Login    Forum    Search    FAQ

Board index » Racing Forum » Engine & Cylinder Head Tech




Post new topic Reply to topic  [ 10 posts ] 
Author Message
 Post Posted: Tue Jul 31, 2012 12:14 pm 
Offline

Joined: Fri Sep 23, 2011 1:23 pm
Posts: 80
My block is cracked and im going to get a new dart block.I want to reuse my crank,cam,connecting rods and possibly the pistons.They are about 5-6 years old, the cam is a year old.crank and rods are eagle 4340 and the pistons are srp forged,cam is from bullet.should i repace the pistons,crank and rods or can I still use them.cam has about 20 runs on it the rest about 100 or so maybe less.

_________________
JEFF WINTERS
1986 SS MONTE CARLO
406 SBC
BEST TIME TO DATE 9.99 1/4 MILE @132MPH.


Top 
 Profile  
 
 Post Posted: Tue Jul 31, 2012 4:46 pm 
Offline
Site Admin
User avatar

Joined: Tue Apr 18, 2006 6:38 am
Posts: 11804
Location: Coming At Ya!
Yeah I kinda expected that block was toast!

Jeff engines run every day on "used" parts! If you're a man of means, ie, got plenty of money, then a complete new bullet would be in order. But, if you're like the rest of us and can't afford all new stuff, then used (servicable) parts are good. I'd have the pistons checked to see how much they've worn and reuse them if possible. Since the block will have to be bored, the machinist can make the bores whatever they need to be for those pistons.

One thing though is that once you buy a Dart (or other) block for the 400 main bearing size then you're married to it. Having said that, I'd look for a buyer for the crank you have and just get a new one with the 350 main size instead and order a block to fit that. That way it gives you a larger market should you decide to sell it.

_________________
Big Boyz Toyz!

Image

Necessity is the plea for every infringement of human freedom. It is the argument of tyrants; it is the creed of slaves.

William Pitt, British Prime-Minister (1759-1806)


Top 
 Profile  
 
 Post Posted: Tue Jul 31, 2012 5:43 pm 
Offline
User avatar

Joined: Sat Oct 21, 2006 11:41 pm
Posts: 768
Location: Morrison, Co
The engine in my dragster is mostly used parts!!! Block, heads, crank, rods, cam, gear drive, dist, carb, oil pan, oil pump, lifters, rocker arms.............

Only new stuff I got was pistons and rings (had too, didn't have any), bearings, gaskets, intake, rod bolts, head and main studs, and pushrods! I've checked everything several times and make it a habit to check them on a regular basis (especially lifters), and no problems at all! As long as they are in good condition and pass inspection, no reason not too!

I recommend this though, mag the crank and rods to check for cracks. New rod bolts, I never skimp here. Recon the rods when you put in the new bolts, as the big end will likely distort differently when you change them, although I've known of people that didn't and never had any issues.

As far as the crank is concerned, Ken is right, you're married to the block if you get the one with the bigger main size, and running the 350 journal size crank would allow you more options.

_________________
Mark Goulette
Owner/driver, Livin' the Dream Racing Dragster
Speed Kills, But It's Better Than Going Slow!!!
http://www.livinthedreamracing.com


Top 
 Profile  
 
 Post Posted: Tue Jul 31, 2012 11:34 pm 
Offline
Moderator
User avatar

Joined: Tue Apr 18, 2006 3:20 pm
Posts: 1457
Location: Missouri
I'm with Ken on this. Use whatever parts are still good. Ditch the 400 main crank. Even if you can afford new parts for the rebuild you don't NEED to spend that money. I've reused plenty of parts.

