I week no updates?
Breathing new life into the 318 in the Scamp!
- Thread starter DaveBonds
- Start date
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DaveBonds
Garage Trash
;)
Yeah, man. It's been a rodeo over here, trying to build this engine with the parts that I want, but here is the prognosis...
So, after seeing the cam and debating everything, I took a closer look at the lower end of the engine.
It looks like the bottom end has had quite a ride during it's 40 years, but I elected to clean everything up. After seeing the self induced valve notches, I think I caught this engine just in time before really screwing something up.
Word to the wise, pull the intake and heads in the car and remove the short block, if you are willing to torque heads on the car.
I managed to gain at least 4" of clearance between the boom and the lowest point of the hood at the safety latch and I could have come up even further, but I had at least 2" between the pan and the radiator support.
Taking the heads and intake off gave me tons of access to the trans bellhousing bolts to get them off with a wrench. I did all of the lower end work, then I set the car back down on the tires to do the bell bolts, skipped the balancer and put the boom down as far as I could to a chain, crossed up on 2 head bolts. Swung the engine hoist to the side instead of going out on to the rock drive. The chain angle helped a lot, as well as the lack of weight and clearance issues with heads.
If I were blueprinting this thing for deshrouding the block or what have you, I'd still elect to pull everything and drop the heads and intake on after the fact. I'll never install a complete engine again on a rear hinge hood car, after doing it this way. Far less weight to swing around, more control, more access, no hood adjustments, no touch up on hinge bolts... no brainer. I spent less time doing this by myself than removing a complete engine on a balancer with someone helping to watch the firewall.
After mowing through about 300 auctions on ebay and on several websites, I found a set of 80's vintage NOS Dynagear .030" slugs that were not low compression units, for a pre-1985 318 that didn't have the lazy 4 valve relief cuts in them for $100 with pins.
Keith Black has some cast units for about $260 and forged for about $550.
I slowed my operation down a bit, hunting for pistons, but I didn't want to murder all of the work I was doing, even with a 2 valve relief piston when I don't need it.
After researching, I could have gotten a late model 318 piston with the same true flat top for about the same price, but the weight is off and I'd need a late model crank or a balance. Pretty stoked on the slugs.
For anyone local or within any interest, Don Hackenberg is the man of the hour. Installed my cam bearings, my freeze plugs, my timing cover seal, hot tanked everything on the engine, hit it .030" ball honed it and removed/ installed my pistons on the con rods, stamp numbered them and the caps and charged me $305 out the door.
If you want good work done by a one man shop on the side of his house, he's built two of my close friends' race engines (9 second NA 340 '69 Swinger and a 9.6 second aluminum 440 '69 Coronet) and is blinding fast on turnover. I called him on my way home to ask him if he could number the con rods and he had already done that, removed the rods and tanked everything before I was at my front door.
Oiled one up and checked the new piston in the cylinder, yesterday as I got everything in the mail when I came home from work, before I took the new slugs down to him for pressing. Everything mic's and feels nice, good clearance for rings.
As I measure deck, index the bell for the trans swap later (so I don't have to wait on parts) and put this engine together, I'll have more updates. It's BBQ time now though for my B-Day.
Catch you all soon! (maybe tomorrow evening)
Yeah, man. It's been a rodeo over here, trying to build this engine with the parts that I want, but here is the prognosis...
So, after seeing the cam and debating everything, I took a closer look at the lower end of the engine.
It looks like the bottom end has had quite a ride during it's 40 years, but I elected to clean everything up. After seeing the self induced valve notches, I think I caught this engine just in time before really screwing something up.
Word to the wise, pull the intake and heads in the car and remove the short block, if you are willing to torque heads on the car.
I managed to gain at least 4" of clearance between the boom and the lowest point of the hood at the safety latch and I could have come up even further, but I had at least 2" between the pan and the radiator support.
Taking the heads and intake off gave me tons of access to the trans bellhousing bolts to get them off with a wrench. I did all of the lower end work, then I set the car back down on the tires to do the bell bolts, skipped the balancer and put the boom down as far as I could to a chain, crossed up on 2 head bolts. Swung the engine hoist to the side instead of going out on to the rock drive. The chain angle helped a lot, as well as the lack of weight and clearance issues with heads.
