Removal and rebuilding of a Twincam

[rgh0]

Got started on the crankshaft and block assembly and installation today. It is always fun putting stuff back together... especially when it all fits and measures as planned


Fitted middle and front jackshaft / cam bearing, the rear did not need changing as I use a short jack shaft and the rear bearing is installed and turned to just block off the oil passage. I have machined a simple "special tool" made from heavy wall pipe that makes fitting the bearings easy as it fits in the bearing and picks up the tapered end cleanly while still fitting through the block bore. This enables bearing to be fitted and driven out also without damage

Fitted sprocket on front of crank and GB input shaft spigot bearing at the rear. Spigot bearing HK1514RS just A$10 from local industrial bearing supplier and made by Koyo ( a Japanese OEM supplier) in Germany. Used the old bearing to drift the new one into place

Fitted 2 off 0.075 thou oversize thrust bearings as required by the Datsun crank thrust spacing. This gave an end float of 0.13mm versus specification of 0.06 to 0.19mm so spot on. Std and 0.05 thrust bearings readily available and currently made by ACL and others but other sizes i.e. 0.025, 0.075, 0.010 not so easy to find . I got a fresh supply from Burtons who have these currently in limited stock. The ones I got from Burton look like NOS Ford / Vandevell.

Cleaned the crank oil passages and fitted the plugs with Loctite. The Datsun crank originally had solid plugs so these drilled and tapped to fit.

Fitted the bearings in the block. 10 thou undersize ACL race series bearings. I number the bearings by scribing in the oil groove so they can go back in the same place during any future rebuild if required.

to be continued... came to photo limit in a post

cheers
Rohan

[rgh0]

Trial fitted main caps and measure bearing clearances with ACL "flexigauge" called "plastigauge" by other manufacturers. Clearance as planned at middle of range for 10 thou undersize main journals at 0.05 to 0.06mm versus spec of 0.04 to 0.08mm. The white mark on the crank and bearing is the squashed flexigauge material after the bearing is trial fitted. The width of the squashed material and hence the bearing clearance is measured versus the chart that come with the test

Fitted bearings and use Redline assembly lube and then fitted main caps and torqued to 65 ft-lbs, using Unbrako socket head bolts with hardened steel washers and I go a little above a little above the factory torque specification of 55 to 60b ft-lbs

It put the oil thrower on the crank and tape in place so I don't forget it when fitting the front cover...... been there, done that

enough for today, maybe back to the gearbox tomorrow.

cheers
Rohan

[alan.barker]

For the assembly of bearing shells i have used STP in the past but some like saint Wilkins use Graphogen.
Alan

[englishmaninwales]

For the assembly of bearing shells i have used STP in the past but some like saint Wilkins use Graphogen.
Alan

Any feedback on Miller’s Assembly Lube, or are they all as good as each other?
(Apologies Rohan for the hijack....Very interesting thread).
Malcolm

[rgh0]

I am sure they all work. I use Redline as I think they have some of the best modern lube technology.

cheers
Rohan

[rgh0]

Finally back to the engine having finished my gear box rebuild.

Next up is fitting the crank rear seal. The holes is the block are blind and standard length bolts can bottom out without properly clamping the seal housing so check the bolts your using have clearance to the hole bottom when tightened.

New seal fitted in housing. I use a little high temperature silicone sealant on the outside. Its a finger push in except for the last few millimetres where I gently tap it into place with a drift

Gasket coated one side with aviation gasket cement. place in correct position on block and seal carrier coated also and placed on top.

The seal normally does a good job of centring the carrier on the crank but I check it to ensure clearance is the same all round and it is correctly centred before torqueing down the bolts.

All done and bolts torqued down.

next step are gallery plugs and then pistons... to be continued

cheers
Rohan

[rgh0]

The old pistons and rings and bore were all in good condition so just the new rods fitted (see previous post in this thread). ready to go with a new set of 20 thou undersize rod bearings to match the reground crank.

Two essential tools -- a ring compressor and a stretch dial gauge.

I spray the piston and bore with WD-40 for assembly and compress the rings and then tap the piston into the bore with a hammer handle while ensuring the compressor is held hard against the top of the block. You don't need to hit it hard and if it stops moving don't hit it harder as the ring has probably caught on the top of the bore. Pull it out and start again.

I use ACL flexigauge ( AKA plastigauge) to double check the bearing clearances which came out as expected at 0.002" or 0.05 mm

Assemble the conrod bearing caps with assembly lube

Use the stretch gauge to get the right bolt stretch. The specification range for the Carrillo rods bolts I am using is 0.0050" to 0.0065". I find the specified "normal" Carrillo bolt torque of 55 ft-lbs of torque gets me right in the middle of the stretch range at 0.0055" to 0.0060" using the Carrillo supplied bolt lube.

I also measure and record the unstretched bolt length so I can check it later if the bolt is ever removed to see if the bolt has a permanent stretch at all. More than 0.001 inch and the bolt needs to be replaced.

Rods all assembled on the crank

As part of this build I noticed an issue that I have never seen before.... you always learn when you look at the details . I also went back and checked a number of used rod assemblies with Carrillo and ARP bolts and I have missed this issue for the last 30 years!!!!

