Building a small pushrod race engine - hints / tips / etc ?

[9triton]

i would have thought you would need to know what revs you will be pulling - ie can the crank take eg 7500rpm . i know the ford kent pushrod fours they end up with a full steel crank for hi revs (not sure what the limit is on the std crank).

if you cant get super revs with the std crank+ rods - then can you get away with a std cam/rocker set up ?

probably no point in going to the trouble of roller cams , rockers etc - and then spending all that time on a dyno to develop a roller profile if its not of that much benefit

as mentioned here its going to boil down to what revs you can do and what the head will support.
maybe TK can do some sums with EAP and pipemax etc to tell you what is possible with the head -and the mods you are allowed

but i would have thought building a simple reliable engine to allow you to develop the car etc would be first up -then chase the power.

i would have a look at what burton power products in the UK have for the ford pushrod kent engine would be a guide as to whats possible.

as for reducing friction - would have thoughttherea re a number of coatings out there that can be applied

but as above - carry on and post plenty pics

[Momus]

My first step with an engine like this would be to get the cylinder head flow bench tested by someone knowledgeable.

This audit will give a general direction to proceed with designing the various modifications.

My questions; 5 main bearings yes? What are the main, rod and gudgeon journal diameters?

What is the cylinder head layout and material, the bore and stroke, and the deck height?

The initial easy friction reductions will come from slipper pistons and a carefully chosen, and narrow ring pack.

[TK]

Yep, first step is to look at the head, valve sizes, valve size that can be fitted, port cross sections (& thickness of casting for port work) etc to work out what sort of power & rpm the engine is likely to be able to support.
From there you need to look at cam profiles & rocker ratio's to figure out if you are able to get the lift that the engine will require into it - if the rocker ratio & cam intensity is not doable to get the lift you need then you can use a bigger valve (if it'll fit) than 'ideal' to get the time/area up to where it can feed the engine.

The head & the rocker ratio are the 2 biggest limiting factors for 2 valve pushrod engines.

Once you have the head sussed out you look at induction & exhaust, runner lengths etc to figure out what will be needed to achieve max VE at peak power rpm.

Bottom end is pretty much along for the ride, it's job is to not go bang & to seal up the bottom part of the cylinders, provided it's built right & the oiling system is prepared for circuit racing use there is not a lot more power to be had, just a little from good ring seal & reduced friction from narrow rings.
Reducing crank windage with crank scrapers/baffles etc is worth a few hp.

[dave1600]

Crank will apparently take reasonable revs, with some oiling modifications (I've seen reports of an engine producing peak hp @ 7800 rpm).

I have both 3 main and 5 main engines (early were 3, later were 5), will be using the 5 main engine. Likewise, I have both cast iron and alloy heads, will be using the alloy one.

Bore and stroke - 87.2 X 66.8

Mains 62.95mm

Big end 51.96mm

little end 22mm

Rod length 152.45mm

Deck height - 227mm

Cylinder head layout is as non-crossflow, see pic. Exhaust ports are square (well, rectangular)

Stock valves are 42mm and 32mm. I have seen reports of 44mm / 34mm valves, no idea if they were easy to fit, etc,

Commercially available roller rockers can be had in ratios from 1.45 to 1.65, I can't find specs for the stock rockers.

Yep, bit of work to be done before it hits the track....



Top head is of the cast iron forklift version of the head, bottom is the alloy version.

[TK]

1.65" intake valve, 1.26" exhaust (stock), peak power at 7400rpm with 108% VE running on E85 = about 160-170hp.

Would need .470" intake lift & .460" exhaust lift & will want quite a lot of duration.

Min intake port cross section = 1.35^"

Pipemax stuff:

97.206 Cubic Inches @ 7400 RPM with 108.0 % Volumetric Efficiency PerCent

Required Intake Flow between 143.3 CFM and 150.6 CFM at 28 Inches
Required Exhaust Flow between 96.5 CFM and 109.4 CFM at 28 Inches

600 RPM/Sec Dyno Test Lowest Low Average Best
Peak HorsePower 151.5 157.7 160.9 164.0
Peak Torque Lbs-Ft 119.2 124.1 126.6 129.0

HorsePower per CID 1.559 1.623 1.655 1.687
Torque per Cubic Inch 1.226 1.277 1.302 1.327

BMEP in psi 184.9 192.6 196.4 200.2
Carb CFM at 1.5 in Hg. 225 250 263 275

Target EGT= 1224 degrees F at end of 4 second 600 RPM/Sec Dyno accel. test
Octane (R+M)/2 Method = 109.5 to 110.3 Octane required range
Air Standard Efficiency = 64.70290 % for 13.000:1 Compression Ratio

