Engine building question

phat46 · April 10, 2012, 07:24:41 PM

I'm entering the buying phase of an engine build. It's going to be a SBC 383 stroker. I have a good two bolt main block. My qiestion is: is it worth it to buy splayed four bolt maincaps or just regular straight fourbolt caps. I ask because in the future this engine just might end up with nitrous on it or possibly a blower. I don't know if the splayed caps would be a good idea or even neccessary for a boosted motor.

enjenjo · April 11, 2012, 01:28:28 AM

If youare going to change main caps, you might as well go with the splayed caps, if your block will accept them. not all blocks will.

phat46 · April 11, 2012, 07:45:49 AM

Quote from: "enjenjo"If youare going to change main caps, you might as well go with the splayed caps, if your block will accept them. not all blocks will.

I didn't know that Frank, how do you know which blocks will take the splayed caps?

enjenjo · April 11, 2012, 11:14:30 AM

Some block have main webs that for want of a better term, are factory relieved, and are not thick enough in the area where the splayed bolts go. Most blocks that have 4 bolt factory versions can be splay bolted. So 010,014, and 015 blocks can be fitted with splayed bolts.

rumrumm · April 11, 2012, 12:47:40 PM

If you are going to spray it, I would suggest 4 bolt mains. But if you were going to build a 383 with around 400 hp, I would simply go with ARP studs and leave it a two-bolt.

phat46 · April 11, 2012, 01:28:43 PM

Thanks Frank, it's a 010 block. I thought about leaving it two bolt, but in the future hopefullythis engine will get some gas or a blower.

Arnold · April 12, 2012, 02:17:13 PM

As said by Rumrumm..and a few other engine builders..(I believe Grumpy Jenkins r.i.p)..2 bolt blocks are good for 400hp. So are cast cranks. If they are together..and have worn well..mains good..don't need align boring..just build them. If you are changing caps..they need to be align bored. For the cost of that AND getting it done right..I would just go to a 4 bolt block. Find a good block with the crank in it and good main bearings..and that should tell you the block is pretty straight. If the bearings are worn odd..(like it needs an align bore..)it probably does need align boring and I would just find another block. My .02

chimp koose · April 12, 2012, 03:21:36 PM

Splayed 4 bolt is better than regular ,the bolt holes go into thicker area of the block,less likely to distort the bottom of the cyl. and less likely for cap walk(think about panhard rod on diff). Nitrous produces incredible torque gains at lower rpm ,more than it does at higher revs,4 bolt mains are a good upgrade.If you are going nitrous or blower at a later date keep that in mind when selecting a cam.Boost motors like a wider lobe separation than n/a motors.

phat46 · April 12, 2012, 03:50:43 PM

Quote from: "chimp koose"Splayed 4 bolt is better than regular ,the bolt holes go into thicker area of the block,less likely to distort the bottom of the cyl. and less likely for cap walk(think about panhard rod on diff). Nitrous produces incredible torque gains at lower rpm ,more than it does at higher revs,4 bolt mains are a good upgrade.If you are going nitrous or blower at a later date keep that in mind when selecting a cam.Boost motors like a wider lobe separation than n/a motors.

Nitrous use in the future was the main thought behind the splayed caps. I know if I go with a blower a cam change and probably dished pistons would be in order.

chimp koose · April 13, 2012, 12:08:20 AM

With nitrous you will want a good piston with lower ring placement. Nitrous likes a wide lobe separation also. Usually a split pattern cam with more exhaust duration is best.Also a bigger header primary pipe ID . For every 50hp of spray we retard timing by2degrees.

phat46 · April 13, 2012, 09:10:36 AM

Quote from: "chimp koose"With nitrous you will want a good piston with lower ring placement. Nitrous likes a wide lobe separation also. Usually a split pattern cam with more exhaust duration is best.Also a bigger header primary pipe ID . For every 50hp of spray we retard timing by2degrees.

All good advice; now for another question...is it worth it to use a roller cam, I see they have roller lifters for the older style blocks. I wonder if the expense is worth the gain.

chimp koose · April 13, 2012, 06:15:41 PM

Yes , on the roller .Hydraulic roller is fine ,but rpm limited(6500 ish, more with special attention),rev kits help a lot. Hydraulic Roller lifters give you no oiling issues with reduced or no zinc oils. Solid roller will give reliability / wear issues in low rpm(2000 or less)street applications. The difference in torque and Idle quality Roller VS flat tappet is a no contest.Roller will cost more but it is a wise choice performance wise.