3.3(200) to 4.1(250) conversion

K

Karlos Cromarty

Hey all,
Looking to convert my one owner mint 1980 XD 3.3 poverty pack BW single rail 4sp to a 4.1, I have a donor 4.1, my proposed build is 4.1 rods, crank and use the 3.3 pistons as believe these are higher compression (10:1), swap the 3.3 iron head with the 4.1 aloy head, mild cam, pacer headers, 2 barrel Holley 2& 1/4 free flow exhaust, why the effort..keep the matching numbers, any feedback on ethos build would be appreciated, good, bad or otherwise, cheers
 
All do-able, couple of issues, A compression with flat top 200 pistons will be too high at around 11:1 for normal petrol. B You might run into trouble getting the pistons off the 200 rods without damaging them. Alloy head have dowel holes, irons blocks dont, they will bolt on however. C, intake and exhaust are different on alloy and Iron heads. If it was me id stay with 250 pistons, unless they are unleaded canyon tops, your bore O/S might be an issue here, use the alloy head and manifolds, get a good stockish cam, but do go to heavier springs and new rocker arms and pivots, get a roller timing chain, get electronic ignition, stock size oil pump is fine, but do get a new JP iron case one. Keep your single rail trans, your axle ratio is probably 2.92. which will work with the 250ci. Ive mixed and matched my engine, earlier iron head block with alloy head, The later big valve head is slightly better, but I wouldnt shell out just to get one when you already have a good one. Ive got some spares if your nearby, (gippsland victoria)
 
Chee
aussie7mains said:
All do-able, couple of issues, A compression with flat top 200 pistons will be too high at around 11:1 for normal petrol. B You might run into trouble getting the pistons off the 200 rods without damaging them. Alloy head have dowel holes, irons blocks dont, they will bolt on however. C, intake and exhaust are different on alloy and Iron heads. If it was me id stay with 250 pistons, unless they are unleaded canyon tops, your bore O/S might be an issue here, use the alloy head and manifolds, get a good stockish cam, but do go to heavier springs and new rocker arms and pivots, get a roller timing chain, get electronic ignition, stock size oil pump is fine, but do get a new JP iron case one. Keep your single rail trans, your axle ratio is probably 2.92. which will work with the 250ci. Ive mixed and matched my engine, earlier iron head block with alloy head, The later big valve head is slightly better, but I wouldnt shell out just to get one when you already have a good one. Ive got some spares if your nearby, (gippsland victoria)
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Cheers aussie7mains, info is appreciated ! I’m based in Nz these days though thanks for the offer re the below ! Thanks mate
 
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