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Hi all,
I’m looking for advice for my B-engine that I cannot seem to make perform as it should… Here’s the deal, bear with me, I’ll try to give the full picture while hopefully staying be as synthetic as possible!
It’s a quite freshly (less than 20k km) rebuilt B-engine with single carb (originally twin carb). The rebuild included waterpump kit, new timing chain and tensioner, brand new pistons and rings, as well as crankshaft & rod bearings. The head was professionally surfaced and a valve job was done. It has the original stock carb camshaft which looks in great shape. Compressions are all at 12+bar with max 3% difference.
The carb is also rebuilt (sonic cleaning, new gaskets and diaphragm). It is adjusted according to workshop manual using a professional grade CO analyzer. The needle and jet have not been renewed, but the carb is out of a 79k km car, so wear should be minimal.
Ignition is adjusted in the same way, and the ignition curve has been checked throughout the rev range – it’s within tolerance. Sparkplugs, cables, rotor and distributor cap are new.
There is a 2’’ exhaust installed on the car (I got it because it was a lot cheaper than the stock one plus the stock downpipe was not available back then).
It has 6 primaries in a chillcast 4gr box, which bring the revs to 3’200/min at local autobahn speed (120 kph)
Issues I am running into are mainly rough running and lack of power at cruising speed. As soon as I hit a small climb in 4th gear, the speed goes down dramatically, and the engine has then a tendency to vibrate and overheat. I have noticed that when running hot, the issue seems to get worse.
I can bring the car to 140 kph when the engine temp is normal and the road is perfectly flat. I will not go beyond 110 in 4th on any small incline or when running hot. I can gun it to 120 in 3rd regardless of the situation, and I have noticed it tends to stay cooler high-revving the 3rd rather than cruising in 4th.
Also, the exhaust becomes extremely hot – to the point when the ignition key is too hot to touch when extracted. There is some occasional self-ignition at switching off, as well as some backfiring when under slight load in 4th gear at cruising speeds – never in lower speeds, higher rpm situations.
Except for the exhaust and primaries, the powertrain is stock. The single carb went in when I got tired of tweaking the twin carb setup constantly using low-quality spare parts. When running the twin carbs, the situation was slightly better but not overwhelmingly so.
Any ideas on what to check and what could cause the issue?
posted by 87.67.20...
, Wed, 6 Mar 2024 07:21:34, Thu, 7 Mar 2024 07:31:12, Mon, 18 Mar 2024 12:59:30
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