Max overbore Daimler V8

Fossil
Posts: 379
Joined: Sat Feb 13, 2016 5:08 pm
Location: Helensburgh, Argyll

Re: Max overbore Daimler V8

Post by Fossil » Wed Oct 18, 2017 3:10 pm

The topic appears to have broadened out to include main bearing caps.

One of the simpler ways of reinforcement appears to be to fit brace bars. During my engine rebuild in 2011 I fitted a set of three from Barry Thorne. I'd not heard of them prior to that, nor do I know whether they are truly beneficial. They seem a simpler option than cross bolting for normal street use. Perhaps someone knows.
SP block assembled 004.JPG
Regards

Geoff

Big Col
Posts: 257
Joined: Tue Feb 16, 2016 12:45 pm
Location: Leeds

Re: Max overbore Daimler V8

Post by Big Col » Wed Oct 18, 2017 8:32 pm

I hope I am not hijacking the thread but it would appear to be a natural progression.

Maybe someone can enlighten me. I have been under under the impression for many years that the bottom end on the V8 was good for at least twice the original horse power than the factory specified. I was also under the assumption that the only problem of breaking the caps was if the crank had been tapped from end to end during building up to check end float etc. Why would it be necessary to carry out modifications on them if this is the case.
Am I getting mixed up with the conrods which I believe have been used in some high powered motors. Can anyone post a picture of cross bolting for the benefit of plebs like myself.
Colin,
I may be slow but I’m rough as well !

ddstewie
Posts: 34
Joined: Thu Feb 18, 2016 8:13 am

Re: Max overbore Daimler V8

Post by ddstewie » Wed Oct 18, 2017 11:06 pm

Hi Colin,
Care, attention to detail and best work practices on rebuilding these engines will give many miles of hassle ,trouble free motoring. Having the engine dynamically balanced by a reputable professional will give the best rewards , plus of course a maintenance plan. An engine that is just thrown together will run fine, but will have a limited life due to vibration ( how ever small ) which induces stress, wear and eventually failure in the form of breakages.
I have just attached a photo of the Forged Ross Racing Piston.
As previously mentioned the Latest "Dart Talk" (28 pages - the best SP250 magazine worldwide , Thanks to Keith Humphreys :D ) has more photos and info on the engine . Dart Talk , the " E " magazine of The SP250 Club of New Zealand is a quality product. It is very well constructed, written and illustrated. Get the news from " Down Under " - join the club.!!! :D :D :D
Attachments
Daimler 2810cc (3).jpg

tjt77
Posts: 368
Joined: Wed Mar 23, 2016 7:01 pm

Re: Max overbore Daimler V8

Post by tjt77 » Tue Oct 24, 2017 7:47 am

The images of the 4 bolt main bearing cap, show a nicely done job.. Im still not convinced that the lower end is sufficiently strong to hold up to increased power in everyday use no matter what one does to it (other than casting a replacement cylinder block with much stronger main bearing housings...and incorporating a crank with thinner webs in order to increase block web thickness and surface area of main bearings... Im also unsure of how many hours a vingage racer would expect to get from a properly built Tuner V8 before bearing relacement.. the last 4 engines i took apart all had noticeable main bearing wear, and none of them had covered high mileages.. I recall exactly the same issues over 30 yrs ago when i last was involved with these cars and engines. My current rebuild is using some steel caps sourced from Barry Thorne in UK.. I feel it will provide sufficient improved strength for my uses and the build is projected to produce less than 160 BHP with max revs limited electronically to 6,500. I did eventually source enough sets of lead copper bearings for 3 crankshafts in the sizes I needed (had to turn rod journals one one crank to fit the -.020" bearings I'd sourced, rather then 1st oversize), but cylinder heads remain an issue and Im out of time and patience and well over projected budget, with no end in sight were I to build all 3 engines.. alternative routes will have to be taken..I have several rover V8 engines on hand in displacements of 3.5. 4.2 and 4.6.. the 4.6 was the one most recently running and has less then 6,000 miles on it (it was purchased new outright) over 200hp unstressed, with +/- 200K mile life before overhaul being common.. 5.0 and the larger displacement 'small block' Ford engines and multiple choices of gearbox to bolt straight up are another practical option.. complete power trains in good order can be sourced here for considerably less than the cost of a 'light' overhaul on the small Turner V8, whilst dimensionally similar.

tjt77
Posts: 368
Joined: Wed Mar 23, 2016 7:01 pm

Re: Max overbore Daimler V8

Post by tjt77 » Tue Oct 24, 2017 8:00 am

Reply to Geoff Douglas.. the steel straps will definately help prolong main bearing life.. anything that reduces the flex on caps or block itself is useful.. I purchased full 'caps' for intermediate main bearings from Barry Thorne (the last remaining set I was told) , and had them line bored to cylinder block, rather than add straps to existing caps.. Straps are known to work well on the BMC A and B series 3 main bearing engines, which remain popular on the vintage race circuits.. however both of those have thicker retaining bolts than our daimlers.. which are a very skinny 3/8" in diameter..

Ian Slade
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Location: Akrotiri Cyprus

Re: Max overbore Daimler V8

Post by Ian Slade » Tue Oct 24, 2017 11:13 am

Tensile strength min of a 3/8 grade2 bolt, coarse thread 5700lbs, 3/8 bolt grade 8 coarse thread 1160lbs double that and more for a fine thread, I suspect that a 3/8 bolt is more than adequate :D , never had a problem with a sheared bolt at any rpm. There's designing and doubling diameter "to be safe" then there's designing using scientific data, the first one ends up with a car so heavy it won't pull the skin of a rice pudding, thus requiring an engine size increase with extra material need to be safe, then is there enough power? need I continue? :roll:
Owner since the 70's, Genghis is slightly to my left.

ddstewie
Posts: 34
Joined: Thu Feb 18, 2016 8:13 am

Re: Max overbore Daimler V8

Post by ddstewie » Wed Oct 25, 2017 1:06 am

Hand crafted head gaskets for the 2.8 :)
Attachments
Daimler 2810cc (4).jpg

Sonus
Posts: 146
Joined: Wed Apr 13, 2016 2:19 pm

Re: Max overbore Daimler V8

Post by Sonus » Wed Oct 25, 2017 5:19 pm

That looks really nice ddstewie!

I am still stuck with finding a supplier for a bespoke camshaft. I am still trying to find an alternative to Catcams €2000 estimate :)

Fossil
Posts: 379
Joined: Sat Feb 13, 2016 5:08 pm
Location: Helensburgh, Argyll

Re: Max overbore Daimler V8

Post by Fossil » Wed Oct 25, 2017 6:45 pm

Tim

Thank you for your reassuring comments about the brace bars, I'm delighted that they may be beneficial; the engine was rebuilt in 2011/12 having bu**ered the bearings after only 20,000 miles from the previous rebuild. It is living proof of the fact that unmatched con rods (not my doing - long story - someone else's fault) will damage your engine; they are now matched and the engine properly balanced, but I thought that a little extra strength would do no harm.

Also Tim, apologies for my failure to acknowledge your two pms, I've only recently discovered the function of the link on the top line!! However will reply to them asap.

Regards

Geoff

daimlersteve
Posts: 279
Joined: Wed Mar 09, 2016 11:20 am

Re: Max overbore Daimler V8

Post by daimlersteve » Thu Oct 26, 2017 3:16 am

This photo of dennis' SP got my vote in a recent club photo competition.
Put some more up Den.
steve

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