Turbo Test Engine - Test Completed

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Turbo Test Engine - Test Completed

Post by pimpdriver » Tue Jun 14, 2011 10:11 pm

Hi
My turbo 875 test engine decided the test had run its course on Sunday at Curborough with it decided that 4 conrods are 1 too many. I just changed into second gear (after getting a bit of traction) when it all went a bit noisy and vibratory behind. It was still pulling (but not very well), so i knocked it out of gear and coasted to the escape road back to the paddock thinking i had broke the transaxle. Whilst waiting for the gate to open back to the paddock, the engine was ticking over, a bit rough and sounding like a selection of spanners in a tumble drier, but the smoke floating past made me turn the engine off.
This engine was a test engine in far as it was an 875 std bottom end with std unground crank, home made block strengthening plate and blocks with M12 studs. The pistons were standard used ones with large cutouts machined in, and the conrods were std with simple lightening and balancing and cap head std size bolts. I deliberately did not spend too much money on the bottom end as i thought that i had more chance of melting pistons and detonating things with the turbo, so built a simple cheap bottom end to see of i can get the turbo to work.
It certainly worked, 2 1/2 season of competing, with the engine producing approx 150 bhp and reving to 9000 rpm at every opportunity. Apart from a headgasket every 3 meetings at the start (now fixed with a Reinz one - been on for 12 meetings), the engine wasn't touched.
Looks like the conrod bolts failed on number four, the big bits exiting through both sides, luckily the piston top stayed in place to protect the head, just a couple of bent valves. The crank turns perfectly. just a bit battered. The exiting conrod and cap managed to smash the starter motor (luckily i know a man who can fix that) and squashed the head drain tube flat.
Any way, must get the 998 turbo engine built now, not to far away.

Oops - things not looking good
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Items recovered by the Marshals
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3 good pistons - been running well
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I thought number 3 had failed first - on closer inspection - big bits escaped there
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And here
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New game - spot the Gudgeon Pin
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Can you see it ?
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Head all-right - phew, the expensive bit - looks like just bent valves.
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Damaged starter and oil drain pipe
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Re: Turbo Test Engine - Test Completed

Post by StuartC » Tue Jun 14, 2011 10:34 pm

Bad luck Eric - or is it good luck that it lasted so long? Have you got time to get the 998 finished for Prescott? I notice they've got you down as 998 - premonition? Good luck with the re-build anyway.
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Re: Turbo Test Engine - Test Completed

Post by pimpdriver » Tue Jun 14, 2011 10:40 pm

Stuart
Yep, it was going so well, it mean't i haven't rushed getting the 998 ready. I have already cancelled Prescott as I really need to put the 998 on the rolling road to tune, as the injection i think will need tweaking. My next event after that is in August so it gives me time to get it sorted.

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Re: Turbo Test Engine - Test Completed

Post by benwick3 » Tue Jun 14, 2011 10:52 pm

A familiar sight! Now I'm not the only one rebuilding engines. Looks like typical electrical failure to me - conrod through the starter motor!

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Re: Turbo Test Engine - Test Completed

Post by Lotus-e-Clan » Wed Jun 15, 2011 12:00 am

Well it's toast alright!

If I had the resources I'd experiment with pistons with EQUAL valve cutouts. A long shot, but with forced induction i can imagine the swirling forces being very significant @ 9000 rpm to the point that there is a rotational moment on the piston top. If the valve cutouts were equal then the rotation might be reduced. I can imagine the piston twisting the rod and transfering that force to the BE.....

Voodoo and bullshit i know, but that's what I'd do next in the name of reliability. Also equal valve cut outs on a turbo means less volume increase needed in the combustion chamber to get the required reduction in static comp ratio...
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Re: Turbo Test Engine - Test Completed

Post by ChrisBenoy » Wed Jun 15, 2011 8:48 am

Well done Eric, as I think Adrian Oliver once told us, you havent blown up an engine properly till you take out the starter motor in the process :lol:

Sounds like when you get the 998 bottom end built up stronger and with ARP bolts it will be reliable and hugely powerful.
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Re: Turbo Test Engine - Test Completed

Post by ImpManiac » Wed Jun 15, 2011 5:38 pm

That's progress, Eric! :P Inasmuch as you'll need to get the 998cc motor built now. :wink: The 875cc lasted VERY well, though! :shock: Those pistons look (from your photo) like new!

