F7P Engine rebuild

Level 1 User Joined: 30 Oct 2004 Posts: 21

well ive just started stripping my old engine on which the big end went it was on 110k when i blew it up. I intend to rebuild it using new parts etc but to a higher spec i.e. williams pistons and diesel crank, ported head, cams, and a proper strengthend bottom end with polished rods, lightened crank etc i have a keen engineer and an engineering workshop to hand for some of this.
I was wondering if anyone else has done this and i would be after any advice they can give also if there's such things as uprated oil pumps and water pumps (if the need be) and where to get them

Dave

Mr Quoter-vator Joined: 16 Feb 2004 Posts: 7405

to start with willy pistons will require the boree to be enlarged slightly, and some of the crankcase wil need grinding out to allow the willy rods and crank to rotate freely without clashing.

have a look in retro-progress reports for my std F7P rebuild

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

hmm I dunno if I woudl follow JB's methods...

Also what do you define as a proper strengthened bottom end?

Will be in 4 figures for that anway.

Mr Quoter-vator Joined: 16 Feb 2004 Posts: 7405

my methods for what?

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

nothing mate.

Mr Quoter-vator Joined: 16 Feb 2004 Posts: 7405

well u must have meant something?

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

just I wouldn't build the engine in the same way as you, its fine but not for ultimate output.

However you should be proud you are building a superior engine to that which remanufacturers builb.

Mr Quoter-vator Joined: 16 Feb 2004 Posts: 7405

right

Gay Rights Activist Joined: 07 Apr 2004 Posts: 1268

you will need willy rods aswell, you may know that anyway.

wouldnt bother "lightening" components....there is no benefit.

Chris, im intrested as to what your method would be??

*edit* i meant balancing is useless!!

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

lightening components does have a benifit stan as does balancing these lumps. You will argue the toss as you always do especially with balancing.

both static and dynamic balancing are usefull benefits. I started a tech article but its still unfinished on this very subject.

The willy is especially bad in this respect, due to its half arsedness, and a diesel wasn't made to rev.

I would have measured a lot more stuff and got a lot more machining done if i was to use the engine.

Thats why engines I build rev and live forever.

Gay Rights Activist Joined: 07 Apr 2004 Posts: 1268

Sorry, my mistake...i meant to say balancing, not lightening!

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

balancing has many benefits especially in these lumps.

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

also the cranks phasing varies, some cranks are ok, others are a few degrees out. Which is not conductive to a good engine.

Gay Rights Activist Joined: 07 Apr 2004 Posts: 1268

There is a huge benefit in lightening when it comes to revving high and reducing inertia loads on the rods, but balancing is a useless exercise. I KNOW you will say otherwise, as will 99% of enthusiasts, but there is logic behind ny madness!
Think about it in comparison to combustion. There is around 4 ton of force exerted on the con-rod during combustion. Balancing each of the rods/pistons to within a gram or whatever of each other is not going to give any change in stress that compares in the slightest to 4 tons....is it?? so why balance them?? It isnt going to "make it run smoother" 4 the same reason. IF there was a huge variation of like kg's, then yes they would need balancing, but like i said its a case of grams versus tons....

Gay Rights Activist Joined: 07 Apr 2004 Posts: 1268

yeah obviously the crank should be perfectly balanced....sorry if you thought thats what i was on about!

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

yes but thats during combustion, you have a full cylce and a bit over a half of non combustion. Also combustions a nice compression load so its DRIVEN but after combustion its a tensile load which peaks on the exhaust stroke so its just spinning on the compression stroke it s a nice soft compresion load.

I don't know how many engines you have built but every one that I have done thats been balanced has ended up a lot smoother. Some more so than others.

The static balance of some cranks is terrible, sit it on a holder then spin it and it swings back and forth like a pedulum. When balanced right they come to rest without this isn't the right word but gives you the idea osciliating.

Also not all the time is combustion at full force, and on over run theres no combustion as such, so it will make the engine smoother in these situations.

Also the fact is these small variations as you should know go up in weight with speed. So a small variation will go up a lot with revs.

Engines are much smoother when balanced PROPERLY, it is after all a reciprocating mass which spins at fantastic speed and any loadings that are not needed are not wanted.

Cranks that wobble due to inbalances at higher revs will touch the bearings. As you know theres meant to be a nice wedge of oil between the bearing and journal to prevent this but it gets 'punted' out the way.

Gay Rights Activist Joined: 07 Apr 2004 Posts: 1268

Im talking about combustion cos thats the worst case scenario. At maximum torque you have max compressive force, and at max rpm you have max tensile load.... BUT the compressive force is greater.
I think we are getting our wires crossed....I fully understand the needs and effect of a reciprocating mass, that isnt my argument. I know that Loads will increase with mass and speed...
What im saying is that people tend to "balance" conrods/pistons between each cylinder because they think it will reduce the liklihood of failure, cos there is less variation. All im saying is that this isnt the case.....
im not talking about crankshafts. BTW if a crank is not statically balanced it cant have been dynamically balanced

Forum Moderator Joined: 18 Feb 2004 Posts: 7432

stan did you do a bit on primary and secondary couples on your course?

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

tensile load is greater in a damage outlook.

A tensile load is always far worse than a compresion load.

I am aware of static and dynamic balancing, but if you whip out your crank and spin it you will find its not statically or dynamically balanced - very well at least

I always tend to get everything even as differing weights put differing tensile loads on the crank so it DOES have a benefit.

Gay Rights Activist Joined: 07 Apr 2004 Posts: 1268

YES, but again, if the crank can withstand the force of combustion (which it obviously can), then the variation in force with the LESSER inertia loads are negiligable....do you not get what im saying?!

Gay Rights Activist Joined: 07 Apr 2004 Posts: 1268

Neal
yeah done shit loads on internal forces, primary and secondary, and the stresses the bring.
I have modelled using EXCELL the inertia and compressive forces for my race engine (shitroen AX), and got some funky graphs! Even modelled the top end of the conrod in IDEAS and done a FEA analysis....all fun!