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Spitfire Speed and Power 75 spit

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chappy444

Senior Member
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Hello again,
the Joy continues....
I recently got my 75 spit running and road "worthy"
after a few days of test driving and tweaking i have reached the end of my knowledge so to speak.

this is my first spitfire...my first LBC actually.

my car has the monza exhaust and the weber dgav two barrel downdraft carb...as far as i know the rest of the engine is stock...good compression +/- 152 across all cylinders.

i remember riding in a friends MGB in high school and it seemed blazing fast off the line compared to my spit now.
also...my top speed is around 60-65 MPH at WOT. is this normal? my wifes 4cyl dodge caliber is wicked fast compared to my spit...i thought these cars were atleast alittle bit fast...

everything seems to be working correctly... except the OD...but really i have not put much thought into it as i can barely get upto a speed to make it worth using.

my speedo is off so my top speed is an estimate.
i have adjusted the carb linkage so that i can get the secondaries to fully open with the peddle on the carpet...

1st gear is good for about 12 mph (or less) at about 3000-3500rpm, second gets me to aobut 23mph at 3000 and so on untill i am in 4th with it winding out....from 0mph to top speed probably takes a half mile or maybe even closer to a mile....
is this normal???? i would think with the carb and exhaust it would be faster...if this is normal i would not drive a bone stock one for fear of getting run over by the normal flow of traffic...
thanks for the inpput.
Bill
 
The only time I have been in a Spit was in 1965 when a co-worker gave me a ride in his. At the time I had a '64 TR4 and in comparison I found it somewhat less than exciting. But to be fair the comparison to my TR4 did not help.

Still your Spit does not sound like it is even close to it's potential.
 
Spitfires are not an inherently fast car. The fun is derived in the fact that they feel fast as they rattle around under you. Every time I drive a Spit, I'm sure parts are falling off as I go down the road. My first guess on the lack of power in your car would be the catalytic converter. If your car still has one, there is a good chance that it's clogged and restricting exhaust flow. Just a guess, but a good place to start seeing how your compression numbers look good. Do you still have a sidedraft carb? If so, there are no secondaries. Just a piston that floats up and down depending on air flow that meters fuel delivery, and a butterfly to control the airflow.
 
Most modern cars ARE much faster than old sportscars, I've been trounced at autocrosses by 4 door econo-Hondas. If your Spit is original overdrive it has a lower rear gear ratio, this would limit your speed in the non-overdrive gears at high RPMs. Need to get that overdrive working. I'm not sure if that's why you can't break 65mph though.
 
tr8todd said:
as they rattle around under you. Every time I drive a Spit, I'm sure parts are falling off as I go down the road. My first guess on the lack of power in your car would be the catalytic converter. ... Do you still have a sidedraft carb?
Click to expand...

Todd,
thanks for the response....
i had to laugh while reading your reply...everytime i drive the car i get a different random noise that sounds as if something just broke loose and fell off...and how about all those rattles...for half of every drive i am reaching around the car pushing on things trying to find the source of a rattle...anyway...
as i said, i bought the car as is about a month ago. it had the monza exhaust and weber 2brl downdraft installed when i got it. does the monza exhaust have a cat? i have been under the car and there are what look to be 3 mufflers (not that they seem to muffle anything, much to the chagrin of my neighboors i am sure.) one is mid car and the other two are on the split tail pipes...is the mid car one the cat? everything seems to be welded in place...there may be a clamp at the Y pipe and another at thedown tube from the manifold.
 
I am not sure about the cat but the one at mid would be the cat if it has one or another muffler. Everything after that is the monza and all it does is make noise. My sons car wakes up the neighborhood.

I would say you have a restriction in the exhaust and your weber is not tuned correctly for the car. You will need to make the restriction is cleaned up before you can tune the weber correctly.

You should have more power and be able to do at least 75-80 in fourth and maybe more.

The issue is your memory. When your 18 you remember all kinds of things better then they were. Like I remember a few girls that were so beautiful when I was 18 and now that I look back a picture of them I must have been drinking a lot back then and wearing beer goggles.

The car is quick but not fast, it is fun to drive when your but is only 6 inches off the ground.
 
My 73 Spit with the original 4 speed would do 60ish at about 3500rpm on the highway.

With the O/D trans it is about 68-70 at the same rpm in O/D

This is with the 3:89 rear gearing.

I am still running the stock CD150 side draft carb. Have my timing (dynamic set) at 14 degrees before and the points set at 40 dwell.

My car runs well but its only a 1300 (big beaaring) and only has so much it can give.
 
My 79 spit is no rocket either, and I'm reminded by my brother in a TR6 how much more power he has. Frankly I don't care!

I love my car, it is fun, it is a quick drive (if not fast), and it never fails to get looks where ever I go. It is a cool car to look at and drive. I have no trouble keeping up with modern traffic, or winding up a B road. I shift between 4 and 4.5k, Plus she never fails to start. At this time she's bone stock, (higher compression, headers, and a new carb are in the future).