Happy 998 building...

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Re: Turbo Test Engine - Test Completed

Post by Turboimp » Wed Jun 15, 2011 5:57 pm

Do you think that would have happened with standard cap bolts? I used all standard parts on my turbo engines .. i didnt go over 7000 rpm however .. does your turbo power keep on coming in a big way over 7000 rpm ?
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Re: Turbo Test Engine - Test Completed

Post by Lotus-e-Clan » Wed Jun 15, 2011 6:35 pm

I'm sure Eric will reply ...but meanwhile, yes, it smashes into the rev limiter around 9000 rpm on an R20 and wants go higher for sure. At Harewood hill climb on a shortish straight into a slow right he needed about 500 rpm more in second gear as it wasn't worth changing to third ..but he was just bouncing off the rev limiter for a second or so losing valuable time!

I was hoping Eric could show us the failed bolt to confirm it did indeed fail....but looks like it escaped completely...at least I can't see it in the pics

.Edited: spelin misttakes :roll:
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Re: Turbo Test Engine - Test Completed

Post by Meltdown » Wed Jun 15, 2011 6:56 pm

I guess it made a bolt for freedom :lol: Sorry :oops:
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Re: Turbo Test Engine - Test Completed

Post by Lotus-e-Clan » Wed Jun 15, 2011 7:07 pm

bummer! ^^^ I wish I'd thought of that one! :lol:
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Re: Turbo Test Engine - Test Completed

Post by Meltdown » Wed Jun 15, 2011 7:14 pm

Lotus-e-Clan wrote:bummer! ^^^ I wish I'd thought of that one! :lol:
You're welcome to it...I felt a bit embarrassed after I'd posted it :oops: :lol:
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Re: Turbo Test Engine - Test Completed

Post by Andy Hillman » Wed Jun 15, 2011 10:41 pm

Nice job Eric but got to say sir oliver still holds the record for the most destroyed imp engine !his engine fell in two when he unbolted the head.
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Re: Turbo Test Engine - Test Completed

Post by pimpdriver » Wed Jun 15, 2011 11:11 pm

Turboimp
Yep as Peter K says i used to take it to 9000 rpm all the time, in fact when i first got it running i was always hitting the limiter too much as it seemed to get too the red line so quickly. The power didn't seem to tail off at 9000 rpm either, i had to have the hard cut injection fuel cut limiter working as the soft cut ignition retard didn't slow it down enough in 1st and second. The engine was abused by me, considering all of the bottom end (apart from the conrod bolts) was std production Imp bits - no special comp bits, i was very impressed with it.

Peter
The cap bolt you can see in the second photo, in the selection of parts the Marshals returned, has broken where the thread stops on the rod & the sheared off thread is still in the rod. The other bolt was found in the engine, but the mating piece on the rod is missing. Definitely both conrod bolts broke, but was it cause or effect ??
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Re: Turbo Test Engine - Test Completed

Post by Lotus-e-Clan » Thu Jun 16, 2011 6:59 am

Ah I see. But like you say ..cause or effect.

The carbon pattern on No1 piston suggests some coolant leak from the right at about 3 O'clock (orientation term ,not the time of day!). No 4 seems to have has less carbon in the squish area adjacent to the valves so maybe the piston deck clearance was slightly different on number 4...ie closer clearance with less flame front penetration....or (maybe less likely) there was excess fuel-wash into that area?

