cylinder head technical question

[cnicholson]

Hi i have just removed the head of my tr6 cf prefix engine, and found it appears to have had a recent rebuild with 0.30 hepolite pistons, and a very tidy bore.

The current  cylinder head is an 516816

i have a refurbished 219016 cylinder head are they compatible as is or, will it need to be skimmed down to correct the compression? i am intending on using a fast road cam and perhaps roller rockers

[GT6 M]

just measure the depth of the chambers, as just cos it says it is a what ever,
dis nae mean its no had a skim in the past.

And also, a bigger bore will increase your comp ratio a wee bit.

that the yan just gone of Flea Bay,!!!!

M

[JohnD]

Take the measurements, do the calculations.
It's not worth messing about with CR.  get it wring, either way and you'll be disappointed.
See: http://www.totallytriumph.net/spitfire/skimming_your_head.shtml
JOhn

[DJB_Harvey]

The 516816 head originally was 3.400" .. The 219016 head is 75 thou thicker .. If it was me with that 30 thou overbore I'd just lightly skim the head to clean the the face and fit . A PI engine I built recently had a 40 thou overbore , 219016 head lightly skimmed ran spot on .

[cnicholson]

thanks for the article on compression ratios very useful, as i intend to use a kent cam th7 with 300 duration, and to tame it i have a megasquirt setup. i think it wont need too much of a skim to get it right

[GT6 M]

the longer the durtion, the higher the comp needs to be,
to low with a long cam, and it will no wurk v well at all.

Static Compression Ratio
(SCR)      Intake Valve Duration
(degrees @ .050" lift)      Power Range
(RPM)
8.00:1      185º      Idle-4,000
8.25:1      189º      Idle-4300
8.50:1      194º      800-4,500
8.75:1      200º      900-4,600
9.00:1      204º      1,000-4,600
9.25:1      208º      1,200-5,200
9.50:1      212º      1,600-5,400
9.75:1      216º      1,800-5,600
10.00:1      221º      2,000-5,800
10.25:1      227º      2,400-6,200
10.50:1      233º      2,800-6,400
10.75:1      236º      3,000-6,800
11.00:1      240º      3,200-7,000
11.50:1      244º      3,400-7,200
12.00:1      248º      3,600-7,400

[cnicholson]

the plot thickens tonight, i have finally got the old cam out, it turns out is is not very old at all, the cam has the following markings

777 IT

Google has suggested it could be an Isky fast road or a Racetorations fast road cam, the question is do stick with it or go for the kent race cam, tempted to stick with what i found given that the engine sounded very sweet when parked it up 18 moths ago?

[tiggrr1]

Some info here that may help

http://www.tr-register.co.uk/forums/index.php?/topic/19580-kent-7771-camshaft/

It seems it may be a Kent fast road profile, granted the info is for a TR4 but I'm guessing TT also used the same profile for the six pots (think)(think)