Xu7jp4-rs Tuning

[decoc182 0]

Ive taken a crazy leap and bought an xu7jp4 engine. I am now in the process of sorting out the fuelling and head combination. I have noticed the xu7jp4 head has very poorly cast ports, that would take a lot of machining IMO to get the perfect shape. Unfortunatly, I cannot afford a custom port machining so will have to look for a head with better port shape.

 

 

 

This brings me onto the RS head. I have found an RS head on this forum which Im gasping to buy. Im led to believe they should bolt straight on give or take and should time up relativly easy.

 

In the process of building up the top end I have been looking at cheap cam options. I noticed that piper do regrinds for their 272 for £193. Any comments on these would be appreciated

 

Finally, can I use the can driven vacuum pump to run servo assisted brakes?

[pip470 61]

This post isnt going to be complete fact because I havn't got any figures and im unlikely to do so either but ill give my opinion.

 

At the moment I have in my road car, a gti 6 bottom end, with a xu7j4 head with the gti 6 cams, exhaust manifold, bike carbs, the head has had the ports opened up by me and been skimmed to give 11 to 1 compression ratio. Now I'd love to tell you what power its making at the moment but I havent had it rolling roaded since putting this head on. I do have a feeling its less than what it made with the standard gti 6 head, it just doesn't feel as fast.

 

So probably no help what so ever, other than if your interested in this head when I swap it back to the gti 6 one.

 

I personaly would just go for the gti 6 head straight away and yes you can use the cam mounted vacuum pump for your servo, thats what its used for on the 306.

[decoc182 0]

Thanks for the info mate. GTI6 head it is. I like the idea of the vaccum pump, its saves having to fiddle with barb take offs on the inlet manifold. Its just strange why the used a vaccum pump. Any one know why?

 

I take it a GTI6 head/cams on the 1.8 bottom end should yield good results with adequate fuelling and ignition. How did yours drive with bike carbs dude?? I have an inlet manifold being made up for me as we speak and Im keeping an eye on some R1s on ebay. What jet sizes etc did you select on your eurotrip 1.8 engine??

[pip470 61]

Ive no idea why they chose to use a vacuum pump on this engine. The head and cams should give more horses, for the least amount of work. Theres a lot of people who want to see what the actual gain is by doing this swap.

 

I never used the 1.8 engine in the end for the trip, this seems like a good time to warn you not to spin the crank with the head off the engine unless the liners are clamped down, so have the bottom end pinned before you take the head off and keep it like that until the head is bolted back on. The reason the 1.8 didnt go across europe, was the liner seals leaked. So i fitted a gti 6 instead, but after the trip the engine was breathing quite heavily so I stripped it, the bores were glazed so, had it rehoned, new rings and then put the 1.8 head I had that was already rebuilt from the broken engine and thought I would try it out. But ill be changing back over christmas. As for jet sizes, I have no idea. I let the rolling road guy sort that out as its a hell of a lot quicker, more accurate than I could do it and alot less hassle, plus i dont have very small dril bits.

[welshpug 1,661]

If you do have the head off, I'd be tempted to fit new liner seals as a matter of course having heard of so many failures of late, especially if its a cheap engine.

 

I'm not sure how much space there is at TDC on this engine, but there's a few threads detaining the finer details of the engine which would give you an idea.

 

do make sure that your inlet has a decent length, it'll need to be curved to fit too

[decoc182 0]

The engine itslef has done 60k, but as Im taking the head off it mite be worth a check at replacing the liner seals. Dumb question, what it is the process to replacing the seals? Is it a similar process to the 1.6 and 1.9 gti engines? In which case Ill have a search

[DrSarty 90 1 Cars]

what it is the process to replacing the seals? Is it a similar process to the 1.6 and 1.9 gti engines? In which case I'll have a search

 

Saved you the effort.

 

I can't see why fundamentally the process isn't identical.

 

Try this thread: Link 1

 

And this (excellent) thread, where you should read through a few pages to find the liner bit. It's clearly detailed, and there's even a link to this thread in the above one: Link 2

 

I asked about this head compatibility thing recently when my GTI6 broke a valve head off ( ), and the answer seemed to be don't bother with the XU7JP4 head; just use the GTI6 one.

 

Good luck. Fit a new timing belt with new tensioners at all costs, and consider a chat with C G Cars in Leicester ('mechanical repairs' on here) as he proved very helpful to me, has many spares and even a custom, lightweight solid pulley (without the rubber bush) which should be suitable for your bottom end.

[danpug 1]

Have you considered a 2.0 xsi head? The gti6 head is way overkill on the 1.8.

[decoc182 0]

Have you considered a 2.0 xsi head? The gti6 head is way overkill on the 1.8.

 

 

What do you mean by overkill ?? Are the ports to large for suitable flow?

[24seven 104]

I read somewhere that they're a little too large for the GTi-6 in standard form. The XSi head is supposed to offer very similar flow to the Mi16 head, though in standard guise is held back by the camshafts.