The Carrillo supplied WMC H6 rods bolts are 1.600 inch Under Head Length with 0.600 in thread length.
All the "normal" suppliers specify 1.500 inch UHL with 0.550 inch thread length ARP bolts for "competition steel rods". These appear to not be the right bolts for at least Carrillo rods. ARP has the rod bolts in three different UHL i.e. 1.500, 1.600 and 1.750 inch ( for original 125E rods). The ARP kit 200-6209 has the correct 1.600" UHL bolts for use with Carrillo rods. With the Carrillo rods you also do not use the washer supplied by ARP as this shortens the bolt thread engagement and is not needed as the Carrillo rods have the right bolt head radius on the rod itself. If you use the 1.500 inch ARP bolts the thread crosses the join in the rod to cap which is not ideal

cheers
Rohan

[rgh0]

A photo of the 1.6 inch Under Head Length original Carrillo supplied WMC H6 bolts for Carrillo rods on the left versus the usual suppliers 1.5 inch UHL ARP 2000 bolt on the right.

The 1.6 inch bolts thread is fully engage in the rod thread with the plain shank crossing the join line which is the optimum design. The 1.5 inch ARP bolts have thread outside the rod thread and almost on the join line without the supplied washer or on the join line if the washer is used, they appear to have worked OK, as thousands of engines must have been built with them, but its not ideal IMHO and potentially the cause for the spun rod bearing in my engine that started this rebuild

ARP supply 1.6 inch bolts but the usual suppliers don't carry them. Its worthwhile chasing up the right bolts. 1/10 of an inch makes a real difference in something as critical as rods bolts in a 9000+ rpm engine.

Maybe it is only the Carrillo rods with the need for 1.6 inch bolts and others like Saenz, Arrow, Cosworth etc actually are designed for 1.5 inch rod bolts. I have always used Carrillo rods and never measured up in detail any others.

cheers
Rohan

[gav]

Hi Rohan

Been catching up on what is a fascinating read. I'm not an engineer so reading about the finesses is really helpful to understand some of the issues that are experienced on an engine that has to endure such a hard life.

I have a question relating to the earlier portion of your article which may appear a little mundane but I think is really important - what do you use to clean components and how do you satisfy yourself that you have removed everything?

Thanks for spending the time writing such an involved article. It is really appreciated.

All the best
Gavin

[rgh0]

Hi Gavin

I normally clean everything with solvent degreaser twice, once with fluid that gets very dirty and then a second time with fresh clean fluid. A close visual inspection and a "white rag" test tells me if I have got it clean enough. A white rag test is rub it with a white rage and if the rag stays clean then the part is clean. I then normally spray with WD-40 and store in closed containers until it time to reassemble at which point I will wipe clean the critical surfaces again and where needed lubricate appropriately.

cheers
Rohan

[1owner69Elan]

Be interested to get your comments on your use of the round cap socket screws paired with larger OD washers vs the ARP 12-pt bolts with the head tapered section closely matching the washer/cap surface as shown in the picture below.

In your application a good portion of the outside annulus of the hardened washer is not loaded, and in places also extends beyond the bearing cap surface.

Rohan main caps 2.jpg (74.99 KiB) Viewed 575 times

Perhaps not a big effect but notionally seems it might result in an uneven loading on the cap or distortion over time? Seemingly, the ARP application would provide a more robust and consistent loading on the bearing cap. But, again, perhaps not a large effect.

Also, I understand the use of the socket head bolts when you had a counter-bore in the bearing caps.

Rohan Main Cap Screws.jpg (90.59 KiB) Viewed 575 times

With an external head and no clearance issues wondering about your reasoning in still using a socket head.

Always interested to learn and appreciate your great attention to detail. Your discussion on the rod bolt lengths for various rods was illuminating.

[rgh0]

I guess its to some degree not changing something that works. As you can see from the photos I have two racing blocks currently. One setup with steel main caps that have countersunk bolts and one with the square cast main caps. I use the same socket headed bolts for both. I have not gone to ARP bolts or studs in this application as the bolt loads are relatively low in comparison to other applications such as rod bolts, so no real need to spend the extra money on extremely good but very expensive bolts. On the cast iron cap I used a standard hardened steel washer that fitted in order to spread the load from the relatively small head of the socket headed bolt to the full diameter of the machined boss on the cap. The excess metal does not interfere with any part of the unmachined top of the cap as the machined boss is slightly above the rest of the cap surface so I saw no need to machine it down to the boss diameter.

And yes I know Colin would not have approved and would have wanted to use the minimum diameter washer possible to save weight and cost

cheers
Rohan

[2cams70]

Most OEMS use flanged bolts these days and not washers. This article explains why.

https://www.boltscience.com/pages/why-use-washers.pdf

[StressCraxx]

The 12point Carillo and ARP bolts have a radiused circumference under the flange and a necked grip. At assembly it is vital the bolts do not sit proud off the ground cap surface. There must be enough relief or clearance in the cap holes so the radius does not contact the inside of the hole. If contact of the radius is made with the edge of the hole, rapid bolt failure will occur from the resulting stress raiser.

Washers are often used with these types of bolts in other applications. The washers are radiused on one side to accommodate the radius under the bolt head.

Carroll Smith's book Nuts, Bolts, Fasteners and Plumbing is nearly an engineering class on the subject of the bolted joint and well worth the read.

[2cams70]

Carroll Smith's book Nuts, Bolts, Fasteners and Plumbing is nearly an engineering class on the subject of the bolted joint and well worth the read.

Time moves on and methods improve. OEMS don't use washers these days.