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Discussion Starter · #1 ·
Hey Guys,

Hey Folks,

I posted this in a nother forum area not knowing this "stroker" forum was here.
Anyway, I have a new 307 (289 w/302 crank & rods) with 1500-2000 miles. This combo has been balanced and converted to a roller. Basically all the parts are new. I want to convert to a 331 using the stroker idea. However, as my pistons/rings are new and on their way to being "bedded in" in this block, I would like to keep them and just change out the rods for 5.40s (if they work) and the crank for a 3.25 throw and have the whole shootin match balanced with a new damper and flexplate.
I know to do this, I need to consider the total length of a 331 kit piston and rod from the top of the piston to the center of the rod big end.
This will save me rings/pistons/installation time and any potential 'boring ssues", as the walls are in super condition.
I'm not trying to "cheap' my way though this, but, to use parts that are still hardly used!
Thanks for any constructive thoughts, considerations, or ideas.
 

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You won't be able to use your 302/289 pistons. The compression height (distance from pin centerline to top of piston) is 1.600". Using a little math, with a 302 crankshaft & 5.090 rods (stock 302 length) you come up with 8.190". The deck height of most 302/289 blocks is 8.20". You get this by adding half the stroke (1.5) plus the rod length (5.090) plus the piston compression height (1.60). Add into this that a 331 uses 5.400 rods and 3.25" stroke. If you add half stroke (1.625) to the rod length (5.400) plus the compression height of the stock 302 pistons, you come up with 8.625...which means that with that combo you'd have the pistons "out of the hole" by .425". That's way too much. What you need is a set of pistons with a compression height of 1.165, which will leave you with the pistons down in the hole by .015"....which is acceptable and allows you to have the block "zero decked" by milling. I guess you "could" go with a set of 4.97" rods which would most likely have to be custom made (expensive) in order to use the 302 factory CH pistons.

I use the same math to come up with all sorts of off-the-wall combinations. Newest one is going to be 6.300" rods, 4" stroke crank and 331 pistons which will work out to 408" or 415" (060 over) in a 9.48 early block. I don't ever remember seeing/reading about a 6.300" rod 408...but I don't doubt that it's been done.

Or, if it was me, "work" on what you have. There isn't THAT much power difference between a 331 and a 302, IMO. There is some difference...but I usually ask myslef if there is so much of a difference to justify spending the time & money to pull it all apart & re-do the whole combination. Usually not...at least that's always been my experience with 302 combinations.

Again, just my humble opinion, I would look elsewhere for some extra power. You can make some power with a 302 even with a stock stroke. Dad's car ran a 3.000" stroke cast (stock) crank for years...running low 11's in a 2500 lb fairmont. My Mustang runs 10.80's, again with stock crank & stock rods and RPM heads. And there are others who have run 9's on motor...again with stock stroke 8.2 deck blocks. It's entirely possible and not all that hard to be honest. What is your combination right now? Heads, intake, camshaft, compression, converter/trans, etc? Perhaps we can help you find some power that is lurking elsewhere...and you may not even have to spend a whole lot of $$$ to find it.

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"it is better to appear ignorant than to open your mouth and remove all doubt"--Mark Twain

<font size=-1>[ This Message was edited by: mavman on 1/6/07 9:38am ]</font>
 

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Well said Mav.

Cris
 

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Discussion Starter · #4 ·
Hey Mav,

Great reply, these comments are not a surprise. I did not fully jump into researching the stoke and piston height differences at the time I ask this question. I just "threw it out there", as they say!
I had to tear into it due to a minor leak from the front seal and a low oil pressure issue. The oil pressure problem is due to something ground up and scoring the "heck" out of the bearings and journals. I found a lot of ground up fragments in the pan. Other than this the engine ran strong with no hesitations. I felt like while I had it apart, I might as well "spark it up" a bit more.

