Removal and rebuilding of a Twincam

[h20hamelan]

I think oems use them because the are faster for production, Ive never heard of a modern production line trying to fit washers.
While both points have merit, if the neck of the bolt and the opening of the washer are exact.
The main reason for washers is even load distribution (many of my trucks have free washers locked in the wheel nuts), as a flanged bolt head can work into the caps.

[rgh0]

I am not an OEM running a high volume automated engine assembly line. This is why flange headed bolts and flanged nuts were invented as managing washers on an automated assembly line is a hassle.

Washers of various types still have their place and are cheaper than converting things like the main cap bolts to ARP flange bolts.

For con rods and cylinder heads I will use the best available as these connections are what gives you problems in a race engine but for other bolts it is not really necessary IMHO

cheers
Rohan

[2cams70]

Washers actually compromise the integrity of the joint in a lot of circumstances. Flange bolts are a much better solution from both a production and design engineering standpoint.

[rgh0]

Another photo of the socket headed bolts and hardened steel washers on the square cast iron caps. As you can see from this angle the size difference between the washer and machined boss on the cap is small. In this instance a hardened steel washer under a socket headed bolt is the best solution IMHO. But if you're building a road engine the original ford bolting is fine (if you can find them) or using ARP bolts also fine if you don't mind the cost.

To some degree its engineering judgement as what is the best solution as many factors at play. This is why just buying what come from the usual suppliers, or following internet advice is a challenge as the factors require mature engineering analysis and judgement for the specific circumstances under consideration

i.e.
bolts strength
bolt stretch
bolt torque versus stretch repeatability
bolt elasticity
joint elasticity
cap material hardness
cap material strength
cap material ductility
washer hardness
bolt hardness
joint dynamic loading
bolt head radius
washer radius under the head
cost

No easy answer..... sorry.....
In the end you build it and it works... or it does not work and you build it again

cheers
Rohan

[rgh0]

Continued with the rebuild, you make progress when you don't have to go to work due to Christmas holidays.

Checked the oil gallery cleanliness and fitted the gallery plugs. Ensure you use the correct NPT tapered plugs. Plugs that are go in to far can block the bearing oil supply branches that come off the main oil galleries or plugs that don't go in far enough can cause problems fouling the front cover. I use Loctite Teflon anaerobic pipe thread sealant

Next fitted the jack shaft. I use a shortened steel shaft. The new bearings were a little tight on the shaft. Measurements of bearing bore versus journal diameter said I had the correct clearance so nothing major wrong, so I mounted the shaft in the lathe to polish it's journals with 1200 grit paper to increase the clearance a little which freed it up nicely.

Finally checked all the front cover components for cleanliness. I decide to not pull the water pump apart as the bearing is fine and only 3 years racing use, so the seal is not worn, in the end I decided a greater chance of failure with a new assembly than with this one that I know works. The water pump is one of the few things I find that does not suffer in a race engine.

I try to do the front cover assembly as one exercise with minimal delays as lots of joins that have to seal and critical alignments to set, so I get it all ready and then do a trial assembly so it can all be done smoothly in about 1 hour. You can see (bottom right) the alignment tool I use that fits the front cover seal diameter to the crank nose diameter so the seal is correctly aligned when it is fitted later after everything is bolted up

cheers
Rohan

[englishmaninwales]

...Checked the oil gallery cleanliness and fitted the gallery plugs. Ensure you use the correct NPT tapered plugs. Plugs that are go in to far can block the bearing oil supply branches that come off the main oil galleries or plugs that don't go in far enough can cause problems fouling the front cover.....

Yes, beware if using Burton’s after market back plate, I found the recess was just not quite deep enough for a correctly fitting front NPT gallery plug and the backplate required fettling (although may, of course, vary from casting to casting).
Malcolm

[1owner69Elan]

Final note on the sub-topic of main bearing cap bolts. For completeness, a view of the ARP flanged bolts and washers as installed.

[2cams70]

Next fitted the jack shaft. I use a shortened steel shaft. The new bearings were a little tight on the shaft. Measurements of bearing bore versus journal diameter said I had the correct clearance so nothing major wrong, so I mounted the shaft in the lathe to polish it's journals with 1200 grit paper to increase the clearance a little which freed it up nicely

I'm not sure where you sourced your jackshaft from but beware beware! You can find that the pattern ones are bent. If you check the end float clearance to the thrust plate you can get a variation around the circumference of up to .002". Also I've found that the steel (as opposed to the standard type) thrust plates you can source through the usual suspects are much better at keeping the end float to the smaller end of the allowable tolerance for better control of ignition timing - i.e to around .002" instead of the usual .006" when using the standard type

[StressCraxx]

Hello Rohan,

How did you plug the oil supply to the #3 jackshaft bearing?

