During the engine teardown of the 305 that was in my 85 Z28 I noted that the bore was .060 over, the connecting rods were .030 under and the mains were .020 under. Dished pistons were installed. The engine was only run a few months (occasionally) after it was rebuilt because it would foul a plug.

I found the #2 intake hydraulic lifter was missing a retaining clip. This made the lifter sit up much higher than normal and my guess is that that valve was constantly open. I believe that is the reason for the fouled plug.

When I started measuring I found that Piston Ring Side clearance was a tight .003. Chilton's says it should be between .010 and .020. Chilton's says that if side clearance is excessive, then the piston should be replace. It doesn't say anything about being too tight. Is this bad?

Calvin

 

The only place I'd be really worried about too tight of a gap is the ring end gap, because the ends can butt together under load and break piston lands.

Besides, I've heard there's a lot of errors in those Haynes and Chilton's manuals anyways.

 

Did you clean the groove before you measured the clearance?

 

Hmm, .010-.020" sounds very wide. I coulda sworn mine was less than that on my speed-pro hypers in the 350.
You need some gap to get the gas in there to help push the rings out to seat.
I imagine you could simply sand the rings down to make them thinner. Maybe a sanding block or something.

Double check that spec. I'll see what I find in my literature.

Do you have calipers? (accurate to a thou?). If so, measure the ring slot height on the piston, and the ring width. See which one is out of spec (if it is). I imagine you have 5/64" rings?

I'm impressed, sounds like you really know what you're talking about. And measuring all that stuff - good on ya! ....Then why are you relying on Chiltons?? That's like the Walmart of engine rebuilding books
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Hmm, I lied - Helm says .012-.032" for top and 2nd.

 

Calvin - I must say, i'm highly impressed with the amount of attention to detail you've got. Your website, the schwack of pictures, the trail of information you're leaving, goal setting... Holy cow, after hearing some of the half witted posts on here with "help my car get faster" type of stuff, your post with pictures and detail is a breath of fresh air.

You've certainly got a frankenstein car. 1985 Camaro, post 1987 vertical grid taillights ( I think post 1987 ) TPI 305 (from a...?), 601 heads... That's just a wacky setup alright.
Did it run when you got it?

 

Sounds like a typical mass-produced over-the-counter budget replacement engine.

 

Thanks for the comment on doing things right. This is my first foray into automotive work. I've always changed my own oil and brakes, little things but have never rebuilt an engine before. Documenting everything so that I can get it back together correctly. Hopefully others can use some of the photos for reference. I've just been reading here and books from the library to make sure I do things right. I'll keep updating that website with new pictures every few weeks.

As for a Frankenstein car...I bought it from a car dealership when the original owner had just traded it in. Bought it in 1993. Ran fine for many years but always had white smoke on startup. The only time it has been out of my hands is when I had given it to my father and he had the engine rebuilt. Taillights and all body should be original. I'm still trying to figure out if the guy who rebuilt the engine replaced the block or had the original machined.

I did clean the ring grooves and rings before measuring. This engine will not go back in the car. Upon advice from folks here I'm looking for a 350 with hydraulic rollers. I will rebuild this one for the experience and to keep it from getting junked.

Ring end gap was spot on at .010.
Is it a bad thing that the ring side clearance is only .003?

 

That ring end gap is a bit tight. It wouldn't burn a spec of oil, but if someone started driving it hard, it could very easily heat up and seize the ring ends together and lift off the top of the piston. Do a search on mwnova66, he posted a few pictures when that happened to him.

I'd like to know which part is out of spec to get only .003" side clearance? Do you have a good set of vernier calipers? If so, measure the ring thickness and the gap in the piston and post them up. Rings should be .078" thick, gap should be in the range of .090". See which one is off, i'm curious.

You need space for pressurized gas to get in there, to help push the rings outwards. Thats what gets them to seal in the combustion pressure.

Are you planning on rebuilding it then selling it? Or saving it for another project? A rebuilt 305 has very little value, I doubt you'll be able to recoup the cost of the parts you put into it.

Post the casting number on the block, someone here could tell you if it's the right number.

Was the car TPI when you bought it? I think 1985 305 TPI equipped cars are EXTREMELY rare. Apeiron, I think you told me the spec, something like 91 of them were made?!?

 

.003" of ring side clearance is a bit on the loose side... about what one would expect from a slap-together "rebuilder" motor (which I agree with apeiron, that's pretty much what you've got there), or a worn-out one. Ideally I like to see something around .001" - .0015" in a new motor.