If I were blueprinting this thing for deshrouding the block or what have you, I'd still elect to pull everything and drop the heads and intake on after the fact. I'll never install a complete engine again on a rear hinge hood car, after doing it this way. Far less weight to swing around, more control, more access, no hood adjustments, no touch up on hinge bolts... no brainer. I spent less time doing this by myself than removing a complete engine on a balancer with someone helping to watch the firewall.
After mowing through about 300 auctions on ebay and on several websites, I found a set of 80's vintage NOS Dynagear .030" slugs that were not low compression units, for a pre-1985 318 that didn't have the lazy 4 valve relief cuts in them for $100 with pins.
Keith Black has some cast units for about $260 and forged for about $550.
I slowed my operation down a bit, hunting for pistons, but I didn't want to murder all of the work I was doing, even with a 2 valve relief piston when I don't need it.
After researching, I could have gotten a late model 318 piston with the same true flat top for about the same price, but the weight is off and I'd need a late model crank or a balance. Pretty stoked on the slugs.
For anyone local or within any interest, Don Hackenberg is the man of the hour. Installed my cam bearings, my freeze plugs, my timing cover seal, hot tanked everything on the engine, hit it .030" ball honed it and removed/ installed my pistons on the con rods, stamp numbered them and the caps and charged me $305 out the door.
If you want good work done by a one man shop on the side of his house, he's built two of my close friends' race engines (9 second NA 340 '69 Swinger and a 9.6 second aluminum 440 '69 Coronet) and is blinding fast on turnover. I called him on my way home to ask him if he could number the con rods and he had already done that, removed the rods and tanked everything before I was at my front door.
Oiled one up and checked the new piston in the cylinder, yesterday as I got everything in the mail when I came home from work, before I took the new slugs down to him for pressing. Everything mic's and feels nice, good clearance for rings.
As I measure deck, index the bell for the trans swap later (so I don't have to wait on parts) and put this engine together, I'll have more updates. It's BBQ time now though for my B-Day.
Catch you all soon! (maybe tomorrow evening)
txstang84
Well-Known Member
Happy Birthday-make it a good one
I know this goes without saying, but if you're running true flat tops, even though those pistons will probably be in the hole about 0.040", and using stock size valves, you're running a .490" exhaust lift cam...please do clay up for P/V clearance and check retainer to guide clearance. I know it's not a big cam, but zero relief pistons don't make for very much wiggle room...especially on the exhaust side.
I'm pretty sure you commented on my cam selection thread earlier and I believe bomber even said anything north of .480" lift is getting close for requirement of guide work.
I know this goes without saying, but if you're running true flat tops, even though those pistons will probably be in the hole about 0.040", and using stock size valves, you're running a .490" exhaust lift cam...please do clay up for P/V clearance and check retainer to guide clearance. I know it's not a big cam, but zero relief pistons don't make for very much wiggle room...especially on the exhaust side.
I'm pretty sure you commented on my cam selection thread earlier and I believe bomber even said anything north of .480" lift is getting close for requirement of guide work.
DaveBonds
Garage Trash
I checked these heads out on a caliper with retainers and seals on and it toggled around .500" in seal clearance between intake and exhaust.
I haven't clay checked, but maybe I will. I don't think it will be an issue. 340 pistons are notched, but they are a closer deck piston.
I'm going to check install height on the pistons to be sure and do some math. I'm not using tight gaskets or anything.
I haven't clay checked, but maybe I will. I don't think it will be an issue. 340 pistons are notched, but they are a closer deck piston.
I'm going to check install height on the pistons to be sure and do some math. I'm not using tight gaskets or anything.
txstang84
Well-Known Member
I get ya, but .490" lift is solidly .080" more than ANY factory 318 cam...perhaps a smidge more. And many of those factory 318s still had some valve relief. Furthermore, you've already illustrated in post #52 that even a stock cam either with stuck valves or over-revving (floating) will kiss a stock piston with no reliefs...clearly a bad thing. P/V clearance isn't about just lift either...0.050" duration and overall cam timing plays a significant part in that measurement as well, and I'm guessing that 210/219 split pattern cam is at least 15-20* larger than the stock 318 cam.
