Difference between 8 port & 4 port engine??

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rossmac
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Is there any differenced between the 4 & 8 port engines ? are all parts, eg pistons, cylinder head, cams etc interchangerble?Cheers


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float_6969
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Cylinder head and lower manifold are the main differences. The block also has different threads for the head bolts. Other than that, they are identical.

4 port head - 4 intake ports, one for each cylinder, matching lower manifold, smaller threads in block for head. 8 port head - 8 intake ports, one for each intake valve, matching lower manifold, larger threads in block for head.

meminto
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Each head has its own unique fuel injector arrangement..

Ie: 8 port has the injector port located on left inlet runner on the sub plenum. 4 port is centered on the plenum..

So you need the correct plenums/rails/gaskets for each application..

Most other bits n pieces are interchangeable as far as I am aware, on a DET motor that is..

Edit: - What float said...

rossmac
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Thanks for that dude,So to convert an 8 port to a 4 port you need the head, lower intake manifold part & the main head studs?

Could you tell me what the difference is between the studs? Are we talking about the head studs?Are they different thread or just longer/shorter?

Thanks

meminto
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They are a different thread...

Talking about headstuds...

rossmac
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Is there any way i could get around this other than drilling & tapping all the holes in the block?

meminto
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It wont worry the head itself as the diameter of the stud holes shouldn't be dissimilar..


rossmac
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Oh thats okay then,Do you think it would be okay to re-use the head studs and cometic head gasket?Reason is I have a clamped up 8 port head & i wanted to remove that & install my 4 port head.

Hopefully it will ba okay to re-use the parts as the engine hasn't even been run yet,

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float_6969
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The holes in the head are fine. It's the threads in the block that are different. Just get bolts/headstuds that match the block and you'll be fine. ARP makes headstuds for both the UK Spec and JDM/USDM Spec CA18DET's.

rossmac
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I already have arp head bolts for the euro block Swap anyone ?

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float_6969
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What? If you have a euro block, and euro headstuds, you can use either head w/o a problem.

rossmac
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JDM engine & block,Euro Head & ARP Studs

rossmac
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Is it possible to re-use standard head bold and a cometic head gasket?the engine hasn't even been run yet

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float_6969
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Yes. I've never found anything in the FSM that states that the head bolts are TTY and would need replaced after removal.

MAKE VERY SURE that the head and block have BOTH been re-surfaced. And make sure they know you're using a metal HG. Cometics have a tendancy not to seal if the shop doesn't mill the block and head to the proper surface smoothness.

rossmac
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Would the block need re,re-surfacing if its already been suitable for a mhg?Thanks for your help gents

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float_6969
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I would. There have been a lot of problems with people getting those headgaskets to seal. IDK if it's a motor thing, or a gasket thing. Cometic swears it's because the surfaces aren't being finished to the corrects roughness.

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Valvebounce
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Ross_Mac wrote:Thanks for that dude,So to convert an 8 port to a 4 port you need the head, lower intake manifold part & the main head studs?
Make sure you get the fuel rail too.

rossmac
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float_6969 wrote:I would. There have been a lot of problems with people getting those headgaskets to seal. IDK if it's a motor thing, or a gasket thing. Cometic swears it's because the surfaces aren't being finished to the corrects roughness.
Really?The engine hasn't even been run since the block was surfaced & the head bolted on.Is there a way to check if the block if in tolerance/ finished good enough for a cometic hg?

rossmac
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Help :D

meminto
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If the block/head has been prepared to the specified roughness, I don't see there being an issue..

If it hasn't, then you either need to do it or use an oem gasket..

Without the finishing process, it will fail prematurely..

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float_6969
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From the Cometic website:"What surface finish is required to us an MLS head gasket?A surface finish of 50 RA (roughness average) or finer, is recommended for a proper gasket seal. Anything rougher may conflict with the gasket design."Talk to your engine builder and ask him what the RA of the head and and block were. Don't tell him it has to be 50 or finer and see what he says. If he didn't do it right, the cometic WILL leak.

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How can you tell if you have the 8 port or 4 port?

meminto
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Without taking anything apart?

Easy visual sign is centered injector bosses on the sub manifold..

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float_6969
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There aren't any 4 port CA18's in the US unless somebody bought a CA18DET motor-set from japan, and then bought a 4 port head from Europe and slapped it on there, and then sold the car.

910bluebird
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ive got one these head laying around somewhere , pretty much the same bar the injectors being centered like others have siad

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ska69
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is there any way to tell which version (4port or 8port) is installed? I have a euro-spec '89 ca18det and up until today I had no clue about the 4port and 8port differences...

ferracing
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Here you can view the version 8port








Modified by ferracing at 1:30 PM 3/14/2010

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ska69
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thanks! but forgive my stupidity, and how does a 4 port look like?

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ska69
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I think I found it

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ska69
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and this one here: zer...age=1



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