Topic: Re: 650 overbore/550 engine hybrid underway...final stages

[bill440cars]

       Hey Paul,

               I am so embarrassed, I've been trying to keep up with your project and just realized that you posted yesterday. I can't believe that I didn't see it. Oh well, at least I'm not too far behind. Sure will be interested to hear how she turns out myself. No way do I have to funds to get that deep into a build, so I'm enjoying what you're doing to yours. Keep up the good work there.

                                    Later on, Bill    

[paulages]

so far, it hasn't really been that expensive actually. all of the bearings and chains, etc. will  add up pretty quick though. wish i could afford new conrods... 

[paulages]

this weekend i started mockup, only to find that the piston shoulder is indeed to high to clear the head, by about .020". we're going to turn off about .050 in order to allow plenty of room for rod stretch and exhaust valve clearance. if it's clear enough to allow the engine to spin, i'll then have to clay and cc the combustion chamber to check the valve and head clearances, and check the CR. i'm hoping the CR will be an acceptable value for street gas, but i won't be surprised if we have to go at the pistons again to get it there.

i promise pictures soon. unfortunately, i forgot to take pictures of the too-tall pistons assembled before disassembling and handing them over to dan today.

[paulages]

still waiting on dan to machine my pistons. in the meantime, here are some pictures:

550 top case, bored to fit the 750 liners and with cam slot moved rearward to accept the 650 cam tensioner:

(here is a stock 550)


650 cylinders with 750 liners:

note the overlap of the cylinder sleeve flanges with each other and with the stud holes and oil passages. the flanges were flattened at their overlap, and the other holes were spotfaced. we were able to retain the potential usage of the stock oil lines, but i've decided i'd rather run them externally and reduce the chance of leaking at the head and oil temperature problems from running so close to the combustion chambers:

[paulages]

finally some pictures of the work Mike Reick did on my head:


exhaust port:

intake port:


heavy duty kibblewhite valve springs were installed and the exhaust valve seats were resurfaced on a surdi machine. can't wait to run it!

[Ingrid]

NICE!!
Job well done.
Grtz.
Ingrid

[andy750]

You are going to love it!! My Mike Reick engine is pulling strong and Im enjoying the new found power 

Keep us updated when you get this thing running!!
good luck,
Andy

[paulages]

got my pistons back from dan today. hope to check valve clearances and find my displacement and CR this weekend...

[MRieck]

got my pistons back from dan today. hope to check valve clearances and find my displacement and CR this weekend...

Nice. I'm very interested in your project Paul. I'm anxious...though not as much as you...to see the results. Someone asked about that 650 head and port design. It blows the 750 port away. You could get at least 5 more HP using that port on the 750. And that depends on the mods but 5 is a very safe bet.

[bwaller]

Yea your parts look good Paul. I had a look at a 650 head just after I finished the work on my 500/550. Two different beasts to be sure. Just for your info, I cc'd the chambers on this one and they are exactly 13cc!

[Pinhead]

Yea your parts look good Paul. I had a look at a 650 head just after I finished the work on my 500/550. Two different beasts to be sure. Just for your info, I cc'd the chambers on this one and they are exactly 13cc!

That's a good number to know! Thanks!!

[paulages]

Yea your parts look good Paul. I had a look at a 650 head just after I finished the work on my 500/550. Two different beasts to be sure. Just for your info, I cc'd the chambers on this one and they are exactly 13cc!

that is good to know, but there's no telling what space these piston crowns take up at TDC until i measure the cylinder fitted up. i'm gonna try and do it today, but i've got a gig tonight and am going for a ride this afternoon.

i was expecting a really large squish ring due to the extreme overbore of the cylinders and pistons much larger in diameter than were in there, but after the pistons were cut it doesn't seem so. shouldn't matter too much though with the hemi head.

more pics soon...

[paulages]

i have to check and recheck and re-recheck my measurements to be sure, but tonight i have some numbers.

i greased the edges of the top ring and filled the combustion chamber with dyed isopropyl alcohol at BDC and TDC.

volume at BDC=185cc
volume at TDC=17cc

..which would yield a compression ratio of 10.88/1.  gotta get that down just a bit i guess.

anyone want to tell me what that makes my displacement? 

[cafe75-550]

Hmmm lets see...185, x4, thats...

740 cc!!!!!!!!

Holy Crap! Is that with the TRW 64 mm pistons?

[mlinder]

i have to check and recheck and re-recheck my measurements to be sure, but tonight i have some numbers.

i greased the edges of the top ring and filled the combustion chamber with dyed isopropyl alcohol at BDC and TDC.

volume at BDC=185cc
volume at TDC=17cc

..which would yield a compression ratio of 10.88/1.  gotta get that down just a bit i guess.

anyone want to tell me what that makes my displacement? 

..................740?

Is that with regular 750 pistons? I'm not sure that makes sense. Same bore as a 750, but less stroke (or should be), but is larger than a stock 750?

