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19064 - autocross project car for SCCA's FSP class  Rating:  Rating
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 Posted: 04-28-2017 03:35 am
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Esprit2
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Location: Minneapolis, Minnesota USA
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Steve,
What will fuel injection do to how the SCCA classes your car for autocross?

If you had another stock head, would you install it just to get the car running until the Lotusbits shipment arrives? There's a fellow south of Victoria who has a JH engine for sale. I've not checked in with him for a while so I don't really know if he still has it, but I could give him a buzz if you're interested.

Also, there's a fellow in the Brooklyn Park area who has a seriously ported Dave Smith head for sale, along with a set of DS2 cams to go with it. Fresh as received, never installed. DS2 cams are a step hotter than the Lotus 104 cam. That one wouldn't be cheap, but it would sure be effective.

Regards,
Tim Engel

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 Posted: 04-28-2017 01:53 pm
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stevegarnjobst
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Tim,

Fuel induction & ignition are mostly unrestricted in Street Prepared, so EFI is probably the single most significant engine upgrade I can make within the rules.

Unfortunately, I have to keep the stock low-compression pistons & cams, so performance gains will be modest. However, I won't miss dealing with finicky carbs - especially as the weather changes. I also had major issues with fuel starvation on the Strombergs on sustained left-hand turns. I could convert to Dellortos, but EFI offers a better (if more expensive) solution.

One other upgrade I'm planning for the EFI is a new fuel tank. The rules provide some leeway for replacement, in cases where new OE parts aren't available, so I'll be installing a new tank with AN fittings that match the Aeroquip hardware used on the LotusBits system.

Regarding the extra stock head, I'm a bit leery of those stock cast-iron tappets, after having one come apart on me last year. :(

Last edited on 04-28-2017 01:57 pm by stevegarnjobst

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 Posted: 04-28-2017 05:03 pm
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Esprit2
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I'm surprised fuel injection is such an open option.

How are your cam's timed. The early J-H timing was 115 IN / 115 EX, and that reduces output by 10 Hp. Later it went to 100 IN / 110 EX. Both of those are emissions settings, and not desirable. The design-correct C-cam timing Lotus used in the early 907 is 110 IN / 110 EX.

Does Street Prepared restrict the cam timing to stock, or can you make adjustments? At least update/ backdate? If that's not a problem, then try re-timing the stock C-cam to at least the design-correct 110 / 110, or more aggressively to 104 MOP IN / 110 MOP EX.

Unfortunately, the latter would require a new 104 MOP green-dot pulley for the intake, and they're expensive for what you get. Maybe Mike Taylor can set you up with a serviceable used one. 115 and 110 co-exist on the same pulley, whether both are marked or not.

Not that I would ever suggest cheating in anything but the holy NASCAR-biblical sense, but the C-cam has 272 degrees of duration, and the 104 cam has 272 degrees of duration. The devil is in the details... just sayin'.

You're right to be concerned about the cast iron tappets. I've seen way too many cracked ones in recent years. Steel replacements are available, but a set of 16 gets expensive. On the other hand, one broken tappet in a running engine gets very expensive in a heartbeat. But then, you now know that... tell the others.

Regards,
Tim Engel

Last edited on 04-28-2017 07:09 pm by Esprit2

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