You're correct in asserting 340 pistons are higher in the bore...high compression 340s were actually 0.040" out of the hole, but X and J heads have a quench relief pad in the combustion chamber for that purpose, and their valve reliefs are rather large to compensate for a factory cam of over .440" lift.
If I had to guess, unless you've shaved down/equalized the decks to true spec (9.58" if memory serves), those stock slugs should be anywhere from 0.030"-0.060" in the hole. I'm not trying to tell you how to build your engine-that's yours to do, but I'd hate to hear you put everything together and see a horror story about this thing eating itself.
You're correct in asserting 340 pistons are higher in the bore...high compression 340s were actually 0.040" out of the hole, but X and J heads have a quench relief pad in the combustion chamber for that purpose, and their valve reliefs are rather large to compensate for a factory cam of over .440" lift.
If I had to guess, unless you've shaved down/equalized the decks to true spec (9.58" if memory serves), those stock slugs should be anywhere from 0.030"-0.060" in the hole. I'm not trying to tell you how to build your engine-that's yours to do, but I'd hate to hear you put everything together and see a horror story about this thing eating itself.
DaveBonds
Garage Trash
Right.
The 340 cam was a .444 lift.
I'll probably check it with a micrometer at the valve spring retainer through 15-5 BTDC and again @ 5-15 ATDC to get a map of lift clearance acrossed the piston crank angle.
I don't think I'll need to clay check if I just use a set of check springs on #1.
The reason I think there was so much garbage in timing with the engine was because this engine ate up 2 timing chains over the course of 170K.
Someone had been inside it and replaced the factory unit with another single roller. I found plastic timing gear shrapnel in the pickup screen and an insane amount of slop in the chain I pulled from it. I was able to move the cam about 12 degrees back and fourth on the old chain. That's double in slop on crank angle! I could only imagine what the original set looked like at the point that it was replaced.
Hughes calls for a minimum of .060" clearance on intake valve to piston and .100" exhaust valve to piston. If I don't see those numbers at each degree of the crank where it's critical, when I check actual lift before assembly, I think I'll just notch them where I need to with a fixture.
Hopefully I won't have to. I know that I have the clearance on the guide end for everything, without factoring in pushrod angle loss in total lift, as well as factory rocker loss in lift ratio. I stuck to 1.5:1 numbers and made sure I had at least that on the top end.
I'll measure actual lift and report that number here, as well as clearance against each degree of crank angle with a light valve spring, so I can over extend the rocker at each degree on the crank until the valve touches, then write the difference down. If anything is less than spec, that should tell me.
The reason I don't think I'll have issues is that max lift on this cam is shorter in it's open span. The duration number is more than a 318, but less than 340, so the piston chasing the valves won't be nearly as abrasive as even a stock 340 spec cam.
I'll have to check and see what's in the 318 running a 340 cam in the '72 outside through a plug hole. I'd be curious, but I know people have run 340 spec duration on stock 318 engines without any issues.
It does depend on the piston, though.
The numbers will tell the truth on this one, once I get my gear back from the machinist, today.
The 340 cam was a .444 lift.
I'll probably check it with a micrometer at the valve spring retainer through 15-5 BTDC and again @ 5-15 ATDC to get a map of lift clearance acrossed the piston crank angle.
I don't think I'll need to clay check if I just use a set of check springs on #1.
The reason I think there was so much garbage in timing with the engine was because this engine ate up 2 timing chains over the course of 170K.
Someone had been inside it and replaced the factory unit with another single roller. I found plastic timing gear shrapnel in the pickup screen and an insane amount of slop in the chain I pulled from it. I was able to move the cam about 12 degrees back and fourth on the old chain. That's double in slop on crank angle! I could only imagine what the original set looked like at the point that it was replaced.