Rick


Top 
 Profile  
 
 Post Posted: Wed Aug 01, 2012 5:16 am 
Offline

Joined: Fri Sep 23, 2011 1:23 pm
Posts: 80
Question:Im' not understanding goin to a smaller crank 350 vs 400,can someone explain the logic to that?I've seen that difference when looking at blocks but dont understand it.
Jeff

_________________
JEFF WINTERS
1986 SS MONTE CARLO
406 SBC
BEST TIME TO DATE 9.99 1/4 MILE @132MPH.


Top 
 Profile  
 
 Post Posted: Wed Aug 01, 2012 7:41 am 
Offline
Site Admin
User avatar

Joined: Tue Apr 18, 2006 6:38 am
Posts: 11804
Location: Coming At Ya!
JEFF69Z28 wrote:
Question:Im' not understanding goin to a smaller crank 350 vs 400,can someone explain the logic to that?I've seen that difference when looking at blocks but dont understand it.
Jeff


Jeff 350 SBC main bearing size cranks are available in stroke lengths up to 4" (and maybe longer on special order) so there's really no advantage to the larger main size.

The larger 400 main journal size was sort of a "bastard child" that GM came up with for their 3.75 stroke cast nodular cranks, which I believe was a strength issue, ie, to maintain a certain amount of crankpin overlap. Those 400 bearing size blocks and cranks are still made by the performance parts industry but are not usually preferred parts for a performance build. I do believe that you'll see them phased out in coming years since the stock GM 400 blocks are getting harder to find and have been proven to be junk as well.

So if you buy a Dart block with a 400 SBC main size, then you'll have a limited market should you decided to sell it.

_________________
Big Boyz Toyz!

Image

Necessity is the plea for every infringement of human freedom. It is the argument of tyrants; it is the creed of slaves.

William Pitt, British Prime-Minister (1759-1806)


Top 
 Profile  
 
 Post Posted: Wed Aug 01, 2012 10:23 am 
Offline
Moderator
User avatar

Joined: Tue Apr 18, 2006 3:20 pm
Posts: 1457
Location: Missouri
Ken0069 wrote:
JEFF69Z28 wrote:
Question:Im' not understanding goin to a smaller crank 350 vs 400,can someone explain the logic to that?I've seen that difference when looking at blocks but dont understand it.
Jeff

So if you buy a Dart block with a 400 SBC main size, then you'll have a limited market should you decided to sell it.

As well as a limited number of cranks in the future to use in the block if you plan to keep it. When you have a good block you may keep it and use it many times down the road. You may want an engine that has a shorter stroke than can be bought with a 400 main size.

The 350 main size is not a problem for strength and opens up many more options for cranks. There is a little power there in the reduced bearing speed of the 350 journal size also. I would not even consider buying a new aftermarket block with a 400 main.

Rick


Top 
 Profile  
 
 Post Posted: Wed Aug 01, 2012 1:03 pm 
Offline

Joined: Fri Sep 23, 2011 1:23 pm
Posts: 80
Now I understand,Thanks for the info.I will be buying a sbc dart block with the 350 journal size.
Jeff

_________________
JEFF WINTERS
1986 SS MONTE CARLO
406 SBC
BEST TIME TO DATE 9.99 1/4 MILE @132MPH.


Top 
 Profile  
 
 Post Posted: Sat Aug 04, 2012 10:54 am 
Offline
User avatar

Joined: Sun Sep 17, 2006 9:52 am
Posts: 402
Location: southern,ohio
i quizzed Callies about using a 350 main when i bought my new crankshaft and they said below 7500 rpm it would be a wash,and with a 400 block you can use either main journal size with an inexpensive set of bearing spacers....just my .02


Top 
 Profile  
 
 Post Posted: Sat Aug 04, 2012 12:01 pm 
Offline
User avatar

Joined: Sun Sep 17, 2006 9:52 am
Posts: 402
Location: southern,ohio
sorry for the double post but this got me thinking so i went to the shop and checked the main size on a new ls-1 crankshaft,it is almost exactly in between the 350 and 400 sizes at 2.559....so that is plus .109 over a 350 main and .091 under a 400.....i just thought that was interesting


Top 
 Profile  
 
Display posts from previous:  Sort by  
 
Post new topic Reply to topic  [ 10 posts ] 

Board index » Racing Forum » Engine & Cylinder Head Tech


Who is online

Users browsing this forum: No registered users and 1 guest

 
 

 
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to: