shepherd-racing

hey there i took my car in for a dyno setup the other day and was well astounded at how crap it is , a quick run down of what it has

oversized pistons + lightend and ballenced bottom end
mfi head witch kent cvh 27 cam shaft with solid lifters + vernier pulley
beleive stage1 headwork
running on a DMTR carb (24 /25 chokes)
manual fuel pump and bosch red top distributor
sportex xr3i manifold on a 2.4 inch ashley competion exhaust system
MSD blaster coil and 8.0mm ht leads

it ran 64 bhp (88 fly) at 5.500 rpm
also since ive got it back it has what sounds like a missfire and revs up extremely slowly also runs far hotter then befor i took it in

any idea's what it could be ? the guy at the dyno (Jeff Bluur nottingham) said that because this cam is such high end it has no vacuum so my vacuum advance distributor doesn't work properly
any help would be much apreciated
ive tryed a few things already thinking the missfire could be because a lead is out of sequence etc tryed a few different ways and it only runs one way
cheers

tabetha

It's a 290 degree cam, which is a hairy cam, the clue is max power at 5500, should be way higher than that, I'd expect 6500-6700 for max power, so first thing I'd do is re check the cam timing.
A 290 cam can be used with a vac advance, on some engines, but the loss/lowered of vac signal can have the advance retard mech bouncing all over the place.
The dyno op should have removed/blocked the vac pipe and tried a dizzy swing at the very least to establish if a better ignition curve would suit it better.
With the mods the engine is likely to need more initial advance lower down but LESS overall.
On x flows etc I used to set the timing so that up to around 1/3 throttle was nice, then bend the stop tabs in the dizzy to limit the advance weights being able to move out so far, to limit the total, worked perfectly, even though you wasted a day going up and down the road.
tabetha

shepherd-racing

he did mention i could change the weights and other bits but he said a mechanical advance dissy would be better , how would i mod it? (im abit new to all this ) , my vernier is set to 1 degree retard i beleive (dyno op set it to that ) when you say check the cam timing what exactly am i looking for?
thanks

tabetha

Quick lesson,
Your current dizzy has BOTH mechanical and vacuum advance/retard, on top of the advance given by the weights being thrown out due to centrifugal action and so rotating the plate they are attached to(and thus the ignition pickup/position), it has vacuum in addition, so it can advance even more that that which the weights give it, it does this by using the high vacuum created under cruising conditions, put your foot down the vacuum depletes and the amount of extra advance given by this for mpg is lost.
Some cams can play havoc with the advance retard plate(on which the pickup is mounted), causing it to bounce around, so we get rid of this bit, and let it rely solely on the mechanical advance retard which is purely speed related(centrifugal force).
All you need to do is disconnect the vac pipe from the dizzy, and plug the pipe so no air leaks.
A lot of people remove the vac can(capsule) on the side of the dizzy body, and fix the plate in position by a screw, spot weld etc, but the vac can if left will hold it static so doesn't need removing.
So long as you know for a fact you have enough valve/piston clearance the valve timing needs swinging, the best way and only accurate way to do this is on the dyno, where you can say dial in 5 degrees retard for example and see what the power does, if worse go the other way, my guess is it needs retarding, 1 degree isn't even worth doing, but the op should know this, as a rule up to about 4 degrees isn't going to make a colosal difference on your spec of engine, I'd speak to the cam maker as i have no idea if you have enough clearance or not.
If you contact aldon automotive, they may well have a ignition curve to suit your dizzy and cam, which can save a lot of work/cash, as no doubt your op won't be happy to alter ignition curves by bending stops etc, unless old skool!!
tabetha

shepherd-racing

thanks for the lesson most informative! ive decided to go to a standard cam for now with new lifters and sort out the rest of my car and go for more power later in the year
is there anywere that sells coilovers for less then 500? cant find them anywere !

bit of a daft question but what sort of power should i expect from a standard cam on my setup? i know its only going to be a guestimate but has to be around 95-105bhp right?
thanks for your help!

