Jp4 engine

7th April 2012, 13:40

Ok guys I've searched this and read a lot of threads on this and found a lot of mixed reviews on the jp4 engine over the j4.
The only thing I'm struggling to work out is unless you get hold of the jp4 from a c2 vts then the others are 110hp.
So they have bigger valves to enable you to fit bigger / wilder cams but are the cams really gonna get the engine up to 120 what the j4 is?

7th April 2012, 15:06

If you use the springs, followers and cams from a J4 it will have 120bhp. I saw a JP4 with just breathing mods make 134bhp on the rollers.

7th April 2012, 15:21

Ive seen a jp4 without j4 cams make 133bhp with 421-filter.

The j4 inlet is bigger than jp4 so more power, jp4 has bigger valves, and the j4 ecu is better than jp4(IRC on last one)

a jp4 head is better than j4
j4 bottom end is better than jp4.(jp4 is weaker)

a jp4 converted(without j4 cams) will still make 125bhp+

When driving a jp4, the power will be alot smoother and less kick at 4k/5k(carnt remember when j4 kick in)
Was a member on axoc who was getting 54mpg from her jp4!!

7th April 2012, 15:22

Quote:

Originally Posted by JoshB

If you use the springs, followers and cams from a J4 it will have 120bhp. I saw a JP4 with just breathing mods make 134bhp on the rollers.

Cheers mate that's cleared that up.
I ask because I'm in the process of having an engine rebuild.
As I use my car as an every day vehicle I'm planning on sourcing another engine having the cylinder head ported and polished and flywheel lightened and balanced and thought it would make sense to rebuild the bottom end as well.
Just un decided on if I should go for another j4 engine or go for the jp4.

7th April 2012, 16:12

So if I go for the j4 bottom end and a jp4 head can my Newman phase 3 cams still be used in a jp4 head.
Noticed this as been asked a few times just wanted to no if anyone is running there's with this set up and cams?
Thanks

7th April 2012, 18:16

Think you'll still have clearance issues, something I'm looking to do currently too

7th April 2012, 18:52

Quote:

Originally Posted by Mathias

Think you'll still have clearance issues, something I'm looking to do currently too

Ye noticed a lot of people have had this problem just don't no if anyone as actually pulled it off yet.
If I can't do this then will have to stick to getting a j4 engine and just have it rebuild, due to me having cylinder head ported and polished and while I'm at it have all bottom end replaced as well.

8th April 2012, 09:56

You can get high lift cams specific for the JP4 head. KamRacing sell them. I know someone who did fit J4 cams and it blew up on the rollers. But then others have run them fine. It's a touchy subject.

8th April 2012, 19:08

Best to buy cams made for a jp4 head with a j4 bottom end as said kamracing sells them, you can use j4 cams but they don't make good contact with the follows as the valves are slightly offset on a jp4 hea

Also its a jp4s engine which has the 125 bhp, but if your fitting aftermarket cams it wouldn't matter which head you get

8th April 2012, 19:15

Quote:

Originally Posted by jeffchiz

Best to buy cams made for a jp4 head with a j4 bottom end as said kamracing sells them, you can use j4 cams but they don't make good contact with the follows as the valves are slightly offset on a jp4 hea

Also its a jp4s engine which has the 125 bhp, but if your fitting aftermarket cams it wouldn't matter which head you get

Thanks fir that mate but if i used jp4 cams would i still be able to use the j4 Springs and followers or would I need to use the jp4 ones?
Thanks

8th April 2012, 19:43

Quote:

Originally Posted by ldavies

Thanks fir that mate but if i used jp4 cams would i still be able to use the j4 Springs and followers or would I need to use the jp4 ones?
Thanks

You must use the vts springs, followers and retainers the c2 ones won't cope with the extra power

8th April 2012, 20:32

Quote:

Originally Posted by jeffchiz

You must use the vts springs, followers and retainers the c2 ones won't cope with the extra power

Thanks for your help mate.
So just to clear this up it will need:

J4 bottom end
Jp4 / jp4s head
J4 springs and followers
Jp4 / jp4s cams

8th April 2012, 20:47

The c2 vts only rev's to 6500 in a c2.. but on saxo management - it rev's to 7200 (mine goes to 7600 with a unlocked ecu for some reason)

I regularly take it to 7k, and no problems / nasty noises - yet

8th April 2012, 20:50

Quote:

Originally Posted by jeffchiz

Best to buy cams made for a jp4 head with a j4 bottom end as said kamracing sells them, you can use j4 cams but they don't make good contact with the follows as the valves are slightly offset on a jp4 hea

Also its a jp4s engine which has the 125 bhp, but if your fitting aftermarket cams it wouldn't matter which head you get

can i use a jp4 bottom end with jp4 head and kam racing cams?

doesnt have to be a j4 bottom end basically?

