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5th gen engine in 6th gen


168sierra

Question

I am considering installing a 5th gen (2000) engine into a 6th gen (2003) to take advantage of the power of the 5th gen engine and gear driven cams (love the sound) and the handling of the 6th gen with an RC51 front end.

Has anyone used the 6th gen FI on a 5th gen motor? From what I have read, the throttle bodies bolt on. I was palnning to use the 330 ohm resistors to bypass the O2 sensors and run a catless header. I am thinking of trying to reflash the ECU with a 5 th gen fuel map. This should be close but will probably need some fine tuning.

Does anyone have any experience with this? I can't be the only one who wants this combination.

Pics to follow

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The specs I have are:

Standard 5th Gen

Inlet open 10deg BTDC, close 35deg ABDC, with 8mm lift and 225deg duration

Exhaust open 35deg BBDC, close 10deg ATDC with 8mm lift and 225deg duration

Standard RC45

inlet open 15deg BTDC, close 40deg ABDC with 8mm lift and 235deg duration

Exhaust open 45deg BBDC, close 10deg ATDC with 8mm lift and 235deg duration

Hope this helps.

I believe that you need to be quite careful on lift as things are pretty close running without the RC45 Race kit.

Cheers

Phil

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Looks that way.. 10 degrees longer duration with 5 degrees more valve overlap

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If you want reeeeeeeeally long timing, these are the specs for the HRC racing kit cams for the RC45.

inlet open 23deg BTDC, close 52deg ABDC with 9.5mm lift and 255deg duration

Exhaust open 50deg BBDC, close 20deg ATDC with 8.3mm lift and 250deg duration

Cheers

Phil

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If you want reeeeeeeeally long timing, these are the specs for the HRC racing kit cams for the RC45.

inlet open 23deg BTDC, close 52deg ABDC with 9.5mm lift and 255deg duration

Exhaust open 50deg BBDC, close 20deg ATDC with 8.3mm lift and 250deg duration

Cheers

Phil

did the racing kits have pistons with deep valve pockets in the tops to accomodate the extra valve lift and opening duration near TDC?

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I take it they did as you're right there would have been plenty of clashing.

Never seen the actual items and I doubt many of us will with the scarseness

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If you want reeeeeeeeally long timing, these are the specs for the HRC racing kit cams for the RC45.

inlet open 23deg BTDC, close 52deg ABDC with 9.5mm lift and 255deg duration

Exhaust open 50deg BBDC, close 20deg ATDC with 8.3mm lift and 250deg duration

Cheers

Phil

That is insane... no wonder they were getting NSR500 levels of power out of the RC45 towards the end.

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Cams are currently off being built up and re-profiled.

I'll need to get some small diameter welsh plugs for the ends of the cam oil ways as they had to remove the plugs to get access to the shaft centres for grinding.

If I can't find welsh plugs, I'll need to get some aluminium press fit plugs turned up and loctite them in.

Once I've got the cams back, I'll update the thread.

Also currently working on the cylinder heads.

Porting them to the HRC RC45 drawing that came with the race kit as below.

post-25941-0-23199900-1407226687.jpg

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Cams are currently off being built up and re-profiled.

I'll need to get some small diameter welsh plugs for the ends of the cam oil ways as they had to remove the plugs to get access to the shaft centres for grinding.

If I can't find welsh plugs, I'll need to get some aluminium press fit plugs turned up and loctite them in.

Once I've got the cams back, I'll update the thread.

Also currently working on the cylinder heads.

Porting them to the HRC RC45 drawing that came with the race kit as below.

Wow! That is really making the intake port divider thin is section BB... I can see why that flows a lot more air!!! Are you having the head work done or are you porting it yourself?

BTW... love the work you are doing!!! This is AWESOME!

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Yes, the divider will be somewhat different once complete.

I'm doing the work myself as I feel if I follow the drawing, and don't chop the ports about too much, i should be OK.

There is quite a lot of mismatch between the throttle body insulators and the ports standard so getting them to flow, and doing the majority of the work in the HRc drawings should make a reasonable improvement.

