a shortblock 350 and transfering all the TPI stuff helps keep costs down and easy.

 

Depends what your long term goals /useage are for the car? A rebuilt 305 is still only a 305.
Given the machining cost are the same and some 350 parts usually cheaper , most on here would recommend starting with a 350
You might find a younger ,low mileage 350 in the JY that only needs a freshen up ,rings and bearings; not a full rebuild
so you have more $$$ for upgrades

 

Is there anything to look out for if I do go with a 350? I was told by one of the guys at the machine shop to make sure I get the right main seal, but is there anything else? Also, will I have A/F ratio issues if I use the same ECM and fuel system?

Thanks for the quick replies!

 

Oh, and I just plan on using the car as a cruiser. Once it's all done I may show it and I may even bracket race locally.

 

'86 TPI was a mass air flow sensing system. It is fairly immune to displacement changes, up to the point the engine can flow more air than the MAF can. The factory used the same hardware for both 305 and 350 TPIs, except 305 TPI uses 19 lb/hr injectors, while the 350 used 22 lb/hr injectors - this isn't an issue until you max out the flow of the injectors under full power. So, if you go with a 350, it would be a good idea to switch to at least 22 lb/hr injectors.

The factory used slightly different tuning in the '87 & '88 MAF systems, but the 305 tune will still run a 350. Of course, as with all these things, a custom tune will help it run even better, especially if you do other upgrades like cam or exhaust.

If the car has had decent maintenance, mostly regular oil changes, most likely all you need, even with all those miles on it, is valve seals. They are a known weak link in the SBCs from the factory. If this is just a cruiser, then freshening up the 305 makes a lot of sense. Valve seals, gaskets, crank seals - these 305s are pretty hardy, that may be all it needs to run well again. Although going through the heads may not be a bad idea while it's apart - valve guides, touch up the valves & seats. Still a lot less time and money than buying a 350, which will probably need to be rebuilt itself, and installing it in place of the 305.

 

Wow, thanks! So now I just need to check with the machine shop and see what I would have to pay for my 305 to be cleaned up. If it is cheaper than finding a low mile 350 or even a rebuilt 350 then I'll go with the 305. I know they have some 350s around the shop, so I'll check into that price as well and compare.

I think you guys pretty well answered my question. Please feel free to add anything else I should consider, but I think I understand and have an idea of what to do. I'll be stopping by the machine shop in between school and work to talk with them. I'll post an update when I get home.

 

I would only pay a machine shop to rework the heads. You should be able to do all the gasket/seal replacement work on the 305 engine.

If they have a 350 laying around, be very careful what you accept. Most 350 factory heads are absolute junk - your 305 heads are better. In fact, if you get a 350 and rebuild it with dished pistons (or it already has dished pistons and you re-ring it), your 305 heads (after being reworked) would do very well on it.

'86 was the last year of flat tappet cams (in 3rd gens - trucks continued with flat tappets through 1995), perimeter-bolt valve covers, and all of the intake manifold mount bolts at 90 degrees (except '86-1/2 thru '91 TPI Vettes with aluminum heads - but you aren't likely to find them out back of your machine shop). It was also the first year of the one-piece rear main seal crank (which affected the crank, block, and oil pan). The '87-up 350s are superior to earlier versions, but if you use the heads that come on them, you'll have to do something about your TPI base (because the center two intake mount bolts on each side are at 72 degrees, the other bolts are still at 90 degrees).

Again, for a cruiser, the chances are very good that your 305 would be the cheapest way to go.

Oh, with 180k miles on it, I'd go with a flat tappet cam/lifter kit as well. Relatively cheap, not hard to replace, very likely worn. And a new timing set.

 

With 180k miles, I'd at least want to inspect the bore and a couple of the bearings. If any of them show any real wear, then it's time for a rebuild. Once you're at the point of needing a full rebuild, then using the 305 starts to look a lot less enticing. If it does come to the point where you're facing a full rebuild, then I would strongly recommend that you consider moving up to a 350. Rebuilding a 305 will cost just as much as rebuilding a 350, so aside from the cost of the 350 core itself, and a couple small parts like new injectors, a 350 will cost you about the same as rebuilding the 305. To take it even further, you could consider a used 350 that's at or below 100k miles, and put it in as-is and run it for a good number of years before it would need a rebuild. Provided you can find the right 350, it's an option to consider. If I was on a very tight budget, it's absolutely the way I would go before I ever considered pouring money into rebuilding a 305.

