More NA power mods

[Babalouie]

Dunno if you'd quite get 100rwkw from a 1600, maybe 90rwkw. Also not sure if you'd need valve springs with the 845C cams, those would probably peak at 7500rpm anyway. I'd get an overbore to 1720cc while you're at it, and I dunno if headwork would be justified. AFAIK, it would only be worthwhile if it was a really good job, and really good jobs would take a porting guru a couple of days.

When I was doing my cylinder head, I was recommended that I should either leave the ports alone and just spend the money on restoring the lifters and doing a good multi angle grind on the valves and seats....or bite the bullet and spend $1200 on porting I think at this age, some compression is lost via poor valve to seat sealing, so you should invest in fixing that in preference to porting, or so I was told.

[Babalouie]

I'm open to cam options aswell. i thought these looked like a reasonable step up (the 725s look alittle much??). other profiles at http://www.tighecams.com.au/cars.htm

Nooo....don't go too wild on them cams, IMHO. Unless you want to spend lots of dosh on valve springs, etc, pick a cam that only needs revving to 7500rpm, and will handle the air con (and idle in hot traffic without stalling) In fact, I don't think you want to go much bigger than the 805C.

[adamjp]

Butters,

100rwkw is a big ask for a NA MX5 donk.

I ran the Tighe cam profiles on the Desktop dyno software I have and from memory the 825s came out looking real good. There is a thread about it from mid to late last year. http://www.aus-cartalk.com/viewtopic.php?t=17675&highlight=tighe

For $3-4k, if you do the engine build yourself you will get a worthwhile improvement over the stock build. Head porting is well worth it, but IMHO only if the shop has a flow bench. My ports flowed like this

Code: Select all

Valve Lift Intake    Exhaust  Int/Exh Flow %
  (inch)   Old New   Old New     Old New
   .050    32  35    36  26      102 75
   .100    58  65    49  53      84  81
   .150    86  92    66  74      76  80
   .200    109 114   78  94      71  85
   .250    124 132   88  107     69  81
   .300    138 145   91  115     66  78
   .350    146 152   93  120     64  79
   .400    148 155   95  122     64  79


[neil d]

neil d: what cams do you use now that you sold the 805s?(or is that a secret) do you do all the engine work yourself? your post in the other thred shows alot of goodies for 5k

No secret I'm now using a B1486C. This cam is similar to the 845C however it has a small closing ramp to save my inlet valves.
I do all of the work myself and hence can save money. For $5000 Gary stewart can build you an 1800 with 200hp at the fly, you will then need clutch, fly wheel, haltec, extractors etc.

Neil