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tr8todd
Todd Kishbach

(390 posts)

Registered:
12/04/2009 07:42AM

Main British Car:
Which spark plugs for the 300 head?
Posted by: tr8todd
Date: May 14, 2010 01:59PM

Machinist is working on a set of 300 heads and wants to know which plugs to run. He says the Buick heads put the plug farther into the combustion chamber than do the Rover heads. He is installing the stage 1 V6 valves with new seats. Valves are 1.77 and 1.5" if I remember correctly.


tr8todd
Todd Kishbach

(390 posts)

Registered:
12/04/2009 07:42AM

Main British Car:
Re: Which spark plugs for the 300 head?
Posted by: tr8todd
Date: May 14, 2010 03:38PM

Got the answer to my question elsewhere. Short reach plugs only. The one that was recommended was Champion 807-L78C. Found out the answer from a guy who was running long reach Champion RN12YC until the plugs failed and blew a hole in his pistons at high RPMs. Seems that with the long reach,the flame won't spread across the combustion chamber evenly and caused the plug meltdown and piston failure. At least that is what the engine builder who built the engine the second time said caused the failure. So far the rebuilt engine is great with the short reach plugs.


roverman
Art Gertz
Winchester, CA.
(3188 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Which spark plugs for the 300 head?
Posted by: roverman
Date: May 14, 2010 04:20PM

Todd, If any of the threads are compromised, I sugest"TimeSerts", as a permanent repair.roverman.
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tr8todd
Todd Kishbach

(390 posts)

Registered:
12/04/2009 07:42AM

Main British Car:
Re: Which spark plugs for the 300 head?
Posted by: tr8todd
Date: May 14, 2010 08:35PM

The heads were in excellent shape. Machinist just needed to know what plugs were going into them so he could cc the heads. Needed that info to properly order the pistons. He has or is going to send out the heads to have them cryogenically treated in an attempt to make them harder. I have heard that the 300 heads are softer than the Rover heads and often end up with rocker bolts pulling out with big lift cams and roller rocker set ups.


7sand8s
Dennis Miller

(36 posts)

Registered:
09/21/2008 10:47PM

Main British Car:
Re: Which spark plugs for the 300 head?
Posted by: 7sand8s
Date: May 15, 2010 10:29AM

Bosch Super Plus
"50% longer lasting than OE copper plugs"
"Premium Copper core plus Yttrium"...from the box
Plug# WR 8 BC+
Stock# 7903


roverman
Art Gertz
Winchester, CA.
(3188 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Which spark plugs for the 300 head?
Posted by: roverman
Date: May 16, 2010 12:37PM

Todd, rumors are best followed-up with a little "science". Suggest, hardness testing,(Rockwell "b"scale), first. This way no one is guessing. I suspect the 300 heads had stronger springs for the heavier int. valves,(oem.), and "many" more duty cycles with out the rocker shaft reinforcements, vs. Rovers ? When all is said and paid for, how much for 300's vs. Merlins ?



Edited 1 time(s). Last edit at 05/16/2010 01:06PM by roverman.


tr8todd
Todd Kishbach

(390 posts)

Registered:
12/04/2009 07:42AM

Main British Car:
Re: Which spark plugs for the 300 head?
Posted by: tr8todd
Date: May 16, 2010 06:25PM

Machinist bailed on the cryo and is planning on installing inserts. Rocker studs pulling out seems to be common with the 300 heads. At least with the half dozen or so sets I am familiar with. Not sure what all this is going to cost. Not my motor. I'll help the guy put it back in his TR8 once it's done. Motor will be broken in on a dyno. so we'll all know what it does. They just ordered 10.8 to 1 Ross Pistons to be run with a gapless ring on the top groove. Motor will be a 4.9 with roller rockers and a solid lifter cam.



roverman
Art Gertz
Winchester, CA.
(3188 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Which spark plugs for the 300 head?
Posted by: roverman
Date: May 16, 2010 09:23PM

Todd, rocker studs,counter bored say 1/4" deep,of smooth dia.latteral support, is also a good up-grade,ARP, etc. Is Dan Jones running a cam program for it ? May the HP. gods, rain down upon it, roverman.


tr8todd
Todd Kishbach

(390 posts)

Registered:
12/04/2009 07:42AM

Main British Car:
Re: Which spark plugs for the 300 head?
Posted by: tr8todd
Date: May 17, 2010 12:04PM

The guy building the motor is going to pick out the cam. His name is Bob Mason. He is in RI and is a highly respected engine builder in these parts. This is his first Rover build. That is why we chose to go with a local Rover specialist the first time the motor was built- or should I say screwed up. Mason is off on an African safari for two weeks. Pistons and gaskets should be in when he gets back, so final assembly should be coming up. It would have been done a couple of months ago had my buddy not needed to go out and get another block. Thanks, Tim Lanocha for coming thru on the block and torque plate.


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