Stroker Question

[tscott9330]

Alright, I get the concept of the stroker motor,(i.e. longer stroke = more cubes). but what i dont get is how the increased stroke doesn't make the pistons protrude past the deck. When i took my 350 apart yesterday I noticed the pistons were pretty close to the the deck.

I plan on building a strker and i'm a little concerned. Please help.

Tom Scott

 

[Tom73]

You change pistons where the wrist pins are closer to the top and/or shorten the connecting rods. That way the pistons do not pop out of the bore

tom...

 

[offshore]

you can't just throw a crank in. con. rods,pistons, & bore come into play.

 

[Mako]

Alright, I get the concept of the stroker motor,(i.e. longer stroke = more cubes). but what i dont get is how the increased stroke doesn't make the pistons protrude past the deck. When i took my 350 apart yesterday I noticed the pistons were pretty close to the the deck.

I plan on building a strker and i'm a little concerned. Please help.

Tom Scott

The piston wrist pin moves towards the crown of the piston. On a 6" rod, the wrist pin actually intrudes into the oil ring area and requires a "ring bridge" be installed to support the ring over the gap.

A 5.850" rod is typically as long as you can go w/o intruding on the lower ring land of most pistons.

I'm personally quite fond of the 6" rod setup for a street rod.

Research the Wisco and J&E piston catalogs for more information.

CYa!
Allen

 

[tscott9330]

Thanks Guys. that helps alot. My stroker should be up and running in about 6 months.

I'll post pictures.

Tom Scott

 

[Blue82]

I am looking at installing a steel crank in a 355 that I built up last year. I called PAW to see if I could find a 5.4" (approx) rod so I could keep the .030 over pistons I already have in it and go up to a 383. They told me they're made for Frods (Fords) but not Chevy engines.

Tom73 mentioned shortening the rods so am I right that there are shorter rods or is there a safe way to shorten an existing one?

 

[offshore]

no you use a 5.7 rod or a 6.0 rod the 6.0 rod will give you more torque. it leaves the piston @ tdc. for a longer period of time. either way you need new pistons. my opinion go for the 6.0. they do make rod{ 5.565 "} that you may beable to use your old pistons with. you need to know the compression height of your old ones. if you do use that combo you will loose torque. in any case the whole rotating assy. needs to bal.

 

[Jack]

I am looking at installing a steel crank in a 355 that I built up last year. I called PAW to see if I could find a 5.4" (approx) rod so I could keep the .030 over pistons I already have in it and go up to a 383. They told me they're made for Frods (Fords) but not Chevy engines.

Tom73 mentioned shortening the rods so am I right that there are shorter rods or is there a safe way to shorten an existing one?

As offshore saiys ... use a 5.7 or 6 rod. You could use an old set of 400 rods (5.565) but you probably don't wanna do that ... you probably would not be too pleased. The ford 5.4 rod is a solution I've NEVER heard of ... wtf? We have put chevy 5.7 rods from a chevy six banger in a ford 4 cyl 2300 ... but with shorter compression distance pistons ... mini-stock circle track car.
JACK:gap

 

[Blue82]

The tech was not suggesting that I use it in the Chevy. I just noticed them in the catalog and thought there would be an equivalent rod for the Chevy. He told me I had to get new pistons because there isnt a shorter rod for the Chevy than a 5.7".

I am using 64cc L31 Vortec heads with .030 over flat top pistons. They were ordered for 9.5:1 compression so I figured if I subtracted the added stroke (from the rods) that ius gained by a new 400 crank and kept the original piston, the compresion and the resulting stroke would be the same as a 5.7" rod with the correct piston.

It won't be worth the money for me to buy new pistons when mine are only 6 months old. I think I'll buy a steel 350 crank, better rods, have it all balanced and stay with the 355. I am getting good power now, but thought I could take advantage of getting a new crank.

Thanks for the clarification guys.

 

[offshore]

I wish it were that easy. Throw in a crank and go.(if it were i'd be looking for a new job) it just starts there after your crank and rod now you have to relive the bolck maybe the bottom of cyl. walls,maybe use a smaller base circle cam. all of these factors come into play and more.(dependig on what your config.is it's a lot of work. if your still intersted in doing it you should buy a 383 kit tha comes with CRANK,RODS, BRGS,PISTONS & BALANCED.( if your using a 400 crank you have to change the fly wheel and harmonic bal.too) There not to expensive most of the guess work that your doing is taken out. if you need to relive the block it seems to me you could do it your self . if you need a smaller base circle cam the kit should tell you. don't give up on your project yet. it's just not as simple as you thought but there are kits out there for relatively cheap money that will guide you through it and once it's done you'll love it. so if you can wait a little longer and sped a few more bucks "DO IT" it's even worth stepping out for a year! 383 done right will burn 50s off your car!

