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1500 build for 100HP-reliable for street

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oldag98 Avatar
oldag98 Jeff and Brittany Brackenridge
Choctaw, Choctaw, Oklahoma, USA   USA
1969 MG Midget MkIII
1975 MG Midget Conversion
1976 MG Midget 1500 "Yellow One"
1977 MG Midget 1500 "Dunkirk"    & more
This thread is for those who have built a reliable performance 1500. I am thinking of doing the same. Looking for about 100 streetable HP, but something that is not going to grenade the engine. How do I do this? What machining operations are required/recommended? What parts are the best for this, crank, rods, pistons, valves, cam, rockers? Lets get a modern recipe for a reliable performance 1500 that anyone can do and that will not cost an arm and a leg... This has probably all been covered on different forum threads, but let's consolidate ideas here.

So far I have a stock engine with LCB headers (TriumphTune- called LCB/Long Center Branch), dual HS4's with heat shield, Accuspark electronic distributor and HO coil and that is all. Basically bolt-ons.

What else can I do/can be done and where do I get the parts?

Any good engine builders with experience doing this?

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Speedracer Avatar
Speedracer Platinum Member Hap Waldrop
Greenville, SC, USA   USA
1967 MG MGB Racecar "The Biscuit"
I encourage Skye to start this forum. You pretty much have read all I have to say on subject, so I'll bow to others to hopefully chime in.



Hap Waldrop
Acme Speed Shop
864-370-3000
www.acmespeedshop.com
Engines, Rebuild Kits and More.


Member Services:
MG/ Triumph Performance Street/Race Engines - Cylinder Head Porting - Modified SU HS Carbs - DIY Engine Rebuild Kits With Free Tech Advice - Alloy wheels for British Sport Cars,and others
Patrick B Avatar
Patrick B patrick bennett
Gainesville, GA, USA   USA
1976 Triumph Spitfire 1500 "Gloria"
Great new idea this site.... I'm wanting to do the same thing so I do hope we get some responses. Looking for a bump from stock without breaking the bank...

britsnspits Avatar
britsnspits Michael Stoliker
Bethlehem, PA, USA   USA
1976 Triumph Spitfire 1500 "The Phoenix"
1978 Triumph Spitfire 1500 "Lucky"
I don't have any experience building a race Spitfire or street/performance, so take everything I say with a salt-lick.

My concern with these engines is that they are weak on the bottom end, especially with oiling. So as far as I'm concerned, the first stop should be the machine shop to drill out oil passages in the crank and get the thrust washers pinned. There has been some discussion on this in other threads but it would be nice to have a definitive treatese on these subjects here.

While you're at the machine shop talk to them about magnafluxing your very old engine for hidden faults that may come back to haunt you later. Talk about balancing all moving parts. A balanced engine is less likely to tear itself apart.

All parts should be checked for wear. Parts that are not within spec should be ground to the next oversize and the correct bearings installed.

Hardening of crank journals? I'll leave that to a pro to discuss.

Volumetric efficiency...flow more air, get more power. For cheapness, make the most of what you've got. If you've got a low compression engine, consider flat top pistons and getting the head shaved to get to 9 or 9.5 to 1.

Port and polish the head yourself with a dremel. You won't get professional improvements, but you'll get some improvement. Use the many tuning manuals as a guide, and don't get over ambitious. When I worked at the Pit Stop i helped a young lady who was into cart racing port and polish the head on her Midget (pre 1500) and she was impressed with her results. I couldn't feel a difference, but I didn't drive the car every day either.

Are roller rockers worth it on the street? Beats me. An external oiler? Maybe with a restrictor so you don't rob too much from the crank. I'm actually disturbed by the lack of oil in the top end of my Spitfire, but then I'm used to seeing how much gets pumped around by hydraulic lifter-fed V-8 top ends. Try adjusting the lifters on a running chevy small block if you want to see profuse oiling. And yes, there is a lifter adjusting procedure on an old chevy small block.

Take the time to read Paul Tegler's website.

That's all I've got to say. Let the experts jump in.

