302 failure - any opinions???

[Mike Pass]

Maybe invest in a rev limiter. It won't protect against a wrong gear change or dropping a gear too soon but willl save a lead foot overrev.
I have been told that because most of these motors are externally balanced they can suffer crank whip at high revs (over 6,500rpm) which knocks out the centre main and tapers the end mains. Not sure if this happened in your case - is you rev counter accurate? However sorry to hear about your fun being spoiled - I hope there is not too much mashed. If you need it I have a spare standard crank you can have for nothing but I would guess you want a steel one now!
Cheers
Mike

 

[Jac Mac]

Extra oil feed line goes to gallery plug that is closest to main bearing bore at rear of block.
Also when having your crank assy balanced find a shop with a late model Sunnen DCB balancer or one of equivalent accuracy and ask around to ensure they have a good man operating it!

Jac Mac

 

[Mike Pass]

Another thought. If you are using an original GT40 style sump then there may be an issue with oil pick up. The genuine GT40 sumps are less deep than normal and if you use a standard oil pickup there may not be enough clearance for the oil to be picked up well and when you are reving the engine you may not get enough flow to the pump to feed the bearings. When you get the sump off check the gap between the oil pickup and the sump.
Cheers
Mike

 

[Gordon Levy]

It is definately a bearing and definately oil related.
You stated that you went out at 40psi of oil pressure. I'm assuming the engine was not fully heated up. This is about 15psi to low for a wet sump track engine A safe rule is 20 psi hot at an idle and 5 psi added for every 1000 revs. 50 psi hot at higher revs is what I tend to look for.
You also stated that the pressure dropped the longer you were in the session. This is obvious oil temp issues. Do you have a cooler in the car? What was your oil temp doing? What type of oil where you using? Pulling the dip stick and smelling the oil, does it smell burnt?
Without a cooler of some sorts, running a 30 minute session and using off the shelf detergent oil can cause the bearings to self destruct. Most detergent oils loose their ability to oil properly at over 280 degrees. At 300-320 degrees it starts to remove babbet from the bearings.
The heat combined with the low pressure will tear the bottom end out of the engine.
You are definately needed a rebuild. Please take the extra precautions of setting up the engine correctly for track use if you plan on continuing to use the car this way.

This is opinion based on the limited information presented.

 

[Frank Catt]

Talking of engine problems, how would you like this one ?

 

[Keith]

Aluminium rod? 1/4 mile motor perhaps? ....

 

[Gordon Levy]

Frank, that one looks like serious Detenation. The crank broke first and took the rod with it.
Drag race engine I'm assuming.

 

[Paul Thompson 'Hooligan']

Frank - Was Stephanie at the wheel? - A lot lot braver than me!!

 

[Russ Noble]

Frank, that one looks like serious Detenation. The crank broke first and took the rod with it.
Drag race engine I'm assuming.

OK Gordon, I'm keen to learn. How did you diagnose detonation?

 

[Gordon Levy]

Russ, The way the crank it broken and the rod was pulled apart, not snapped.
It also could be from hydraulicing the engine. Both would cause a faily clean break like that.

 

[Frank Catt]

Dodge Avenger methanol Funny Car 3000 hp Keith Black Chrysler Hemi, Santa Pod raceway, England. Driven by Stephanie Milam ( 50 year old housewife ) Engine grenaded at 203 mph and lifted the car 4 feet into the air. Steph kept it as straight as possible and did not destroy the car, but the bit of engine in the picture was one of the few larger pieces found.

 

[speed220mph]

Julian: The knock you heard was probably the piston striking the bottom of the head. Once the bearing is out of there, the piston moves up farther in the bore, eating up deck clearance. Oil pressure, once it burps for an instant, the rod bearings go first. We had this happen on a 302 in a Group 7 McLaren. We were spinning it up to 9,000 rpm when the oil-filter seal blew out. It actually blued the big end of the rod. We turned the crank 0.010 under and reused it. Only the rod and piston needed replacing. Chances are your crank is okay, but it should be checked for straightness. Also check the mains to make sure they are still straight.

Check the picture. This is a Carrillo rod we just pulled out of a 351. The bearing had standard oil clearances and the engine wasn't turning over 8,500 rpm when the bearing grabbed the journal and broke the cap bolts. The cause was super low viscosity oil being used for qualifying. Squeezed out the oil under load and it was metal to metal . . . bang. The crank is being reused, but the rod and piston is junk.

 

[Julian West]

Speed220,

THx for the info. I'm part way thru pulling the motor out & hope to have it in the engine shop soon.

I'd be really interested to know what spec bottom end would be required to cope with higher revs, ie more than 6000 but probably not as much as 8000!!!!

regds,

 

[Julian West]

The cause was super low viscosity oil being used for qualifying. Squeezed out the oil under load and it was metal to metal . . . bang. The crank is being reused, but the rod and piston is junk.

Just a thought, the oil I was using was Mobil 15W-50 fully synthetic.... would this be related??