You ask what I my current configuration is:
This engine, 289 'D" code block, bored .040 over and the aformentioned 302 kit, has about 1500-2000 miles on it and was balanced and bluprinted when assembled. I'm running Windsor Jr heads with 1.94/1.60 valves, mild porting and bowl blending with roller rockers. the intake is a 600 cfm Edlebrock on a Performer RPM manifold. The compression is 9.3-9.5 range. It's running a nice street "roller" CompCam. The exhaust is coated Tri-Ys into a 2.5 system with a "X" type balance pipe. The rear is a 3.25 posi-lok. It has a C4 fully redesigned for better performance.
The ignition is a complete Jacobs system with a rebuilt and recurved autolite w/pertronix with "all-in" by 3100 rpms. The engine seems to like 12 degrees of initial advance with 24 degrees built-in for a total of 36 deg. with ported vacuum set at 15 hg. I've worked the edlebrock techs and using an Innovate AFR meter have dialed in the carb AFR from mid-range thru WOT. I built it to work well in the low 3000 RPMS and it does.
Thanks for inspirational thoughts.
 

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Discussion Starter · #5 ·
Hey Mavman,

Again, thanks for the comments. You got me thinking about the whole deck height/rod length/compression height stuff.
You made mention about why I would tear into this. Wel, the truth of this matter is, my oil pressure went south as the reesult of a wiped cam. This wiped out the front crank journal. I'm not so sure sprat welding and re-cutting then re-balancing is worth th effort. So, I thought, I might as well put the rebuild crank money into a new crank along with rods pistons etc. Not to mention, the wiped out oil pump.
So, as they say, that's "the rest of the story".
Thanks again mavman.
 

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Any time you consider something like this, you must consider the interference that will occur between the bottom of the piston and the crank counterweights. My 331 with 5.155 rods and 1.405 CH pistons (a 383 Windsor stroker piston) required me to remove almost 1/8" from the 331 crank counterweights to obtain the necessary .060 recommended clearance. That's not a bad thing since it lightens the crank. It balances out without heavy metal but not by much. Trying to do what your considering would require some tricky balancing with heavy metal unless you found a really light rod and piston...not likely.

Your rod angle is starting to get up there too which can cause cylinder wear but at least the piston (something other than 1.600 CH) would have a large skirt face to help spread the load.

_________________
Tracy Blackford: Corona, Ca
'65 FB Mustang 331, 282S cam, ported 351W heads. T5z, 3.50 9" posi.
346 [email protected] on a warm spring day (335 RWHP SAE corr.)



<font size=-1>[ This Message was edited by: blkfrd on 1/19/07 12:09am ]</font>
 

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Discussion Starter · #7 ·
Hey Tracy,
At this point I'm going with a 331 kit frm CHP.
That's a great shot of your ride. How do get a pic posted like that? I'm new and not sure how this is done.
thanks,
 

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Kenash , YOu listed that you were running a rooler cam . I have not heard of anyone wiping a roller ca. Can someone fill me in on this ??
Mav ?
Take Care
Earl


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Earl - Ranchero_65 Restomod Slowley in Process !
www.ranchero65.com

<font size=-1>[ This Message was edited by: Ranchero65 on 2/1/07 10:26am ]</font>
 

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Discussion Starter · #9 ·
Hey Ranchero,

Perhaps, I wasn't clear on that issue. I wiped a hydraulic flat tappet cam prior to installing the roller. The "break-in" of the flat tappet did not go well. I did not find this out until after the "dusted" lobes washed through the system. I removed the cam and lifters, sent them to CompCam, and they gave me a complete roller setup for "chump change". The roller installed easily and fired up without a hitch. "The engine ran like a sewing machine", up until I tore her down. However, not having pulled the pan (only changed the oil several times and filter), did I learn of the reason for my deteriorating oil pressure. I have, since learned of the issues with our less than perfect oils, i.e. low zink (ZDDP) levels etc.
So, there you have it!
 
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