A small SS grove in the squish pads to even out combustion across the entire piston top might be beneficial because even though number 2 and 3 look to have very good carbon penetration (not least due to forced induction), even these could be improved as SS grooving would set off better flame front penetration into that area....and you'd get more miles per gallon :wink:

Ok I don't expect you to take any notice of that last comment (or indeed any comment) ...and to be fair I haven't taken the head off mine to see what the carbon pattern is like since SS grooving...and hopefully I won't need to for a while yet :lol:
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Re: Turbo Test Engine - Test Completed

Post by bks974c » Thu Jun 16, 2011 8:34 am

Peter

If we ignore no 4 for the time as it has had a fairly torrid time lately. :( What makes you think the clean areas are due to steam cleaning rather than fuel wash ?

The clean areas ignoring 4 seem to graduated 1-3, is there any significance in this - one that pops into my mind is temp with no.1 getting the coldest water - distance from turbo ?

Just thought I join you sitting outside the box for a moment :lol:

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Re: Turbo Test Engine - Test Completed

Post by benwick3 » Thu Jun 16, 2011 9:04 am

Andy Hillman wrote:Nice job Eric but got to say sir oliver still holds the record for the most destroyed imp engine !his engine fell in two when he unbolted the head.
Had that happen several times. Last time at Hockenheim when also all that was left of the starter motor was the reduction gear. The rest was missing. Amazingly the crank was undamaged and straight.

The very best one was when a crank broke at the end of the Revett Straight at Snetterton - Engine in two halves and held together by the head and also the bellhousing came away from the transaxle when the engine was removed.

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Re: Turbo Test Engine - Test Completed

Post by Lotus-e-Clan » Thu Jun 16, 2011 9:36 am

Scott.
The only piston top I suspect has been steam cleaned is Number one on the three O'clock side. The resolution on my screen isn't great but it looks like there is a small nick in the top of the liner on that side as well.

The clean areas in 2 and 3 (which are the best of the carbon patterns and look pretty matched to me ) are confined to the upper squish pad area above the valves in the picture. The clean areas on Erics pistons (2&3) are relatively small compared to mine before I SS grooved, but forced induction obviously creates mega turbulence and will reach a wider area in the cylinder compared to N/A. Before SS grooving I had quite large clean areas at both squish regions ..above the valves and on t'other side of the combustion chamber....the carbon pattern on mine mirrored the std Imp combustion chamber shape...and unlike mine, Erics combustion chamber has relief around the inlet and you can see that working in his carbon pattern too.

Assuming a water tight HG, cleanness in the squish areas is definitely a sign of less flame front penetration due to low clearance @TDC ...my squish clearances are currently at the minimum 25 thou inc WR gasket. Piston crown rock @ TDC further restricts flame front penetration into the outer area of the piston ring lands and so you get unburnt fuel /fuel wash. The claimed benefit of SS grooves is that they create a jet(s) of turbulence into the squish areas on the compression stroke and then allow early flame front penetration out into the piston ring lands during combustion....hence more mpg.

Not what Eric's looking for though! :lol:
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Re: Turbo Test Engine - Test Completed

Post by voodoo » Thu Jun 16, 2011 9:59 pm

Hi Eric,

Gutted to hear about your problem's at Curborough, and the fact you will miss the meeting at Prescott.
-Was looking forward to catching up with you!

Are you aiming for Gurston?
-Be really great to see you there for the customary feast of "Ashes Donuts" :wink:

Hope the 998 build goes well!

Best wishes, Gra.
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Re: Turbo Test Engine - Test Completed

Post by Grumpyoldmen » Sun Jun 19, 2011 7:22 am

pimpdriver wrote: .......home made block strengthening plate and blocks with M12 studs........ [/img]
Can you show us how you have made it?

It's always the conrod bolts?
Can ARP bolts be found?
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Re: Turbo Test Engine - Test Completed

Post by Grumpyoldmen » Sun Jun 19, 2011 3:12 pm

I don't get this. In another tread many experts has emphasize the need for "high-end" or "special prepared" stuff when power exceed over 100bhp.
Then we have this turbo powered (150 bhp owner enthusiastically claim) engine using standard bottom end parts. OK the inevitable happened: a conrod went, but only one!! According to the law of physics the engine should have blown into small pieces as soon as the turbo pressure came to it's highest point already at the first time but the car has been used for a long period.

