Rebuilding my 250

[xy500]

Alright, so i've got a temporary engine in my car atm while i rebuild the 250. And i'm looking for any general advice on where money would be best spent as i don't have much. I'm trying to keep the engine reliable and streetable, but also with as much performance that is reliably attainable.
The engine is the original and has never been rebuilt, though it looks like at some point a reconditioned head has been installed (must of been a while as the valves look a little burned.)
I was looking at getting some flat top pistons, but they'll put my cr right up to about 11:1 which i assume is a little risky. So besides that she needs an overbore probably to 30 thou as when i took the pistons out, they slid straight out over the ridge without much of a push and the bores are glazed and probably out of round, a new cam as the original is badly worn, with pitting and what looks like rust somehow, new big and little end bearings and cam bearings (one of them disintegrated) as well as having the crankshaft re ground and then the head needs a little tlc.
I'm rebuilding the thing myself as i dont have much money and i want to learn. I have it all apart right now ready to go to the machining shop but i'm not 100% sure what to get done. I was thinking about a stage 2 cam if they don't cost any extra over a stock cam, but would this be ok with stock springs lifters and pushrods?
is it worth the extra money to get moly rings? How much should i get the block decked? I'd like a CR of 10:1 but i think its going to need so much milling that i'll need new pushrods, and i'd rather re-use everything i can get away with. I'll probably go with a slightly smaller dish piston (5.7cc over 20.5cc) though these pistons have a higher pin height which counteracts their smaller dish volume.

With the head, i would like to put in some stainless seats and valves but i'm sure thats expensive, so hardened seats might have to do, as i drive the vehicle on LPG (propane + butane) mostly. It probably needs new springs and valves also.

Any help or advice would be appreciated, does anyone know a good machining shop in Perth, WA?

 

[JackFish]

Ebay had some great prices on main and rod bearings lately.
I got two sets for about $50, Clevite and Federal Mogul.
But get those moly-rings from AZCoupe, I couldn't find 'em anywhere else.

EDIT: I just noticed you're not here!
I'm sure you can get all your parts where you are!

 

[rbohm]

8) moly rings are definitely worth the money, but remember that the cylinder walls must be very smooth. they will seat on the smooth walls though.

since you are replacing the cam anyway, the cost is going to be about the same either way. as for push rods, as long as they are straight and the ends are not worn, they will be fine. as for the springs, go with the ones the cam manufacturer recommends. the stock ones are likely worn out anyway.

as for decking the block, my advice is to take enough off to make sure the deck is flat and no more. better to shave the head as needed to get the desired compression ratio. you can always shim the rocker arm shafts to allow for how much the head is milled.

 

[addo]

I've got spare standard cam bearings here, and standard crank bearings too. Dirt cheap if they will work (mic your journals).

Get the cam reground, and your lifters resurfaced. It saves money, and gives you back a known quality of metal. Also means the distributor drive gear is matched nicely.

Decking can't really be estimated until you mock it all up.

 

[gb500]

Xy500 - the trick is to pick what you are doing with the engine -- is this for an XY ( 1600kg/3500lbs)- and is just a cruise machine ?

is it the log head or 2v 250 ?

is it an auto? or manual?

rear diff ratio?

do you want to run 98 octane - or just std unleaded - big cost difference

if its daliy driver /cruise machine then you dont want to pick to much of a cam for road tractability - there are plenty of threads here on picking a cam.

if its an auto then even more critical - otherwise you need to hi stall the converter.

when you pick a std /or mild cam the dynamic compression becomes a problem if you have too high a static comp and will ping like crazy

i would say that with an iron head 6 , std/mild cam that 10 to 1 statitc is too much for std unleaded(91 RON in australia).

you would need to be around 9.3 - 9.5 - BUT have a really good squish(Quench in USA) of 40thou.

you need to match the comp ratio to the cam - and the cam to the type of driving you do- and then sort out the drive line - ie manual/auto /rear axle ratio.


i'm (slowly) building a 200 log head for daily driving- with 260 deg ivan tighe cam(AT300), 38thou squish (pistons poke out of deck to compensate for the head gasket thickness( 50though),9.4 static comp ratio( i think its 7.6 dynamic) all behind an aussie 3 speed BW35 auto and 3.2 diff.

