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View Full Version : Spitfire race modifying a spitfire 1500



waltesefalcon
05-22-2002, 12:09 PM
Hello All,

I am the owner of a 79 spit, and I am also a member of the local SCCA club. I would like to make my car competitive and I was wondering if any of the memebers here could give me some pointers on modyfiny my engine into something a bit more powerfull.

Cheers

aeronca65t
05-22-2002, 07:41 PM
Depends on what type of competion you're into.

For Autocross, you might be best to leave it stock....otherwise, you'll be bumped up into a class that would require extensive mods. This is especially true if you're "new" to Autocross.

For more serious high speed stuff, the Euro-spec twin SU carb and manifold setup is a good modification, especially combined with a header. The carbs (HS-2s) are easy to find but the Euro-manifold is sort of rare in the U.S. I'm told the earlier 1300 Spit twin carb manifold won't fit (but I'm not sure why that would be true). You can get the header from JC Whitney , VB or Moss.

Pierce Manifolds sells Weber DGV carb/manifold kits for the 1500 but they're not cheap and I'm not sure if they're as good as the SUs. I saw at least four of these kits for sale "used" at the last Brit flea market I was at....a few folks told me they're not that great. I had a Weber DGV carb on one of my old cars....it was no improvement over the stock carb (plus, IMHO downdraft carbs look funny on a Brit car).

The sidedraft DCOE carbs can be fitted to that engine too....they look great but I don't know any thing about them. They seem complicated and expensive (Basil may disagree.....he's got them on his 1500).

If you do anything else (cam, pistons, flowed head) be sure to re-build the bottom end. 1500 Spit crankshafts aren't the most durable for racing.....be sure your rod bearings and crank journals are in good shape.

waltesefalcon
05-23-2002, 12:25 AM
Thank you Aeron65t,

I was not planing on rebuilding the bottom end, I was only planing on milling the head, porting and polishing the head and putting in a hotter camshaft. I apreciate the help. I believe that unless anyone has a really good reason for me go with a weber set-up I'll use the twin SU carbs. I have already found two carbs and a manifold.

Thanks Again

05-24-2002, 10:00 AM
I had a previous Spit 1500 with a set of HS2 carbs off of a 1300 Spit. They bolt on without any problem.
The European and UK Spit 1500s all had the HS4 Su's. I have those on my current Spit, and they breathe better at higher rpms.
I see setups regularly come up on ebay, or you can try Ted Schumacker for setups(www.tsimports.com), or teamtriumph.
So twin SU's, header, electronic ign,tires, and some suspension tweaks will make for a very fun autocrosser...

ron

'78 Spit
twin HS4's, header, Pertronix, Konis

waltesefalcon
05-24-2002, 11:45 AM
Thank you Canadaspit,

I already have two HS2 off of a 1300 spit I found in a junkyard. I think I will start looking for a couple HS4s though if they are better. Also what sort of suspension tweaks are you taking about? Just stiffer spirngs and shocks or something more dramatic?

Cheers graemlins/thirsty.gif

Z28Quetzal
05-26-2002, 11:54 AM
Ron,

Some questions:

The HS2's you were running, did you use a different needle? I have a pair of HS2's that I would like to use on my 78 Spitfire too. I have already a set of headers (4 into 1) with a Supertrapp muffler. What needle did you use?

Regarding the Pertronix on your car: I presume your car had the Lucas electronic system, just like mine. Is the Pertronix superior to the Crane system? Any thoughts would be appreciated...

Regards,
joe

05-27-2002, 09:48 AM
Hi Joe, I'm not positive on the needle size in the HS2's I had. I'll go through my log books... I think they were AN's.
My Spit had been retrofitted with an earlier points dist. It was supposed to have the factory electronic ign.
What I like about the Pertronix setup is that it's totally concealed so it looks stock, easy to install, and totally reliable so far. Improved the idle and power up of the engine. I'm using a Lucas Sport coil along with it.

Ron

piman
05-27-2002, 12:20 PM
I would advise you to ensure that all the basics are 100% before doing any modifications. To rebuild the bottom end of the engine first ensures that it will endure the stress of racing. This aplies to all aspects of preparing the car.
To loosely quote Smokey Yunick, " all the trick bits in the world are useless if you car falls to bits".
I am sorry I cannot give any specifics for a Spitfire as all my Triumph motoring (20+ years) has been with the big six saloons,(sorry sedans)
Godd luck,
Iain graemlins/hammer.gif

waltesefalcon
05-27-2002, 11:45 PM
Thank you Piman,

I appreciate the reply. Do you have any preferences to the bearings in the bottom? I was thinking of using cleavites.

