Medium Bore Prod Forum

I'll start things off here. Can some of you guys who run vintage give me a general description of your racing engine? What kind of parts and machine work did you use?

Hi Joe, I run a 1275 in a 63 Sprite. When I first started racing, I had some good advice to keep my first engine build simple and learn the car and how to drive it. The advice was from two racers, one of which built the engine. They said if you build essentially a "hot street motor" it will do well and last. It was built 13 years ago, refreshed once since then, and rebuilt once since then. Other than high ratio rockers and an additional cylinder boring, it has remained the same. Mechanics guess is 85-90 hp. This is pretty vague but it gives you an idea. BTW, it has been very competitive and very dependable.
Just over 10:1 compression
Stock flywheel lightened 8 pounds
1 1/2" Su carbs(probably not necessary)
Mild port and polish
Balanced
1.5 high ratio rockers
Stock rods
Nothing fancy about the Pistons
Stock oil pan with built in windage tray
Remote oil cooler and filter
Accusump
Valves? Can't remember
Stock starter

Pete

Thanks for the response Pete. Your Sprite is very nice. Your build sounds like what I am planning to do with my MGB engine. I was looking for affirmation that this type of engine would be viable in vintage racing.
Here is what I have tentatively planned;

Stock type early shallow dish .060 pistons
Maxspeeding rods
Head & block deck milled to achieve approx 10.5:1 compression
Prosport Harmonic balancer
Aluminum wp pulley
Aluminum flywheel w/ 7 1/4 clutch
Aluminum engine back plate
1 3/4 SU carbs w/ Maniflow manifold
Street ported 1326 head with 1.625 intake
HS 1.5 ratio roller rockers w/ hardened shaft
Tubular push rods
Maniflow race header
Delta S5 cam & hardened lifters
Dbl row Vernier timing set
Baffled aluminum oil pan w/ windage tray
Hi volume oil pump

I am hoping to achieve 120-130hp.

Your car is quite nice as well Joe. That sounds like a good engine build. I believe suspension and talent will help you more in the long run. I am guessing we both have previous scca cars . ( mine used to have flares) I am a fan of having a roll cage as apposed to just a bar. I like the way yours is the same color as the car.
Pete

Thanks, yes it was an SCCA car. I will probably run some SCCA as well as vintage events with it. I agree with you that HP is not the most important thing to being quick.
I just want a reliable engine that makes decent power.

Joe, check the rulebook for the vintage club you are most likely to run with. I think most vintage clubs (including VDCA and SVRA) will allow a .040" overbore, but not 0.60". That is if you want a logbook.

I have no idea what the historic racing clubs might require.

Heavily ported 12H1326 head with 1.685" intakes, 1.344" exhaust valve, race valve springs, HS sharp 1.625 ratio rocker arms shim with custom length Smith Brothers push rods .
040 JF flat top pistons
The rods in the engine right now are modified stock 18GK rods, due to the fact I have done some mods to the rods to see if I can improve the bearing wear, and didn't want to do that the Pauter Machine rods, which will be introduced to the engine again at some point. The moded stock rods, of course have ARP rod bolt, and have been lightened, and polshed to about 680 grams, I am playing wider side clearances and oil grooving on the thrust faces of the rods to help not overload the King CP rod bearing at rpms over 7000. However for this rebuild I also want with ACL Duraglide tri metal rod bearings, and main bearing for that matter too.
The crank in this engine is nothing special, just index ground to my spec, and balanced, although I have lighten them in other race engines.
Pro sport harmonic balancer with top timing pointer made by me.
APT VP-18 race cam with CF-04 lifters
Block modded for better oiling, all galley to main oil feed are drilled out to 5/16" and the center main has a bit more modding to it.
Powertune vernier cam gear set p, with a Jag tensioner.
Headley aluminum backplate
Fidanza aluminum flywheel
Super duty clutch
It makes .525" valve lift after valve lash
Custom oil race pan for use with a TDC external oil pump
CR about 12.5 to 1 with this current head. Payen composite head gasket
I shift it at 7000 rpm, and occasionally see as high 7400-7500 rpm.

HP, well that depends on the dyno, chassis or engine and no two dynos are alike, too many variables, the track and lap times tell if you are going in the right direction. my car run low 1:26s at Roebling Road on Nitto NT-01 tires and it is capable of going even faster on a good day.



Edited 1 time(s). Last edit at 2021-02-11 04:36 AM by Speedracer.

1959 MGA - My primary engine was developed by Hap (Speedracer) (Acme Speed Shop) as a mild race build. When the stock crankshaft broke, the engine was salvaged and reconfigured with input / advice / help from Hap and from Dave Headley (Fab-Tec).

