Please excuse the garbled message recieved yesterday, Subject: Uprating the
1500 mill. Something happened during transmission beyond my ken. Here,
hopefully, is a cogent version.
This message was originally intended for the Morgan list but so much of it
applies to all small four banger engines I thought it may be of interest to the
LBC hamfisters I have come to know and love as a long time lurker.
In reply to Mr. W. Zehering's thoughtful tract on uprating the 1500 mill- I
have to admit "There is no substitute for inches", however a great deal of urge
can be coaxed from the original 1500 non-cross flow engine and still retain
complete reliability.
I was fortunate in that my 1966 4/4 Series V came with a Weber 40DCOE on a
Lotus intake manifold and a four to one extractor exhaust header. All else was
stock.
Since the "all else" was rather tired I decided to pull the engine and
bring it to the brink of a Formula Ford racing engine while keeping it
reliable and tractable on the street.
The block was done by a local racing engine builder who align bored it,
decked it-- bored it .060 over-- balanced everything (a must)-- trued and
refaced the flywheel and lightened it by 7 lb (This aids acceleration and
reduces torsional loads on the crank) polished crank journals reconditioned
rods etc. etc.
Being an old hand at flowing small four banger (MG-XPAG) I had the shop skim
.080 off the head and did the rest myself.
Admittedly extra inches in the bores are nice but they have to breathe and
I'm convinced the secret to an outstanding engine is in BALANCING and
BREATHING. So- from Quicksilver Racing Engines in Rockville Maryland I bought a
street cam - (27-65-65-27) along with larger valves and slightly stronger valve
springs (stay away from extra strong valve springs)
Without removing much metal the combustion chambers, ports and the intake
manifold were lightly ground to a very smooth finish (polishing is nice but
not recommended and hardly worthwhile. How much time do you have?) Spend
time carefully matching the ports to the intake and exhaust manifolds. At each
mating point allow the downstream port to be slightly larger than the upstream
port. The resulting small step will aid alignment and help entrain any liquid
fuel flowing along the sides and bottom of the manifold (controversial? Yes,
but it works.) The same care should be taken at the carb. end of the manifold
and at the exhaust manifold.
The gaskets must me reworked to ensure they do not enter the air flow.
Rocker ends were lightened, pushrod cup lips ground down, cam followers
lightened, valve spring caps lightened, new rocker shaft fitted with phosphor
bronze spacer bushes in place of springs (this is fun getting the rockers to
line up exactly centered on valves but after a lot of filing and fitting they
look
great and eliminate spring friction.) Added .080 pads under rocker towers to
retain proper rocker geometry. (Don't forget the oil holes in the pads.)
Put it all together- Turn the exhaust pipe out under the door ahead of the
rear wheel and you will have a happy, free revving, eager to go engine that
will sing your song and stir your blood! All this happened in 1975 and I
haven't laid a glove on it since. Still 185-188 compression strait across and
going strong. Vive la 4/4 long may she wave!
Required reading:
David Vizard Theory and Practice of Cylinder Head Modification
Annand & Roe Gas Flow in the Internal Combustion Engine
Helpful reading:
Martyn Watkins Introduction to Tuning
Tuning engines and transmissions
Clive Trickey Modifying Production Crylinder Heads
Colin Campbell Sports Car Engine - Its Mod. & Tuning
Philip Smith Design and Tuning of Competition Engines
Sir Harry Ricardo The High Speed Interal Combustion Engines
Suppliers: Quicksilver Racing Engines
Rockville MD. (301) 340-2700
Shankle Automotive Engineering
Van Nuys CA. (213) 988-5190
--
Ralph Cadwallader Lakewood, OH
72GT 66 4/4 68 FBird Old age and treachery will prevail.
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