Chip

iTrader: (3)

Get it on management instead of pissing around with distributors and carbs, they are crap at the best of time and its getting harder and harder to find people who really understand them.
Will cost you far more in fuel and rolling road time to get it work on the carb than it would on management.

Its not the 60s anymore!

shepherd-racing

would need a new fuel tank an efi inlet and whole car loom and ecu ,cost in the region of 300-400 ? maybe consider it when my bodys sorted

tabetha

There's millions of cars running 100% perfectly with carbs, although efficiency wise carbs don't touch efi, they can still do a ace job when set right, they did so for a lot more years than efi has been about for example.
tabetha

rst in breaking

iTrader: (2)

to be honest id def go efi, mate has carbs, sounds great but can be a pig getting started and is very thirsty, any pics of the car?

shepherd-racing

my cars in need of desperate TLC ,plan is to sort engine then suspension and then body (have an xr2i kit to go on it )

will do a project page at some point but a quick scoop of atm , bought it as a 1.3 rattle bag for 200 quid (first car and cheap insurance) broke my wrist whilst changing the clutch so in went a 1600 cvh with a few borrowed spares from my cousin and his mates who race in a stock car cup ,as carb was easiest option just three wires! that was the way to start pics time
old 16 cvh out


new one in with new parts!


then i got some xr2i dampers


rs2000 calipers and disks


how they fitted in the 14" rims


last pic of old alloys swapped out for zetec S 15's


new rims

and thats pretty much how she sits now

chaffe

old cvh probably has eaten the cam lobes....
plus carbs are crap, how can you get the laptop out and tune a bit of fuel out here and a bit more timing there with them? things of the past, get with the schedule.

Chip

iTrader: (3)

My idea of perfectly is that they give the correct fuelling under all circumstances, so for best possible economy at part throttle and best possible power at full throttle.

NO carb engine has ever acheived that IMHO

They were better than walking, but they are massively out of date now and 1.35 a litre, petrol is worth worrying about so economy DOES matter IMHO

tabetha

Maybe the op already has carbs or wants carbs ?, as per his question.
You've obviously never seen a reece fish carb, carbs can still give ace results, the op might be a millionaire and not need to care about fuel costs.
I know of peeps still on carbs, doing limited miles some on track cars others are every day used cars.
The point is carbs can be made to work perfectly well, and run perfect start perfect etc, no they won't beat a efi, but that wasn't the question.
tabetha

scoooby slayer

iTrader: (4)

to be fair i think the op is obviously quite young, thinking back to my youth i wouldnt of been spending money on converting to efi i couldnt of afforded it, i wouldnt say your a mile out at 88 bhp anyways what were the mk3 xr3s ?
no doubt some dizzys are interchangeable last year i put a fiesta 1100 dizzy on the 1600 crossflow in the dutton and it works a treat
as tab says alter ignition timing and see how it alters, i had a 1600 crossflow years ago in a mk2 escort and it had naf all advance so i just set it so it pulled up top perfectly, only problem was it wouldnt idle below 2500 rpm the joys of youth

chaffe

if it is a dizzy problem i wouldnt even piss about, i would go to the scrappys and get a hybrid (red) edis four set up for a few quid. And tabetha, you told me about six months ago you have never seen a reece fish carb in real life too maybe you have now

shepherd-racing

im not so young just inexperienced ,hence why my cams already fooked as i used second hand lifters firstly hydro then solids ,so im returning to standard (new) , going efi would ofcourse be best option but for the time being i just want it running good have other things to sort after a breif car chase involving a couple lads with bats and a few speed bumps my suspension is in dire need of repair

on the debate about going efi
efi is better no matter what
carb is easyest for first conversion ,parts are cheap ,three wires ! who would say no to that!
@Tab thanks for all you advice

also im told the vacuum problem is due to duration ,dyno op said basicly the pistons are on the compression stroke long befor the valve closes witch forces the fuel air mix back into the inlet , as my inlet is joint (and were the vacuums are located ) that backflow nulifies the vacuum , easy fix if i had the cash though ,twin 40's or bike carbs would alow each cylinder back flow and vacuum to not disturb each other , or somthing along those lines im not all that technial