Hughes calls for a minimum of .060" clearance on intake valve to piston and .100" exhaust valve to piston. If I don't see those numbers at each degree of the crank where it's critical, when I check actual lift before assembly, I think I'll just notch them where I need to with a fixture.
Hopefully I won't have to. I know that I have the clearance on the guide end for everything, without factoring in pushrod angle loss in total lift, as well as factory rocker loss in lift ratio. I stuck to 1.5:1 numbers and made sure I had at least that on the top end.
I'll measure actual lift and report that number here, as well as clearance against each degree of crank angle with a light valve spring, so I can over extend the rocker at each degree on the crank until the valve touches, then write the difference down. If anything is less than spec, that should tell me.
The reason I don't think I'll have issues is that max lift on this cam is shorter in it's open span. The duration number is more than a 318, but less than 340, so the piston chasing the valves won't be nearly as abrasive as even a stock 340 spec cam.
I'll have to check and see what's in the 318 running a 340 cam in the '72 outside through a plug hole. I'd be curious, but I know people have run 340 spec duration on stock 318 engines without any issues.
It does depend on the piston, though.
The numbers will tell the truth on this one, once I get my gear back from the machinist, today.
MopaR&D
Nerd Member
FWIW I ran my Voodoo cam with .475" lift on the exhaust in my otherwise-stock 318 with no issues...
Yeah. I've run a .500 lift cam on a 71 360 which has the highest compression height of all the small blocks and never had a problem. It's not the lift. It's the duration. As long as the duration isn't super long, you won't have a problem.
DaveBonds
Garage Trash
Good to know on the stock bottom ends against lift! Thanks.
Duration is nowhere near even a stock 340 cam, so the intake valve won't chase the piston down too quickly and the piston won't chase the exhaust valve up too close, either.
I think since I've got a dial indicator, I'm going to double check actual zero against the old balancer by going .060" piston drop BTDC and again at ATDC and mark on a degree wheel, then center and remark zero with timing tape.
After that, I'm thinking I should check the head with a dial indicator and a super light spring on the retainer, on the cam dry with a blocked hydraulic lifter and watch what the rockers do when I over extend them off of cam lift, until the valve touches and record how many thousandths the valve moves before touching.
If I can do that and mark it at each degree on the crank, from 15 BTDC to 5 BTDC and again from 5 ATDC to 15 ATDC, I should get a good idea of what the valve to piston clearance is at the entire crank angle map where it's critical.
I'm waiting for my pistons and rods, currently.
If I have to cut these pistons, Hughes rents a fixture to do it on the engine, so I'll only be clearancing it in the places I need, if I need to. I'm convinced that the crappy timing chains bounced the valves at times under odd acceleration and deceleration conditions. I'll check the numbers, because I'm not going to do any guess work on this engine, but I doubt it will come to that.
Duration is nowhere near even a stock 340 cam, so the intake valve won't chase the piston down too quickly and the piston won't chase the exhaust valve up too close, either.
I think since I've got a dial indicator, I'm going to double check actual zero against the old balancer by going .060" piston drop BTDC and again at ATDC and mark on a degree wheel, then center and remark zero with timing tape.
After that, I'm thinking I should check the head with a dial indicator and a super light spring on the retainer, on the cam dry with a blocked hydraulic lifter and watch what the rockers do when I over extend them off of cam lift, until the valve touches and record how many thousandths the valve moves before touching.
If I can do that and mark it at each degree on the crank, from 15 BTDC to 5 BTDC and again from 5 ATDC to 15 ATDC, I should get a good idea of what the valve to piston clearance is at the entire crank angle map where it's critical.
I'm waiting for my pistons and rods, currently.
If I have to cut these pistons, Hughes rents a fixture to do it on the engine, so I'll only be clearancing it in the places I need, if I need to. I'm convinced that the crappy timing chains bounced the valves at times under odd acceleration and deceleration conditions. I'll check the numbers, because I'm not going to do any guess work on this engine, but I doubt it will come to that.
Nice find,on the pistons,Dave. As for the Hughes tool,Car Craft did a remain 360 buildup ,around y2k. They used it.Pics included.
