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Discussion Starter #1
Hello,

Quick question about Stroker applications?

I just talked to my engine rebuilder and he said that for my 289 engine rebuild he has used Flat Top Pistons, a 289 crank and 302 connecting Rod.

What's the difference/benefits with the 302 connecting Rod's ?

Thanks, Greg.
 

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Although that's a unique approach to lowering the CR (by leaving the piston 1/16" down at the top of the stroke), I wonder about the wisdom of changing the combustion area shape with the additional squish space of the entire piston being down in the hole...

Never tried it so can't comment with authority...

Well, if you ever want to raise the CR and increase your CI with one easy swap, now you can just throw a 302 crank in there (provided there's enough deck clearance; likely something the builder didn't check since he used a short rod)..

Let us know how it works out!
 

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Were the pistons stock pistons 289/302 or custom pistons. If the pin height on the piston has been changed it may put everything back where it should be.
 

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That begs the question, why buy expensive, custom made pistons for this odd ball arrangement, when you could buy cheap 289 rods and use cheap off the shelf pistons?
 

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If the pin height on the piston has been changed it may put everything back where it should be.

While that is a possibility, the cost of such an animal would be prohibitive for a mild street engine. A stock 335 series piston would have the right CD (1.650") to achieve this goal but any valve reliefs would likely be wrong for the Windsor application (due to the 335's polyangle valve arrangement)..

I think the builder just left the pistons down the hole...
 

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Discussion Starter #10
I am assuming there is mis-communication somewhere. He said that he went with TRM Flat top pistons and stroked the engine so that the pistons went right up to the cylinder heads. There is a possibility that it is based on a 302 crank and connectors? Maybe that's what he ment. He is very knowledgeable and has been building 289 race engines for years.

Anyways....we are going to Dyno the engine when it's done so we'll know for sure but he is telling me that it should be about 325HP and that I should jump-up to an 800 CFM carb (from a 600).

Thanks, Greg.
 

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That's a BIG jump .. and be sure to have your machinist build your complete motor based on certain specs. Obviously he knows you want more performance, so just be sure you communicate well with what you want. Match the cam to the valve springs to the lifters to the pushrods and port the heads and intake if you're using a huge carb like that. On a well built stroked small block .. you could probably get 350 RWHP if everything is tuned and with the right accessories like pulleys, ignition, big cam, etc especially with 800 CFM flow. Let us know what you decide.
 

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Maybe he meant a 302 crank and 289 rods. Use a TRW-L2305F with .065 to .068 (which is the depth of the dish) cut from the top of the piston. I have thinking of building one of these using a Hawks Racing 302 nodular crank from that auction site and my HiPo rods. Crank isn't that much more than the machine work on my damaged 289 crank. Might be cost prohibitive due to cost of pistons and machine work cutting down and possible recutting of the valve reliefs. But, I need pistons anyway. And if I can catch an auction bargain on them I could be in the money.
 

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Here is a formula for carb choice.

(rpm x displacement/3456) x 0.85

The result of this equation will give you the cfm needed for your application. The 0.85 is the volumetric efficiency of a typical street motor (est.). The rpm would be the peak rpm for your engine.

As an example, a 347 cid engine, with a peak rpm of 7500, operating at 99% volumetric efficiency, needs a 745 cfm carb.

If your engine builder said you need 800 cfm, maybe there has been a mis-communication somewhere. Best to get things straight before you shell out your hard earned money.

Good luck.
 

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It appears he is, if IIUC, building the same rod/stroke ratio as a Boss 302, and has installed a 302 crankshaft. The Boss pistons have a shorter CD to compensate for the .062 longer stroke in combination with the stock 5.155 rod length, which is the same as the 289.

As was mentioned, 289/302 pistons can be used, with .062" nominal removed from the top, and this combo will have a slightly better rod/stroke ratio, IMO, than a stock 302. Is it worth the cost of the extra machine work? IMO, no, not unless you can do it yourself.

Not knowing the rest of the details, I can tell you it's definitely possible to achieve the 1.1 hp/ci level he's shooting for, although doing it on pump gas might be problematical as, IME, a high CR is helpful in these applications. I've produced 1.3+ hp/ci from such combinations (with iron heads) in the race car but all of them have been at or near 13:1 CR.

I'd need more info on the engine and the rest of the drivetrain and use to recommend a carb. I can say with some authority that an 800 double pumper will be the wrong choice, unless this is a race car with a manual trans and a lot of gear (4.86's and up). I ran a 3310 780 Holley on all the race car engines and found it to be a consistent performer. But even that carb might be too much for a street car (heavier, lower compression, tighter converter, etc)...

Let us know if we can help further!
 

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Discussion Starter #15
Hello,

Would this lower my compression ratio? If I did a compression test on my cylinsers would the numbers come up lower? And vice-versa, a longer stroke would make the compression numbers higher?

Thanks, Greg.
 
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