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GT6Steve Avatar
GT6Steve Steve Smith
North Las Vegas, Nevada, USA   USA
Here's a link to some thoughts I was working on for competition oiling. It's just a draft so feel free to dispute spelling , grammar or observations.

http://sideways-technologies.co.uk/forums/index.php/topic/5712-competition-oiling-draft/



Knowledge speaks, but wisdom listens

http://s206.photobucket.com/user/GT6Steve/library/GT6%20views?sort=3&page=1

claytoncnc Avatar
claytoncnc Gold Member Marcus Clayton
Melbourne, Ivanhoe, Australia   AUS
Jeff,

My intention here is not to get into the minutiae of how to do everything, just to give a recipe which will achieve what you want

100 streetable horsepower is not a difficult thing with your 1500 spitfire. I am assuming that you have, or have access to the knowledge to put a standard engine together, as your new thing will not be much different to standard.

The 1500 in European spec came with 9:1 compression, the US spec with 7.5, the torque figures being 81, and 69 ft lb respectively.
If you could maintain your 81 ft lb at 6500rpm, you will make 100 hp. 6500rpm is too much for reliability with a 1500 engine, so Torque must be increased. If you can achieve 90 ft lb, then your 100 hp will happen at 5800 rpm, which is OK.

Essentially, you will build a mk3, standard spec engine, with a few subtle improvements.

At least 9:1 compression, is required, so use standard euro pistons, a standard mk 3 camshaft (25 65), or slightly bigger (30 70) is all that is required. 9.5 is better, and is just fine on 98 octane fuel. The crank should be checked and reground if out of spec. The factory balance is pretty good, and hardening or balancing can often create more problems than it solves at this state of tune. Buy the bearings before you get the crank ground, measure them, then, using clearances in the manual, specify the finished size and finish to the crank grinder. If he will not accept this, find someone who will.

I am not familiar with the US low comp head, it may be the same as the euro head. If it is, the valve sizes and ports do not need looking at, but a small amount of material should be removed from the chamber wall where the inlet valve is masked. This just requires a ball end grinder to give a curved wall allowing a better flow at low lift around the inlet valve. I have not explained this particularly well, but it is really easy to do at home, and quite self explanatory with a picture or two. Others can advise you if obtaining a euro head is a better start than the US one. Do not port/polish the head, just clean up any dags.

1.25 in SUs will not support 100 hp, so a 1.5 in setup adapted to a mk3 manifold is better, as they will support about 120 hp. Use a #4 needle and heavy spring as a start (probably 1 too rich). Finish setup on a dyno and if the SUs and particularly the linkages are rebuilt, they will hold their tune for a long time. Your existing exhaust is probably fine. The best distributor is a Mk3, rebuilt to standard spec, and use points not electronic at this stage. Points are reliable, can be fixed on the side of the road, and just require checking every so often to keep them in spec.

The most important part of this build is to be thorough. The motor should be stripped and all castings hot tanked. It is worth while looking into the oil and coolant galleries and smoothing any casting flash, removing sharp edges, etc. Many engines do not perform as they should because of hot spots caused by scale, flash etc resulting in localised steam traps, hot spots, and detonation. The water pump you use should have a cast impeller, the tin ones do not pump water, they just make milk shakes.

Invest in a set of micrometers, dial gauges, calipers, and learn how to use them, ensuring the cam, crank assemblies are all smooth, round and square where they should be, the rocker arm, bearing clearances and ring gaps are correct, the bore finish, valve seat concentricity etc.
There are several items on these engines that are set by shim, measure and set everything as described. If for instance, the distributor end float is incorrect, a few thou can cost 15 HP, and cause inconsistent idle and rough running.

