mark kibort

has anyone done this????

Ive actually run the 82 euro cam (milder cam than the 85) with the 84 US 4.7.

i made the valve reliefs on my 5.0 4 valve pistons to fit the big euro valves when i installed those heads.

my main concern is are the cut outs large enough? are the pockets deep enough. the cams we are using could actually be euro or higer perf. than the euro. (we do see titanium retainers and purple springs, so its not stock, but the valves are stock euro 40-45mm)

i think the 10 :1 vs 9.3 compression will not be an issue as the US heads have a larger combustion chamber. does this mean that the valves sit deeper in the heads on a euro?? it also means ,if it does work, that the US 4.7 may be pretty close to the euro 4.7 with the US pistons. i forget the cc's of the euro vs US, but i think it was 48cc vs 52cc euro 84 pistons were 2cc for valve cuts, while euro 82 were around 8ccs. If so, looks like 6cc = .5 :1 compression ratio.
may have to pull out the dremmel if we use a 4.7 US block!

Mk

mark kibort

com'mon guys! anyone know or know someone that has done this?

Mk

John Veninger

Mark,
Looks like it's clay time!

mark kibort

I hate when they say that. now, if i can just find my lift numbers to see if we are in trouble there too!

MK

Herr-Kuhn

The lifts should be 12mm intake and 11mm exhaust. I have some specs from people who have mapped these cams...let me know if you want them. I'm going to put a set of Euro 82 cams in the Callaway this summer. 80-82 US cams are the worst. I know you can't drop the big valve euro heads on withiut cutting pistons for the bigger valves...for me the biggest bang will be in camshaft profiles..I don't think the bigger valves will yield much for me, but it could be substantial on a NA car.

mark kibort

thats the answer i was looking for. so, you are saying that the US pistons and big valve euro heads wont fit? If so, i guess ill need to get the dremel out and take out the 1 mm difference on the outside edge that the bigger valves theoreticaly will need. (ie 45mm vs 43mm on diameter so, 1mm on radius)

However, if you have seen a US piston, there is a dish cut out in the middle and little flared cuts for the remainder of the cuts. cant believe that porsche would cut it that close, but certainly is a possibilty. im most concerned with the lift, but that shouldnt be a problem as ive used 82 euro cams on a US 84 motor without issue.

the interesting thing will be the compression differences. as you know the 84 is 9.3 and the euro is 10:1. However this is not only done by the head chambers, its the pistons too. since we are using the euro heads with 6ccs less chamber volume, we should see close to euro compression. (plus any differences in the piston which should be close due to the BIG cuts in the euro 82 pistons)

mk

mk

Rob Roy

Mark,

Not meaning to hijack, but I am also going to be fitting the big valve euro heads onto a 5.0L 85/86 block. Any tips or process recommendations for cutting those reliefs?

Thanks

Stan.Shaw@Excell.Net

Hi Ken,

I have extra pistons already with valve reliefs cut for such a motor. I probably don't have a complete set, but even if you want to borrow or buy one to use as a template, we could work something out.

Rob Roy

Thanks Stan - I'll be in touch over the next week

mark kibort

sure no problem. (thats what this list is for!!)

anyway, yes, the way i did it, was to use a euro 84-85 piston as a template. this is the piston with the shallow valve reliefs. (there is no way you can cut the 82 euro valve cuts into the US 85 4 valve pistons! just not enough meat, nor would you want to)
take the euro 82 piston and the 85 pistons to a machine shop and have them match the cuts. if you need a template, i could trace my 82 pistons (scots for you) you just put this over the 85 pistons and cut. after cutting, assemble with head gasket but dont torque down. move each one of the vaves down to make sure there is no contact at .5" lift equivant. I had some contact, .5mm over the edge of a couple of cuts. I took a air grinder and dug out every valve cut by 1mm or so, by hand. just sealed off each piston hole and the rest of the motor with that blue tape and some plastic wrap.

you end up with 10:1 compression or so with the new valve cuts.

have fun, its worth the effort!

MK

Stan.Shaw@Excell.Net

I think David Lloyd calculated much higher than 10:1 compression, at least 11:1. JV, DL and I all have the same piston valve reliefs with early Euro S heads (80-83) and '86/'86 shortblocks. We all run a mix of race gas with pump gas to get an octance of at least 100, and run timing in advance of 30+ degrees. JV will likely correct me if I am wrong (and that is good!)

mark kibort

Dont think so Stan. but, correct me if im wrong.
48cc for combustion chamber
2cc for '85 valve reliefs (8cc for 82 piston valve reliefs that could never be used with the 85 US pistons due to lack of "meat".)
7cc for '85 piston dish area
6cc for head gasket

take the total displacement of one cylinder, add the volume of the head and pistons with gasket, divide the entire deal by the volume of the head,piston gasket, etc. (ill check my numbers, as im going off memory, but i think they are close)

how could it be possible, when a piston that is totally flat, except for the valve reliefs is 10.5:1, and the replacement piston (ie 5 liter) has a big 7cc valley in it?

Just checking the math, but i think it calcualted to 9.9:1 sure ran like it, had 155 psi compression and i ran only pump gas 92 octane and never race gas, (well, a couple of times in speedGT, but it was a 50/50mix)
timing was 42degrees max, and 10 degrees at idle.

mk

mark kibort

Just found my compression notes:

48cc euro combustion chamber
7cc gasket
2cc valve cuts *euro 85 style*
6cc dish of 85 piston (US 4 valve converted)
total 63cc

Total displacement of 5 liter cylinder is 619cc. compression ratio equals 619/63 or 619+63/63??? (either 9.8:1 or 10.8:1 )

(total displacement of 4.7 liter cylinder is 583cc)

i have a hard time believing the later 10.8:1 ratio, as the euro '82 piston is 8cc total for its deep valve cuts and that works out to be the same volume of the '85 US piston with shallow 2 and 4 valve cuts and its valley. ( ie 2cc + 6cc = 8cc)
That euro engine with 8cc cuts is rated at 10:1 but 4.7liter , which does work out to 10.25 :1 using stan's and JV's math. hmmmm. if its a euro 85 2 valve cut , this calculates to 11.23 :1 so that doesnt work. using my math, the euro 85 4.7 becomes 10.23 (i.e. 583cc /57cc)



so, ???

how do you calculate compression ? stroke volume plus combustion chamber divided by combustion chamber? or stroke volume divided by combustion chamber volume?

the interesting thing here, is with a US 4.7 piston, the compression should be somewhere between the euro 85 and the euro 82. (ie between 10.5 and 10.1) up a full point from the stock US 4.7 9.3:1 numbers. (due to 54cc combustion chamber) Just found some more notes on US 4.7 pistons. actually 11cc as is.
(3cc more than euro '82 plus the 6cc more in the combustion chamber for a total of 9cc more or 72cc !! vs '82 euro of 63cc)

watcha think?

mk