8th April 2012, 21:03

Quote:

Originally Posted by Mathias

can i use a jp4 bottom end with jp4 head and kam racing cams?

doesnt have to be a j4 bottom end basically?

Isn't the j4 bottom end better / stronger tho?
Could be wrong.

8th April 2012, 21:04

Quote:

Originally Posted by Mathias

can i use a jp4 bottom end with jp4 head and kam racing cams?

doesnt have to be a j4 bottom end basically?

the cams im referring to were developed to work with a c2 head on a saxo bottom end so im guessing they are made so they hit the followers where they should and the valve clearences have been measured etc so you would need a saxo bottom end for these cams, i would guess

if you're using a full jp4 engine then you would just buy cams made for a c2, when then do the usual changes to make the jp4 engine fit (j4 inlet manifold, exhasut manifold, sump, engine mounts etc)

these are the cams
http://www.kamracing.co.uk/citroen/c...s-1322705.html

8th April 2012, 21:19

thanks mate, think ill just phone kam racing tuesday and explain!

8th April 2012, 21:24

Quote:

Originally Posted by Mathias

thanks mate, think ill just phone kam racing tuesday and explain!

well its kinda self explanitory, if your using a full c2 engine then just use c2 cams, if you're using a full saxo engine then use saxo cams, if you're using the saxo bottom end with a c2 head then use the cams that have been develped for that combination, but yea i would advise talking to them dont take my word for it lol

8th April 2012, 22:12

Quote:

Originally Posted by jeffchiz

well its kinda self explanitory, if your using a full c2 engine then just use c2 cams, if you're using a full saxo engine then use saxo cams, if you're using the saxo bottom end with a c2 head then use the cams that have been develped for that combination, but yea i would advise talking to them dont take my word for it lol

i know its preety easy to understand mate, thanks. i'll need the c2 cams, however they have a few listed so i'll give them a call / pm

9th April 2012, 15:11

So found a jp4 head but is just bare, so if I use the springs, followers etc from my j4 what valves do I need to use as this head dosent come with valves.

9th April 2012, 15:20

Quote:

Originally Posted by ldavies

Thanks for your help mate.
So just to clear this up it will need:

J4 bottom end
Jp4 / jp4s head
J4 springs and followers
Jp4 / jp4s cams

you would use the cams made for a saxo/c2 combination engine (thats if you want after market cams)

http://www.kamracing.co.uk/citroen/c...s-1322705.html

i know people fit saxo vts cams in to the jp4 110 bhp engine to bring the power to to around 125bhp, im not sure if saxo vts or the c2 jp4s cams would be best to use if you want standard cams, that im not sure off, as i dont know about the valve clearences etc but i would have though thte jp4s cams would be best to use as the saxo cams dont hit the followers properly but double check first i dont want your engine blowing up lol

Quote:

Originally Posted by ldavies

So found a jp4 head but is just bare, so if I use the springs, followers etc from my j4 what valves do I need to use as this head dosent come with valves.

you would use the c2 valves as the valves are bigger, the saxo ones would be too small

9th April 2012, 15:24

Quote:

Originally Posted by jeffchiz

almost right you would use the cams made for a saxo/c2 combination engine

http://www.kamracing.co.uk/citroen/c...s-1322705.html

or you can fit the standard saxo cams but again these wont fit quite right but will work

you would use the c2 valves as the valves are bigger, the saxo ones would be too small

Mate thanks for your help much appreciated you seem clued up on this, but new to me the jp4 lol

9th April 2012, 15:28

Quote:

Originally Posted by ldavies

Mate thanks for your help much appreciated you seem clued up on this, but new to me the jp4 lol

well its just from what ive read up on, i wouldnt take what i say as fact lol

the only thing im not sure on would be what cams to use if you want standard cams, but logically you would use the jp4s cams

9th April 2012, 15:39

Currently I have Newman phase 3 cams but if I go through with the jp4 I would do away with the phase 3s and go for the saxo/c2 cams you mentioned mate.