2 other thing - always replace the lifters- on mine the face had worn concave(should be convex)- they are the same as Ford FE V8 lifters- not the ford 6 crossflow ones
and get the dist recurved for the new cam(plus electronic ignition)

heres a cut and paste from a reply i did on aussie ford forums - some guy had built a clevland V* with an 11 .1 comp ratio , closed chamber iron heads, std cam and 2.75 diff and was wondering why his engined pinged like crazy - so was using 98octane + octane booster and 3deg static timing to get it to run.

few more bench engineering views-


heres a link to a discussion on dynamic comp ratio (DCR)

http://www.empirenet.com/pkelley2/DynamicCR.html

the author gives the following statement :
'Race engines, using high octane race gas, can tolerate higher DCR's with 8.8:1 to 9:1 a good DCR to shoot for...Caveats: Running an engine at the upper limit of the DCR range requires that the engine be well built, with the correct quench distance, and kept cool (170º).'

and can plug into this DCR calculator:

http://www.wallaceracing.com/dynamic-cr.php

the yanks call it quench - the brits call it squish - but its the meaurement from the top of the piston to the underneath of the head ( on a closed chamber head ) and includes the gasket thickness- ( its NOT how far the psitons are down the block).
this is a link from a site ( harley! i think) - but there are plenty of sites

http://www.rbracing-rsr.com/squishcalc1.html

and most advocate a quench/squish aprox 40thou. this minimises pinging.

so if you had a 50thou head gasket to get 40 thou the pistons would actually sit 10 thou out of the block.

reducing sqish - ie larger can actually be worse
discussed here:
http://www.speedomotive.com/t-showbymodel.aspx


speak to the head builder as to options for reducing- you will need to get the CR down and as said before get the timing right with a regraphed dist.


brett
melbourne

 

[gb500]

whoops -missed that bit about the LPG used - (red face)

octane rating is higher so you may be ok with 10:1..unable to guess as i have no experience with gas... but still need to match the rest of the cam /squish/driving style etc

 

[xy500]

wow, thanks for all the advice!
the engine is out of an xy, which weighs around 1300kg with the engine and everything, I've just put a four speed manual transmission in and it runs a 3.23 diff. With the 3 speed manual it really needed the low down torque, but with the four i'm sure it could sacrifice a little for more top end (4000-4500).

The car is a daily driver so it needs to be well behaved in traffic, but not be so slow that people laugh at me! It has the log head which i might slightly modify, but i want to prepare it now for when i get either the 2v head or the aluminium head. When i'm not running it on LPG i run it on 98 octane as i run quite a bit of initial advance with LPG.
If having a wilder cam means i need lower compression, i might just keep compression stockish at around 9.5:1.
The lifters need replacing anyway, as they are badly worn and a couple have been noisy.

I think i will need bigger bearings on the little and big end, as all of these had scoring and you can feel grooves worn into the crankshaft, so i was going to get the crankshaft machined true.

Are you sure i can get the original cam reground? in some places it has worn about 1mm. Besides, the original cam has too small lift anyway so wont regrinding it reduce the lift?

 

[addo]

If you replace the cam with a new item, you'll also need to buy the hardened distributor gear from Crow. It's more spending.

For the same reasons of economy and a known substance, I'd strongly suggest checking into resurfacing your lifters. Quality control is just too vague in some aftermarket supplies. Call Tighe, Waggott, Camtech or Watson about the regrind, and ask about the lifters while you're talking.

 

[gb500]

nah - wilder cams mean you can run higher STATIC compression . as the cam is longer duration the dynamic compression is calculated from when the inlet valve closes- and also uses the static compression in the calculation
hence a std cam inlet valve closes earlier- and hence with a high static comp -the dynamic comp is too high. ergo a wild cam closes later and thus the dynamic comp is less .( but added to a higher static comp gives you the right numbers)

what a wilder cam does is push the usuable rev range higher- so if too wild is a bugger on the street.

you are a manual box - and four speed then approx 265deg-270 cam will pep it up a lot.

again look at the info on cam selection on the classicinlines website

yep you can get the orig cam reground - Tighe did mine - $140
and can regrind lifters- approx $4/5 each - but new were approx $7 (although he did sell me the ford crossflow 6 ones - extra height+ central pushrod oil hole- so i got the correct ones off ebay)

obvioulsy if cam is rooted it wont be worth it ( as they can build up lobes with weld but ford 6 cams aint exactly rare.)

brett