Peak HorsePower calculated from Cylinder Head Flow CFM only
600 RPM/Sec Dyno Test Lowest Average Best Potential
Head Flow Peak HP = 149.3 166.4 183.4

----- Engine Design Specifications -----
( English Units ) ( per each Valve Sq.Inch area )
Engine Size CID = 97.206 Intake Valve Net Area = 2.107
CID per Cylinder = 24.302 Intake Valve Dia. Area = 2.138
Rod/Stroke Ratio = 2.281 Intake Valve Stem Area = 0.031
Bore/Stroke Ratio = 1.304 Exhaust Valve Net Area = 1.205
Int Valve/Bore Ratio = 0.481 Exhaust Valve Dia. Area = 1.247
Exh Valve/Bore Ratio = 0.367 Exhaust Valve Stem Area = 0.042
Exh/Int Valve Ratio = 0.764 Exh/Int Valve Area Ratio = 0.583
Intake Valve L/D Ratio= .303 Exhaust Valve L/D Ratio= .397
CFM/Sq.Inch = 67.0 to 70.4 CFM/Sq.Inch =77.4 to 87.8
Curtain Area -to- Valve Area Convergence Intake Valve Lift inch= .412
Curtain Area -to- Valve Area Convergence Exhaust Valve Lift inch= .315


Intake Valve Margin CC's Exhaust Valve Margin CC's
1.00 CC = 0.0285 1.00 CC = 0.0489
0.50 CC = 0.0143 0.50 CC = 0.0245
0.25 CC = 0.0071 0.25 CC = 0.0122
0.10 CC = 0.0029 0.10 CC = 0.0049

------- Piston Motion Data -------
Average Piston Speed (FPM)= 3243.67 in Feet Per Minute
Maximum Piston Speed (FPM)= 5216.26 occurs at 78.167 Degrees ATDC
Piston Depth at 78.167 degree ATDC= 1.1850 inches Cylinder Volume= 179.4 CC
Maximum TDC Rod Tension GForce= 2493.55 G's
Maximum BDC Rod Compression GForce= 1597.03 G's


------- Current Camshaft Specs @ .050 -------

IntOpen= 14.00 IntClose= 46.00 ExhOpen= 48.50 ExhClose= 16.50
Intake Duration @ .050 = 240.00 Exhaust Duration @ .050 = 245.00
Intake CenterLine = 106.00 Exhaust CenterLine = 106.00
Compression Duration= 134.00 Power Duration = 131.50
OverLap Duration = 30.50 Lobe Center Angle (LCA)= 106.00
Camshaft installed Straight Up = 0.00 degrees

-Recommended Camshaft Valve Lift-
Minimum Normal Maximum
Intake = 0.437 0.470 0.517
Exhaust = 0.426 0.459 0.505
Max-effort Intake Lift = 0.542
Max-effort Exhaust Lift = 0.529
Minimum Intake Valve Lift to prevent Choke = .470 Lift @ 7400 RPM
Minimum Exhaust Valve Lift to prevent Choke = .459 Lift @ 7400 RPM


- Induction System Tuned Lengths - ( Cylinder Head Port + Manifold Runner )
1st Harmonic= 28.558 (usually this Length is never used)
2nd Harmonic= 16.208 (some Sprint Engines and Factory OEM's w/Injectors)
3rd Harmonic= 11.316 (ProStock or Comp SheetMetal Intake)
4th Harmonic= 8.906 (Single-plane Intakes , less Torque)
5th Harmonic= 7.226 (Torque is reduced, even though Tuned Length)
6th Harmonic= 6.079 (Torque is reduced, even though Tuned Length)
7th Harmonic= 5.247 (Torque is greatly reduced, even though Tuned Length)
8th Harmonic= 4.615 (Torque is greatly reduced, even though Tuned Length)
Note> 2nd and 3rd Harmonics typically create the most Peak Torque
4th Harmonic is used to package Induction System underneath Hood

Plenum Runner Minimum Recommended Entry Area = 1.529 to 1.720 Sq.Inch
Plenum Runner Average Recommended Entry Area = 1.757 Sq.Inch
Plenum Runner Maximum Recommended Entry Area = 1.795 to 2.124 Sq.Inch

Minimum Plenum Volume CC = 275.1 [typically for Single-Plane Intakes]
Minimum Plenum Volume CID= 16.8 [typically for Single-Plane Intakes]
Maximum Plenum Volume CC = 1592.9 [typically for Tunnel Ram Intakes]
Maximum Plenum Volume CID= 97.2 [typically for Tunnel Ram Intakes]