Not really altering the port profile but am removing the steps under the valve seats etc. and smoothing out the casting part lines etc.

If I don't stuff with the port throats then the gas speed should be good.

Time will tell.

Yep, there should be some good gear whine once it is all going.

It will be interesting to see if anyone picks the changes, externally, just from the sound.

I'll post some pics of the ports in the next day or so.

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This is a intresting tread. I have never ridden a 6th gen, but as I had to take off my CarbonFiber "race" muffler (whit a PC map) as it broke and did put a stock muffler on and unplugged the PC, well I need to downshift to get same level of accerelation as before on hightway speeds to pass cars, so is it this you mainly miss on a 6th gen?

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Finished the port work roughing out today so thought I'd post a couple of images, before and after.

I still need to finish the ports off, but you'll get the idea.

post-25941-0-06815200-1407747983.jpg

post-25941-0-71703700-1407748003.jpg

Should be all done next weekend.

Got the crankcase back from the borers and it all looks good.

Now need to modify the head gaskets to suit the 74mm bore.

Cheers

Phil

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I read somewhere it is a good idea to keep a bit of roughness in the ports. If they are polished too much, the gas vapor has tendency to bead or shmear on their surface similar to what happens to a windshield when Rain-X is applied and that is contrary to what we are trying to achieve.

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Yep, you are right, if they are polished you end up with a boundary layer and the fuel droplets all out of suspension in the air flow.

Finishing with 120 grit drums etc. is about all you need.

Don't go any smoother.

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Yep, you are right, if they are polished you end up with a boundary layer and the fuel droplets all out of suspension in the air flow.

Finishing with 120 grit drums etc. is about all you need.

Don't go any smoother.

The man knows his stuff! :beer:

How did they hone the bores after the cuts? Any pics?

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The machine shop contacted their honing supplier and they suggested to use the standard honing process that they use on the car blocks with MMC.

They did not outline it much further than that but it looks and feels fine.

Sorry, haven't got any shots of it as yet.

I'll grab a couple tonight and post.

Next job is to enlarge the head gasket bores to suit the 74mm.

Thought I'd try it on the old ones first just in case I make a boo boo.

Then it is Plasticine the piston crowns and check the valve reliefs.

Hopefully I don't have to carve too much out on them seeing I've already balanced the pistons and brought their mass down towards the original VFR pistons.

I'll let you know.

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The machine shop contacted their honing supplier and they suggested to use the standard honing process that they use on the car blocks with MMC.

They did not outline it much further than that but it looks and feels fine.

Sorry, haven't got any shots of it as yet.

I'll grab a couple tonight and post.

Next job is to enlarge the head gasket bores to suit the 74mm.

Thought I'd try it on the old ones first just in case I make a boo boo.

Then it is Plasticine the piston crowns and check the valve reliefs.

Hopefully I don't have to carve too much out on them seeing I've already balanced the pistons and brought their mass down towards the original VFR pistons.

I'll let you know.

Nice info... good to know.

Are you enlarging and blending the lower part of the combustion chamber to match the new bore size?

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No, I can't see any real benefit in changing the combustion chamber at all for the level of tune I'm aiming at.

If it was all out, then I'd get someone with a flow bench to do the whole shooting match.

As it stands the 1mm increase on radius should really not alter much bar the squish area at TDC.

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Hi, Maybe i can provide you some helpfull information when you going to tune your Engine.

I have an VFR800 Engine 2002(right now but have also tried 2005 vtec)

Engine is total stock no mods,

I have MSIII and turbo fitted Control both injection and ignition curve

Lots of Electronic to control servo for adjust wings in turbo

All stock sensors and pickup

My experience with engine is that about 140HP in engine there is no problem

140HP= stock injectors

140HP= you need stronger springs for clutch

150HP New bigger injectors

200HP new harder springs and more plates in clutch

320HP=engine breakdone, stock piston will crack

What i do have is alot of work done with ignition curve an injection curve that can be usefull for you when you are going to dail in ignition and fuel map, if you are intrested in that make a PM and i send my mapping to you.

/W

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