Lets assume it's the conrod bolts that goes ever time we have a hole in the block. The result would be to have a batch of conrod bolts made of very high quality steel. Every engine needs 8. There must be least 20 engine owners that would gladly drop the oil sump and replace the old one immediately. The cost to make 160 special made bolts is the question.
Now I expect this ideas has came into your minds long time ago, so my question is where do I find these bolts?
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Re: Turbo Test Engine - Test Completed

Post by bks974c » Sun Jun 19, 2011 3:31 pm

Eric's bottom end is basically a competition bottom end, the only upgrade might be bigger bolts in the conrods, though not all comp engines use these.
Eric comments regarding price refers to using an 875 rather than 998 until he was sure it would last, a big cost in the build would be the conversion to 998.
Eric is a very competent engineer and is happy to do a lot of machining and design so the bottom end he achieved would not be within the capabablity of most owners.

The cause of a failed conrod bolts is always difficult to pin point in that they are usually just part on the debris left in the aftermath but I think the cause is often due to partial seizure of the conrod to the crank. In the imp the common one is no 3 so Erics might have been caused by something out of the ordinary.

Scott
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Re: Turbo Test Engine - Test Completed

Post by Grumpyoldmen » Sun Jun 19, 2011 3:50 pm

bks974c wrote:Eric's bottom end is basically a competition bottom end, the only upgrade might be bigger bolts in the conrods, though not all comp engines use these.
Why not?
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Re: Turbo Test Engine - Test Completed

Post by bks974c » Sun Jun 19, 2011 4:06 pm

Grumpyoldmen wrote:
bks974c wrote:Eric's bottom end is basically a competition bottom end, the only upgrade might be bigger bolts in the conrods, though not all comp engines use these.
Why not?
Probably because some engine builders don't believe its the conrod bolts that are the cause of failure so see no point in upgrading beyound ARP bolts.

Scott
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Re: Turbo Test Engine - Test Completed

Post by Grumpyoldmen » Sun Jun 19, 2011 4:34 pm

bks974c wrote:
Grumpyoldmen wrote:
bks974c wrote:Eric's bottom end is basically a competition bottom end, the only upgrade might be bigger bolts in the conrods, though not all comp engines use these.
Why not?
Probably because some engine builders don't believe its the conrod bolts that are the cause of failure so see no point in upgrading beyound ARP bolts.

Scott
No, not beyond ARP bolts. I thought they where "this side" ARP bolts. In reality I don't know what kind of conrod bolts you have. How big can they be?
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Re: Turbo Test Engine - Test Completed

Post by pimpdriver » Sun Jun 19, 2011 5:03 pm

The thing is, power doesn't stress the conrod bolts. Under the power stroke, the piston is pushing down on the conrods, the bolts holding the big end cap on aren't really under too much stress,( although on the imp they are a bit as the joint line is at 45 degrees). Its revs that do in conrod bolts, the faster the revs, the more the piston needs pulling back at the top of each stroke - hence a lot of stress on the bolts.
When i built this engine, i didn't envisage it reving so high. An R20's max power ( normally aspirated ) is at 8200 revs. With the turbo on, the engine would still pull well upto 9000 revs, so i let it. In competition, especially hillclimbing with some very tight uphill corners and some flat out straights, gearing is everything. I have a very expensive JK 4 speed box, and the ratios are nicely spaced but 4 speeds is always a compromise. On some short straights, it was worth over reving the engine to save a gearchange.
As Scott says, some people fit ARP bolts, which are pretty much the best, but they are £70 a set. I tried to do it cheaper, using £10 worth of capheads - a mistake, but the engine had proved its worth so i'm not upset at all.
Building a competition engine is all about money, you can spend a hell of a lot of money getting the best engine built for you £10,000+ with all the best bits, billet crank, ARP bolts (every single one), custom forged pistons, custom forged rods etc, which should be powerful and reliable. Or like i have done, tried to do the best for a limited amount of money - expecting the odd blow-up on the way. The engine i just blew up cost me ( for the bottom end), approximately £200 and lasted 2.5 years. The uprated oil pump, block strengthening plate, sump, baffles etc are all reusable in another engine.
For the engine i'm building now, i'm using std conrods with 3/8" caphead bolts, mainly because I've got a set i was given. If i didn't have these, i'll probably use ARP bolts.

