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

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arturo64 Avatar
arturo64 Arthur T
Billings, MT, 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, MT, 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, MT, 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, FL, 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, MT, 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, FL, 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, MT, 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, FL, 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.

JimG Avatar
JimG Jim G
Aurora, CO, USA   USA
It's usually cheaper with bigger gains to improve the driver. Get as much seat time as you can stand or afford. Read, study & ask lots of questions.
Drivers school if you can get one. My club, RMVR has a competition and performance drivers school every year for about 300.00.
SCCA is going to start sending their rookies to us this year.
Make it reliable, make it handle, stick with the 1300 for reasons already stated. Get the best tires SCCA will let you have. If you have to use treaded tires
the Toyo RA-1s get faster the more rubber you wear off. If they let you use a D.O.T slick then the Hoosier R7/SM7.
For incremental engine changes, increase your compression ratio until you have to run premium if you are going to still street the car. 10:1+
Build a bulletproof bottom end. Maxspeeding makes a good forged rod for a good price & they come with ARP bolts.
I nitride my cranks and use antifriction coatings on all the bearings. ( like Calico but local )
A good cam & header to match the increased comp ratio and I've always been a believer in the Mikuni HSR carbies. They worked wonders on my car
until I went with DCOE's. I only went with the DCOE's because the tr4 intake wouldn't flow as well as the head, no matter what I did to it.
A good dyno tune isn't that expensive. In Colorado you can get dyno time for 60.00 / hr.
Don't forget the ignition in all that. A pertronics unit is a good start.
Before you know it you will be going dry sump on a 9K RPM motor at 14:1

Speed costs money, how fast do you want to go?

http://www.britishracecar.com/RichardBrown-Triumph-Spitfire.htm

just another .02
good luck
jim g

Oh, Get Kas Kastner's books.

arturo64 Avatar
arturo64 Arthur T
Billings, MT, USA   USA
yeah the motor question came to mind because I'm going to be looking at a rebuild sooner rather than later. thus "which engine to choose". but I've kinda come to the conclusion to stick with the 1300 and with a fresh build with good materials hopefully the extra pep will be enough for me. obviously i'll always be a long way from the modern crap running around, will just have to take a deep breath and focus on having fun. as for classes, I'd have to start traveling a fair distance and it seems the focus would be on high speed applications. both of those things are not my interest for now(to many other mountains to climb). I do feel I'd be very well off solving a difficult understeer problem I'm having. and maybe learning to downshift into non-syncro 1st.... so still much to play around with.



Arthur
68 spit
70 gt6+

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
What speeds and rev range are you running?

I found the 1500 to be very good on the courses we were running. The engine would most often be between 3k and 5k sometimes flashing up to over 6k (if the cones were too far apart)
A mkIII type cam profile helped and a 4-2-1 manifold was better than a 4 into 1

However in my case sorting the ignition paid the biggest dividends.

JimG Avatar
JimG Jim G
Aurora, CO, USA   USA
If the front is pushing check your camber & tire pressures. You can tune that out. If you can't get to a school there must be some good Auto- X videos.
I have my students watch videos by Scott Mansel, Nigel Mansel's son. They are about road racing but the fundamentals are the same.

https://www.youtube.com/channel/UCtbLA0YM6EpwUQhFUyPQU9Q


good luck
jg



In reply to # 1513794 by arturo64 yeah the motor question came to mind because I'm going to be looking at a rebuild sooner rather than later. thus "which engine to choose". but I've kinda come to the conclusion to stick with the 1300 and with a fresh build with good materials hopefully the extra pep will be enough for me. obviously i'll always be a long way from the modern crap running around, will just have to take a deep breath and focus on having fun. as for classes, I'd have to start traveling a fair distance and it seems the focus would be on high speed applications. both of those things are not my interest for now(to many other mountains to climb). I do feel I'd be very well off solving a difficult understeer problem I'm having. and maybe learning to downshift into non-syncro 1st.... so still much to play around with.

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