mastiff

I have been trying to take in all the info I can find on stroker kits so that I can buy one for my 72. there are some things I still don't understand. Maybe ya'll can help me out.

1) What are some good companies that sell kits. I have heard recommendations for http://www.speedomotive.com but would like to see other kits as well.

2) If you decide to go with 5.7 rods, does the rod need to be ground down or modified in anyway, or is it only the block. If you buy a stroker kit, are the rods always ready to bolt on, or is it posssible that some modifications might need to be done. Does the problems with clearance issues with 5.7 rods justify using the shorter 5.565 rods.

3) On speedomotives site, I see the option for external balancing for $150. This is different than just providing a flywheel, flexplate, and harmonic balancer for the engine, right? What is actually meant by this?

4) All stroker kits give a compression ratio with their kits for certain combustion chamber sizes. They are obviously making assumptions about deck height and gasket thickness. Did the deck height of the 350 stay close enough to the same for all those years that the compression estimates are accurate?

Thats all my questions. Thanks in advance.

Andrew
Austin, TX

Black&Silver78Pace

do seaech on CRATE ENGINES you'll find a couple of sites

Black&Silver78Pace

here is one http://www.rebuiltcarengines.com/highperfengines.html

rayray

I got my stroker kit from PAW. The kit starts at $650.00, but I just had to add alittle extra to it. I got harden rod bolts, 400 rods, a steel 383 crank, main & rod bearings, moly rings, forged 4-valve relief pistons, B & M flexplate, harmonic balancer, had piston put on rods, and had it all balanced, for $ 1260.85. :chevy

Fevre

Where to start...

Rods: How are you going to drive this bad boy? If you like to rev high and race it a lot, I would get the 6" rods but they do cost a little extra but I would not go lower than the 5.7" or you will redline at 5000 rpm's with the shorter rods. I know that with the 5.7 rod a few of the rod bolt heads have to be ground to clear the cam but most people just grind all 8 so they weight the same.

Balancing: Most kits are externally balanced. I can't give a scientific explanation on what the difference is between int and ext balancing but I do know that ext balanced engines have a heavy recipricating mass because of added material in the fly wheel and balancer. Most people say that int balancing is better but for a mild street machine, ext is fine. Int balanced assemblies usually cost a little more but you can reuse your balancer and flywheel if you choose. With ext you need ext balanced flywheel and balancer.

Comp ratio: You have to take into consideration everything you mentioned in determining comp ration. Unless your block has been decked then you should be able to figure the comp ratio using the cc of your heads. If you bore your block it will lower the comp also but add about 6 or so cubic inches for 30 over.

Make sure you have who ever builds your stroker checks EVERY where there is tight clearences, mainly the cam AND block. I am chasing down a problem with a stroker motor I had built by speed-o-motive. I am not sure why but I had a rod tap the block upon start up and take out a bearing. I thought it was beause of over casting on the block but I pulled the rod today and noticed that the rod casting for that rod was little bit more than the other rods. Although this may have been a manufactuting defect, speed-o-motive should have checked EVERYTHING before shipping the engine to me. They do NOT warranty their engines so I am stock figuring it out myself. I guess you don't have to ask my opinion of speed-o-motive. :U

Paul 75 L82

I'm thinking about a stroker kit myself. I went to Sprrd-o-motive's site. They have a budget 383 kit for $460. It says that it has the chevy 400 rods @5.565" long. I thought that the 400 rods were 6" long. Is this what you mean by shorter rods makes for a lower redline rpm?

Fevre

I am no engineer so here is a simpleton's explination: the longer rod decreases the speed (velocity) of the piston so it allows higher rpm's without chance of failure. I think it is at the point of transition between upward and downward travel the longer rod decrease the speed(velocity). Some engineer will chime in with the exact reason/theory behind it. Plus the geometry lessons the chance of piston scuff because the wrist pin is higher in the piston so it is not pushing so much towards/against the cylinder wall. Again, you will get the theory behind this if the right people read this post.

As in life:

longer rod: good :D

shorter rod: not so good :cry

:lol:

The Money Pit

I was going to do the 383 myself and the machine shop talked me into a 400. The kits cost the same (got mine from Storm Speed),you still need block work,and end up with 20-40 more hp/tq. The 406 in my 80 just pulled 15mpg with the 3.73 rear! WHOOHOOOOO!!!!!!!!!!

fauxrs

400 SBC rods are NOT 6" long they are the short 5.565 as advertised. you can invariably identify the inexpensive kits from the more pricy kits by their inclusion of 400 sbc rods.

I wouldnt touch a 383 with 400 rods, at the very least you want the 350 sbc rods (5.7") many argue for 6" rods however in a street only motor the difference will be negligible.

Scat makes an excellent stroker kit complete with rods and pistons for less than 1K that includes a new cast steel crank that will internally balance - therefore you will not need a new flexplate and harmonic balancer.

External balancing is fine - the Small block chevy has been externally balanced since they went to the single piece oil seal some time in the 80's I think.

gkull

When I first blew my motor and needed something fast I bought a used 391 ci so called hot rodded stroker roller camed shortblock. I was told that it did over 7000 every day of the week. It actually showed me what you don't want to do.

When I tore it down it had some cheaper crank. The 5.565 rods TRW budget forged pistons and externally balanced. The outer faces of the piston were begining to show ware and the outer face of cylinder wall was worn out of round. I was pissed because it sold as a really nice high powered motor ready to slap in your car. So any way I gave him and offer that he could refuse and I got my money back.

It taught me to never buy an externaly balanced motor with short rods. They just wore away the outer cylinder bores. I can't remember the specs but it would have been close to clean it up at .060

fauxrs

I would be willing to bet the wear was due to teh short rods and had nothing to do with internal/exteral balancing. The 400 SBC rod is notorious for the excessive side loading on the piston causing the kind of wear you describe.

I think the differences between internal and external balancing are over stressed - what is more important IMO is balancing the rotating assembly with all the parts.

The benefit of getting an internally balanced system when stroking the motor is that you can reuse your nuetral balance flywheel/flexplate and damper. Saves $$$$

jerryjfunk

"I know that with the 5.7 rod a few of the rod bolt heads have to be ground to clear the cam but most people just grind all 8 so they weight the same."

Don't grind the rod bolt heads... this would be bad. It will be neccessary to grind the block a little bit for the rods to clear, I'll be doing that as soon as my kit comes in (I bought mine from a company called PME racing). That way there is no weakening of the rods or rod bolts, and there is no problem with balance between them. I hope this helps!

Jerry

KorbenDallas

This is a newbie suggestion, but make sure you get all forged parts. You might want to go with nitrous later so with forged parts you can just bolt it on.

Fevre

Jerry

NOT grinding the rod bolts would be VERY bad, they will hit the cam if not ground. I am talking a standard set of rods, not the stroker type. You just grind the ends just a touch at about a 45 degree angle and take off just enough to clear the cam, and that ann't much. It is a common practice. You could get a small base circle cam (think that is the term) instead of grinding if you like. Mine where ground by the engine builder and I bet many others have it done the same way.