DaveBonds
Garage Trash
I actually did read that article. I had a subscription at the time, I had just picked up a 360 and had it in mind for my Charger.
It will definitely work if I need it. I'm hoping the numbers tell me otherwise.
It will definitely work if I need it. I'm hoping the numbers tell me otherwise.
DaveBonds
Garage Trash
Called the machinist, piston/ rod assemblies are ready to go. Gonna swing up there and pick them up tomorrow, after work.
After working on the Stude Commander all day, I finished up some work on the tin for the engine, while I'm waiting to assemble the block.
I have a factory 340 windage tray that I bought a while ago with some new ARP adustable height studs, but I think I may let it go to someone who is building a stroker and needs the adjustability of the ARP fasteners.
I'm also toying around with some different valve covers and cool matching breathers. I've got them set up for paint, at the moment. I'll get pics in a little bit, once I shoot them.
I checked the fit on the baffle and it's nice and clean. If anyone wants the template, I can scan it and post a PDF with measurements.
After working on the Stude Commander all day, I finished up some work on the tin for the engine, while I'm waiting to assemble the block.
I have a factory 340 windage tray that I bought a while ago with some new ARP adustable height studs, but I think I may let it go to someone who is building a stroker and needs the adjustability of the ARP fasteners.
I'm also toying around with some different valve covers and cool matching breathers. I've got them set up for paint, at the moment. I'll get pics in a little bit, once I shoot them.
I checked the fit on the baffle and it's nice and clean. If anyone wants the template, I can scan it and post a PDF with measurements.
Nice work on the pan.
Pistons with love taps, 80K is about the max life on a plastic timing gear set, I bet the first one went while somebody's foot was in the floor board.
The old truck just hit 80K and it has to be due for a chain, I know it is loose....
Pistons with love taps, 80K is about the max life on a plastic timing gear set, I bet the first one went while somebody's foot was in the floor board.
The old truck just hit 80K and it has to be due for a chain, I know it is loose....
DaveBonds
Garage Trash
Oh yeah. The 2nd single roller replacement on this one was toast at 170k!
Valve cover paint is too wet to unmask tonight. I'm going to let the engine paint set up for a day and update tomorrow, when I get the lower assembly assembled and mic'd.
Valve cover paint is too wet to unmask tonight. I'm going to let the engine paint set up for a day and update tomorrow, when I get the lower assembly assembled and mic'd.
DaveBonds
Garage Trash
Got the pistons in.
They're coming right back out.
Box reads .075" deck clearance, seller tells me it's .75mm which is .030"
Set the dial indicator to check TDC, ran the depth end of a dial caliper against the indicator magnetic base to hold it square against the deck and get this; .154" in the hole with everything torqued.
I asked the seller if the pistons were in fact calling .075" deck clearance. Guy tells me .030" The listing shows .100" and .075" pics, so I ask.
At this point, I might throw the budget, buy Keith Black casts and throw these f--kers in a homemade potato cannon if he won't refund them.
I'm not interested in owning anything powered by 7.73:1
I wish people would stop selling things that they can't advertise properly.
They're coming right back out.
Box reads .075" deck clearance, seller tells me it's .75mm which is .030"
Set the dial indicator to check TDC, ran the depth end of a dial caliper against the indicator magnetic base to hold it square against the deck and get this; .154" in the hole with everything torqued.
I asked the seller if the pistons were in fact calling .075" deck clearance. Guy tells me .030" The listing shows .100" and .075" pics, so I ask.
At this point, I might throw the budget, buy Keith Black casts and throw these f--kers in a homemade potato cannon if he won't refund them.
I'm not interested in owning anything powered by 7.73:1
I wish people would stop selling things that they can't advertise properly.
txstang84
Well-Known Member
Wooooooow...over .150 in the hole? Holy schnikes...hell, grind the mains down on a 360 crank and drop it in there...might actually be useful then...
