Hello everyone! I need some help. I have a mk1 GTI 1.6 and the injection is dead so I decided to get a crossflow head, keeping the 8v and some bike carbs for it. I have a deal with an AFT head from a MK3 1.6 GT 101bhp. I have not yet made the deal so the head is still on the original engine but from what I could search I may have some compatibility issues. the EG original head (heron I think) is flat with the pistons making the slope for the combustion chamber (I think I'm not wrong) and the AFT is the opposite, flat pistons and sloped head... So, is this head compatible? will I loose too much compression? Does the head have enough material to remove and be flattened? If its not compatible what head can I get? Best Regards, Joo Ruivo
My first concern would be head to block machine alignments. I suspect the two headgaskets would have hole patterns that aren't compatible. I am on about waterway , oilway, as well as the more obvious cylinder and holding down bolt pattern Jon I have stripped an X flow recently and have a 1588 heron block on the bench now ready to be built
Well the guy has agreed to take the head apart to check the alignment. If some work is required I'm a welder myself, so filling holes will be no problem. My main concern is the possibility of dropping too much the compression ratio...
Pistons come in many shapes/sizes and configs. three main dimensions are gudgeon pin diameter, compression height and bore size, Less important is comb bowl shape. Ford BDA pistons fit if you rebush the small ends, for eg... If you can get the head gasket alignment right, you will find a piston set. I have been there before on building mongrel engines. You next task will be getting the cambelt drive end to match. Good luck, and let us know how you get on. We need 'experimenters' to push forward understanding.. IMHO Jon
Hi all!! Things are moving! From the gasket the heads are the same (except one oil drain witch I have to weld. Now will I use the gasket made for the original block or the one from the AFT head? I still have the combustion chamber issue, it will get way bigger since the head have the slope for the combustion chamber... Can I machine the head so it can be lowered? Still have to measure the height of the bolts place but I think a parts one or two little differences the heads are the same The link to some photos I've taken. https://drive.google.com/open?id=0B72UpZZJcA1FU2ZzOGtSZHJVRFE
Putting a normal head on a heron bottom end will give very low compression ratio. It IS possible to machine the pistons to remove the dish and then deck the block to suit. I've decked an EG block 12mm in the past! although you will only need about 5mm if memory serves me correctly, but you will have to make sure you make all the correct calculations yourself, or get someone to do it for you.. You will also need to shorten the head bolts if you deck the block.. Alternatively replace the pistons with ones from a non heron 1.6 engine (FR etc..)
I have another problem now haha! The heron head has a water nozzle for the radiator and the AFT head does not -.- Is there any solution?
I do not know anyone that can make those calculations... If I take 5mm from the block, I will have to take 5mm from the Pistons too? Sorry for the too many questions, I am a noob on this but I just love it
If only it was THAT easy You need: target compression ratio i.e 9.3:1 combustion chamber volume (30cc I think, you need to check) bore diameter (79.5mm) stroke (80mm) compression height (35mm?) deck height (in relation to crank centreline) (220mm) head gasket thickness (1.6mm?) A stock EG piston has a compression height of ~40mm, if you machine it down 5mm to remove the bowl and give it a flat top, its compression height will be 35mm. With a stock 220mm block your compression ratio would be ~8.5:1 Deck the block to 212.6 and your compression ratio would jump to ~ 9.3:1 These figures are purely representive, but you get the drift..
When I ran a heavily decked EG rallycross motor the cambelt ended up too long, so I cut the tin cover off the idler bearing and tuned up a larger diameter 2 piece pulley that bolted around the OE bearing, so the adjustment worked the same and the larger diameter tightened the belt. It worked fine Jon
Well this is getting on a stand still... The AFT engine pistons are 81mm in diameter (heron is 79,5mm) and for now I can't seem to find a possible match for flat head pistons in 79.5mm diameter. Michey marrows suggested lowering the pistons and the block but in portugal it's extremely difficult to change anything on a car and if I loose the original engine the whole car may be lost bcause of the original engine number... The possiblity I am cheking is the clearance for boring to 81mm and if the AFT pistons will fit fine on the heron (height). Is there any 81mm pistons fit for the heron head? Just in case I bore for the AFT crossflow head and then want to put the original head on it Cheers!
I have a set of new cosworth forged pistons spare. At 79.5mm, high compression obviously. pm me if interested. Also, just measured my heron rods and they are 22mm big end. This jogged my memory a bit as I have some spare G60 rods that are a 1:1 fit Jon
All other 1588cc engines have 'flat top' pistons. Its ONLY the GTI 1588cc engine that has the heron head. Although you will need the matching rods due to 20mm gudgeon pin. Not really feasible, nearly every dimension is wrong on an AFT in relation to fitting into an EG block. Yes. G60 pistons can trace thier origins back to the heron headed GTI. I've fitted G60 pistons to an EG in the past, but again the block needs to be decked to bring compression back up. Its a shame you're in Portugal as I have an 1588cc engine sitting in my garden waiting for me to take it to the scrap yard.
Good point, I haven't measured the BE diameter. I know the early 1588 crank come in large and small 'nose' something else to bear in mind, as the crank drive pulley is different. Will measure and advise, if anybody needs this Jon