 

I spoke with the machine shop and I think I'm going to rebuild my 305. My next step (At the beginning of December) is to tear the engine out, get it in the hot tank and take the block and heads to him to have them inspected to see what we need. He recommends getting the bore machined(if needed), polish or turn the crank, and having them machine the heads. I won't have to pay to tear it down, clean it up, or reinstall it, so I think its a fairly affordable way to go. He did say it would be ideal to start with a 350 block, but that there are a few things to watch out for such as the rear main seal and the heads fitting correctly for the TPI. I'm going to keep an eye out for a block, but since this is my first build I think I'm going to keep the 305 because I know everything that comes out will fit back in, haha.

I'll probably have to put new pistons in after 180k miles of wear, so what issues would I run into if I was to bore the cylinders out?

 

Just keep in mind that everything that comes out of a 350 fits back in too, and you can get a running 350 out of a junk yard for a couple hundred bucks.

Your TPI will bolt up to any 350 heads except Vortec heads. At most you'd have to slot the 4 middle intake manifold bolts so that they'll work with the newer style heads, but otherwise, everything fits. You wouldn't even need to upgrade the injectors if you kept the 350 stock-ish.

I'm not trying to talk you out of the 350 (ok, I am), but I don't want you to shy away from it because you think it'll be too hard or too expensive. That's a common misconception that just isn't true.

 

Sorry, I meant everything I pull from the car will fit back in. But I'm not sold on my 305 quite yet. I just seems like a bit of a hassle to make sure to get the right rear main seal (Not sure if I need a One or Two piece) and at the machine shop he said I would new/different heads if I upgraded blocks. He said the 305 heads wouldn't work. He also said that I needed to get the correct heads that would allow me to reuse my TPI.

Like I said, I'm still going to look for a 350 for the next month and a half before I have to do anything. Can I truly just pick any 350 up and just tear it down for the block and be good to go, or do I need to be wary of some things while I look?

 

Oh and I've seen some selling as 2 bolt or 4 bolt. What does that mean?

EDIT: The bolt patterns are regarding the flexplate.

So my only concern is getting the correct rear main seal?

 

Don't worry about the rear main seal. The 1-piece is the superior design, but the only issue a 2-piece will cause is needing to get a different flexplate ($50 if you don't try hard).

2-bolt vs. 4-bolt refers to the main bearing caps. There are 5 main bearing caps for the crank in a small block Chevy. With a "2-bolt" block, all 5 will have just 2 bolts each. With a "4-bolt" block, the middle 3 bearing caps will have the same two bolts that a 2-bolt has, with an additional bolt farther out on each side of each cap - therefore, "4 bolts" on those 3 caps. They are a little more robust, mostly keep the caps from any back-and-forth movement ("cap walk"), but it isn't critical. It isn't worth it to hold out and pay more for a 4-bolt block if you have a decent 2-bolt block.

 

You will get better fuel economy while cruzing with the 305, but if someone comes beside you and wants to test you out the 350 would be nice to have.

 

Any SBC heads will fit any SBC block. This isn't like Ford where they have a half dozen semi-compatible designs. With the exception of steam holes in heads that go on 400s, they're all completely interchangeable. The only compatibility issues are between the heads and the intake manifold, but they're very easy to sort out. There were 2 different bolt angles used for the interior 4 bolts on intake manifolds. There was the "early" style that was used on every SBC through 1986 (through 1991 on Corvettes), and the "late" style that was used on 87+ SBCs. This bolt angle is easily rectified by slotting the 4 holes in the intake manifold, and if required, buying some tapered shims to go under the bolt heads. The only real issue is with "Vortec" heads (062 and 906 casting heads found on 96+ truck motors). These heads are not at all compatible with traditional SBC intakes. Not only is the bolt arrangement different (8 5/16" vertical bolts instead of 12 3/8-16 angled bolts), but the intake port location is revised. This makes a new intake manifold MANDATORY, but that's still an easy fix. SDPC and Edelbrock offer a TPI intake base for those heads.

