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1 Anonymous Users
#1
bigger valves?
jeffroj
Posted on: 2008/9/18 9:00
I am chasing more power for the a14. When I had the engine built, the builder said that bigger valves may be an option in the future if I require "want" more power. I went and visited him the other week and he said that it would cost around $700 for the job maybe 10 hp or so increase.
The front runners in my class road reg under 2l are all moving up to open under 2l next year this will enable me to be nearer the front so some extra power will be handy. do you think bigger valves will be worth the money? does around 10 hp sound about right?
#2
Re: bigger valves?
bert
Posted on: 2008/9/18 9:07
No.Bigger valves on thier own won't give 10 H.P.In no particular order you also need to address:Fuel supply,Manifold,Exhaust,Valve Springs,Camshaft,Compression.
#3
Re: bigger valves?
ZigZag
Posted on: 2008/9/18 9:08
10 HP is a pretty big increase on the A series motors
#4
Re: bigger valves?
cheater_5
Posted on: 2008/9/18 9:36
from the pic of your a14 on the site, specs are:
"70 30 cam bored 60 thou match ported head double valve springs higher compresion fully balanced" carbs, ports, valves, compression, cam, v.springs, exhaust, timing/spark, flywheel/crank lightening All things to consider, some you have already. Valves are definately going to help but reducing rotating mass, maybe a beafier cam, and carbs are prob more important. What carbs are you running?
#5
Re: bigger valves?
jeffroj
Posted on: 2008/9/18 9:57
my cam is 280 276 duration 295'' valve lift the cam really comes in at 3500 rpm. and pulls hard to 7200.
my carbs are twin 1.5 su's with fairly rich needles. I am using ABZ needles I have tried ABT and ABW theses last 2 rev out at 5500 and 6200 respectivly (see chart at this site to compair needles it is a great site for su's, ) http://www.mintylamb.co.uk/suneedle/ the distributor is electronic with fire ball ignition and I have matched the timing to be 34' at 3500rpm Ive got extractors and straight through muffler 2 inch pipe the fly wheel and crank have not been lightend how much difference will this make?
#6
Re: bigger valves?
nzdatman
Posted on: 2008/9/18 10:32
put some dellortos on it and if your .295" is indeed valve lift and not at the cam you need a decent camshaft as well
#7
Re: bigger valves?
jeffroj
Posted on: 2008/9/18 10:40
''295' cam lift'' sorry didnt read the specs properly . are dellortos better than dcoe webers
#8
Re: bigger valves?
WhiteSedan
Posted on: 2008/9/18 11:56
Quote:
are dellortos better than dcoe webers. They both have their ups and downs, webers are easy to find new parts, dellortos are very hard although a lot of parts are being reproduced these days. If you get 40mm Alfa dellortos (DHLA 40-F/G/H suffix) you will have trouble with lower revs on a smaller than 1.8 - 2L motor as there are too many progression holes causing a lean mix, you can mask this with larger idles. If you can find some universal 40mm dellortos (DHLA 40 no suffix or C/E i think) or 45's then by all means grab them, but for easiness get some webers. On a road car alfa dellortos are great as you don't have to worry so much about a slightly lean progression phase and they are supercheap to come by. I would go webers, dowel and match port manifold for starters, then look at bottom end if your not happy with the results. You will also need to get rid of vacuum advance if you go for webers and then get dizzy regraphed to run about 12-15 You can view topic.
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