New engine , wanting input .....

[Holman58]

alright guys

So I'm in the process of getting my new (second hand ) engine rebuilt,I was going to do it myself but I just haven't got the time so have enlisted ktec (I know some are of mixed opinions on them) to do the work.
I got a 830 lump on which I have requested

Wossner pistons
Arp con rod bolts
Cat 403 cams
Cat springs
New pumps
New belts
Ktec manifold
Ktec induction

Along with my already fitted decat and ktec exhaust

I'm really interested into anyone's experiences or thoughts on anything else I should do.
It will be going back on track once I bolt it back together , so I just want it to be reliable and hopefully not snap anymore Pistons

I have read through TB Richs thread so have some idea of what to expect

Cheers

 

[TB Rich]

I'll have some 403's for sale in the next month or 2. About 15k on them.

However if you read my thread then you'll see don't use them with forged pistons, not designed for it and you'll have too high dynamic cr to run the right ignition timing. Use 403's on oem pistons or run a bigger cams with forgies (another world of cost done right though).
Also 403's don't need springs, they're unnecessary and you'll probably actually lose a couple of hp. Peak power on 403's is 7k, always been a couple of hundred rpm less than stock cams I have found on my many plots, also in terms of max lift they are within whisker the same as 402's and you don't run springs on those either. Just run some new oem ones. Cat actually tell you to use oem springs on them.

 

[TB Rich]

Also on your list if you do go forged pistons you'll want to swap out the valves for a set of Supertechs, pointless having forged pistons and shitty oem valves. Stock rods fine for 7k peak with arp bolts as you mention. Do not consider PEC, just dreadful rods.

 

[Holman58]

Excellent , so I'll add supertechs to the spec

I see you are running quite a high CR (12.7:1) if I remember , so as long ( if available ) as I run standard CR wossner pistons it should be able to get the ignition timing required

I'm very reluctant to run oem pistons as I've had one bad experience with them and can't really afford to get it wrong

Cheers for the help

 

[TB Rich]

yeah but I had the issue on the 12.5:1 forged pistons before these. Iirc is the Wossners are all 12.7:1 anyway? Avoid the PEC pistons, the crown is for a mk2 and the squish bands etc are all suited to the mk2 combustion chamber.

I think if you get some custom ones, 11.8 or 12:1 would be perfect on those cams. I'd speak to somewhere who supplies CP pistons and see what they do, seen plenty of custom ones on other makes from CP. (Think RS Tuning do CP).
Running more cam to suit 12.5 is not an option unless you want to go extra on standalone, r3 mani & head work too!

In fact head work is an interesting point, the stock head will have the exhaust ports choking the engine around 220bhp. Now this is about all 403's have to give anyway, so could be viewed as optional - however you'll pick up a bit from doing it for sure.

Best spec on these without going silly to the point where everything ends up having a knock on with other stuff elsewhere, would be essentially:
403's
oem compression
arp bolts
ktec manifold

As yours is being rebuilt though, it raises a question on pistons (because the above spec fitted to an otherwise healthy car doesn't need much labour to fit that all - pretty much p'n'p)...personally I'd keep stock pistons, but as above could try for custom.
Issue with forged pistons (irrespective of CR) is you will limit life before re-ringing, just a fact of needing to gap the rings bigger. So I don't see that as a worthwhile compromise for building a 215-220bhp spec engine around 403's. Look into piston grades, essentially you have 2 (4032 & 2618), ideally you'd go 4032 as it has a higher silicon content which means it expands less - so you can run closer to oem ring gaps. 4032 is not quite as strong, but it's perfect in a street driven n/a car. However I'm not sure of anything other than the PEC ones for these engines in 4032.
Anyway that spec will be safe in terms of dynamic compression and the trade-off with ignition advance, plus won't be running above 7.5k really and so no need to consider rods.

oh and go for the Gates cambelt kit from Engine Dynamics - same oem manufacture but the powergrip kit has got a metal idler pulley.

 

[Holman58]

Ok cheers, it does seem like you have had your fair share of "hard times" thing this all out

I did think about using the wossner's (12.7:1) but then running at .85 head gasket, which would bring the CR down to 12.2:1 I believe ( may have to double check my calculations )

Yes I have heard some interesting stories around pec products so was happy to stay well away

 

[TB Rich]

ha, hard times doesn't even come close to where this car has taken me!! lol

Anyway had mine back on the dyno today, signed off now and happy that there is no knock going on - so sure 403's and high comp are achievable. But I think for my money it's just not worth it as the negatives outweigh the positives if the rest of the spec is basically mild. Want huge cams and all the spec to go with, sure no choice in the matter - but based on experience now I'm very sceptical about using forged pistons unless a justifiable reason presents itself.

However I think my last engine failed from fuelling related issues rather than out-n-out overly aggressive ign mapping. But without a doubt had it been a stock CR engine it'd have taken it on the chin, and in fact this isn't saying it was 'lean' as such, just that it was leaner than the compression/heat/ign needed. We have had to run this new engine richer than normal certainly to aid cooling, so if the last one was even say 'normal'/ish, then on track the elevated heat likely caused det - it's a pretty viscous circle at times. - Why put yourself in that position though for 403's??

Thicker gasket ok to a point, I'd speak to an engine builder about thickness as it's not something I've looked into - I know you go too thick and obv a weak point but also fucks with squish and flame propagation etc. But I don't know at what point is considered too thick as simply never read up on that topic. It's usually a band aid from what I've seen mind.

 

[Foxspeed]

i wouldnt want to keep the standard rods...compared to alot of engines they are a bit "flimsy"...if spending the time/money
would future proof with better rods...

biggest failures we saw on the f4r were valves and rods...

 

[TB Rich]

For what it's worth the Maxi 230 uses stock rods, makes peak power at 7800rpm. Though they get replaced very frequently!

But yeah better rods are always good, though you should be looking for the likes of Arrow and Saenz, basically rods you actually want are going to be ~£1000+. False economy otherwise.

And this is the point, where do you draw the line! Blink and you've spent 5 figures

You need a spec commensurate with your goals and expectations. and a 403 engine as spec'd (assuming no rebuild) is by far the most cost effective. Your next 20-30bhp will cost you 5/6 times again, if you want it to hold together it will anyway.