Inside Plug/Outside Plug

I think the 250 GT is more agile on curvy roads because of the shorter wheel base an dthe 250 GT/E i snetter to go straight

 

Same 2.6 m wheelbase. Engine moved forward in GT/E.

 

oh? I thaught also the wheelbase changed. so learning again new things here.
this with the engine I had known

 

Gentlemen, perhaps incorrectly, but I think Henk was referring and looking forward to performance comparison, feel, etc between inside/outside plug engines, not the chassis.

 

It is always more about the car as a package than the engine alone. If you want a real comparison, you have to drive maybe a Boano first with an inside plug engine tipo 128 C with let's say 240 hp, then take out the engine and put an outside plug tipo 128 F also with 240 hp in and drive again. I bet, there will be no difference in the driving characteristics.

 

To me, the IP throttle response is more sewing machine like.... going back to when I waited till mom walked away from her Singer and I'd put my foot in the electric pedal and pretend I was Phil Hill. Boy, that pissed her off to no end.

john

 

I hope that I am not repeating something already explained on this thread. Anyway:

I had thought that the original Colombo engine had 1.5 liters because it was meant to be a supercharged F1 engine which had a 1.5 liter limit. Mouse trap springs were chosen to reduce the valve weight so they were easy to open and close fast. But this did not leave much space on the heads so that (fewer) studs had to be placed in such a way as to not leave much space for the intake ports that then had to be siamesed. This reduction in flow was of no concern because of the supercharging.

 

Mousetrap springs were chosen because no "coil" springs of that era were reliable at the rpm the engine was capable of achieving. A mousetrap spring also has the advantage of applying consistent pressures throughout the valve opening and closing events.

 

Dyke, just so folks know what we are talking about:

Best regards,

Robert

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the only thing they are bad is at higher rpm`s

 

I specifically sought out an inside plug 250 when I bought my first vintage ferrari. I wanted all the experience I could afford, pre 60's car, inside plugs, interesting and documented history, etc. I was very happy with my choice and had a great time with that car.

 

Reading some of the comments/replies here and elsewhere, I’ve been wondering if anyone more acquainted with the hairpin-to-coil spring conversions done on early engines would have an (percentage) estimate on how many have received this treatment ?

Also, does such conversion/treatment add or subtract from perceived resale value or have any affect on point scoring at IAC/PFA level judging ?

Just curious.

 

Timo: Without the cam covers removed, you cannot tell if the conversion has been done, so no effect on judging. I know quite a few motors have been converted since we began doing them in the mid 1970s. The problem then was no supply of factory hairpin springs. There were repros available then, but they failed almost immediately in service. I believe there are now good quality hairpin springs available. The original springs wear where the retainer rides on them and that is why they go bad. However, I have seen springs almost 1/2 worn away and still functioning perfectly. When we encounter a motor with hairpins, we almost always convert them to modern coils. You will probably need new valves anyway, so might as well have modern reliable parts that will run for years.

 

Dyke,
Thanks for your insight.

I know/realize the visual inspection or verification of original design/construction details or features inside any mechanical components are not feasible/possible during judging, but as someone who often "struggles"(?) to support justifications for some improvements or upgrades, I just find these issues intriguing.

Would I be fortunate enough to face this particular "dilemma" on my own, I'd probably modernize it too to maintain practicality and safe use, but would probably look into spare, perhaps reproduction(?) heads or entire engine to do it with and leave original ones "as built".

 

why not use new heads instead of modifying the old ones. because so you could save the old ones and pee then original

 

Regarding engine responsiveness for IP vs OP: what about flywheel weight? Lighter flywheel, quicker response.

 

sorry, misstyping: wanted to write ..... and keep the original

 

Joe: In the 1970s, there were NO "new" heads, either original or reproduction. Good quality repro heads have only been available in the last 15 years or so. Also cost is a major factor with modern valves being easily custom made here for very reasonable prices and off-the-shelf valve springs not costly. You can convert MANY engines for the price of a pair of new repro heads.

 

once converted, can it be reversed to original if so desired(even if not a good idea).

 

Ed: You have to do some careful machining on the head, and while I never tried, this could make reversal more complicated. There is NO reason to ever go back to hairpin springs.

 

If anybody would like a properly produced and bound full colour re-print of the “outside plug” 250 GTE manual..feel free to drop me a PM