Technical Stroking 289 - Budget Build

Hello everyone,
I have a question regarding stroke and piston compression height. The engine I am building is a 289 that is currently in the machine shop & has been bored to 0.40 over. Picked up a 2M crank on ebay that checked out ok. It has been turned .20 under so displacement will be 308. My goal is to build a nice little street motor. Higher compression ratio and torque would be a big bonus.

Paired with a set of aluminum heads, decent cam/lifter package, dual plane Weiand intake and 450 cfm carb, C4 with a slightly higher than stock converter & 8 inch with a posi & 3.25's I'm hoping to have a nice little street motor.

Time to balance & assemble the rotating assembly. So I was hoping someone could offer me more insight as to the ins and outs of stroke ratio & compression height of the pistons to help me select a set that will be correct for this engine. I have found a set of pistons in my price range that appear to fit but the stroke length is 2.870 & not 3.00. So here is my predicament, will these be too far below the deck at TDC? I do not want to loose compression. The cc listed for these flat tops is +8.00 cc & compression height is 1.605. Also will those 5 hundred thousandths cause an issue?
https://www.summitracing.com/parts/slp-h273cp40

On a side note selection seems to be limited on a set hypereutectic pistons ($200 - $300) range. Summit seems to have everything on back order and calling Jegs was about the same.
Machine shop has given me the following requirements...
Pistons:
Flat top - hypereutectic
Rod - 5.090
Stroke - 3.00
CC - +5.00
Also would like to extend a big thanks to Crazy Steve for all of his direction and advice.

Thanks in advance,
Mark

 

What cam? And I think I’d throw a 600 on there..I’ve got a 289, 10.8:1, TF 170’s, Performer RPM, Holley 625 carb, Comp XE 274 H, C4, 3:55, and a Coan 3200 stall in my 65 Falcon…

I’ve got flat tops on mine, notched for valve clearance and heads were milled for compression..runs on 93 octane with zero issues

 

Where any piston sits in the bore at TDC relative to the deck is determined by crankshaft stroke, rod length, and the compression height built into the piston. So a piston is built to fit those specifics. As an example I have two sets of pistons for the same stroke and rod length, but have different compression heights. So one set sits 0.025".down in the bore and the other sits 0.017". And while related, don't confuse compression height and compression ratio. The above assumes the block height is standard. Changing the block deck height changes the piston placement in the bore.

 

Haven't come to what cam yet. I have an old crane cam card somewhere that is what I am leaning towards. I can dig it up and post it...

 

So since it's a 289 block (2.870) OEM stroke basically with 302 rods and pistons they need to match the (302 - 2M crank) I would need to have a piston that's made for the 302 stroke (3.00) correct?

 

I wasted some of the best years of my young life building SBFs. Today, any kid with a credit card can order a complete stroker kit and make more power than Shelby American on their best day.

Bottom line - OP has gotten too far into piecing together a 289" without understanding the interrelationships of pistons, crank, et al. The way out is to sell all those pieces, source a 302" block and order a complete 331" or 347" kit. This will cost less in the end and make way more power.

jack vines

 

I didn't see what rod you are using. 289 and 302 pistons have the same compression height, the rods changed to make the stroke difference. 289 rods (C3AE) are 5.155 and 302 rods(C8OE) 5.090 as I remember. To use the 302 crank you will need the 302 rods as well. I like to use the longer 289 rod and cut the top of the pistons, if flat tops, to the deck height I want.

 

Have plans for a 331 one day but not now. Machine work and kit together would be around 3 grand. Scat kit around $1300 and machine shop has quoted me about $1500 for the machine work. As it stands now my machine work is about $800 that included turning the crank a line hone and boring the block to 0.40
Right now I'm under $500 for main and rod bearings, set of molly rings, and Scat rods. Just need a decent set of hyper Flat top - hypereutectic pistons for about $200-$300 which would have me at total about $1600. Half the cost of the stroker.
I can install my cam, heads etc. So that saves me some $.
-Mark

 

Ye sir I have already found a set of Scat rods at 5.090 so I'm good there...

 

Yes sir because the crankshaft is a 302/2M crank which is why I need the shorter 5.090 rod.
The 289 @ 0.40 over will have the displacement at 308.
Piston Criteria:
Flat top - hypereutectic
Rod - 5.090
Stroke - 3.00
CC - +5.00 (I assume this could be larger if need be)
And from what I read the standard compression height for a 302 piston should be 1.600

-Mark

 

You will definitely need to check valve clearance before installing the heads, it’s likely you will need open up the valve reliefs because of valve size alone. That’s all sixteen valves.