Cheers graemlins/cheers.gif

RHWins
05-28-2002, 11:50 PM
Dial in some negative camber in the front and rear,this can be done at the front by spacing out the lower A arm. Start with 1/8" and see how the tires sit. Another cheap fix is to remove the choke shaft and butterfly. That reduces the restriction in the carb, but plug the holes where the shaft use to go, so it doesn't draw air and lean out the mixture. Spend $ on tires, light wheels (not wires, they are heavy and can go out of tune) and school. Headers and less restrictive exhaust help too. Next, move the battery to the right side of the rear boot to put some weight over the wheel with the least weight to improve the balance. Do you have a radiator fan driven by the fan belt? That takes HP to drive. Consider switching to an electric one, but use a thermal switch. Check your plugs and learn how to read them. You might want to go to a hotter plug, especially in the #2 and 3 cylinders. Don't hog out the intake ports too much,you lose intake air volicity at lower rpms which reduces torque (coming out of turns). I found that a 3 stone brake cylinder hone works pretty well to open the ports. When you have the valves ground, see if the machine shop will bevel the valve guides round to reduce obstruction in the area. Wash the head with soap and water thoroughly before reassembly. Before you fire it up, turn it over awhile with the spark plugs removed and gas disconnected to get teh oil flowing.
Finally, don't forget to make offerings to whatever higher power you perfer!

piman
05-29-2002, 02:14 PM
Hello Maltese,
I just use the standard bearings that the engine shop supplies, but I don't race my car. I have not heard of Cleavite, American brand?.
On the last engine I built I had it 'Tuffrided, to harden the journals, took some weight off the flywheel and had the lot balanced.
Iain.

graemlins/hammer.gif

waltesefalcon
05-29-2002, 04:47 PM
Thanks Piman,

I'll go ahead and make sure I harden my gournels. And I was already planing on getting an alluminium flywheel for it. And yes Cleavite is an American brand. Thanks again I would never have thought of the tuffriding thing.

Cheers graemlins/cheers.gif

06-10-2002, 10:00 AM
Hi there, the aluminum flywheel conversion is not recommended by many. I guess it makes the car more difficult to drive smoothly. A lightened stock flywheel is a good compromise. Unless you're racing it, then any less weight is a good thing...

Ron

Basil
06-10-2002, 10:18 AM
I had considered a lightened flywheel on my Spit but was convinced by a guy in my local club that it was not a good idea if I wasn't actually racing. The gain in top-end HP is at the expense of low-end torque.

Basil

waltesefalcon
06-10-2002, 05:38 PM
Thanks Basil, and canadaspit,

I believe that I shall leave the factor flywheel in, I would rather keep my low end torque in lieu of the high end HP. Thanks again guys and if you can think of anything else let me know.

Cheers graemlins/thirsty.gif
Walter

Bill J
06-12-2002, 12:29 AM
I'll chime in on the other side of the lightened flywheel issue. I've had lightened flywheels on several of my street cars and never had a problem. The only one that was at all difficult to drive was the Mazda RX3 I autocrossed/daily drove years ago which had an aluminum flywheel/clutch combo that was only 12lbs total. Considering the stock flywheel alone on those was ~45 lbs it made a noticeable difference and was somewhat more difficult to drive smoothly initially. With practice it wasn't that bad however, and it made a huge difference in acceleration. I'll be putting in a lightened flywheel in my GT6 as soon as I get to rebuilding the transmission. A couple of side notes here also, a lightened flywheel doesn't change the amount of torque or hp you have, it changes the rotational inertia of the engine allowing it to gain RPM more quickly. The lower inertia of the drivetrain can in extreme cases make the car harder to drive when leaving from a dead stop which is what most people who don't like them complain about. I've never had any real problems personally as I said above. The other thing to consider for a car being used in autocross (or just being driven hard) is that due to the lower inertia the rest of the drivetrain has less shock to deal with when shifting, causing those components (trans/diff/axles/u-joints) to tend toward less wear/breakage and you also don't have as much problem with tire spin.

My $.02

waltesefalcon
06-12-2002, 07:40 PM
Thanks Bill and RHWins,

Bill thanks for your imput on the light flywheel. I'll now have to consider it some more and after all if I put one in and don't like it I can always put my old flywheel back in.
RHWins thank you for your advice my apologies for not acknowledging you till now. I somehow managed to completely miss your post. I apreciate the advice, especially the bit about using a cylinder hone on the head.

Cheers graemlins/thirsty.gif
Walter