TRExp

Spitfire & GT6 Forum

Spark Plug recommendation for high compression motor

Moss Motors
AutoShrine Sponsor
AutoShrine Sponsor
AutoShrine Sponsor
AutoShrine Sponsor

70tbolt Geoff Ullmann
Morgan Hill, CA, USA   USA
Getting ready to fire up my mystery high performance motor from Newark Engineering in the UK. Unknown compression ratio. Current plugs that came with the engine purchased by the previous owner are Champion RN9YC's which appear to the standard for the stock motors? I assume I should use a cooler plug. Any recommendations?

Thanks!
Geoff
Morgan Hill, CA

. Hide banner ads & support this website by becoming a > Gold Supporting Member <
Lizzard d id
san jose, CA, USA   USA
Start with the plugs you have . After running it some see if they are working for the motor or not . If they show the need for cooler , then go cooler .

quikrx Ralph Hansen
Antioch, IL, USA   USA
1962 Triumph Herald 1200
1969 Triumph Spitfire MkIII "Gloria"
1987 Mazda RX-7 "Mistress"
2003 Toyota Celica GT-S "Natasha"    & more
run the coldest plug you can to help prevent pre-ignition - with the unknowns you have only try going colder 1 step at a time

. Hide banner ads & support this website by becoming a > Gold Supporting Member <
TheZster Avatar
TheZster Steven Z
SAINT LOUIS, MO, USA   USA
Mystery high performance motor - with no specs? That's a story I've just got to hear someday.... LOL

Z

clshore Carter Shore
Beverly Hills, FL, USA   USA
In reply to # 1504895 by quikrx run the coldest plug you can to help prevent pre-ignition - with the unknowns you have only try going colder 1 step at a time

What ignition system are you running?
Stock points systems are quite sensitive to plug fouling with wrong heat range.

Electronic systems, are more tolerant .
Capacitive Discharge systems will fire plugs no matter what.

Unless your motor is a True Fire Breathing Dragon (unlikely), don't sweat it too much.
As Lizzard and Ralph said, get it running first, and then install colder plugs based on how it runs.

70tbolt Geoff Ullmann
Morgan Hill, CA, USA   USA
Thanks!

It has a True Spark electronic system. I tried firing it today and it turns out the correct plug is now the least of my problems. There was no compression. Turns out the previous owner fiddled with the Kent Cam timing chain and gearing. #1 cylinder on compression stroke has the intake valve open. Must be out 180 degrees? Now I need to find out info on setting up these cams. The Kent Cams site did not provide really any helpful information. Tried contacting them before but they did not respond. TH5 Sports "R" cam.

Geoff

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
In reply to # 1504992 by 70tbolt Thanks!

It has a True Spark electronic system. I tried firing it today and it turns out the correct plug is now the least of my problems. There was no compression. Turns out the previous owner fiddled with the Kent Cam timing chain and gearing. #1 cylinder on compression stroke has the intake valve open. Must be out 180 degrees? Now I need to find out info on setting up these cams. The Kent Cams site did not provide really any helpful information. Tried contacting them before but they did not respond. TH5 Sports "R" cam.

Geoff

That was the Triumph Tune fast road 83 (a Ford cross flow cam) the specs are here.
http://www.jagclub.ru/tr_cam.html

. Hide banner ads & support this website by becoming a > Gold Supporting Member <
tapkaJohnD Avatar
tapkaJohnD John Davies
Lancaster, Lancashire, UK   GBR
If a cam is "symmetrical" (yours is) then use the Equal Lift on Overlap method to reset the timing.

With Crank at TDC on No.1 cylinder (and No.4), adjust the cam so that BOTH the intake abd exhaust valves are open an EQUAL amount.
This occurs between two full four-stroke cycles, when both valves are open, exhaust closing, intake opening, by a small amount.
Best done with two dial gauge indicators, but the Triumph workshop manual descrbes how to do it with feeler gauges.
With the cam in this position and crank at TDC on 1 and 4, fit the timing chain.
As you may know, there are 42 teeth on the timing sprocket, so 8.6 degrees per tooth, but Triumph provided two pairs of bolt holes in the sprocket, slightly offset so that you can adjust to half a tooth, and by turning the sprocket front to back, by a quarter tooth. That's as close as you can get, except by a vernier sprocket.
Also in the WSM.