Follow the Triumph manuals, be thorough, and pay attention to all these little details, and the results you achieve will far exceed any number of bolt ons. Your aim is a low speed engine, 6000rpm max, with 100 ft ib of torque, and will comfortably exceed 100 HP, and pull seamlessly from 1300-5500 and will not leak oil. The bottom end and oiling is more than adequate for this application.

britsnspits Avatar
britsnspits Michael Stoliker
Bethlehem, PA, USA   USA
1976 Triumph Spitfire 1500 "The Phoenix"
1978 Triumph Spitfire 1500 "Lucky"
I recall that there is a pretty complete treatise on Spitfire cylinder heads on the Tegler website. There is a big valve head that I've heard about, and there is also a high compression head. I'm not sure if they are the same thing.

The exhaust manifold on a US Spitfire is probably NOT adequate to develop best flow. I've heard that you are best served with a European exhaust manifold that matches the HS4 carbs and intake manifold for best power. A 4-2-1 header would be a good alternative.

I'd like to hear more about the MKIII dizzy swap. Any particular year, or would ordering one from England be best?

claytoncnc Avatar
claytoncnc Gold Member Marcus Clayton
Melbourne, Ivanhoe, Australia   AUS
Remember the parameters, inexpensive, reliable, streetable powerful.

The above is almost just a stock engine rebuild, using mainly stock though not the same replacement components

I was assuming you would use the LCB manifold you mentioned, anyway primary should be 1.25 or 1.375, (yes that small) preferably with long secondaries, into a 1.75 collector at about 42 in from the port, although this is not critical for this application.

Big valves are not appropriate for this power level, they will hurt performance as they are more masked at low lift, and mixture would need to be enriched, which is not good for clean responsive running. A 68 or 69 distributor is good. A genuine 64-67 Cooper S distributor is also excellent, but has to be reworked to fit.

The above recipe I gave is for around 100 HP. The only way to increase HP is by increasing torque and/or RPM.
As torque is a direct function of compression, and you are limited to commercial fuel the torque option has already been taken with 9.5 :1 compression.

The RPM option is limited by the mechanisms ability to hold together.


If you want more HP, use a 1300, small journal, as they will hang together happily at 9000 RPM plus. That is where big valves (and a lot of other mods) are required, but it would cost about 5 times as much to build, and would require a 4.5 or 4.8 axle ratio. Every part of the engine would have a different spec, and to achieve 145 HP it would have to run on avgas, and SUs would not work so well.

A high revving 1500 is possible, but in full race tune will not produce significantly more power than a 1300, and costs a lot more to build.

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britsnspits Avatar
britsnspits Michael Stoliker
Bethlehem, PA, USA   USA
1976 Triumph Spitfire 1500 "The Phoenix"
1978 Triumph Spitfire 1500 "Lucky"
Thanks, good information.

Patrick B Avatar
Patrick B patrick bennett
Gainesville, GA, USA   USA
1976 Triumph Spitfire 1500 "Gloria"
One step closer with the 9:1 (1976) head.....grinning smiley

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BillyB William Bonbright
Rincon, Puerto Rico, Puerto Rico   PRI
1979 Triumph Spitfire "Verde"
1979 Triumph Spitfire 1500 "Verde"
Just want to follow this thread as I am in the process of making the change myself. I have an after market Mikuni carb and a 4-2-1 header into a straight pipe. I'm going to run that for a while until I get the nerve up to shave the head about .08 to .1 and port the head. I'll see where that gets me.

Triumph Racer Avatar
Triumph Racer Patrick N
south bend, IN., USA   USA
1962 Triumph TR4 "My First Triumph"
1962 Triumph TR4 "Big Red"
1964 Triumph TR4 "Ugly Duckling"
1971 Triumph Spitfire MkIV    & more
Well I am pretty passionate on the Triumph racing thing and speaking my mind. How ever I will try to take Hap's approach and stay fairly quiet to see what you all figure out is best for your budget and needs. I will mention a few things I use and believe are essential. Stock or modified if your engine is apart do the oil galleries and crank,it's cheap insurance.Consider an external head oiler pipe.Balance all your rotating parts assembys.Flow the head,port&polish and match to manifolds. I run 1.1/2 S.U.s on the 1300 and the 1500 motors. Keep the compression down enough so it is still streetable and so you don't get beat up at the pumps.Premium street gas is still crap compared to what we use in our race cars, 108-114 octane.Everything else I use is race car specific or gt6 upgrade for safety or reliabilty. For a street engine that will not be torn down much look into the rear main upgrade that adds another set of thrust washers where you need them! Patrick.



