jp4 hi comp build check list

[quiky11]

Hi guys and girls I'm going to be doing a hi comp jp4 build and just want to check that I've covered all of the items needed for the hi comp build and what items are not nessary I'm looking for 160 bhp reving to 7500-7600 rpm in a years time after this build I plan to add tbs and p&p. the engine has already been set up and run in a 106

Couple of questions:
do I need to use forge con rods?
and do I need to light and balance the crank?
what head gasket will I need to use?

what pistons should i use-
wossner grp A 79/80mm 12.2:1
wossner super 1600 79mm 12.7:1
wiseco 79/80mm 12.2:1


Uprated valve springs
high comp over sized pistons
737s
standalone
arp bolts
race bbearings
rebore for oversized pistons
182 injectors

cheers

[blackie_2k5]

what ecu do you plan to use?

you need both crank and mains bearings, just so you're aware

all the obvious things like head gasket, belts, water pump, head bolts etc etc

[quiky11]

what ecu do you plan to use?

you need both crank and mains bearings, just so you're aware

all the obvious things like head gasket, belts, water pump, head bolts etc etc

i plan to use a predator.

do you know if id need to use a different headgasket compared to the standard. yeah got those on the list

thanks for your input

[blackie_2k5]

just a stand mls head gasket will be fine

will need to work out the compression you want to run, so the gasket size will be dependand of that, and the condition of your cylinder head once its removed

[quiky11]

okay thanks! well the head should be near mint as its only done 19k and it was stripped 2k ago to put 106 gti cams valve springs etc in

Anyone else able to add knowledge?

[welshpug]

all standard bits other than rods and pistons will suffice, std gasket is MLS, std bearings are good enough, no need to lighten the crank but getting it balanced with your chosen flywheel is a good idea.

choosing a cam profile wisely will help massively, depends on use, you may be better going solid tappets.

[Ryan]

Revving under 8k standard rods should be perfectly fine if you are on a budget.

[quiky11]

i will be adding rods to the list. what pistons out of the 3 above would you think would be better off getting?

[Ross]

i will be adding rods to the list. what pistons out of the 3 above would you think would be better off getting?

Why? Ryan just told you you don't need them. Save your money for something else :)

[welshpug]

Cp pistons, or omega, carillo or farndon rods

[Ross]

Why this obsession with rods on an engine revving to 7500 rpm?

[quiky11]

because isnt the standard rods in a jp4 weak as sh*t?

[Ross]

because isnt the standard rods in a jp4 weak as sh*t?

Mine were ok at 300bhp and a 7500 rev limit...

[greyjasper51]

Mine were ok at 300bhp and a 7500 rev limit...

But 1.1's with a jap can a diesel box make that ross...

Lol

Sorry back to topic

[Ross]

Lol

I'm just reiterating what Ryan said. Standard rods are not shabby. People pushing products might tell you otherwise though. Throw in a set of rod bolts and theres nowt wrong with them IMO.

[greyjasper51]

Rods 300? With bolts
Crank 450
Pistons 180?
Valve seats 250

So pretty much fairly safe

[welshpug]

Rods 300? With bolts
Crank 450
Pistons 180?
Valve seats 250

So pretty much fairly safe

Dreamland

Rods £600
Pistont £600
Crank £700
Bearings £150

Main reason to use rods is that standard dont suit decent pistons, however the jp4s are used in the c2r2 rally engines by citroen, as they are already bushed.

[Sandy309]

JP4 rods aren't bushed, J4 rods are. But there are perfectly fine to 8000rpm in my experience, as are the OE bolts. Many budget aftermarket rods are not as reliable as the OE ones, don't assume they're better!

[Ross]

Dreamland

Rods £600
Pistont £600
Crank £700
Bearings £150

Main reason to use rods is that standard dont suit decent pistons, however the jp4s are used in the c2r2 rally engines by citroen, as they are already bushed.
I think he's talking about power they may handle reliably rather than price. I thought he meant price also at first!

[Ross]

JP4 rods aren't bushed, J4 rods are. But there are perfectly fine to 8000rpm in my experience, as are the OE bolts. Many budget aftermarket rods are not as reliable as the OE ones, don't assume they're better!

I have no thanks left sandy but "thanks". :)

[welshpug]

oh right :wacko:

note the "S" when I was talking bout rods.

[jeffchiz]

for 160 bhp cams throttle bodies cams and a remap will get you 99% of the way to that figure of not more, I'm selling my jenveys, 708s in a recon head, preadtor ecu already mapped and my adapted loom for £1500, my j4 made 155 bhp at nms with worn piston rings so more would be expected with a healthy bottom end

[quiky11]

Thanks for your input people

for 160 bhp cams throttle bodies cams and a remap will get you 99% of the way to that figure of not more, I'm selling my jenveys, 708s in a recon head, preadtor ecu already mapped and my adapted loom for £1500, my j4 made 155 bhp at nms with worn piston rings so more would be expected with a healthy bottom end

The thing is I'd be looking to get 180 bhp out of it in 2014 which is why ill p&p and tb it then. That way I won't need to touch the bottem end again when it comes to that. If a pair of good condition second hand 705s came up I probably would do that until i come to port and polish a year later but what's the likely hood of them coming up second hand? And as there basically the same price as 737's brand new which is what I'd like when I want to make 180bhp I may aswell buy them and same me money in the future

[blackie_2k5]

for 160 bhp cams throttle bodies cams and a remap will get you 99% of the way to that figure of not more, I'm selling my jenveys, 708s in a recon head, preadtor ecu already mapped and my adapted loom for £1500, my j4 made 155 bhp at nms with worn piston rings so more would be expected with a healthy bottom end

Why has your loom been adapted mate?

For tps?

[nazmitocak]

as ı know jp4 gasket is thinner than j4 gasket ...
İf I use Jp4 gasket on my saxo head, what will be the comp. rate ?

[Ross]

as ı know jp4 gasket is thinner than j4 gasket ...
İf I use Jp4 gasket on my saxo head, what will be the comp. rate ?

you can calculate this yourself easily enough.

[nazmitocak]

you can calculate this yourself easily enough.

I dont know the formula

[Sandy309]

The gasket area is approx 50cm2, 5cc per mm. So JP4 gasket (0.66mm compressed) is about 3.3cc, J4 std (1.35mm) 6.75cc and so on. If your starting compression ratio is say 11:1 with 1600cc (400cc per cyl) swept volume, you'll have a total chamber volume of about 40cc overall (piston cc + squish/gasket cc + head chamber cc).

CR = (swept + total chamber vol) / total chamber vol

(400+40)/40 = 11

Adjust the total chamber volume for the change of gasket and re-calculate.