Removal and rebuilding of a Twincam

[nmauduit]

thank you for sharing your thoughts and work.

I would sure follow just as closely as this thread the rebuild of a gearbox with Quaife inards, as the original gearbox of my GTS project is the standard 2.5 helical which I would not feel confident to heavily pull on...
I have on the back shelf used Quaife parts from 2 sets to go over and trying to make one good set, eventually to replace by a better one if all turns out well and keep as a spare.

[rgh0]

When I get the needed parts delivered by TTR I will try to document the rebuild of one of my spare boxes with the new components. Hopefully what I need to reuse from the old box which is essentially the casings, synchro clusters and shift mechanism will be OK . I have a couple of old boxes and parts left over from other rebuilds so i should be able to sort whats needed without resorting back to the credit card and long delivery times I hope:D

cheers
Rohan

[rgh0]

Got a present today from my crankshaft rebuilder Nicely delivered in a wooden box in a covid safe manner to my door as I could not go and collect it during the current lockdown in Melbourne

Looking at it after removal from the box it has been refurbished perfectly - crack tested, straightened, reground and polished journals and reheat treated and rebalanced. Ground the journals to 10 under on mains and 20 thou under on big ends to remove the damage from the bearing failure and partial seizing. These Datsun L16 forged cranks are very tough. For $50 from wreckers were also very cheap, but unfortunately NLA at this sort of price. Luckily I got three many years ago, two currently in my competition engines and one still waiting to be machined down to fit a twin cam.

I have plenty to get on with this weekend now

cheers
Rohan

[Matt Elan]

Hi Rohan
Great thread and pictures. A question - do you use washers on the main bearing cap bolts? Oddly the parts list shows then but advice given to me says don’t use them but they do seem to be used in Miles WilkIns book. What is your take for a round cap engine?
Regards matt

[rgh0]

Hi Rohan
Great thread and pictures. A question - do you use washers on the main bearing cap bolts? Oddly the parts list shows then but advice given to me says don’t use them but they do seem to be used in Miles WilkIns book. What is your take for a round cap engine?
Regards matt

Yes I always use hardened washers suited for high tensile bolting under main cap bolts. Make sure the washers have an adequate radius on the inside diameter to avoid creating a stress raiser on the inside of the bolt head. Any bolt that screws into a stationary fixture such as a main cap bolt into the block should have a washer under the head to aid in getting a consistent bolt load. Any nut on a bolt should have a washer under it for the same reason. A bolt that has a nut on the other end does not normally need a washer under its head as it is not turned to tighten but in some circumstances it may be needed to spread the load.

The Carroll Smith book " Nuts, Bolts, Fasteners and Plumbing Handbook" is an excellent basic guide to understand the technology of bolting joints which is much more complex than it appears. After a mechanical engineering degree, much subsequent study and 45 years of experience with bolted joint challenges I am still learning

Standard round bearing caps should be fine for a road engine in most circumstances provided it is assembled right. Just less margin for error and much more vulnerable in a higher rpm engine. For FIA race engines in Europe they make special round bearing caps to meet the regulations that specify the shape but not the material in order to overcome the limitations It does not really make sense but shows you what happens with race regulations


This weekend I start to assemble the block with any luck

cheers
Rohan

[Matt Elan]

Thanks Rohan - every day’s a school day!

[prezoom]

Having all 3 of Carroll Smiths books should be a must when preparing or rebuilding a car. The information contained in these books will provide a significant boost to one's existing knowledge of cars.

[USA64]

Somewhat off-topic but Smith also warns against mixing copper and aluminum because they weld themselves together. I read a lot of people are fans of copper anti-seize but it should not go on the bobbins, head bolts, or plugs.

[2cams70]

The OEMs never use washers under bolt heads where the item you are bolting onto is hard and solid like a flywheel or main cap. When it's something soft like an aluminun head head they may use washers but these days they tend to use flange bolts instead. I haven't read that book but I tend to be a bit selective in the information I use and don't use from gurus. Knowledge isn't static and moves on through time.
ARP used to supply washers with their flywheel bolts but now they don't and don't recommend you use them in that location.