The big issue with 305 heads is that they use much smaller combustion chambers than 350 heads (58cc vs. 64cc), so in order to keep your compression ratio manageable, you need to use dished pistons. This in itself isn't a problem, but if you decide to upgrade to better heads later on, a normal set of 64cc heads is going to lower your compression ratio quite a bit. This isn't a huge problem, but something to be aware of.

 

Right on. Thank you for clearing that up for me. I've already found some 350s selling for a decent price. Now the only question I have right now is which heads can I run TPI on on the 350 block? I was told and I've read that there are different bolt patterns for some heads. So does that mean if I get the wrong heads that I can't bolt the heads to the block? Or does it mean I can't bolt my TPI and intake down? Or maybe even both?

 

re-read my last post. I just answered all of that.

 

Sorry those two posts hadn't loaded on my phone yet. Thanks for the info!

 

Update for those of you who have contributed:

I've decided on a Blueprint 355 here: http://www.jegs.com/i/Blueprint+Engi...12CT1/10002/-1

I will be purchasing this sometime at the beginning of January once my wallet survives Christmas.

I'm going to use my same TPI intake and fuel system, so I was researching what I may need to do to correct for a bigger motor and I found this site: http://tpiparts.net/305_tpi_to_350_tpi_conversion Can anyone confirm or deny that those are required to switch from a 305 to a 350(355)? I was planning on switching to 22lb injectors already, but I'm not sure about how to go about doing the PROM stuff. (I'll check that forum if I need to tinker with it.)

 

Definetly want to go up to larger injectors, you might be ok with 19's but they'll be maxed out, so you'll wanna go a little bigger to leave some room for improvment. I have no clue about the tuning/computer part of it though.

 

Do a google search for Blueprint motors, as well as "Marshall engines", which is the company that makes Blueprint.

 

Answered in post #6 above.

 

I may have spoke too soon. I found an '85 Camaro for a decent price with a clean TPI 350 and T5 for less than the crate motor. I'm sure I can swap a few other pieces as well (especially interior).

If I buy this and swap the drivetrain in, do I just need to pull my engine/tranny, ECM, and Wiring Harness and swap for his? He said he has a high flow fuel pump and supposedly the car is tuned with a "stage 2 chip." Would I need to swap fuel pumps as well?

 

'85 Camaros did not come from the factory with 350s. So, that should be your first flag - verify it really is a 350 by getting the casting #s off of the block, then find that # in the sticky in the top section of this forum.

See my post above about factory 350 heads. Unless you want the car, pull the valve covers and get the casting #s from the heads - pull them both, don't rely on just one. Then find the casting # in the sticky in the top section of this forum.

Whether you swap fuel pumps depends upon which is "better". You probably don't "need" to swap pumps, but it's possible the one in the other car is "better".

"Stage 2 chip" is next to meaningless. If it runs okay, it's probably okay. But, the '85 ECM wasn't a very good one, the '86 version is generally considered superior.

 

just my opinon because i use my 85 iroc for the same purpose, i got ahold of an 87 305 tpi motor with 61,000 miles (mine blew up and put about 10 crackes in the block) i used my 85 tpi heads with some mild work to them and i used a mild cam, plenty enough for the cars intedned purpose but thats just my opinion, id love to see how this build goes

 

Sorry for not being clear. The 350 in the '85 Camaro is out of an '89 Camaro. I'll ask if that's the case about the ECM.

Why do I need to check out the heads? Other than the "I should know what I'm putting in my car" reason, its running (not sure how well yet), but if it runs well I should be able to swap everything over and it work the same. Unless of course I mess something up along the way, haha.

Oh, and I'll probably swap out fuel pumps because my sending unit isn't displaying my fuel properly on my dash. Everything between the tank and the dash works, just an issue within the tank.

 

Unlesss they've changed them out for something else, they should be '89 350 heads which you said was superior ('87+).

 

Just to be sure what you're getting. Too many stories about a 3rd gen bought with a 350 that turned out to be a 305.

If it really is the engine and all out of an '89 Camaro, and really is a 350, you should be good.