How do I determine if my 302 is worth rebuilding? (It wasn't, bought long block)

Vragor · Jul 26, 2010

I have limited wrenching experience. Oil, brakes, belts etc. But never serious motor work.

I have a 70 bronco with a 302. The motor was rebuilt by a good mechanic when I got it in the late 80s. It was rebuilt again in the mid 90s by a questionable mechanic and has been gutless and unreliable eve sincer. It became virtually unusable about 2 years ago. Now it just sits in my garage. FYI, my grandfather bought it new in 70 so it has allot of sentimental value to me.

A daughter recently totalled her car and now drives mine. I'm on my motorcycle for the summer (I really don't mind that so much) but I have to have something before the snows start falling.

Instead of debt and buying something, I want to get the Bronco going.

How can I tell whether the motor is worth rebuilding? How do I go about measuring whether the cylinders have been rebored beyond reason, and what other things should I check?

If I opt to rebuild it, what do you usually keep and reuse, and what do you usually buy new?

My budget will be $2,500

bmc69 · Jul 26, 2010

The simplest and quickest 'test' is to simply pull a head off. Then clean off the top of one piston and read the overbore..its stamped right in the middle of the top of the piston. If that numer is already greater than .030...yr done and its time to spend 100-150 bucks for a good core engine instead.

OR...with the budget you are talking about...just buy a complete long-block already assembled from a reputable source and go that way..

OR...for much less $$ and some astute shopping and you should be able to find a good low-mileage used takeout...

broncnaz · Jul 26, 2010

Welcome.
Sounds like you either need to find a friend who can help you out or as was suggested get a rebuilt/crate engine. Eitherway your going to have to do some wrenching to keep it within your budget. A repair manual like a Chiltons or Hayes can e of great help.

Most long block engines you purchase will be pretty much bare. Sometimes they will come with oil pan valve covers and timing covers sometimes not and since its going in a bronco you need to keep the bronco oil pan, oil pickup tube, bolt that the pickup tube attaches to. You'll want your timing cover, accessories and harmonic balancer, intake carb and distributer. Basically anything that bolts to the engine you'll need to swap over.

If you get a long block engine make sure it has a 28 oz balance so it will be compatible with your stock bronco stuff. Hopefully it still has all the stock parts on it.

Nightstick · Jul 26, 2010

Check out my 351w rebuild thread, should be on the first page here in the tech section. Starting around post 15 or 20 I made up my mind on what I wanted to do with it. I'll probably end up spending more than $2500 but I'm adding the serpentine system and EFI. If I stuck with carb, V belts, and stock heads, even with machine work I mighta come in under $2500.

Here's what I've spent so far (don't tell my wife)
- Assembled '89 351w $350
- Machine work $1165... that includes the rebuild kit with new pistons, bore .020, turn crank .010, balanced assembly, hot tank bath
- Cam, lifters, timing chain $300
- GT40 lower intake $375

- Future expenses will probably be in the range of $2000 for a complete explorer motor to get the serp stuff, heads, and some EFI parts then some other wiring harnesses and EFI stuff

If you just want a stock motor with carb subtract the intake, and if your core is good subtract that expense. Chances are though if it's already been rebuilt twice it is probably time for a new block. I have a guess for ya though. It's possble the guy who rebuilt it last put the incorrect size rings in there and you may be losing compression with will definitely make the motor feel like a dog. May wanna check that out, could save you a lotta money.

Where are you located? Oh, and we like pictures round these parts!

patterdale · Jul 26, 2010

With that much work already done on the existing engine I would side with putting in a long block. It should have hardened seats so no valve issues with unleaded gas. It should come with a warranty to back it up also. Something I take it the last guy didn't give you.

Vragor · Jul 27, 2010

I'm a programmer so I tend to think in terms of steps leading to decision trees.

It sounds like my first step is to pull the current motor, remove intake and heads, then check to see just what that last mechanic did to it. More than likely I will find the heads overbored and possibly even mismatched.

The first big decision is rebuild vs buying a long block 302 with many things already pointing in favor of the long block. Bmc69 mentioned buying from a "reputable source" and I've searched the forum for a while looking to see who others have purchased from.

No one seems to have anything negative to say about Ja$per except the cost. They quoted ~1.8k not counting shipping. Others mentioned GearHeadMotors who quoted ~1.4k inc shipping. I haven't called Napa or Advance Auto yet, but they would charge tax on top.