Good luck!
John

clshore Carter Shore
Beverly Hills, FL, USA   USA
In reply to # 1505020 by tapkaJohnD If a cam is "symmetrical" (yours is) then use the Equal Lift on Overlap method to reset the timing.

With Crank at TDC on No.1 cylinder (and No.4), adjust the cam so that BOTH the intake abd exhaust valves are open an EQUAL amount.
This occurs between two full four-stroke cycles, when both valves are open, exhaust closing, intake opening, by a small amount.
Best done with two dial gauge indicators, but the Triumph workshop manual descrbes how to do it with feeler gauges.
With the cam in this position and crank at TDC on 1 and 4, fit the timing chain.
As you may know, there are 42 teeth on the timing sprocket, so 8.6 degrees per tooth, but Triumph provided two pairs of bolt holes in the sprocket, slightly offset so that you can adjust to half a tooth, and by turning the sprocket front to back, by a quarter tooth. That's as close as you can get, except by a vernier sprocket.
Also in the WSM.

Good luck!
John

Elaborating a bit on Johns excellent posting, each degree at the cam sprocket = 1/2 degree at the crankshaft.
Keep that in mind if you are using a degree wheel for checking and setting the cam timing.
A quarter tooth at cam sprocket, 8.6 / 4 = 2.15 degrees, or 1.07 degrees at crankshaft.

By all means get a Vernier sprocket set if you can, it's worth the money.
But most of them are double row, great for big journal 1296 and 1500 motors, not so much for 1147 and 1296.
Finding a double row crankshaft sprocket for a small journal motor can be challenging.

Absent that, the sprocket holes for the two cam bolts are always a bit loose,
since the bolt shanks are as wrought, not precision ground to fit.
You can 'nudge' the sprocket a bit in either direction before tightening the bolts,
or even elongate the sprocket holes with a small file.

My advice is to just use the ELOO method as John suggests (see attachment from workshop manual).
That will get the motor running well. You can always pursue the last few bits of ultimate power later on.

. Hide banner ads & support this website by becoming a > Gold Supporting Member <

Attachments:
Triumph ELOO cam timing.pdf    63.1 KB

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
Are you sure this IS a symmetrical cam?

If it is not, the ELOO method will not work!

If this cam is the Fast road 83 (AKA Ford crossflow cam) the specs are:

TT10505N Fast Road 83 Large bearing 37-63 74-28 280˚ 0.288” 103˚ 0.022” 0.024”

70tbolt Geoff Ullmann
Morgan Hill, CA, USA   USA
Thanks for all the replies! Appreciate it.

I also found this from Kent Cams. See second page. Geoff

Kent Cams Timing Instructions

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
While setting the cam timming you would be wise to just check the valve opening times and lift just to be sure the cam IS what you think it is.

Also, honestly, knowing what you know so far eye popping smiley you might want to pull the oil pan and check things out (bearing clearances, oil pump ect.) Before you move on and attempt to fire that engine up.

donnieb Avatar
donnieb Donald B
Council Bluffs, IA, USA   USA
1978 Triumph Spitfire 1500 "Beatrice"
As far as the spark plug question goes I've run NGK BP6ES for years. I think a lot better than the Champion plug you are running now

. Hide banner ads & support this website by becoming a > Gold Supporting Member <

To add your reply, or post your own questions




Registration is FREE and takes less than a minute!


Having trouble posting or changing forum settings?
Read the Forum Help (FAQ) or contact the webmaster





Join The Club

Sign in to ask questions, share photos, and access all website features

Your Cars

1970 Triumph Spitfire MkIII

Text Size

Larger Smaller
Reset Save

Sponsor Links