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Old 07-17-2020, 08:27 AM   #1
Board Member
Join Date: Sep 2009
Location: Aberdeen, Scotland
Default B20A Improvements

Iíve got my B20A in my 142 running lovely but she feels like she could handle more zip and acceleration. This is not a quest for max HP numbers or trying to one up but I want to improve acceleration in the 1000 to 3500 rpm and 3500 to 5000rpm ranges. Now there is a reasonable size BUT as well, my car is lovely and original and I want to keep it looking like that so Iím keeping the single 175CDSE stromberg carb. I will be converting to an adjustable jet so I will be able to play with mixtures to a limited extent with the carb but I donít think thereís a huge range of needles available so might have to do it the old fashioned way of removing thickness from the needle at certain areas. Will have to see. Currently running a all new ignition with a 123 dizzy and like I said the car engine runs spot on.

Iíve contacted Ben at Tinus Tuning and the TT3 cam seems like a very decent upgrade from the A cam. Other changes nailed down in my head are a 7kg flywheel and 2Ē exhaust. Now what Iím not sure of is what head changes if any to do considering my remit of improved HP at low to mid range rpm. Ben suggested his stage 1 head which Iíve replied asking him will this improve HP in the 1000 to 3500 rpm and 3500 to 5000rpm ranges. My initial thoughts for the head were to increase CR up to 10 : 1 and add 44mm intake valves. CR increase is a no brainier I think but what Iím not sure of is there any point doing anything else to the head as I might not get any gains in my rev range or maybe even make it worse?

The B20a single carb and B20B dual SUs are pretty much identical to 3500rpm but the B engine gets about 16hp more at 4500rpm and 23hp at 5000rpm. The B20E injection engine seems to be consistently higher at all revs which is probably a mixture of Cam, CR and FI. So I know doing all of the above with twin SUs will be better than a B engine so if I have to put a number on it what Iíd like to achieve is for my single carb engine to get 110hp at 4500rpm. Possible?
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