Ring end-gap should be in the neighborhood of .004" - .005" per inch of bore. Since the 305 bore is about 3.8", the end gap SHOULD BE something around .018" - .022". Less than .015" is asking for trouble.

Sounds to me like, if you have a worn block that's already .060" over, it is garbage. You cannot bore it out any more. Throw it away and get another. Except this time, get a junk 350 block instead. Same price, costs the same or less to build, gives you about 15% more bang (power and torque output) for every buck, uses about the same amount of fuel in normal driving. What's not to like? Your plan to get one of those instead is the way to go.

I don't know about 305 TPI being rare in 85.... that was the year TPI was introduced, and there were thousands of them. Maybe tens of thousands. Not too much different from the production numbers of other years of TPI cars.

The lifter coming apart didn't cause the motor to smoke. More likely, it was the result of the rocker adjustment being too loose, OR valve float (the result of having weenie stock springs that were worn out besides) while over-revving.

Typical causes of mystery smoke in a newly rebuilt motor include broken valve guides; a damaged intake gasket, across the bottom of runner, such that there is a direct connection between the crankcase and the intake runner; faulty ring - bore match, from rings that didn't seat, bores that weren't round, rings that damaged a bore surface (typically the end of a ring having a burr that screatched the bore), broken rings, or damaged bores from inadequate end-gap which sounds very probable in yours; or faulty assembly, particularly the oil rings having the ends of their "expanders" incorrectly butted together, i.e. "stacked" rather than "butted".

 

Well I feel supremely stupid. Upon re-checking helm, and *counting the zeros*, they do indeed say "between .0012"-.0032". So yea, you are on the high side.

I coulda sworn *someone* on this board told me that TPI came out late in 1985, so it was ultra rare. Then in 1986 it was all over the place. Maybe it was 1984 that it was extremely rare...

 

Guys pretty much covered it here but I'll add one thing. Reason that lifter is sitting up higher is becuase the spring inside pushed the plunger all the way up when you backed off the rocker arm- there was no clip there to retain it from just pushing right out the top of the lifter. Also agreed, chances are the lifter was adjusted too loose which is what caused the clip to come flying off in the first place. Look around in the motor- you might just find it.

Yes, you can replace the clip and put the lifter back to proper working order (don't try this if you've never taken a lifter apart before). But at this point, why bother? Like others have pointed out, that engine is on at least it's 3rd life and probably not worth throwing money at to use again.

 

It was indeed a 305 TPI motor from the factory. That very may well be the original block from what the casting numbers say and only rebuilt once. In that case the only thing that could explain the .060 over bore and journals ground undersize is because of mucho wear and perhaps a fool doing the rebuild.

To clarify, It didn't smoke after the rebuild. It only fouled a plug. It is .060 over but there was no ream in the compression area. Bore is super smooth throughout and I can still see all cross-hatching. It was only run ~300miles or so (guess) after that rebuild.

Sonix, my calipers are Harbor Freight Chinese junk but they tested pretty accurate against my feeler gauges and they have an advertised accuracy of .001. Here are the pictures you requested:

Bottom compression ring and groove spec at the same numbers.

From advise posted here, I won't use this engine for my car but someone may want it. I'll repair what damage there is, fix it right and let someone have it for little $$.

 

No Sonix. It was MY BAD. I stated a much higher clearance in my first post. Indeed upon re-checking the manual it is supposed to be .0012-.0032' ring side clearance. Explanation for the mistake: I have a fridge full of beer in my garage.

Since the .060 over bores are not worn and the pistons seem to match well, I'll clean this up and put it back together as best I can and will offer it to a board member near Tulsa when done. Yes, It can't be bored any more but everything I've measured indicates that it is within tolerance, ringside clearance notwithstanding but if I put it back together clean, this should make a nice bottom end for someone that will run many years.

The heads are 601 casting. I'm told I should keep those for possible use on a 350.

Thanks for your help and sorry for the mistaken clearance quote.

Calvin
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Damon, as for the retaining clip on the lifter? I didn't find it in the engine. I have everything out of it but the cam bearings (have to buy a tool for that), opened up the oil pump as well and I don't see it anywhere. I'm thinking the genius that rebuilt it just missed it.

 

PS - I bought the summit house brand cam bearing tool and it was machined a bit too large so it wouldn't work whatsoever.
I returned it and bought the name brand one from summit ($3 more) and it was fine. Just an FYI.