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+--- Thread: Engine - rebuild or replace? (/showthread.php?tid=2033)
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RE: Engine - rebuild or replace? - Colin Wilks - 21-11-2018
Thanks all for your thoughts. I think the consensus seems to be that I'm on the right lines. The Chromidium block has had liners fitted and these are bored +.060" if memory serves, so some work needed there.
My primary concern is to preserve the crankcase, which is at risk if the crank lets go and/or if the sports cam continues to try to separate it from the block - hence the replacement of these items. Interestingly, Paul Bonewell reckons his fast road cam will give similar performance but with a much less aggressive action.
Forgot to mention I shall be boring the oil pump +.020" and fitting new steel timing gears from David Dye.
RE: Engine - rebuild or replace? - Bob Culver - 21-11-2018
Unless the camshaft or timing of has been meddled with, or the spark timing is wayward, or perhaps the valves hopelessly pocketed, it is hard to see what can be done wrong in a rebuild to significantly affect the performance.
RE: Engine - rebuild or replace? - dickie65 - 21-11-2018
Hi,
If your Type 65 Crankcase is the early solid mounted one there is the possibility of a foot breaking off when driven hard.
My car came with a non original engine but I have the correct head and manifold.
I am happy running a Mongrel Engine in my car up to 7500 RPM
Most people do not know what they are looking at under the bonnet anyway.
The experts among us generally would rather see the car being driven and enjoyed whatever 7 engine is fitted.
The original Type 65 crankshafts are worse than the standard crank as far as oil pickup goes which is why they are so rare now.
A modern crank and rods are the sensible way forward.
Nippy / Type 65 camshafts are not recommended for use with a sleeved block ( according to the old publications )
A standard re-profiled camshaft can be fitted with a custom front bearing and alterations to the roller set up.
I have also known owners to copy the side pockets from the original Crankcase and make resin versions which when attached and painted will fool most people.
Decide your budget and choose what suits you not other people.
Above all enjoy your Type 65
I have been enjoying mine since 1992
RE: Engine - rebuild or replace? - Colin Reed - 22-11-2018
Hi Colin.
There is no problem removing liners an fitting new ones,
which means you can start with STD slipper Pistons ,
this all so gives you a chance to inspect the bores before fitting new liners.
Best of luck
Colin
NZ
RE: Engine - rebuild or replace? - Robert Foreman - 22-11-2018
Colin , you are definitely on the right track. I've rebuilt a couple of Speedy engines and a couple of Nippy ones. One customer chose to keep the original camshaft so I used an unsleeved block the others have all had a Kent Cams fast road modified standard camshaft fitted. With these I have machined a phosphor bronze bush and suitable rollers.
I would recommend not using the original rods as they have a design fault and are invariably worn.
As Colin says you can push out and replace liners if necessary.
Good luck with the rebuild.
RE: Engine - rebuild or replace? - JonE - 22-11-2018
(21-11-2018, 11:11 PM)dickie65 Wrote: Nippy / Type 65 camshafts are not recommended for use with a sleeved block ( according to the old publications )
Could I ask what is the technical explanation for this? Are sleeves less inherently stable than unsleeved blocks where there is the extreme pulling pressure between head and block?
RE: Engine - rebuild or replace? - Charles P - 22-11-2018
Once you've bored out the block for liners there's not much metal left between the bore and the base flange. A cam with high acceleration coupled with overly strong valve springs can lead to failure. This is why Chris Garner rightly suggests a more mild cam. I'd also recommend that you think hard about valve spring strength. The general rule is use the weakest ones that will do the job.
Charles
RE: Engine - rebuild or replace? - Colin Wilks - 22-11-2018
(22-11-2018, 10:50 AM)Charles P Wrote: Once you've bored out the block for liners there's not much metal left between the bore and the base flange. A cam with high acceleration coupled with overly strong valve springs can lead to failure. This is why Chris Garner rightly suggests a more mild cam. I'd also recommend that you think hard about valve spring strength. The general rule is use the weakest ones that will do the job.
Charles
When I got the car the valves were sticking and the camshaft gear was damaged so the camshaft had to come out. On Nick Turley's advice I reaseembled using only the outer valve springs. I plan to use standard single valve springs on this rebuild.
RE: Engine - rebuild or replace? - Ruairidh Dunford - 22-11-2018
Colin,
I am currently undertaking exactly what you propose to do, i.e. fit a standard crank, cam and rods into a Nippy crankcase. I have learnt a lot along the way and am very happy to talk to you about that.
My number here is 01419428037.