 

Positive there plenty of shelf pistons for the 331 347 kits also. Part of the machining process is square decking the block so all decks are perfectly square with crankshaft centerline. I’m sure you could get a combo that would get you a .005 deck and 10.50 to 1 cr., it’s been done a million times.

1.090 compression height piston
1.7. half crankshaft stroke
5.4 rod length
8.19 is the stack height. So 302 blocks are 8.20. Deck the block .005 and have the pistons .005 in the hole.

 

Ok will do. Seems like the technical support line at Summit is hit and miss because not one agent has mentioned that before or has gotten that thorough. They basically just ask me the basics like engine, bore, rod size etc. Might have to call a piston manufacturer instead, thank you very much for the information.
-Mark

 

Thank you sir. I'm definitely going to build a stroker in the future.

 

Found these using your formula...after subtracting from the deck height came up with 0.008 - Need to find what cc for the heads would work best (58cc,60cc,64cc etc.) ? Don't mind milling them if it came to that as long as I don't have too re-work the intake.
Pistons
https://www.summitracing.com/parts/sum-17370fc-40

 

When using the 302 crank and a 289 rod you would need the same compression height as the Boss 302 piston. When using the 302 crank and 289 rods with 289/302 pistons you would need to cut the top of the piston to make a zero deck. With the longer 289 rod the difference is .065 then depending on which block you have for deck height you trim the piston for zero deck. It will also give you a faster piston speed which you may not need with a stock type head.

 

speed Pro 289 pistons don’t work with a 302 crank and rods. The skirt hits the rod with the longer stroke crank.

I found out the hard way. Some day I’ll build a 289, I guess. Already have a new set of 289 pistons.

 

I don't have personal experience with this but I read that Ford slightly extended the cylinder walls into the crankcase when they transitioned from the 289 to a 302 to give better piston stability at BDC. The story was that testing showed that the ring life was shortened without the extra support.

Again, I don't know this from personal experience, it's just something I read on a forum when discussing using a 289 block to build a stroker.

 

Not sure where you got your info, but you are posting incorrect information. All 260/289/302/BOSS 302 engines have an 8.209" spec deck height, except for about 4-5 years in the mid/late 70's when Ford made them 8.229" for emissions reasons. In rhe early 80's when the 5.0 came about it was again 8.209".

Muncie, you're hodge podging this engine without fully grasping the particulars. Ford smallblocks make great power when setup right. But can be ho-hum when haphazardly slapped together.

 

The ones you bought are they the long skirt pistons or the short ones? Would you happen to have the part number?
Thanks,
Mark

 

I have heard the same as well. I have a 69' 302 block and I need to measure the cylinder walls on each block. I will let you know what I come up with.

-Mark

 

Well that is what I am hoping to do but it's my first complete engine build and I am trying to figure it out as I go. I do have several 289 cranks that I could use if the idea of using the 302 crank is making this harder than it has to be.
I am open to any suggestions and advice. I would greatly appreciate it.

Thanks,
Mark

 

Well called the machine shop and they said they could locate something and call me back. I will follow up tomorrow and see what they come up with...

 

IIRC, the 289 and 302 shared the same bore, only the stroke was different.
When you use a 289 block, with a 302 crank, you are building a 302.
Bore is the same. Deck height is the same.
Why can't you use 302 pistons ?
Shouldn't be that hard.

 

Different rod lengths....so different compression height pistons.

 

Boss 302 and 289 share the same rod length. Prod pass car and truck have unique rods, not common with the 289 or Boss.

 

I didn’t buy them. I used to get free “ engineering sample” engine parts through vendors. Miss those days.

They must have been long skirts. I think they were 271 hp hipo equivalents. Still have them in the shop, but I’m a snowbird now…..

 

You might be money ahead to start with a roller 302 block It also lets you go with a roller cam and no cam break in issues plus less parasitic hp loss.

 

I thought it would be simple enough, grab 302 rods and pistons and go but with all these headaches I might just give up. I guess I could always run one of my original 289 cranks but I wanted to see how the engine responded with the 302 crank. Tell you guys what though I'm gonna save my coin for a stroker 331 come next year and I've been collecting parts to convert it over to a 4 speed. Just need a toploader and that should be the last piece of the puzzle.
-Mark

 

Sounds like they are the long skirts.