Thanks,
Dan

[rgh0]

Hi Dan

I just rotate the jackshaft No.3 bearing shell to block off the oil feed hole.

cheers
Rohan

[rgh0]

Next fitted the jack shaft. I use a shortened steel shaft. The new bearings were a little tight on the shaft. Measurements of bearing bore versus journal diameter said I had the correct clearance so nothing major wrong, so I mounted the shaft in the lathe to polish it's journals with 1200 grit paper to increase the clearance a little which freed it up nicely

I'm not sure where you sourced your jackshaft from but beware beware! You can find that the pattern ones are bent. If you check the end float clearance to the thrust plate you can get a variation around the circumference of up to .002". Also I've found that the steel (as opposed to the standard type) thrust plates you can source through the usual suspects are much better at keeping the end float to the smaller end of the allowable tolerance for better control of ignition timing - i.e to around .002" instead of the usual .006" when using the standard type

End float between 0.004" and 0.005" using an original locating plate with no measurable wear, which is in the lower middle of the specification so good. Variation of less than 0.0005" by feel with the feeler gauges ( no pun intended ) So shaft and end flange appears straight and at right angles.

cheers
Rohan

[rgh0]

...Checked the oil gallery cleanliness and fitted the gallery plugs. Ensure you use the correct NPT tapered plugs. Plugs that are go in to far can block the bearing oil supply branches that come off the main oil galleries or plugs that don't go in far enough can cause problems fouling the front cover.....

Yes, beware if using Burton’s after market back plate, I found the recess was just not quite deep enough for a correctly fitting front NPT gallery plug and the backplate required fettling (although may, of course, vary from casting to casting).
Malcolm

The cover and back plate I am using were new from SJS 3 years ago. I presume they all come from the same source. The back plate hole depth was Ok with the recess for the plug but the alignment was a bit off so I need to fettle the side of the hole a little to get clearance to align the bolts and front cover with the crank at the seal.

cheers
Rohan

[rgh0]

Time to fit the front cover onto the block.

Paper gasket with Loctite aviation gasket sealant between block and back plate. I locate the backed plate with bolts through to the block while tightening the central clamping bolt.

Fitted the jack shaft chain sprocket and chain and Loctite 518 on the metal to metal join between backplate and front cover. The oil slinger is in place on the crank also.

Positioning and bolting up the front cover, note centralising tool that fits the crank and holds the front cover oil seal location central versus the crank. I also put a very thin smear of silicone sealant where the
water pump spacer inserts into the back cover to give a double seal of silicone plus the spacer o-ring. This also helps prevent the spacer corroding into the back plate and make removal easier later.

Fitted front oil seal into cover. The centralising tool also makes the ideal drift of perfect diameter to tap the seal into place.

The three lower RHS front cover bolts that screw into the block are drilled so they can be wired and a seal attached by my racing class eligibility officer verifying the engine capacity when he measures it in a couple of days time before I put the head on.

cheers
Rohan

cheers
Rohan

[rgh0]

Time to fit the flywheel and clutch assembly. I clean off the anti corrosion sealant I had applied to the face of the flywheel and pressure plate. Despite 3 years of racing use the original machining marks still on the flywheel

The flywheel is a lightweight steel version with 5 bolts to suit the converted Datsun L16 crank. I use the original Datsun flywheel bolts shortened a few millimetres to suit the depth of the holes in the modified crank. I lock the flywheel with a toothed tool that bolts to the block so I can apply the 60 ft-lbs for the Datsun flywheel bolts

I use a heavy duty AP clutch pressure plate and an Exedy heavy duty clutch plate. A centralising tool ensures the clutch plate is correctly aligned with the spigot bearing in the end of the crank. This combination works well and can handle the engines power and torque and repeated drop the clutch racing starts while being very easy to drive with smooth engagement.

A few other final bits added to the block, dizzy clamp, oil tapping adapter, fuel pump cover, block coolant drain plug. It just now needs the head on and then the oil pump and sump which I will do next weekend once the engine is measured and sealed. I always put the sump on last as always some risk of dropping things down the front cover when fitting the head

cheers
Rohan

[gjz30075]

Rohan, I like that flywheel locking tool. Made? or obtained from?