Sometimes you succeed,other times you learn.

bluecrab Avatar
bluecrab tom broring
Maryland, USA   USA
Jeff, based on my experience the exhaust, carb and ignition parts you have are all on track to what you are looking for. You should rebuild with the flat top pistons. You would probably also need to mill the head further for increased compression at reach your hp target. The question is how high is reasonable. I would keep it ti 9.5:1 max for street use. The good news is you can always mill the head more later. If you mill the head too much you will get into rocker geometry changes and need to look at pushrod length adjustments. Tubular pushrods are a good upgrade so changing the length when you order those is not a big deal.
The cam you choose and what you do to the head will have alot to do with reaching your hp target. You will want increased lift without much overlap for street use. This will minimize any compression loss due to the overlap. One way to do that is to get a mild street cam and increased ratio rockers. You can also shop for just the right cam, with springs and lifters to match. The head should also get gasket matched, any rough casting flash in the ports smoothed and on the exhaust side there is a ridge that can be ground away where the exhaust port passes the head stud holes. A good machine shop can do a 3 angle valve job for street use, but you would be well served by upgrading to hardened valve seats and bronze guides all at the same time as the valve job. If the machine shop does performace machine work, talk to them about some minor porting where the valve seat meets the port. Many heads are cast with a machined edge at that transition due to the quick, low cost factory machining. All this machine work on the head will probably be the most costly part of the build. Also, the 1.38 sized intake valves should be fine for your target build if you are running a good cam. The larger valves won't help much until you get to the next stage of a build which will cost much more.
I have never had an issue with stock thrust bearings on race engines but they are checked often and replaced as needed. If you plan to build the motor once and leave it you may consider improving the thrust bearing. Frankly, I believe that if the thrust clearance is checked carefully and is on the small side of the range that the bearings should live a very long time with a stock clutch and synthetic oil in the motor. Just the improvements in modern oil and gasket materials that keep Spit engines from leaking would have reduced many of the issues with thrust bearings that have been seen over the years.
Finally, resign yourself to a 6800 to 7000 RPM firm redline. Anything over that would cost alot more to prepare for or be on borrowed time while it lasts.

oldag98 Avatar
oldag98 Jeff and Brittany Brackenridge
Choctaw, Choctaw, Oklahoma, USA   USA
1969 MG Midget MkIII
1975 MG Midget Conversion
1976 MG Midget 1500 "Yellow One"
1977 MG Midget 1500 "Dunkirk"    & more
Ok, excellent info guys. My list of parts and machine shop operations is growing steadily.

Speedracer Avatar
Speedracer Platinum Member Hap Waldrop
Greenville, SC, USA   USA
1967 MG MGB Racecar "The Biscuit"
Good deal, I thought it would be a good idea to start such a forum for you Triumph go-fast guys, and it looks like it well on it's way. There's alot of folks out there vintage,and SCCA racing, Triumphs, plus on the MGEx MG motorsports section we also have quite a few Brit,and Aussie MG racers hanging with us as well, so spread the word, this is all good for our sport. It took a couple of years for the MGExperience MG Motorsport forum to take off, but now it is easily the #1 MG racing forum on the net, so you guys are off to good start thumbs up

I know, I'm a MG guy, but at the end of the day, were all still on the LBC team, and FWIW my first race car was 1500 Sprifire smiling smiley



Hap Waldrop
Acme Speed Shop
864-370-3000
www.acmespeedshop.com
Engines, Rebuild Kits and More.


Member Services:
MG/ Triumph Performance Street/Race Engines - Cylinder Head Porting - Modified SU HS Carbs - DIY Engine Rebuild Kits With Free Tech Advice - Alloy wheels for British Sport Cars,and others
. Hide banner ads & support this website by becoming a > Gold Supporting Member <

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