 

[offshore]

The tech was not suggesting that I use it in the Chevy. I just noticed them in the catalog and thought there would be an equivalent rod for the Chevy. He told me I had to get new pistons because there isnt a shorter rod for the Chevy than a 5.7".

I am using 64cc L31 Vortec heads with .030 over flat top pistons. They were ordered for 9.5:1 compression so I figured if I subtracted the added stroke (from the rods) that ius gained by a new 400 crank and kept the original piston, the compresion and the resulting stroke would be the same as a 5.7" rod with the correct piston.

It won't be worth the money for me to buy new pistons when mine are only 6 months old. I think I'll buy a steel 350 crank, better rods, have it all balanced and stay with the 355. I am getting good power now, but thought I could take advantage of getting a new crank.

Thanks for the clarification guys.

If thats all your going to do don't buy a steel crank! (because it looks like one day your going to stroke it) for now put the block back together do head and valve train work. All the time keep in mind that some day your going to strock it, so what ever you do know will work with your stroker! you'll probably be much happier with this engine doing that and when your ready to stroke half the job is done. DON'T WASTE YOUR MONEY ON A STEEL CRANK AT THIS POINT YOU DON'T NEED IT. (if insist on a forged crank for that eng. call me i=I'd be glad to sell you one. I have 6 in stock.

 

[Blue82]

Offshore, let me share my sad story with you (everyone) and MAYBE a stroker kit will be in my future. I rebuilt my motor last fall. The bits and pieces are in my signature. About 3 weeks ago I had a power steering pump bolt break off while driving home. I had to drill it out and cleaned up the hole with a tap, couldnt start the new bolt in the hole and broke the #$%@ tap off in the block while cleaning it up again. Soooo I moved on to replacing the balancer and noticed I could see about 1/4 inch of clean metal where it meets the timing chain cover seal. Turns out the threads stripped in the snout of the crank. At this point I put away the tools and had a shower and several beers.

I don't have a problem at all having to go back in to rework the motor, but I see it as an opportunity to improve on my previous buildup. The reason I wanted to go with a steel crank is that I nicked the original crank with a rod bolt when I was disassembling the motor last fall. I had it turned and polished, but I don't understand why the crank was that soft...and now with the stripped snout I thought I better go with steel.

I have seen entire stroker kits for less than I will spend for a steel crank but they have cast cranks which I feel brings me back to my original problem with a soft crank.

PLEASE shed some light on this so I can understand if I can really trust a cast crank vs steel.

Also, I have 3.73 gears in the car so I built the motor to spin up to 6500 RPM. Will a stroker be able to turn that much rpm? I heard they work more in the 5000 range.

Thanks for any help you can offer.

 

[offshore]

Offshore, let me share my sad story with you (everyone) and MAYBE a stroker kit will be in my future. I rebuilt my motor last fall. The bits and pieces are in my signature. About 3 weeks ago I had a power steering pump bolt break off while driving home. I had to drill it out and cleaned up the hole with a tap, couldnt start the new bolt in the hole and broke the #$%@ tap off in the block while cleaning it up again. Soooo I moved on to replacing the balancer and noticed I could see about 1/4 inch of clean metal where it meets the timing chain cover seal. Turns out the threads stripped in the snout of the crank. At this point I put away the tools and had a shower and several beers.

I don't have a problem at all having to go back in to rework the motor, but I see it as an opportunity to improve on my previous buildup. The reason I wanted to go with a steel crank is that I nicked the original crank with a rod bolt when I was disassembling the motor last fall. I had it turned and polished, but I don't understand why the crank was that soft...and now with the stripped snout I thought I better go with steel.

I have seen entire stroker kits for less than I will spend for a steel crank but they have cast cranks which I feel brings me back to my original problem with a soft crank.

PLEASE shed some light on this so I can understand if I can really trust a cast crank vs steel.

Also, I have 3.73 gears in the car so I built the motor to spin up to 6500 RPM. Will a stroker be able to turn that much rpm? I heard they work more in the 5000 range.

Thanks for any help you can offer.

Don't put your name and add.beside gutted cats!:eek Sounds like you had one of my days.

 

[offshore]

9.5:1cr and your combo of parts,acast crank should be fine for normal driving and the occasional beating. now on the other hand your talking 6500 rpm. that engine can't take that! it's onlt a mater of time before you blow it up. the rods won't take the crank won't and parts of your valve train probable won't (where are you running your car at 6500 anyway?) is your car stick or auto? other ? you asked about strocker rpm. you can run a strocker or any other engine at high rpm BUT this COSTS not only a lot of money to build ie: light weight crank,light weight rods & pistons (not the pistons you probably have) light weight valve train comp. then the countless hours of balancing. its very costly! then at these high revs every thing wears out very quickly.(plan on freshening the motor every winter) you want a motor that pulls to 5500 redline 6000.300 to 400 hp (am I right?) get back to me with my questions so i have a little better idea.