1662cc MGA/MGB Hybrid Ghost Main Engine

1600 Engine # 16GA-U-H-26612
Bore: 3.040”
Stroke: 3.5”
Displacement: 1662
Block decked for zero clearance
Compression Ratio 9.8-1(estimated)

Ghost Main MGA/MGB Hybrid Crankshaft, by Marine Crankshaft, MGB style flange for the 65-67 MGB 5 main using a 3 synchro gearbox.
Custom rear engine plates for MGB style flange by Dave Headley, Fab-Tec
Fidanze flywheel part number #126681
King tri-metal bearings #MB 312CP

Camshaft: APT SPB-VP16 BK race cam. Power band 3800 – 7500 rpm with stock ratio rockers.
Durabond camshaft bearings.
Lifters: APT CF-04
18V Pushrods: Moss part # 460-619 for MGB 18V tappets.

Pauter MGA Connecting Rods.
Venolia custom flat topped pistons: 3.040” diameter
TotalSeal piston rings, 2nd ring gapless set

MGA 15 head, resurfaced .037”, fully ported and polished, bronze guides shortened and reshaped for port job; hardened exhaust and intake valve seats, three (3) angle cut.
Valves: 1.625” stainless intake, 1.344” stainless exhaust: MGB “Late style”

Stock rocker arms; Nylatron spacers, stock: dual valve springs - MGB style ST race; Steele valve retainers; MGB later type valve cotter set / retainers.
Payen head gasket

Powertune vernier timing gear set.
OEM Jaguar French made timing chain tensioner.
Pro-Sport Harmonic balancer / damper 18.1
Oil Filter Spin On conversion

Clutch
1) stock MGA transmission: MGB Pressure Plate and throw out arm & bearing; clutch disc oversize 8 1/2”, 10 spline, 1” shaft (8.5-10-1) from a Triumph GT6
2) early MGB/MGA hybrid close ratio transmission: Pressure plate - MGB by AP, part #CA3517; Exedy clutch disc, 24 spline, part MBD001U,

Ignition: Mallory dual point dist. #2332001H
Bosch ALRACE 1 Alternator

Induction: Dual SU H6 with BB Bullock velocity stacks and K & N Air Filters #RU-4410



Edited 1 time(s). Last edit at 2021-02-15 07:22 PM by Blueosprey90.

Those both sound like great builds. Thanks guys.

Pete is it you that has the ex Chris Fox car?



Edited 1 time(s). Last edit at 2021-02-17 02:56 PM by Speedracer.

That is correct Hap. I new her for less than a year, and I am proud to have her car and she was happy to see it back in the area.

Chris was one of my favorite friends at the track, she could do it all, work on it and drive it just as well. She knew race cars from top to bottom. She was racer's racer for sure. I miss her.

'69 TR6
Later block with reinforcing on lower skirting, block has been decked to zero clearance, cam bearings installed, rear main bearing cap modified to retain extra thrust washer. Originally run with stock crank, rods and pistons, after several failures went to a billet crankshaft, MaxSpeed rods and Venolia pistons, .040" over. Crankshaft has dummy main bearings, bell shaped counter weights and hollow pins. Crankshaft is 8 pounds lighter than stock.
Oil pump has been cleaned up by removing poor casting and increased flow. Harmonic balancer replaced with a GoodParts ATI harmonic balancer, all parts balanced. Originally cam was a D9 cam which is similar to a TR5 cam which worked well with PI. Cam is timed using a Vernier cam gear to get precise timing
Head has been milled to 3.30 giving a compression ratio around 12:1. Ports have been mildly cleaned and ported, valve springs are stock TR5 with titanium retainers. It has roller rockers at 1.65:1 ratio. Aluminum parts on engine for weight savings are front and rear plates and water pump housing. Oil pan is also aluminum to add rigidity to the block.
Motor runs a stock TR6 dizzy, switching between points or Pertronics ignition with a Lucas Sport coil or Pertonics Flamethrower.
The clutch is a Tilton Rally clutch attached to a steel flywheel which is about 11 pounds compared to the 28 pound stock flywheel.
Induction has been triple Weber carbs, twin SU's, twin Z-S's, Lucas PI (fuel injection) and most lately a triple Z-S carb set-up by GoodParts.
Pistons, lifters(which have been modified), cam, cam bearings, main and rod bearings, and oil pump have all been heat coated by Performance Coatings, as well as the header, which is sourced from GoodParts, having equal length primary and secondary tubes connected on opposing cylinders.
Head studs, main bearing cap bolts and rod cap bolts are all ARP.
Motor is routinely run to 7000 rpm's and horsepower is unknown but estimated at 175.



Edited 1 time(s). Last edit at 2021-03-16 10:37 PM by Charlypm.

Oh come on Charly....don't sand bag us. I've watched you run down many lighter cars with similiar hp, you're well over 200+ hp.....Nice try
Plus, your times on the hill climb are always very respectable.