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Guest Message by DevFuse

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Would like your opinions-EA81 rebuild

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1 reply to this topic

#1 tweety


    USMB Regular

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  • 343 posts
  • Euroa Victoria Australia

Posted 21 August 2014 - 07:25 AM

Have a trike, been on here many times. It has VW type 3 full automatic trans


Auto has had a clean inside and full gasket set and has been reinstalled


EA81. Regular readers will know my engine has had a 32/36 weber, all anti pollution stuff discarded and H section exhaust going to twin exhaust. Engine then had suck thru SC12 supercharger then SPFI conversion. Both head gaskets were blown) Now I've decided on the following.


Rebore with possible pistons from EA81/71 or EJ20. Left that decision to the engine builder.


Towing cam 16/56 for high torque at low revs (I dont like revving engines and I tow a camper)


Raising compression to around 9.2:1


SPFI manifold


Weber 38/38 synchronic with adapter being made to suit.


Stock electronic distributor


Stock lifters, new oil pump, water pump etc


3 step valve grind (is large valve model heads) light porting


When I ran the 32/36 weber it didnt suit the auto very much, sluggish is the word, always looking to kickdown when I didnt really want to. I'd like to know how the 38/38 carb will perform with the larger SPFI manifold???  any guesses? It will need correct jetting eventually.


Anyone used a 38/38 and anyone used a SPFI manifold with a carbed engine? and know the difference?




#2 tweety


    USMB Regular

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  • 343 posts
  • Euroa Victoria Australia

Posted 22 August 2014 - 04:26 AM

Ok, no replies so how about some theory?

Larger SPFI manifold. What is the increase in percentage of volume? Measurements taken...


internal diameter stock manifold about 36mm. area of cross section = 36x36x3.14(pi) = 40.69sq mm


SPFI manifold is 6mm larger all round = 42x42x3.14 = 55.38 sq mm


This mean the SPFI manifold has 25% extra volume over the stock manifold.


I assume 2x 38mm venturi's on a 38/38 weber will now be more suitable for the ea81 with the larger manifold Am I right???

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