My two pennies:

First day I drove mine home I was crestfallen, no power and hard to keep running. Problem turned out to be a corroded and stuck enrichment needle in that foul water choke. O rings, some light wire brushing, then some lube and she has run like a top. I'm guessing fuel delivery issue.
 
3000 rpm is just the bottom end of the power band for a Spit 1500; max power is something like 5500 rpm. If you are having trouble getting it to pull over 3000 rpm then something is seriously wrong.

And while you're certainly not going to win many drag races; you should have no trouble exceeding the legal speed limit. Again, if it won't do over 60 mph then something is wrong.

I know absolutely nothing about the Weber downdraft conversion, but I'm always suspicious when people try to defeat emission control systems as doing so frequently makes the engine run worse than before. So I would start with the basics (are both throttles opening all the way, is it getting enough fuel) and then try to look at mixture at WOT.

Also make sure the vacuum retard is disconnected, as the Weber won't have the right port for it. If someone has arranged the retard such that it kicks in while driving, that would certainly kill performacne.

Wouldn't hurt to verify that the centrifugal advance is working, either.
 
Hi guy's...not to brag or anything BUT MY WHITELIGHTNING(1979 1500)Spitfire doesn't have the above problem(s)it goes like a BAT-0UT-O-heck.I'll put my restored Spitfire up against any comparable Spitfire,TR250,TR4,AND OUT RUN IT.Its ALL ABOUT THE DRIVING ABILITY,BUT a well running car helps ALOT.Come and see for yourselves.Cheers Mate's
KEN&WHITELIGHTING....10% ethenol helps alittle.
ALL STOCK BUT WITH A FEW BUMP-UPS W/a little help from Paul Tegler's site.
 
I'll have a go, going to Mid Ohio?
 
timing or fuel delivery.

double check your static timing,

make sure that the carb is set up for your engine. The previous owner might have gone cheap and picked up a carb out of whatever thing was laying in the pick-ur-part. The weber dgv's were used on all manner of engines because they are infinitely variable. I gotta fried chicken tv dinner that you are going way lean at the top end either because the fuel pump isn't, the fuel filter is clogged or the main jets are too small.

don't be afraid to let the engine rev. It sounds awful to anyone used to an automatic transmisioned modern car, but it's how these tiny engines were meant to be run.

mine would win no stoplight drags but would get out of it's own way.
 
71MKIV said:
timing or fuel delivery.

double check your static timing,
Click to expand...

about 10 degrees advanced at idle.

71MKIV said:
make sure that the carb is set up for your engine. The previous owner might have gone cheap and picked up a carb out of whatever thing was laying in the pick-ur-part. The weber dgv's were used on all manner of engines because they are infinitely variable. I gotta fried chicken tv dinner that you are going way lean at the top end either because the fuel pump isn't, the fuel filter is clogged or the main jets are too small.
Click to expand...

Carb origins and jet sizes are unknown...PO install

71MKIV said:
don't be afraid to let the engine rev. It sounds awful to anyone used to an automatic transmisioned modern car, but it's how these tiny engines were meant to be run.
Click to expand...

it sounds awful now...the monza exhaust does little in the Db department

71MKIV said:
mine would win no stoplight drags but would get out of it's own way.
Click to expand...

it is so bad right now that i try to only go to intersections that have stoplights for fear of having to pull out in front of someone and making them wait so long for me to get up to speed.
thanks for the helpfull response...i am just down the road from you in Bel Air, MD maybe i'll see you on the road one day.
 
chappy444 said:
it sounds awful now...the monza exhaust does little in the Db department
Click to expand...

Your right about that, they are not supposed to. Monza's are LOUD exhaust systems. They also get annoying at a steady speed.
 
myspitfire said:
I'll put my restored Spitfire up against any comparable Spitfire,TR250,TR4,AND OUT RUN IT.Its ALL ABOUT THE DRIVING ABILITY,BUT a well running car helps ALOT.Come and see for yourselves.Cheers Mate's
Click to expand...

Ken, Just because you can still see the taillights doesn't mean your keeping up. :jester: My TR6 just has a few tweeks too. :devilgrin:
 
Bill,

Do you still have the Cat converter on your car or are you running a header for the exhaust. ?
 
Don_R said:
Bill,

Do you still have the Cat converter on your car or are you running a header for the exhaust. ?
Click to expand...

I am still sorting out the mechanicals...it seems that the harder i look the more stuff i find that i want to replace or need to fix...lol...go figure.
i believe that the exahust does not have a cat...although i am not sure...my Monza exhaust seems to bolt right to the stock manifold. then there is a unit that looks very similar to an old "cherry bomb" muffler about mid car and then two smaller "cherry bombs" further back (one on each side of the split before the tips)
does anyone know if that mid-car unit is a cat or a muffler??? (it appears that the inner edge of the frame rail is flared out to accomedate it).
 
Bill,

Stock spit cat is located right at the exhaust manifold.

if you go to the Victoria British catalog it gives a nice pic of what the pipe looks like.

Monza exhaust has a resonator mid pipe and resonator/mufflers right before the tips.
 
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