 

[Jack]

Any difference between a cast & a forged crank's abilities to resist a rod bolt nick or stripped damper bolt thread is imperceptible ... you can nick / strip forged quite easily.
JACK:gap

 

[Jack]

Blue82:
Have you tried to chase the snout with a good tap? That bolt doesn't do a whole lot. The damper's press-fit & keyway does most of the job ... early sbc did not have a hole ... no thread ... no bolt. Maybe if you can chase the thread enough to get a grip on new bolt ... or even a bolt with intentionally scarred threads for better grip. You should be able to get 375-400 reliable hp from cast crank, good rod bolts 350 w/ Vortec heads.
JACK:gap

 

[Blue82]

My intake and cam are rated for a 1500 to 6500 powerband so that is where I got that rpm from. I used the recommended springs and lifters for the cam and I had screw in studs installed. The reason I need the RPM is the th7004 xmission and the 3.73 gears. In 4th gear at highway speeds I am fine, but if it kicks down to 3rd the rpm swings up pretty fast. It usually doesn't go past 6000 rpm but it will if I'm not careful. They also come up quick off the line. 1st and 2nd are ok but I can run out of 3rd fairly quick.

Offshore, the cars an automatic th700r. I'm looking for 350 to 400 hp and around 350 ftp of torque.

 

[MaineShark]

If you're looking for power, and not as much torque, a stroker probably isn't best. Some people wanting high RPM's actually de-stroke the motor (shorter stroke, same bore).

Basically, what you're looking at is the bore-to-stroke ratio. When they are equal, you have a "square" engine. When the stroke is longer than the bore diameter, the engine is "under-square." When the bore is larger than the stroke, the engine is "over-square." Most modern engines are square or over-square. The higher the RPM's you want to turn, the more over-square you want to be. The more low-end grunt you want, the closer you want to be to square.

Now, if you don't want to worry much about highway driving, an engine with a lot of low-end torque, combined with the gear ratios of that 700R4 and the 3.73 rear gears... well, that should perform nicely off the line. If you're worried about the 700R4 kicking down into 3rd, you should probably have it checked out - it should just kick down for no reason.

Also, there are aluminum guides that screw over the rod bolts for assembly, to protect the crank. No crank is really all that hard: with the beating it takes, a crank has to be soft - a hard crank would shatter. The bolt guides will protect the crank, and I don't think they cost much.

Joe

 

[offshore]

If you're looking for power, and not as much torque, a stroker probably isn't best. Some people wanting high RPM's actually de-stroke the motor (shorter stroke, same bore).

Basically, what you're looking at is the bore-to-stroke ratio. When they are equal, you have a "square" engine. When the stroke is longer than the bore diameter, the engine is "under-square." When the bore is larger than the stroke, the engine is "over-square." Most modern engines are square or over-square. The higher the RPM's you want to turn, the more over-square you want to be. The more low-end grunt you want, the closer you want to be to square.

Now, if you don't want to worry much about highway driving, an engine with a lot of low-end torque, combined with the gear ratios of that 700R4 and the 3.73 rear gears... well, that should perform nicely off the line. If you're worried about the 700R4 kicking down into 3rd, you should probably have it checked out - it should just kick down for no reason.

Also, there are aluminum guides that screw over the rod bolts for assembly, to protect the crank. No crank is really all that hard: with the beating it takes, a crank has to be soft - a hard crank would shatter. The bolt guides will protect the crank, and I don't think they cost much.

Joe

3/8 dia. hose works just fine. and I dont think he wants to run 9000.rpm and have his friends push the down the street to get it rolling!

 

[offshore]

My intake and cam are rated for a 1500 to 6500 powerband so that is where I got that rpm from. I used the recommended springs and lifters for the cam and I had screw in studs installed. The reason I need the RPM is the th7004 xmission and the 3.73 gears. In 4th gear at highway speeds I am fine, but if it kicks down to 3rd the rpm swings up pretty fast. It usually doesn't go past 6000 rpm but it will if I'm not careful. They also come up quick off the line. 1st and 2nd are ok but I can run out of 3rd fairly quick.

Offshore, the cars an automatic th700r. I'm looking for 350 to 400 hp and around 350 ftp of torque.

I'll get back to you later some ******* smashed into my 87 (14,000 mi mint) in my drive way about a half hour ago can't think to good right now!