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How long was this pull - how many seconds did it take for the engine to go from 3200 to 4700? Assuming you loaded it in a tall gear that lean period looks like it persists too long to be a pump shot issue, although the lean spike at the start of the pull might be. After checking the pump shot...

Can't shed any light on whether your exhaust leak has been a factor but am sceptical that going from a 6.5 to 4.5 PV would change much in a situation where an engine was rapidly loaded to WOT on a dyno - that's mostly the domain of the pump shot. When the engine is wide open, either power valve...

Just curious and no experience on this set-up, but is there not edit software for the GM ECU that allows you to tailor the throttle tip-in and dashpot functions? There is no physical reason why a DBW can't be very direct if you can access and tailor these. Cheers, Andrew

Hi, the return style carb set-ups I have been involved with use an electric pump capable of 20+ psi without an internal bypass and a return style reg such as the mallory 4309 to control pressure: Mallory Ignition 4309 - Mallory Fuel Pressure Regulators - Overview - SummitRacing.com...

Looks great Leon. It's going to be a thing of beauty. Cheers, Andrew

Gidday Brett, I've always used a -12AN nipple welded to each rocker cover and run 3/4 inch hose from each to a 2 litre puke tank with a single small-ish K&N airfilter on top of the puke tank and a drain so it could be emptied easily. I retain one oil filler cap on one cover but not a breather...

KB I got all mine HPC'd in the std header coat when I did the headers, looks good and I think thin enough to enable decent visual inspection. Sounds like you're really ripping into it. Cheers, Andrew

Cliff, basic answer - no. Accel enrichment (which is present in both carbs and EFI) is simply there to manage transition from a lower engine load to a higher load. Accel enrichment compensates for the momentary lean condition that occurs in both carb and EFI set-ups when a sudden increase in...

Hi Alex, looks too fat 3000-3500, slightly on the lean side of safe but pretty good 3600-6100, too lean 6100-6400. I use 12.8 as a rule of thumb, or 12.5 if I'm being a bit lazy and want some safety margin and don't mind dropping a few HP. Have you checked your high speed air bleeds...

KB, AFAIK the GT40 suspension set-up is virtually identical to what I have in the McL canam replica. My chassis came from Autotune with springs that they had found to work well in racing, and they indicated that they were on the soft side for a track set-up - i.e. a good place to start - i.e...

Hi Russell, I agree with KB and emphasize the point that you're really shooting in the dark if you don't have accurate measurement of mixture under load. Cheers, Andrew

Russ thats pretty bloody rapid - good stuff. Cheers, Andrew

Leon, got this clarification/correction on the rear uprights from Richard at Autotune yesterday: "I saw you post on GT40's last night, the rear uprights on your car were originally designed here in the UK by Manchester University (I think, I will have to check) the only Sierra Cosworth part...

Hi Leon, I'm not one of those intrepid souls like yourself doing a scratch-built car - very much admire what you guys can do. The chassis was built up to about 85% complete by Autotune in the UK, and they also supplied the suspension, rear uprights, and body panels taken off an original...

Hi Russ, What I found when dragging my race and road cars previously was that a big burnout was not beneficial because usually the rubber I was running was not drag racing rubber, so I did enough to warm the tyres a bit and clean them up then staged the car. I have found that high intake...

All, Just to make things ultra confusing or interesting(?) - in the backwards and forwards discussion with the axle supplier, he went aheead and freed up clearance on the axles so now I have 930 CVs which are designed to float in themselves also now floating nicely on the axle!! I'll let you...

Hi Terry, outlet has been trimmed to finish level with the bottom of the chassis and points down. Cheers, Andrew

Hi All, bit of an update - chassis done and back from the powder coater, hardware now going in. Halfshafts and rear brakes to go on, then I'll move to the front and fit steering and front suspension. Have a good week. Cheers, Andrew

Hi Russell, do you have a wide band o2 sensor like the Innovate LC1 - readily available for probably less than the cost of a dyno session (for example Innovate LC1 Lambda Cable + O2 Sensor for sale - TradeMe.co.nz - New Zealand ) and can be used with a digital multimeter to get a pretty accurate...

Randy, Trevor, Scott, Cliff, and Terry: Thanks for the sharing all your knowledge and experiences. My axles are 375mm long (14.76in) and from memory I have about 10mm total effective length change as the suspension moves through its full travel. It sounds like the CVs could comfortably chip...