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greed...which way to go with an engine upgrade

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arturo64 Avatar
arturo64 Arthur T
Billings, Montana, USA   USA
so I'm having a ton of fun with SCCA autocross and I feel my handling on my mk3 spit is really pretty good. I could just look to make small tweaks to the car while making the most adjustments to the "nut behind the wheel" but now that I'm catching up with people...ugh...more power comes to mind. I can't tell you how many freakin times someone suggests an engine swap to something new, and I will never do it! but I'm either going to need to refresh my 1300 or go for the bigger 1500. I'm not looking to make a full on race motor but want something on the hotter side. when driving I am getting near redline but not really that often. I feel like it would be sacrileges to build a 1500 over the 1300. thoughts???

current motor; unknown CR ratio/build. dual HS2s with really pretty large paper filters but held together via 'fashion over function' pancake style, 4:1 header with nicely cleaned/shaped ports(not full on matched though), drop in electrical ignition in stock dizzy, mechanical fuel pump and cooling fan removed for electrical components, and puffs a wee bit smoke on hard shifts.

thoughts on upgrade with 1300; mid to high 9:1 CR. bigger intake valves?, dual HS4s, K&N filters with proper cool air plumbing, same header as above, stock cam? or a "stage 2"(whatever that means...),

1500: same stuff as above but not scared to go to HS6 carbs( I have a million of them on the shelf).

I'm running in the Heritage Class which is fairly lenient, so lets hear some opinions!!



Arthur
68 spit
70 gt6+

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arturo64 Avatar
arturo64 Arthur T
Billings, Montana, USA   USA
1300 vs 1500??? Anybody??



Arthur
68 spit
70 gt6+

A. Bradley Aaron Bradley
Erwin, TN, USA   USA
1969 Jaguar E-Type 2+2 "The Jag"
1975 Triumph TR6 "The TR"
Hey man, 'glad to hear you're having a blast auto crossing your Spitfire in the great Heritage Classic Street class. I run my TR6 in that class also but usually by myself because no one else shows up or is interested in running their classic Brit car. There's just no competing with anything more modern and/or more powerful.
I noticed your post a few days ago but I didn't want to comment since I don't know the difference between those Spitfire engines. However my first car was a tired 1500 Spitfire so I guess go for the 1500. I'd be glad to converse about some mods and whatever else is involved having fun auto crossing these old Triumphs.

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arturo64 Avatar
arturo64 Arthur T
Billings, Montana, USA   USA
Man I really am having fun. I'll never truely win but I'm just trying to have fun, get better, and use the car as a Sports Car! I do wonder that if I could approach the 100hp mark, if I'd be able to jump a tier on the time tables. But then I think that is a slippery slope cause when is it ever Enough??



Arthur
68 spit
70 gt6+

65or66 Gold Member Jim B
Lake village, IN, USA   USA
1965 Triumph Spitfire MkII
1973 Triumph Spitfire 1500 "Jusanudda Munny Pit"
you could keep the 1300 in while you rebuild a 1500, then swap out the 1500 when done. The 1500 are plentiful and cheaper to get in rebuild condition, both from Spits and later Midgets. Hard to make sure it is rebuild-able from the outside tho'. Lots of past discussion on the Spitfire forum about getting to the 100hp mark with the 1500. Some say it's not too difficult, some say it not worthwhile. And then the discussion about low redline in the 1500 is another big ol' can o' worms tootongue sticking out smiley

There was a recent post over there with some dyno numbers about some minor upgrades on a 1500. The numbers were a decent gain, worth looking into. I think about 2-3 weeks ago.

clshore Carter Shore
Beverly Hills, Florida, USA   USA
Due to the longer stroke and larger diameter rod journals, 1500 do not tolerate higher RPM well.
The Spitfire rod bearings are the weak link, and they are marginal even on a 1300.
The 1500 rods are far heavier than 1300 rods.
A 1500 can be optimized to take advantage of the longer stroke and greater displacement,
which favor low and midrange torque over high RPM horsepower.
On most autoX courses, this may be precisely what is needed; short straightaways and tight turns,
rather than high speed straightaways.

Proper cam selection is the key, then optimize the rest of the motor to promote Volumetric Efficiency at low & mid RPM.
Ignition timing and precise control will yield big gains, along with an aluminum flywheel and gearing choices (gearbox as well as final drive).

Carter

arturo64 Avatar
arturo64 Arthur T
Billings, Montana, USA   USA
ugh.... part of me wants to say "it's only money".... but then other part of me remembers I have a Peerless to rebuild... and a gt6 and tr4a.... will be keeping my eye open for a motor in my area to get for nothing.



Arthur
68 spit
70 gt6+

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clshore Carter Shore
Beverly Hills, Florida, USA   USA
In reply to # 1469889 by arturo64 ugh.... part of me wants to say "it's only money".... but then other part of me remembers I have a Peerless to rebuild... and a gt6 and tr4a.... will be keeping my eye open for a motor in my area to get for nothing.

Much of what you need can be had from judicious choices from the stock parts bin, and a bit of sweat equity.
The heavy 1500 rods weight about 715 g. Each.
A few hours spent with a 1" x 30" belt sander and a craytex wheel mounted on a bench grinder allows you to lighten them to
about 600 g. Follow the instructions in the Spitfire competition manual.
Smooth out the runners and ports in the manifold and head.
Either fit cam bearings and a Mk II camshaft, or get the Mk II grind on a 1500 cam blank that some vendors offer.
Or, Ted @ TSI offers reground cams, Kastner 'B', or Ted's TSI275-4, for $140.
A Fidanza aluminum flywheel is about $300 on eBay, but you can keep your eyes peeled for a used one.
A stock dual HS2 setup from a Mk III will yield good results if you are looking for low and midrange torque rather than high end HP.
Rework the centrifugal advance in the dizzy with stiffer springs, about $15.
Mill the head, and try to find the least restrictive exhaust.

arturo64 Avatar
arturo64 Arthur T
Billings, Montana, USA   USA
well when you say it like that! sure sounds good to me. will look to be my winter project.

just to clarify though, I thought the MKIII was the best cam. and no HS4s??? I'm not gonna be that scared to run it in the higher RPMs (for me that's up to 5,000)

always a lot to learn



Arthur
68 spit
70 gt6+

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clshore Carter Shore
Beverly Hills, Florida, USA   USA
You are correct, the Mk II and Mk III have the same cam timing and duration, but the Mk III has a bit more lift, and so is generally better.

HS2 are not the limiting factor for low and mid RPM torque, even on a 1500.
Smaller ports and runners yield greater mixture velocity at low and mid RPM, which helps with cylinder
filling, upping the Volumetric Efficiency and torque.
Unless you are ready to spend thousands on a fully ported cylinder head, optimize what you have.
Gaining performance is like a chain, you are limited by the weakest link, whatever component performs worst.
Get all the components working together for the best result.

Lacking an engine dyno, a stopwatch works, even better an iPhone app to time and record results.

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