------- Operating RPM Ranges of various Components -------

Camshaft Intake Lobe RPM = 6161 Exhaust Lobe RPM = 5937
Camshaft's Intake and Exhaust Lobes operating RPM range = 4105 to 6105
Note=> Lobe RPMs are only BallPark estimations

Minimum Intake Valve Lift to prevent Choke = .470 Lift @ 7400 RPM
Minimum Exhaust Valve Lift to prevent Choke = .459 Lift @ 7400 RPM

Current (Intake Valve Curtain Area -VS- Time) Choke RPM = 7867 RPM
Current (Exhaust Valve Curtain Area -VS- Time) Choke RPM = 8065 RPM

Intake Valve Area + Curtain Area operating RPM Range = 5699 to 7699 RPM

Intake Valve Diameter RPM Range = 5867 to 7867

Intake Flow CFM @28in RPM Range = 5343 to 7343
__________________________________________________ _________________________

Best estimate RPM operating range from all Components = 5326 to 7326

Note=>The BEST Engine Combo will have all Component's RPM Ranges coinciding
__________________________________________________ _________________________


--- Cross-Sectional Areas at various Intake Port Velocities (@ 28 in.) ---
133 FPS at Intake Valve Curtain Area= 2.592 sq.in. at .500 Lift
161 FPS at Intake Valve OD Area and at Convergence Lift = .412
199 FPS 90% PerCent Rule Seat-Throat Velocity CSA= 1.732 sq.in. at 7400 RPM
350 FPS Velocity CSA= 0.982 sq.in. at 7400 RPM Port Sonic-Choke with HP Loss
330 FPS Velocity CSA= 1.042 sq.in. at 7400 RPM Port Sonic-Choke with HP Loss
311 FPS Velocity CSA= 1.106 sq.in. at 7400 RPM Smallest Useable Port CSA
300 FPS Velocity CSA= 1.146 sq.in. at 7400 RPM Recommended Smallest Port CSA
285 FPS Velocity CSA= 1.207 sq.in. at 7400 RPM Recommended Smallest Port CSA
260 FPS Velocity CSA= 1.323 sq.in. at 7400 RPM Recommended Port CSA
250 FPS Velocity CSA= 1.376 sq.in. at 7400 RPM Recommended Port CSA
240 FPS Velocity CSA= 1.433 sq.in. at 7400 RPM Largest Intake Port Entry CSA
220 FPS Velocity CSA= 1.563 sq.in. at 7400 RPM Largest Intake Port Entry CSA
210 FPS Velocity CSA= 1.638 sq.in. at 7400 RPM Torque Loss + Reversion
200 FPS Velocity CSA= 1.720 sq.in. at 7400 RPM Torque Loss + Reversion


--- Cross-Sectional Areas at various Exhaust Port Velocities (@ 28 in.) ---
125 FPS at Exhaust Valve Curtain Area= 1.979 sq.in. at .500 Lift
198 FPS at Exhaust Valve OD Area and at Convergence Lift = .315
245 FPS 90% PerCent Rule Seat-Throat Velocity CSA= 1.010 sq.in. at 7400 RPM
435 FPS Velocity CSA= 0.568 sq.in. at 7400 RPM Sonic Choke at Throat Area
350 FPS Velocity CSA= 0.705 sq.in. at 7400 RPM Port Sonic-Choke with HP Loss
330 FPS Velocity CSA= 0.749 sq.in. at 7400 RPM Port Sonic-Choke with HP Loss
311 FPS Velocity CSA= 0.795 sq.in. at 7400 RPM Smallest Useable Port CSA
300 FPS Velocity CSA= 0.824 sq.in. at 7400 RPM Recommended Smallest Port CSA
285 FPS Velocity CSA= 0.867 sq.in. at 7400 RPM Recommended Smallest Port CSA
250 FPS Velocity CSA= 0.988 sq.in. at 7400 RPM Recommended Port CSA
240 FPS Velocity CSA= 1.030 sq.in. at 7400 RPM Recommended Port CSA
225 FPS Velocity CSA= 1.098 sq.in. at 7400 RPM Largest Exhaust Port Exit CSA
210 FPS Velocity CSA= 1.177 sq.in. at 7400 RPM Largest Exhaust Port Exit CSA
190 FPS Velocity CSA= 1.301 sq.in. at 7400 RPM Torque Loss + Reversion
180 FPS Velocity CSA= 1.373 sq.in. at 7400 RPM Torque Loss + Reversion

[TK]

PS - you sure it's got 6" rods? - we're talking centre to centre length, not overall length.
Just seems unlikely a little jap 4 banger would have 6" rods.

