I need help for this has been an out going battle between what makes the block stronger. Extra dowel pins with stronger tension bolts or having over sized tension bolts? iv heard that sometimes the over sized tension bolts and the stronger aftermarket tension bolts leak coolant. I know the 20B's flex alot easier then the 13b's (since they are alot longer) and im just trying to figure out the best solution to not flex this motor with alot of HP. Iv started off well by buying a D series 20b # D626 so the rotor housing are alot stronger then the earlier model 20B's.
Any help would greatly be appreciated

 

There is a huge argument about this, but basically the answer is, either one is better than nothing. The important thing either way is that it is done right. Dowels or studs require precise machining, and if it is not done to the correct spec and tolerance, it will only make the block weaker rather than stronger.

Depending what your goals and resources are, there may be more important areas for you to focus as well. Getting a really good tune, a good fuel system, some sort of aux. injection, a good ignition system, etc is much more important than messing around with the block IMO.

Even more so than that is the 1 major issue for the 20B: heat. you need a really good oil cooling system and a really good radiator with appropriate fan and ducting. A lot of the stresses in these engines are caused by thermal expansion, and high temperatures also promote detonation.

If your goal is under 650 whp, you should focus on that stuff and not worry about the block. If its over that, no offense, but you shouldnt have to ask these kinds of questions. If you want this kind of project, you either need the knowledge and skill or the money to pay someone who has it. Find a decent shop and get them to take care of this stuff. Or at least get a 13B to learn on if you want to do everything yourself.

 

On my 13B rew i have put extra dowels inside with regular sized hardened tension bolts and i was pushing out 527HP with a large street port gt35r on 23psi on the dyno and pushed the motor hard and never blew it. I actually have taken the block apart 2 weeks ago to see if there was any wear and everything was amazingly clean on it. ( reason i have taken it apart is im going to bridge port it for more power) iv never built a motor with just hardened over sized tension bolts and i knew it was a big ongoing battle about what is better. I know for 13Bs ether one is great (extra dowel pins with regular sized hardened bolts or over sized hardened bolts) but my question is about 20B's since they are a lot longer and prone to flex because of the extra rotor and length. I actually need experience on people that have been pushing over 1,000 hp on a 20b and what kind of modification they have done for it to not flex

 

I think youre going to run into the same issues here as you would in the 13b forums-
The people with that kind of experience tend to keep it to themselves.
The ones who will talk will tell you the same thing as the high horsepower 13B guys. Guru A will say that dowels are great and studs are crap, while Expert B will say just the opposite. This may be a longer, higher power engine more prone to flex, but all the principles are the same. If you did it one way and liked it on a 13B, just go ahead and do that on the 20B as well.

One more note- the 20B already has a pair of oversized tension bolts, but the bigger issue is that not all of the tension bolts go all the way through, so there is even more machining required to stud the engine. Studding also doesnt work as well unless you through drill the studs and put a nut on both ends, (which allows them to be torqued tighter and spreads out the load so there arent strength issues with the cast iron housings) so that adds another layer of complexity.

 

If you dont want to crack the thick center iron, go with the machine work and the stud kit..

Next option is the billet thick center plate.. but thats double the cost of the studkit and machine work..

 

then use dowels on your 20B. it's experience that you already have and seem to be pleased with. the principles are the same. in terms of flex, you can also look into having a custom oil pan made with reinforcement in mind.

that said, i think Patman's advice is probably the most sound advice you'll get. you never mentioned your goals though, so i suppose there is a small chance physical flex may be a true issue for you and your project.

good luck with that one.

 

actually, there is another thing i forgot to mention

The casting on the 20b thick center iron is very thin around the tension bolts in some areas. This causes a problem when pinning the engine because there isn't enough material left over if you counterbore the holes for stock size dowel pins. On my engine I turned the last 1/2" of some stock pins down to compensate, but there is still a pretty thin land for them, not to mention that the dowels are weaker. I have not had any problems with breaking them or anything, but it is an issue.

 

so your telling me i should be careful in other words putting extra dowels or oversized tension bolts will make it weaker and prone to crack?

 

well- extra dowels will unless you custom make them. Studs should be OK because generally stud diameters are still pretty small, and because they go all the way through instead of seating in the irons so the force is spread out better.

 

thank you so much Patman for noticing that. That's a very important thing Im just going to go with over sized tension bolts definitively now. Like i said from the start im new to 20B's and there had to be a difference between the 13b to 20b's not just because it has an extra rotor