[paulages]

mark,
they are 3mm over (64mm). when doing bore x stroke, the number comes up as 718cc, which is what i've been assuming my displacement would be. i assumed that maybe some of the alcohol had seeped  past the grease and top ring, but there was none in the cases. then i thought i had just miscounted when adding the 10cc's at a time with a plastic syringe. but when the CR came up so ballpark correct, it seems like it might be right. there are probably a few cc's that will be lost in spark plug displacement (it's hard to see when the liquid has exactly reached the base of the plug hole).

the 650 pistons are 1mm taller, from pin center to crown than the new ones. 5mm per cylinder is not that hard to come by, especially if the piston geometry is fairly different. if the face of the piston is in the ballpark of 25mm, and is 1mm shorter, that would yield about 5cc's of volume, not to mention potential differences in the valve pockets.

i still haven't checked my valve clearances, so it's possible this demonstration of how a subtle difference in combustion chamber geometry may show itself again if the pistons need even more material removed.

and remember, i did say that i need to recheck it tomorrow.. 

[cafe75-550]

Paul's engine also has a 650 crank (55.8 mm stroke vs. 50.6 with the 550) with the 3mm over pistons. With 13cc chambers on the 650 head, just straight math 64mm bore with a 55.8 mm stroke gives 718cc, which could give up to 770 cc if the pistons were flat. They're not, so 740 actually seems reasonable, thats about 7.5 cc of piston crown into each chamber, and the CR does make sense...Plus those numbers don't account for machining tolerances...

I'd check about 3 times myself, but on paper it seems to make sense. Now just get some of Cycle Exchange's 65.5mm pistons for those 750 liners....

On another note, Honda's 736cc figure for the 750 does not include the chamber volume...

[bwaller]

cafe75-550, I mentioned combustion chamber volume of 13cc, but that is on the 550 head.

[cafe75-550]

cafe75-550, I mentioned combustion chamber volume of 13cc, but that is on the 550 head.

Whoops! Guess I read that one a little fast. 

The 650's chambers look to be quite a bit larger than the 550's, although that doesn't change the 740cc figure, just the numbers I ran to see if that was reasonable. So that means that the 650 piston crowns have no relation to the 7.5 cc figure I came up with, and the 770 total number is also bogus. All of which makes sense seeing as how the TDC volume Paul gave was 17cc (I guess it was a little late when I looked at those numbers).

[pae]

cafe75-550, I mentioned combustion chamber volume of 13cc, but that is on the 550 head.

Whoops! Guess I read that one a little fast. 

The 650's chambers look to be quite a bit larger than the 550's, although that doesn't change the 740cc figure, just the numbers I ran to see if that was reasonable. So that means that the 650 piston crowns have no relation to the 7.5 cc figure I came up with, and the 770 total number is also bogus. All of which makes sense seeing as how the TDC volume Paul gave was 17cc (I guess it was a little late when I looked at those numbers).

I calculated that chamber volume should be 17.4cc to get the 9:1 CR (UK model, don't know if all are the same). A 'roughly accurate' measurement of the chambers showed the actual volume to be about 25-26cc, plus about 3.5cc for the head gasket, giving ~30cc above the deck. To get that back to the 17.4cc suggests that the piston crown takes up about 12cc above the deck.

regards, Phil

[paulages]

just before i rushed to the scene of billy's crash (only a few blocks away from our shop), i landed upon my final CR numbers. i measured and remeasured, and was coming up with enough variance to throw the CR off by .2- .5. then i realized what i was doing... when lifting the engine from my stand down to the crate (which was using to tilt it so that the spark plug hole was facing straight up) i was grabbing the crank end without thinking about it. i think a few times i rotated it just enough to move the piston a few degrees. 

that said, it is still difficult to measure with absolute precision, as 1cc is a very very small volume, but is enough of a variable with each addition of fluid to add up to a big difference at the end.

anyway the mean reading results were:
BDC    198cc
TDC    18.8cc
COMPRESSION RATIO= 10.53/1

if i clay the cylinders and the valve clearances are sufficient, i think i'll leave the pistons as they are. that CR might be on the high end for street gas, but from the advice of others on here running similar CR's, it should be fine.

[Pinhead]

Have you considered trying to imitate PowreLynz to aid in detonation tolerance?

[paulages]

Have you considered trying to imitate PowreLynz to aid in detonation tolerance?

no, i can't say i have.

[paulages]

finally got around to claying up one of my cylinders tonight to check my piston/ head and piston/ valve clearances. can't remember what tolerances my machinist told me i need, but the valves seem to have plenty of room:

exhaust valve to piston:  .098
intake valve to piston:    .116

if i remember right, he told me i want at least .050 at the valves, and at least .020 at the head.  it was difficult to measure exactly, but there seemed to be .020-.027 just at the piston shoulder.

if the head clearance is tolerable, then i have little left to do...well, little experimental anyway.  still have to lighten and balance the crank and stator, add the oil feed to the cam and primary chains, tap for external oil lines, etc..

[bwaller]

Sounds good Paul, it's great to have all that measuring behind you. Remember to be safe, just double check clearances when you time the cam and have the degree wheel in place. At 10 degrees or so before & after TDC gingerly push the valve down until it just contacts the piston and get the true reading from the dial indicator.

I'm sure you're all set to do this anyway, but the rest of us feel a part of this process too! Ha