Hi all,
I'm in the process of re-building a Kent 1600, it's been bored to .060, steel rocker gear, GT valves, Kent 234 camshaft, flywheel lighted, balanced etc and I will get R6 fuel injection working on it, Thanks to a few tips on this forum. Photos will go up when I get it running.

Due to an oversight on my machinist, I have ended up with Low comp 1300 or 1600 pistons instead of the 1300 high compression pistons that I wanted, I only found this out after getting the pistons cut to clear the 234 cam and picked it up during a CC check prior to decking the block.

I've only got .9mm clearance deck to top of pistons, good valve clearance 4mm plus on exhaust, 6mm on inlet, I have to do some maths but I'm hoping I might get by without skimming the pistons and lower the deck height to level and place the minimum thickness 82.5mm exhaust gasket to allow piston clearance, I'd love any input.

Would anyone know what the minimum compression ration I should chase to get good power out of the 234 cam (stage 2 type build)?

Does anyone know the minimum safe piston to head clearance (revving occasionally to 7K)?

Cheers,
Rick

So, are your pistons currently below the deck?
I've run several engines with the pistons above the deck and into the head gasket area to achieve the desired CR. You should be safe with 1mm between pistons and head if all is well with the bottom end. Make sure you know the compressed thickness of the HG you're using.
As for CR, with a 280deg cam I'd personally be looking for 10.5-11:1.

The big problem with xflo's is if you run the piston 'above ground' (protruding from the block) you will have to machine more clearance for the valve heads and this is generally about the same in volumes. The best way to raise CR on a 1600 is to use 1300 pistons as the chamber is smaller. The CR will depend of the cam you are using, for something around 280 duration 10.5 is probably going to get the job done with modern fuels.

If your machinist supplied and modified the wrong Pistons I would argue the case with him , especially if you told him you wanted high compression Pistons. Sounds like he perhaps isn't too familiar with X flows?

Hi Nick,
My pistons are below deck by .9mm, it looks like I can achieve 10.4 CR by decking off .9mm and using a 1mm head gasket.

Thanks for your reply, it make me feel better about running down this route.

Hi Chillis,

You are correct but I'll work with what I've got.

Hi Rusty Nuts,

I asked my machinist for 1300 pistons and they came labeled as 1300/1600 pistons, I wrongly assumed that they were high
compression, I will cop this one as my fault.

Thanks for everybody's input.

Would anyone know where to get a 82.5mm 1mm head gasket from? I'm awaiting on a reply from Redline in South Africa, Burtons seem to have most sizes but are a bit light on the 82.5mm range.

Cheers,
Rick

quote:

---

Originally posted by Rickta
Hi Nick,
My pistons are below deck by .9mm, it looks like I can achieve 10.4 CR by decking off .9mm and using a 1mm head gasket.

Thanks for your reply, it make me feel better about running down this route.

Hi Chillis,

You are correct but I'll work with what I've got.

Hi Rusty Nuts,

I asked my machinist for 1300 pistons and they came labeled as 1300/1600 pistons, I wrongly assumed that they were high
compression, I will cop this one as my fault.

Thanks for everybody's input.

Would anyone know where to get a 82.5mm 1mm head gasket from? I'm awaiting on a reply from Redline in South Africa, Burtons seem to have most sizes but are a bit light on the 82.5mm range.

Cheers,
Rick

---

Hi Nick,

Burton have a good selection of 83mm head gaskets but I thought I might run into problems with turbulence or erosion with a 0.5mm difference from my 82.5mm bore.

Am I being too fussy? it would be easy if I could get away with an 83mm gasket.

Cheers,
Rick

quote:

---

Originally posted by Rickta
Hi Nick,

Burton have a good selection of 83mm head gaskets but I thought I might run into problems with turbulence or erosion with a 0.5mm difference from my 82.5mm bore.

Am I being too fussy? it would be easy if I could get away with an 83mm gasket.

Cheers,
Rick

---

Most OEM gadgets are built to accommodate all over sizes
I’ve run 94.5 on a 93mm Pinto with no issues

Mines been bored 0.060" oversize with 1600 cc Pistons and I've used a standard Payen head gasket for the last 10 years with no problem . It has a Kent BCF2 cam with a Vulcan head running without any extra machining to the Pistons although I did check valve to piston clearances very carefully checked. Revs to 7,000 rpm on occasion . One thing you may need are big bore exhaust manifold gaskets depending on head and exhaust mods.

Nick, Rusty Nuts and Snapper,

Thanks for your info, my block is at the machinist getting decked 0.6mm, a quick recheck of the CC and piston clearance and I'll order a head gasket to suit.


Cheers,
Rick

I'm at a similar stage of a 1600 xflow rebuild and i'd be very interested to learn how to accurately measure the piston to valve clearance and what is considered a safe clearance.

My spec is:

1600 Xflow
GT head
Kent BCF2 cam
1600 +0.060" oversize pistons

Cheers

Hi Gary,
I removed my head, placed plasticine in the cutouts, fitted the head with an old gasket, fitted the rocker gear with push rods only in #1 exhaust and intake, with correct valve clearance set I turned it over twice, removed the head and used a vernier caliper to measure the thickness of the plasticine.

1.5mm is the minimum valve to piston clearance quoted for a Kent 234 camshaft.

Cheers,
Rick

I checked mine on all cylinders using much the same method but make sure the cam is timed correctly before hand . I have seen a X flow with the timing cover machined and a cover fitted to allow easy access to the vernier cam sprocket . If going this route it allows the cam timing to be "swung" when on a rolling road to optimise settings but check the valve lift at the full range of the vernier adjustment.