Quicksprint (aka Nº47) Update

[xvivalve]

Engine out and apart.

Transpires to have been previously overbored to +20 thou. Cylinders 2 & 3 have picked up and advice is to rebore again. I have a s/h set of +30 thou pistons, but they are AE and slightly dished.

Ted M has offered me an option of a brand new block which has been bored out to match some ST pistons he picked up many years back (he runs the other set he had in his Carmine Sprint.

What do you guys reckon?

[Sprint36]

Of the two I went for option 1, but there are other options, such as boring an 1850 block for standard, or buying some +40 sprint pistons from me and boring your block +40.

David

[DavePoth]

Ooh hang on though. I had an email conversation with Hans a few days ago talking about pistons (the block from PRO is +40 thou) and he said:

I can only strongly tell you NOT to use any oversize piston for a serious Sprint engine.
Remember the casting was designed for 1850cc and not 2000.
By the factory upgrade to 2000 cc where the blocks already bored to the limit, in my opinion over the limit, but that is what they had in those days.


By going further you will end up with to week liners and stability of the already not to strong block.

[xvivalve]

By the factory upgrade to 2000 cc where the blocks already bored to the limit, in my opinion over the limit, but that is what they had in those days.

This is what Ted has offered me, it was an ST modification. Its only 0.5cc per cylinder or there abouts...

I have a set of new Mahle standard pistons I was going to use in the original block, but the surprise its non standard already prevented this.

[rich]

alun , i had the same advice from hans, but how many race engine must be overbored now
if i were you i'd get a new 1850 and have it bore'd out too suit the pistons you 'have'.

i read a couple of posts resently about new or rebore and something people never take into consideration is the wear on the block that the jackshaft creates and shifting all that gunge in the oilways , i had damage to an engine after a major rebuild due to tiny bits of crud blocking the rockershaft oil feed holes.

my thoughts

rich

[Hans ten Broeke]

The keeper plate construction of the jackshaft is one of the weakest point of this engine, and most of the time made worse by a far to tight clearance of the impeller - waterpump cover. It can get pretty hot because of this and the wear starts.
The very first engine of the hill clime car we bought in the UK had this problem, (and before), the jackshaft bearing was already replaced by a brass bush, buth till it seased later. Made a total other solution but that is for an other time.

Back to the oul feed holes, for a serious engine I prepair ALL the oil pasages with simple Flex hones, several diameters.
I know they are not made for that, but work greait and are relatively cheap.
Some pictures can be seen here
http://sprint.smugmug.com/gallery/45234 ... #266353497

Hans

[xvivalve]

Ted's block is new and has been matched to the pistons

The alternative of a new 1850 block and my standard pistons would require boring anyway.

I think the Ted option will be the better, and in the long run slightly cheaper.


Now the only decision is to put my new old stock head on it or not...

[David6214]

or the quicksprint head....rebuilt?

[xvivalve]

Spent a couple of hours at Ted's goldmine yesterday. We found the block quite easily...but mot the matched pistons

So...any opinions on sourcing a new 1850 block and making it fit my new standard pistons? Is it a matter of rebore, or will that render the liners too thin? Or is it better to resleeve it with standard sprint liners?

[Sprint36]

You have pm Alun.

David

[xvivalve]

OK, couldn't decide which way to turn for a while there but thanks to all those who offered me engines of various descriptions.

I have now instructed the mechanic to assemble two engines for me!

The original Quicksprint block is to be relinered with standard sized liners (thanks to S&S Preps at £19 each, neither Fitchetts or Rimmers having them in stock, special order only) and will be spoiled with my set of new standard Mahle pistons.

My kitchen now has one less engine in it; I stripped one down to find clean standard bores and Mahle pistons that Tim is now going to measure refurbish as necessary and rebuild as a known good spare...or it may find a home in one of the shells I have later this summer.

On the horizon is also a local standard bore clean stripped engine which may also be finding a home near me soon...


Oh, whilst it is obviously aftermarket gear, S&S also do a timing chain kit (chain, tensioner and 2 x guides) for £35 which is nearly half the comparable at F and R...

[xvivalve]

Re-assembly has commenced. New liners have been fitted, all moving parts have been balanced and lightened where possible. Replacement head has been stripped and cleaned and awaits rebuilding. Vernier cam sprocket arrives at Heathrow from Oz on Wednesday.

LT77 has been checked over and earned a stay of execution