Eric
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Re: Turbo Test Engine - Test Completed

Post by pimpdriver » Sun Jun 19, 2011 5:09 pm

Scott
I've been stripping the engine right down today and there is no evidence of the rod seizing to the crank, all the bearings are in good condition (those that are left) and the rod bits have no blueing (overheating) on them. As you say its usually number three that goes in that situation, because of the shared oil supply with number two.
I must conclude ( CSI style), that the bolts failed.

At least its proved my sump baffles work anyway.

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Re: Turbo Test Engine - Test Completed

Post by bks974c » Sun Jun 19, 2011 6:31 pm

Eric

Your last posting got me thinking so I've just gone and looked at an engine I'm currently rebuilding, I don't have any expertise in this area so I'm only thinking aloud. :?

I rotated the crank and observed the conrod, it looks like the reason for the angled cap/rod is the loads on the bolts are sideway which are assisted by the serrations on the cap and rod in resisting movement.

If the rods or piston stopped moving even for fraction of a second that would be enough for the loads to change from sideways (compression ?) to vertical (tension ?) and cause failure.

Since it would only need to stop/slow for a fraction of second to overload the bolt would there necessarily be any blueing ? Is there any sign of the piston picking up ?

Scott
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Re: Turbo Test Engine - Test Completed

Post by cov_climax » Sun Jun 19, 2011 7:18 pm

main reason for the 45 degree split is to get them down the bores (especially on an 875), to my mind the bolts are only really in tension on the inlet stroke, and being forced induction in Eric's case they're actually getting an easier ride.

i'll throw in another consideration: with the change in bolt quality/size you use higher torques to exploit them fully, it's worth assembling the rods on the bench and torquing them to the build value then measuring the big end bore to check that the increased clamping force hasn't ovalised them,

anyway nice one Eric, looking forward to hearing how the 998 goes :D . give me a shout if you're stuck for any bits off standard engines
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Re: Turbo Test Engine - Test Completed

Post by Lotus-e-Clan » Sun Jun 19, 2011 7:47 pm

I agree with Brian.

I use the std torque 18 lb/ft on my rod bolts even thought they are uprated and would easily take 40 lbft. I tried higher torques (25lbft) and got slight binding on rotation.

So the torque figure probably does have an impact on cap to rod ovality...if those serrations were engineered perfect and allowed no movement/slide then you could torque to the max of a particular bolt spec..but the cap would need perfect location..which the std Imp serrations don't have.
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Re: Turbo Test Engine - Test Completed

Post by bks974c » Sun Jun 19, 2011 7:52 pm

cov_climax wrote:main reason for the 45 degree split is to get them down the bores (especially on an 875),
Good shout on that one 70mm into 68 would'nt go :wink:

Trying to imagine what the effect of straight rods and caps would have, it looks like the angle of the imp might be better in keeping the loads sideways - is that is better ?

Scott
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Re: Turbo Test Engine - Test Completed

Post by Grumpyoldmen » Sun Jun 19, 2011 8:09 pm

How often do you experience crankshaft breaking into two pieces?
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Re: Turbo Test Engine - Test Completed

Post by ChrisBenoy » Sun Jun 19, 2011 9:38 pm

I've seen a couple.

Also seen straight rods and caps and they seem to do fine 8)
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Re: Turbo Test Engine - Test Completed

Post by onomatopoeia » Mon Jun 20, 2011 10:19 pm

Grumpyoldmen wrote:How often do you experience crankshaft breaking into two pieces?
I've seen one. Just after I bought my first Imp (20 years ago :shock: ) and turned up in Dashwood Avenue in High Wycombe with a big list of parts that I needed there was an Imp crank in two pieces sitting on Malcolm's workbench.
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Re: Turbo Test Engine - Test Completed