[rgh0]

The OEMs never use washers under bolt heads where the item you are bolting onto is hard and solid like a flywheel or main cap. When it's something soft like an aluminun head head they may use washers but these days they tend to use flange bolts instead. I haven't read that book but I tend to be a bit selective in the information I use and don't use from gurus. Knowledge isn't static and moves on through time.
ARP used to supply washers with their flywheel bolts but now they don't and don't recommend you use them in that location.

I am sure OEM's will not use washers where they think they can get away without using one, as it makes assembly more complex on a production line. The move by manufacturers to flange headed bolts is driven by this to further reduce where separate washers are needed. Washers can and should be used in some locations where the OEM many not have used them to ensure a higher and more consistent bolt load is achieved at the specified tightening torque during maintenance work so I may add washer in some locations. I certainly would not remove a washer where the OEM has used one without very careful thought.

There are also examples of different practices in the same situation. i.e. Carrillo supply their rod bolts with their rods without washers where as ARP supply them for the same application with washers. I suspect this is because the detailing of head seating surface on the rod and the matching Carrillo bolt has been designed for not needing a washer where as the ATP bolts are designed for use on multiple manufactures rods and the detailing of the washer to the bolt head by ATP allows for the detailing of the bolt hole in the rod end to not be critical. As rod bolts can and should be stretch tightened you are not so dependent on repeatable torque specifications to get the correct bolt load also.

cheers
Rohan

[rgh0]

Having all 3 of Carroll Smiths books should be a must when preparing or rebuilding a car. The information contained in these books will provide a significant boost to one's existing knowledge of cars.

I have 5 Carroll Smith books v- looks like you need to buy a couple more

Tune to win
Drive to win
Engineer to win
Prepare to win
Nuts, Bolts, Fasteners & Plumbing

cheers
Rohan

[rgh0]

Started on the block assembly with the crank

Checked the newly machined journals to confirm they are all within tolerance. They all came up nicely in middle of the specification range

10 thou under mains equals 53.733 / 53.756 mm... I measured 53.740 to 53.745 mm on all main journals
20 thou under big ends equals 48.691 / 48.703 mm... I measured 48.695 to 48.700 mm on all big end journals.

I have ACL race bearings in these undersizes ready to install. I will double check installed clearances with plastigauge when I bolt the crank in place

Fitted the crank chain sprocket. Make sure you have the twin cam one which has a longer boss to move the sprocket forward to fit the Lotus chain cover compared to the standard Ford one.

Went to fit the needle roller in the rear of the crank and discovered I did not have a new one in my spares stocks like I thought I will source one next week.... so no more progress on the block and I put the crank away and went back to my gearbox.

I bet I have just misplaced the new needle roller bearing as I remember checking I had one along with all the other bearings when I pulled the crank out. I will find it about a week after I have purchased and fitted and new one and bought another spare

cheers
Rohan

[alan.barker]

Hi Rohan,
i see you are using ACL race bearings. Are these better than the "old school" Vandervell and if so why are they better.
Thanks interresting topic.
Alan

[rgh0]

The ACL race series bearings have a number of modifications intended to make them more suitable for a competition engine

i.e
stronger bearing metal layers
higher clamp compression of the shell in the bearing housing
different taper from middle to join of the two halves at the split intended to improve lubrication at high revs


I don't know how much of this is "real" versus "marketing" but the ACL guys know what they are doing so I trust their approach and from what I can measure it looks real. I have not used the race series before in an engine build but having had a big end bearing spin in the engine I am currently rebuilding I certainly am interested in trying the "greater clamp compression" in the housing.

The downside is the stronger bearing surface layers can maybe lead to greater crankshaft wear. Not a real issue in a race engine but perhaps more in a road engine with more cold starts and a desired longer life of the crank.

cheers
Rohan

[rgh0]

Somewhat off-topic but Smith also warns against mixing copper and aluminum because they weld themselves together. I read a lot of people are fans of copper anti-seize but it should not go on the bobbins, head bolts, or plugs.

I always use Loctite nickel antisieze where Aluminium is involved.

cheers
Rohan