Nightstick - I'm in Colorado Springs.

Patterdale - I took the Bronco back to the last mechanic 4 times. The first 2 times he claimed he found something and fixed it but it still didn't run right. The last 2 he just said it was running as well as a vehicle that old could possibly run. Finally he told me not to come back again.

jedblake · Jul 27, 2010

I'd stop in my local speed shop and ask who the reputable rebuilders are (and/or post here to the CO guys). Shipping on a long block will be high, on the other hand you can load it the back of your truck and drop it off in CO local.
You have a few choices on a replacement 1) find a good used runner in the paper or internet 2) go to the salvage yard and find a clean 302 to rebuild and swap your EB engine parts 3) AutoZone motor w/ warranty (but who knows the orgins) 4) new crate motor.

Hank_ · Jul 27, 2010

You might want to take the bronco to a good garage and get an opinion on the motor. Perhaps the last guy did not assemble something correctly. There may be no reason for a total rebuild. Could be intake or carb problem. Before I pulled the motor have someone check the compression. If your compression is good it may be a simple and far less expensive repair.

Henry

blubuckaroo · Jul 27, 2010

Why ne rebuild it yourself? There are shops that will do the inspecting / machining and let you do the assembly. I used this place https://shop.enginekits.com/osb/specials.cfm
They bored, honed, turned the crank, installed cam bearings, and fitted the pistons for $300. They sold me the kit and I assembeled it without any real issues. It was a great learning experience for me.

broncnaz · Jul 27, 2010

While many mail order engines may seem cheaper if you ever have any warrentee issues your local parts store engine will be much easier and quicker to deal with.

While I agree a compression check would be the first order of buisness before tearing it down as it will tell you a lot about the condition of the engine a tear down of your current engine is the only true way to figure out what route to take if its the orginal 302 and has already been rebuilt 2 times I would say its probably not going to be rebuildeable again.

Skiddy · Jul 27, 2010

broncnaz said:
While many mail order engines may seem cheaper if you ever have any warrentee issues your local parts store engine will be much easier and quicker to deal with.

While I agree a compression check would be the first order of buisness before tearing it down as it will tell you a lot about the condition of the engine a tear down of your current engine is the only true way to figure out what route to take if its the orginal 302 and has already been rebuilt 2 times I would say its probably not going to be rebuildeable again.

I agree and other issues could be causing your problem. what exactly is it doing smoking,using oil, blow by ect.....?

Nightstick · Jul 27, 2010

blubuckaroo said:
Why ne rebuild it yourself? There are shops that will do the inspecting / machining and let you do the assembly. I used this place https://shop.enginekits.com/osb/specials.cfm
They bored, honed, turned the crank, installed cam bearings, and fitted the pistons for $300. They sold me the kit and I assembeled it without any real issues. It was a great learning experience for me.

Are those 1975 prices!!?? If not I got robbed!!!

73azbronco · Jul 27, 2010

Those are old prices.

If you go "crate motor", go local, do a websearch for local engine rebuilders then go there yourself and look see. DO not go Ebay or mail order, I even avoid a normally good place like NAPA. i want to see the guys who build the motor, check them out on BBB, web etc...

Since when did the definition of "crate motor" change from a new OEM motor to "anything a bunch of dudes can throw together and call a motor"?

Vragor · Jul 27, 2010

Since the last rebuild in 97, it has been to about 5 different mechanics and had many many friends heads under the hood. No one has a clue about what's ultimately wrong.

Major symptom - gutless and often stalls. Currently won't even run well enough to drive up my driveway into the garage thus it sits there.

Minor symptom - recent - idling with dual exhaust - right side shows a white puff mingled with 3 black puffs. Figure one cylinder isn't firing but I have no idea which or why. Revving continues to show a white puff.

Timing (many many times)- no help.
Plugs and wires - no help.
Changed to electronic ignition - no help.
New intake and carburator - no help.
Check compression - seems fine.
A friend helped pull intake and both heads. Nothing visibly wrong. Re-assembled with new gaskets. No help.
Power brakes did become poor about the time I finally stopped driving it. Couldn't find a vacuum leak but didn't look very hard.