EDIT: just for grins I ran the numbers..if I did it correctly, a 360 crank would put the pistons about .019" in the hole...but then you'd waste money grinding a perfectly good crank, and would need all the 360 balance parts...not even talking balance the reciprocating assembly
EDIT: just for grins I ran the numbers..if I did it correctly, a 360 crank would put the pistons about .019" in the hole...but then you'd waste money grinding a perfectly good crank, and would need all the 360 balance parts...not even talking balance the reciprocating assembly
DaveBonds
Garage Trash
Hahaha... Plus, 360 cranks are induction hardened cast pieces. I've seen people cut through the hardened area and try to pass it off as finished/ polished when you can see a color change in the metal.
Oddly enough, as my optimism sets in here, I'm not going to throw them away if the guy will not take them back.
I ended up getting a set of 318 heads back from a machinist that were believed to be 360 heads and treated like they were with 1.6 valves in the exhaust. They have hardened seats and new guides with no port work done. I'm starting to accidentally accumulate the right parts for a boosted 318, which I may just end up doing to another car that I have ('72 Dart).
That may be a pipe dream, but I could give it quite a bit of PSI on a 7.75 squeeze.
I'm going to spec some 318 Keith Blacks and buy exactly what I want. I'm tired of this.
Oddly enough, as my optimism sets in here, I'm not going to throw them away if the guy will not take them back.
I ended up getting a set of 318 heads back from a machinist that were believed to be 360 heads and treated like they were with 1.6 valves in the exhaust. They have hardened seats and new guides with no port work done. I'm starting to accidentally accumulate the right parts for a boosted 318, which I may just end up doing to another car that I have ('72 Dart).
That may be a pipe dream, but I could give it quite a bit of PSI on a 7.75 squeeze.
I'm going to spec some 318 Keith Blacks and buy exactly what I want. I'm tired of this.
Dave,. Been quiet,love the thread. Time to ante up,or get creative.. Think outside the box....
DaveBonds
Garage Trash
Yeah, I'm thinking I either pitch the heads on the market and fire up another set of 302's that I have with big valves, file the rings and supercharge it, or...
get new pistons and keep these with the 360 valve open chamber heads or the other 302's with big valves later for doing that on the Dart.
Either way, I'm shopping for a set of $250+ pistons or 10x in boost parts to get what I want at this point. Either way, I've got to get them out so I can do something with the rings... file them for boost or put them on another set of slugs.
get new pistons and keep these with the 360 valve open chamber heads or the other 302's with big valves later for doing that on the Dart.
Either way, I'm shopping for a set of $250+ pistons or 10x in boost parts to get what I want at this point. Either way, I've got to get them out so I can do something with the rings... file them for boost or put them on another set of slugs.
I am at the same point,Dave. Chose overlap,over supercharged. I know spray,when needed.
DaveBonds
Garage Trash
2nd thought;
These are right about what I'd be looking for in comp height and leave me with .067" -
http://www.ebay.com/itm/DODGE-318-5...es&hash=item5649ddc058&vxp=mtr#ht_1653wt_1255
but I'm almost positive that they would need balanced.
That set would land 8.96:1, which I could live with and I would still have the piston to valve clearance that I needed.
So... Do I juggle $50-75 between the higher cost of a set of KB's or get magnum pistons and spend the coin on balancing? It almost seems like it would make the engine run better if I got the late pistons, lighten up reciprocating weight, lighten up rotating weight and make it run smoother, but I can see benefit for a better quench, I'd almost have to mess with cc to blend the heads with KB's on pump gas.
http://www.summitracing.com/parts/uem-kb167-030
Those would put it at 9.56:1... I don't know if going that high in comp ratio would be the right move? I could mod the head with some blending on the close/ heart shape side for flame and it would go slightly higher cc in head, but would it be more beneficial than the magnum piston + balancing?
IRL, the cc may be even higher in the head. I won't know until I get some plastic this week. if I blend it for flame propagation, it will go even higher, drop compression from 9.56 and help keep it from detonation.
I'm just wondering if a 9.5 ish CR is too much?
These are right about what I'd be looking for in comp height and leave me with .067" -
http://www.ebay.com/itm/DODGE-318-5...es&hash=item5649ddc058&vxp=mtr#ht_1653wt_1255
but I'm almost positive that they would need balanced.