Regds,

 

[Ross Nicol]

The engine in my race car at the moment has a standard(cast) crank and rods with ARP fasteners, even has hydraulic lifters. I rev it to 6500+ while racing and it has not failed. It has done at least 2 years service with no problems.I use Castrol mineral oil. I have been warned off Synthetics by A competent V8 engine Guru.I believe a dry sump is the only way to go for track work.
Ross

 

[Gordon Levy]

Julian, I believe the whole problem was low oil pressure. It wouldn't matter what oil was used. The pressure was not enough to protect the friction surface of the bearing and it eat itself.
I would be happy to answer any specific questions you may have. Please feel free to ask.

 

[speed220mph]

Just a thought, the oil I was using was Mobil 15W-50 fully synthetic.... would this be related??

Regds,

Julian: Don't think the type of oil you were using had anything to do with it, but more the lack of oil. You mentioned over revving, but that would have more impact--pardon the pun--on the valves. You didn't mention whether you were cornering when this occurred. But if you were hard in a turn, could be the oil moved away from the pickup for an instant, which could be enough to starve the oiling system long enough to cause a pressure drop at the rod bearing. That's why I over-fill with oil before rolling out on the track.

This is problem plagued us in the early TransAm days. The Boss engines had plenty of power, but at high rpm and cornering g caused oil starvation because were required to use wet-sump systems. The result was frequently the same failure as your engine experienced.

A cure short of going wet sump is to install an Accusump. Coated bearings are another insurance policy. My $0.02 worth.

I hope my ramblings help.

Tom

 

[Howard Jones]

These hyd roller lifter 302's will live longer, run better lap times, and in general work as designed if you shift them at something like 5600 -5800 revs. Even with a complete upgrade of the valve train, roller rockers, valve springs, pushrods, the works and a cam that will work for you above 6K, you will still be shifting atwell below 6500 in a hyd lifter motor.

With the exception of top gear and a long straight their just isn't a need to rev them much higher than 6K anyway.

Now on the other hand. If you are talking a solid roller cam engine, forged internals, with racegas compression ratios and first rate heads, then the skys the limmit $$$$$$$$$$$$$.

The main points of your rebuild should be, use ARP rod bolts, really get the clearances right, and have the engine rotating assembly and it's external parts, dampner, pulley, crank, clutch, as close as possible to a perfect ballance job as you can. After that, the first upgrade I would do is a set of quality valve springs and cam. You will still be at or below 6K revs but the idea is to get the power to continue building beyond 5400 or so where these FMS crate engines run out of steam and up to 5900ish. These are practical revs limmits (long useful reliable live) for the cast cranks, stock rods and production cast ports in FMS heads such as the XB303 that are used on a lot of the Ford crate motors.

 

[Ross Nicol]

Howard did you read my post above? Can't agree with you on hyd lifter/rev limit and I've raced this motor a lot.It's only back in my car temporarily because I destroyed the real race motor.
Spec of current 302
-------------------
Block- 2 bolt main-source: mid 80s Mustang-modified for dry sump
Crank- 50oz ext balance (original cast unit)
Rods-Original cast (weight balanced)
Pistons- +20 thou hypereutectic
Cam-FMS B303
Lifters- Hyd Roller
Push Rod-Chrome moly
Rockers- Yella Terra Rollers 1.6 ratio
Heads- FMS X303 Heavier valve springs fitted, 10:1 Comp
Manifold-DC&O 8 stack
Motec injection
100 octane ULP pump fuel
----------------------------
If I could turn better lap times by changing at 5800 instead of 6500 I would have been doing it at last weekends race meeting.I will admit there is not much after 6500 but it climbs to that point very well.I'm very impressed with this motor and it's performance/cost ratio.
Ross

 

[Mike Drew]

Jools,

Providence has smiled upon you in the form of a grenaded engine.

I'm far from an expert compared to many on this board, but I would agree with the general concensus that you should view this as opportunity to go through the entire engine from front to back, top to bottom. Anything that could be touched by metal bits (including things like your oil pump) is now trash.

You could try to piece together a new bottom end by shopping through the Summit catalog for this piston, that rod, those bearings etc., but for my 331-inch stroker, I went with a complete kit from Coast High Performance. I didn't buy their assembled short block, as I'd heard that their assembly standards might not be all that you would hope for, but the individual kits are said to be of good quality.

CHP - We Build Horsepower!

Note that they come in several di$tinct flavors; I have the Street Fighter Pro Street, which should be perfect for your application too.

The more displacement you have, the more bottom-end torque you'll have, and the less RPM you'll be able to turn safely. The 331-inch option was reckoned to be the ideal compromise between bottom-end torque and high rpm power.

What kind of cam are you running? Maybe you should hope that it's trashed too so you can buy a new one.

And then there's the rocker arms, pushrods, aluminum heads, etc. etc. etc.

The possibilities are endless, and with the dollar continuing in free-fall vs. the UK pound, within weeks all this stuff will be practically free for you!