[dave1600]

Thanks for taking the time to have a look at that for me ! Much appreciated, I'll try to digest it all tomorrow.

Yep, workshop manual lists the rod length as 152.45 centre-to-centre. Pin height is 40.6mm, plus rod length 152.45, plus half stroke 33.4 = pretty close to 227mm, which is the deck height.

[Gammaboy]

I dunno what your case is like, but back in the 80's the Austin Healey 6cyl guys were making more HP with the iron heads because the valve seat inserts and cracking were limiting factors regarding how far they could develop the heads, so don't immediately discount the iron heads...
Not surprised at the 6" rods, Alfa 4 bangers have had 6"+ rods since the mid 50s.

[Motherfucker Jones]

Also an iron head holds more heat in the combustion chamber which makes for better thermal efficiency. With a non cross flow head though it might get too much heat in the intake ports and kill power that way.

Looking at that head you can see where the L series head design came from

[dave1600]

Looking at that head you can see where the L series head design came from

Especially when you see the "missing link" - the Fairlady U20 head. They took the R16 pushrod engine, stroked it to 2 litre, replaced camshaft with a jackshaft that in turn drove the overhead cam, fitted a new head and that was it. Plenty of stuff interchanges between U20 and R16, including the crank.

[Gammaboy]

Also an iron head holds more heat in the combustion chamber which makes for better thermal efficiency. With a non cross flow head though it might get too much heat in the intake ports and kill power that way.

Dunno about thermal efficiency improvement, but certainly increased chamber temps which ultimately works against you in terms of detonation control - alloy headed windsors/clevos will take more compression day in, day out when compared to an equivalent iron headed setup. On the healeys is was all about what you could do with valves and portwork - the weight and half a point of compression was outweighed by the flow advantage and reliability of the cast head.

I expect the short turn of those exhaust ports is going to suck badly, but it's a good high intake port...

[Motherfucker Jones]

Of course an alloy head will take more compression. It transfers heat energy faster. The heat energy you're using to make power. Ultimately you need that extra comp to make the same power. It's probably a two way street though and depends on how good your combustion chamber design is and how much timing it needs.

The other thing on a circus car is do you want a big lump of iron up that high on a car that you want to go around corners?

[Nero]

Of course an alloy head will take more compression. It transfers heat energy faster. The heat energy you're using to make power. Ultimately you need that extra comp to make the same power. It's probably a two way street though and depends on how good your combustion chamber design is and how much timing it needs.

The other thing on a circus car is do you want a big lump of iron up that high on a car that you want to go around corners?

Am I correct in paraphrasing you then, that you think an iron head will make the same power as an alloy head at a lower CR because it retains more heat?

The the OP. crack test crank and work hard on the oiling system. Sump, pickup, oil return, crank scraper, wind age tray, etc.

[TK]

Am I correct in paraphrasing you then, that you think an iron head will make the same power as an alloy head at a lower CR because it retains more heat?

Yes.

All else being equal & both ally & iron heads set with comp ratio to be just below the det threshold they'll make the same power (or close enough as to make no difference).
Alloy heads can take more comp - but they NEED more comp to make the same power as an otherwise identical iron head.

[Momus]

1500 cc Ford/Kent looking head that pushrod unit. Datsun was still displaying their Brit influence- the ohc stuff that came later was via Prince and the influence the Germans- BMW and Benz- had. That ohc head looks 'L' intermediate.
Coincidentally a mate has just finished rings and bearings in the iron headed version in his old Nissan fork.

TK has given some useful information- basically boiling down to about 100 hp per litre with relatively low specific torque production (BMEP) and hence a fairly high peak horsepower rpm.
The engines dimensions are very over square- with the right breathing it would be 10 or 11000 rpm capable.
The crank journals are massive- 6 to 10 mm bigger on the mains and big ends than a modern engine. Even for a hobby type build analysing the crank material would be informative. I assume it is forged steel. if it had a bit of chromium and nickel in it I would very strongly consider regrinding it down to a Honda size big end journal- either the 47 or 48 mm- perhaps even 45 mm and re rodding it. The mains are much bigger than the 57.15 journal size used on a 5 litre Windsor so looking at doing them down to that size or smaller would pay off very significantly in reduced friction and inertia. If the crank was alloy steel it could also be reasonably cheaply nitrided which is very advantageous. Those Honda bearing sizes are the ones a lot of 6 litre V8's use in professional competition and the bearings are available from Clevite/Mahle in very high quality race versions for not a lot.
The head has a very open, large combustion chamber which will work fairly hard against you. A weld up to the sort of shape seen on a modern aftermarket pushrod V8 head would also be a good foundation modification.