At this point I get so depressed when I look at it that I find it hard to contemplate "fixing" the engine yet again. I'm trying to take the angst of trying to find a new car and funnel that into energy to repair the Bronco. But I really don't want to spend thousands and just have the same ol' gutless wonder again.

It was such a fun vehicle those first years right up until my daughter's boyfriend siezed the motor which caused the second rebuild. I still don't know what he did and her story keeps changing about what they were doing at the time.

73azbronco · Jul 27, 2010

Whoa Nelly, I just read this part:

It was such a fun vehicle those first years right up until my daughter's boyfriend seized the motor which caused the second rebuild. I still don't know what he did and her story keeps changing about what they were doing at the time.

My guess is if it is running weird, it was seized, it was maybe gone through by maybe someone who maybe did something, you have some bad bearing issues which are binding as it runs. let alone the host of bad cylinder or other issues.

My thoughts?

was a leak down compression check accomplished? Does the motor turn over easily with the starter, no binding ?

With what your saying, I would pull the motor and open the bottom and look at the mains, pull a piston out and look at it, go from there. Either way, that motor is not doing what it's getting paid to do and needs to come out.

When you replaced all those parts di you put the old stuff back on to verify the old stuff was not bad?

Just reading again you have multiple errors, intake leaks, oil consumption.

You say 5 mechanics, like guys you paid to look at it or just five guys who looked it over real quick like? Are they carburetor guys (old school) or EFI guys (new school)? You need to call and find a guy who knows old school.

White smoke is oil, my guess bad seals on valves, bad valve guides. or worse, bad rings on pistons.

DirtDonk · Jul 27, 2010

Could be a flat cam I suppose. Was the cam changed after the engine seized, or was the older one retained? If new and a flat-tappet kind, it could have been improperly broken-in, or the lack of zinc in the modern oils just finally too their toll. If old, it could have taken some abuse from the engine seizing. Either from lack of lubrication, overheating, or too much metal gunk flowing through the oil.
That's a long shot, but certainly possible. If compression numbers seem good and consistent though, that can sometimes rule out a flat cam lobe or ten. But if the cam is flat on exhaust lobes only, compression numbers might still be high.
Worth measuring some pushrod travel anyway.

So it did it right out of the box then, so to speak? If so, then maybe the cam was wiped out immediately (due to a bad break-in) or was put in wrong, or is a different firing order and you're timing it using the wrong cylinder?
Just thinking out loud there. Merely having a different firing order (302 vs 351) won't make it un-driveable, like you describe. It'll run rough, but won't completely fall on it's face.
Timing it using the wrong cylinder could make a huge difference, but still shouldn't make it seem as if it has no power. Either it'll run lousy, or not at all. But if it runs, it should still have enough power to get up a driveway (even a steep, Colorado-mountain-pass type driveway) I would think.

Good luck.

Paul

DirtDonk · Jul 27, 2010

How about "all of the above" and just go the short-block-with-warranty route?

Paul

blubuckaroo · Jul 27, 2010

You may want to pull the timing cover off to see if the sprockets are on correctly. I've seen them put on one tooth off and run pretty poopy. Also, the timing marks might be incorrect because of a slipped harmonic balancer or incorrect pointer.

Vragor · Jul 27, 2010

Over lunch I happen to mention this project to a co-worker. Turns out he has an engine hoist and stand that he's willing to let me use for as long as I want.

Enough lollygagging! I'll pick up the hoist tonight and the engine comes out this Saturday.

Nightstick - I'll try to get you some pictures of it all.

bmc69 · Jul 27, 2010

Vragor said:
my daughter's boyfriend siezed the motor which caused the second rebuild. I still don't know what he did and her story keeps changing about what they were doing at the time.

You don't know what the 'rebuild' consisted of after it seized?..or you don't know what he did to seize the engine in the first place?..or both??:?

How do I determine if my 302 is worth rebuilding? (It wasn't, bought long block)

Jr. Member

Bronco Guru

Bronco Guru

Bronco guy

Bronco Guru

Jr. Member

Sr. Member

Bronco Guru

Grease Monkey

Bronco Guru

Bronco Guru

Bronco guy

Bronco Guru

Jr. Member

Bronco Guru

Bronco Guru

Bronco Guru

Grease Monkey

Jr. Member

Bronco Guru

Similar threads