Post by Meltdown » Tue Jun 21, 2011 5:08 am

onomatopoeia wrote:
Grumpyoldmen wrote:How often do you experience crankshaft breaking into two pieces?
I've seen one. Just after I bought my first Imp (20 years ago :shock: ) and turned up in Dashwood Avenue in High Wycombe with a big list of parts that I needed there was an Imp crank in two pieces sitting on Malcolm's workbench.
Malc's never dared argue with Joyce about going shopping since :lol:
Do me a deal? Employ me for 3 days and pay me for what I'm currently being paid for 5, then I'll have time to do everything!
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Re: Turbo Test Engine - Test Completed

Post by Grumpyoldmen » Tue Jun 21, 2011 7:25 am

But the crankshaft is not considered as a weak link in the chain of "survival".??
The standard conrod bolt looks very tiny. What is the size of special made bolt?
http://historicracing-photo.blogspot.se/
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Re: Turbo Test Engine - Test Completed

Post by ImpManiac » Tue Jun 21, 2011 10:04 am

Grumpyoldmen wrote:The standard conrod bolt looks very tiny. What is the size of special made bolt?
I think the ones I ordered were THESE (CLICK HERE). It is not the size that counts so much as the material grade and quality and the manufacturing process. For example, cold worked steel can be tougher than hot worked. ROLLED THREADS (CLICK HERE) invariably lead to a stronger fastener, which is why "expensive" fasteners tend to use them.

It's all about the quality of the components you use. But it's also all about using them correctly. :!: Note on the Burton Power page about the ARP bolts the torque settings, both with ARP assembly lubricant and with engine oil. Torque is critical to getting the full benefit of the fasteners. The cyclical loading on connecting rod (big end) bolts is often referred to as fatigue and the much greater preloading on the ARP bolts (higher torque setting) tends to reduce the effective fluctuating component of the cyclical load, greatly reducing the probability of fatigue-induced failure.

WIKIPEDIA ON FATIGUE IN MATERIALS (CLICK HERE).

:D

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Re: Turbo Test Engine - Test Completed

Post by bks974c » Tue Jun 21, 2011 10:15 am

[quote="Grumpyoldmen"]But the crankshaft is not considered as a weak link in the chain of "survival".??
The standard conrod bolt looks very tiny. What is the size of special made bolt?[/quote]

The upgrade in size is redrilling the rod and cap to take a 3/8 bolt rather than 5/16 with the option of upgrading the quality of the bolt.

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Re: Turbo Test Engine - Test Completed

Post by Grumpyoldmen » Tue Jun 21, 2011 10:35 am

ImpManiac wrote:
Grumpyoldmen wrote:The standard conrod bolt looks very tiny. What is the size of special made bolt?
I think the ones I ordered were THESE (CLICK HERE). It is not the size that counts so much as the material grade and quality and the manufacturing process. For example, cold worked steel can be tougher than hot worked. ROLLED THREADS (CLICK HERE) invariably lead to a stronger fastener, which is why "expensive" fasteners tend to use them.

It's all about the quality of the components you use. But it's also all about using them correctly. :!: Note on the Burton Power page about the ARP bolts the torque settings, both with ARP assembly lubricant and with engine oil. Torque is critical to getting the full benefit of the fasteners. The cyclical loading on connecting rod (big end) bolts is often referred to as fatigue and the much greater preloading on the ARP bolts (higher torque setting) tends to reduce the effective fluctuating component of the cyclical load, greatly reducing the probability of fatigue-induced failure.

WIKIPEDIA ON FATIGUE IN MATERIALS (CLICK HERE).

:D
IM 8)

I understand this very well as I am a mechanical engineer.
The ARP bolts looks super! As if I have design them myself!! 8) Give me 8 of them!!
http://historicracing-photo.blogspot.se/
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Re: Turbo Test Engine - Test Completed

Post by KiwiHusky » Tue Jun 21, 2011 10:38 am

benwick3 wrote:A familiar sight! Now I'm not the only one rebuilding engines. Looks like typical electrical failure to me - conrod through the starter motor!

Pete Richards

That's a euphemism for "blown engine" that the ferrari GP team used in the 50's!! :lol:
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