That set would land 8.96:1, which I could live with and I would still have the piston to valve clearance that I needed.
So... Do I juggle $50-75 between the higher cost of a set of KB's or get magnum pistons and spend the coin on balancing? It almost seems like it would make the engine run better if I got the late pistons, lighten up reciprocating weight, lighten up rotating weight and make it run smoother, but I can see benefit for a better quench, I'd almost have to mess with cc to blend the heads with KB's on pump gas.
http://www.summitracing.com/parts/uem-kb167-030
Those would put it at 9.56:1... I don't know if going that high in comp ratio would be the right move? I could mod the head with some blending on the close/ heart shape side for flame and it would go slightly higher cc in head, but would it be more beneficial than the magnum piston + balancing?
IRL, the cc may be even higher in the head. I won't know until I get some plastic this week. if I blend it for flame propagation, it will go even higher, drop compression from 9.56 and help keep it from detonation.
I'm just wondering if a 9.5 ish CR is too much?
Should be doable,if your quench is on. A note on Magnum pistons: they probably require narrowing the width of the small end of the rod.
DaveBonds
Garage Trash
I'm beginning to think that the KB pistons with some blend work on the heart shape end is going to do what I want it to do.
I have a feeling that the cc is higher than 62cc anticipated, because the valves are tapered face rather than flat.
I think a piece of plexiglass, some grease and colored fluid is going to give me my answer. If the cc is somewhere near 64 and I can stay below 9.5:1, I can snake by with some nice blend work.
If I do blend, I'm gonna have to cc everything, but I'm beginning to think that keeping the quench up in the head, rather than down low is going to be better in the long run. I'm thinking 65cc finished is the magic number I'm looking for with these pistons and if I do some blending to open up cc, it will help deshroud.
@65cc, it puts everything at 9.23:1 on those KBs.
I have a feeling that the cc is higher than 62cc anticipated, because the valves are tapered face rather than flat.
I think a piece of plexiglass, some grease and colored fluid is going to give me my answer. If the cc is somewhere near 64 and I can stay below 9.5:1, I can snake by with some nice blend work.
If I do blend, I'm gonna have to cc everything, but I'm beginning to think that keeping the quench up in the head, rather than down low is going to be better in the long run. I'm thinking 65cc finished is the magic number I'm looking for with these pistons and if I do some blending to open up cc, it will help deshroud.
@65cc, it puts everything at 9.23:1 on those KBs.
MopaR&D
Nerd Member
What's important is the dynamic compression ratio which depends on intake valve closing and intake air pressure. My engine is 10.42:1 static compression and with the short-duration cam and our 5500 ft. elevation the dynamic works out to be 8.72:1 which is near the max for pump gas with closed-chamber heads and good quench. If you get the piston-to-head clearance below .055" at the very most (.035" is optimal but more risky if your rods and such aren't all exact) it will greatly increase combustion speed thus lower octane needed etc.
With your setup at 62cc and KB flat tops static should be around 10:1 or less which is just right for pump gas, you should be able to run mid-grade 87 no problem. And it will be way more snappy, better gas mileage, power, etc. than if you went with factory-style 8:1 or whatever. Just round off the chamber edges to a radius and smooth down that point in the center so it's not poking out so much, also smooth down the edges on the valve reliefs for the pistons when you get them.
With your setup at 62cc and KB flat tops static should be around 10:1 or less which is just right for pump gas, you should be able to run mid-grade 87 no problem. And it will be way more snappy, better gas mileage, power, etc. than if you went with factory-style 8:1 or whatever. Just round off the chamber edges to a radius and smooth down that point in the center so it's not poking out so much, also smooth down the edges on the valve reliefs for the pistons when you get them.
Dave,
Something to keep in mind, if I remember correctly stock magnum pistons takes an odd size ring that is way more expensive than rings for the KB's.
Something to keep in mind, if I remember correctly stock magnum pistons takes an odd size ring that is way more expensive than rings for the KB's.
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