Engine spec (not yet finalised)

[jonlem]

After reading a post from another mig user, I thought I'd post up the engine spec for an engine I'm having built for a mate of mine

Engine:

2L Xe, Accralite 86.5mm Flat top pistons, Blydenstein head, QED 450 cams, solid lifters, titanium retainers, double valve springs, Steel rods (supplied by rob at RSC) Weber 45's or 48's on flowed inlet manifold, mbe or weber alpha ignition
Steel flywheel with ARP flywheel bolts,

looking for approx 230bhp from this unit,

A few queries are if to use the ARP head stud conversion, and possibly changing the pistons for the high intruder type andmaybe some Tb's if some come up for the right money.

how much difference are wasted valves going to make as were not looking for 250bhp from this engine but I'd like to know if it is neccesary for approx 230bhp

anyones opinions on anything else that you feel is missed out or may be needed would be appreciated

[BEN LEE]

one probem with the weber management is only dearlers can acsess it to map it.

[Gary]

waisted valves aren't necessary for any spec unless you can't live without the 2-3 peak bhp they'll probably net you.

free aspirated bhp comes reluctantly over about 230bhp, so bung em in

[ctunnicliffe01]

Take a look at my spec. very simlar.
I make 200bhp dead on( ok on some of these other rollers being used id probably make quite a bit more ). Only thing i dont understand is why my peak power comes so low with the setup i run.

I make 200bhp @ 6323rpm which seems low for a 283/290 combination.
Id have thought over 7k would have been more appropriate.
weird but still it goes well!

Sounds like a nice engine build tho mate. good luck!!

[novarallycar]

Also you won't make any more peak power using tb's over carbs if you have them correctly jetted. you will however get better low rev response at part throttle .

[jonlem]

Also you won't make any more peak power using tb's over carbs if you have them correctly jetted. you will however get better low rev response at part throttle .

I've been reading up quite a bit about the pros and cons of tb's and really i'm seeing them as a road item as they are a lot more responsive low down and can be mapped for cold start etc.., as the engine is just about only going to be used for track days etc.. which means it will spend most of its time high in the revs I couldn;t see a reason to use tb's.

the main issue is to make sure it makes 230bhp, the guy who originally had the head and cams on tb's had the same spec without the rods, but had a big issue with the bores being too large and was told this could of been where he was losing his power as he only made 204bhp.

looking at the specsheets for the cams it seems that really we should be using the high intruder pistons and not the flat tops but as the chambers in the head have not been altered from standard I dont know if it is neccesary, the guy who's engine it is would be quite happy to spend a little extra if it will make the extra h/p,

This is what I have on the QED specsheet

225bhp@7750 165lb ft
250bhp@8250 180lb ft

using solid lifters, higher c/r (which the flat tops still give) race springs and all manner of port sizes and valve sizes.

the head has been extensively ported and does not look anything like a standard xe head, the valves are standard size and the raest of the inetrnals are to QED spec.

[stewart]

What sort of car is this going into? QED450 cams don't work very well with standard Vauxhall gear ratios which tend to let the engine drop off the power every time you change gear. This is especially true if you intend to use carbs rather than injection. If you are using mapped ignition and buying new carbs then this won't work out a great deal cheaper than injection and will be a lot less effective. I know that in principle a track car only needs top end but in practice most circuits have somewhere that doesn't let you keep the engine on the boil and this is where injection really shows an advantage over carbs.
Personally I would be inclined to go for slightly milder cams that don't need over 8000rpm (and so don't need steel rods) and spend the money on throttle bodies and mapping instead. I compete in my Astra and would trade 15bhp of top end for midrange that starts 1000rpm lower down every time.

[Rob_S]

sounds fine to me, lots of cars with that spec making 230-235bhp depending on headwork and ecu
i would look at mbe or dta personally, they tend to be the most consistant, although with ign only you could look at cheaper options maybe...
dont bother with waisted valves mate, at 230 you wont need them

hey stewart, you have mbe & jenveys now yeah? why dont you have a midrange? mines very useable indeed even on standard gearing, but with a 4.5 final drive this top end power issue wouldnt be an issue at all tbh, never out the power band

[jonlem]

I was offered a set of half a season old weber 45's on weber alpha gear with aeroquip connectors etc.. for 800, which is a damn site cheaper than rrp, the guys whos they are though cant find the disc yet so without it we cannot unlock the ecu, the guy who is selling the carbs mainly uses mbe on his rally cars so i might just ask him to trade the weber gear in for some mbe that he might have laying around, we'll see what goes when he gets back from the rallying this weekend.

the engine is going in an nova, i wouldn't say it matters what gearing you use with that sort of power it will be ok due to power to weight, if not i'll have the box altered but i think it will be fine

[stewart]

I'm using SBD 278/284 degree hydraulic cams and TBs, the midrange is very good (over 160lbft from 4200 - 7000rpm) and they work fine with standard gear ratios. My point was that I've already made the choice between an impressive peak power figure and a more tractable, easy to drive engine and am very happy with the results.
I've also driven another competitors car with Q450s and carbs on a standard 'box and didn't like it at all. It was great above 7000 rpm but was very rough below 5000 (possibly a jetting problem) and bogged down unless you changed gear right on the rev limiter. The person that owns it has since changed to Q420 cams - draw you own conclusions.

[ctunnicliffe01]

I cant stress enough the advantages of a quaife sccr box.
Since we fitted mine the car has been transformed. Power is really strong in all gears. NIce long 1st and 2nd allow for real hard acceleration then followed up by nice close 3 and 4th which keeps the engine constantly ont he boil and int he revs. then i have the longer 5thf or motorway stuff.
Run a 3.94 fd which still gives me a peak speed of around 126mph
But its how it gets there that really makes you smile.

Dta with the carbs works a treat. Never looked back really since i got mine sorted. Debated the throttle boddie route many times. But the cost of change for what iw ould get isnt worth it by far. !

Id look at pypers cams also. Never letme down!!

[DarrenH]

Also you won't make any more peak power using tb's over carbs if you have them correctly jetted

debatable. but theres no denying a open bore of 48mm will outflow a 48mm carb with a 40mm choke.

i agree with sbd site really, unless youre entering a championship that is restricted to carbs, then its false economy.