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Author Topic:   Engine bottom end suggestions...
spray004
Dirt Full Roller

Total posts: 29
posted May 17, 2005 08:46 AM  
Looking to build an engine for the Thundercar Series at the local track. 1/3 mile high bank (18 degree).

I have a 4blt main block I plan to use as well as some GM X rods. I'm undetermined as for the crank so far (Scat, Eagle or GM). My main question is which pistons to use. I have two sets .030 Speed Pro Hypo (new)546 grams and a set of .040 Speed Pro teflon coated forged (used)615 grams. I know that the forged are stronger, but they are heavier. I'm new to the sport so not really looking to spend a lot of money for an engine or not yet at least. The specs for both are pretty weak in regards to compression ratio but i know its not hard to get it up with some machine work.
Below are the rules listed at the track for the class. Thoughts?

B. 362 cubic inch maximum in Ford/Chevy. 374 cubic inch maximum in Mopar.
C. Block must be OEM with .060 Maximum overbore.
D. Flat top pistons in Chevy and Ford and cannot be above deck of block.
E. Crank must be OEM steel or cast with MFG numbers in place.
F. No lightening of crank except for balancing purposes.
G. Rods- any steel (I beam). Must match block and crank being used

Xtreme12x
Dirt Forum Champ
Total posts: 874
posted May 17, 2005 11:54 AM  
I'd stick the .030 pistons on the X rods, use either the GM crank or Scat crank. THe big difference here will be balancing. Have the whole thing balanced, and put some good rings on there and you'll be more than happy with the motor.

spray004
Dirt Full Roller

Total posts: 29
posted May 17, 2005 01:06 PM  
Some good moly rings or will some quality cast rings suffice? Would an 11:1 CR be about the max on the hyperuetetic pistons?

GO 24
Dirt Freak

Total posts: 366
posted May 17, 2005 02:07 PM  
I'd go .030 and use the speed pro's on the GM x-rods. I know alot of guys will disagree but I'd stay away from the Scat crank unless you have to go with a real cheap one due to claim rules....for reliability GM & Eagle both make pretty decent cranks.
I dunno, there's alot of Scat 9000's out there in the claimer motors & you see alot of them being run over on the track.
Balance the whole thing!
I didn't see anything about head rules but 11-1 should be plenty with flat tops. Something like the Total Seal Moly "claimer" rings would be a good choice.

spray004
Dirt Full Roller

Total posts: 29
posted May 17, 2005 02:15 PM  
quote:
Originally posted by GO 24:
I'd go .030 and use the speed pro's on the GM x-rods. I know alot of guys will disagree but I'd stay away from the Scat crank unless you have to go with a real cheap one due to claim rules....for reliability GM & Eagle both make pretty decent cranks.
I dunno, there's alot of Scat 9000's out there in the claimer motors & you see alot of them being run over on the track.
Balance the whole thing!
I didn't see anything about head rules but 11-1 should be plenty with flat tops. Something like the Total Seal Moly "claimer" rings would be a good choice.

There are no claims, just protests.

Here are the rules for the heads
A. Must be steel OEM Chevy Bowtie, Dart, or World Product. Ford Sportsman, World Product, or Dart cast iron heads allowed a maximum valve
size of 2.05 intake/ 1.60 exhaust.
B. No titanium valves. Stainless steel permitted.
C. No titanium retainers allowed.
D. No porting or polishing allowed.
E. Roller rocker arms are permitted.
F. Flat tappet cams only.
G. Guide plates and screw in studs ok.

GO 24
Dirt Freak

Total posts: 366
posted May 18, 2005 12:21 PM  
In that case I'd use a good crank...probably an Eagle ESP 4130 or if the budget allows, the 4340. I think the best crank on the market for the price is the Callies Dragon Slayer plus it's American made! I wouldn't be scared of a GM 10/10 crank as well for the money.
What carb are you allowed to run?
Solid cams fine.
I would run the Dart Iron Eagle heads, probably 64cc, USE screw in studs & the roller rockers.
Not sure where your from but JR Motorsports has alot of what your looking for & could give good advise on cam selection etc... www.jrmotorsports.com

spray004
Dirt Full Roller

Total posts: 29
posted May 18, 2005 02:23 PM  
quote:
Originally posted by GO 24:
In that case I'd use a good crank...probably an Eagle ESP 4130 or if the budget allows, the 4340. I think the best crank on the market for the price is the Callies Dragon Slayer plus it's American made! I wouldn't be scared of a GM 10/10 crank as well for the money.
What carb are you allowed to run?
Solid cams fine.
I would run the Dart Iron Eagle heads, probably 64cc, USE screw in studs & the roller rockers.
Not sure where your from but JR Motorsports has alot of what your looking for & could give good advise on cam selection etc... www.jrmotorsports.com


An Eagle ESP or Callies has OEM MFG #'s on it? I am familiar with JR Motorsports, I have their catalog,along with about 3 other racing supply companies. I'd def run a set of Dart Heads (budget allowing). You can get a new set of heads with better perf #'s for cheaper than you can upgrade factory heads.

GO 24
Dirt Freak

Total posts: 366
posted May 19, 2005 01:52 PM  
Absolutely! We have to run Bowties on our limited late model engine & their awful expensive for no more than you get out of them. NO oem numbers on those cranks at least that I know of.

GO 24
Dirt Freak

Total posts: 366
posted May 19, 2005 02:04 PM  
I just reread your 1st post & didn't realize that those numbers had to be stamped on the cranks..sorry about that. I'd go with an aftermarket GM crank, 1053 I think is the number or a good "seasoned" 10/10 from a reputable machinist.
Ron @ www.gustafengines.com does a good job right off the top of my head, www.schwankeshortblocks.com is another.

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted May 19, 2005 02:16 PM  
If your crank has to have oem cast numbers on it then your pretty much stuck with stock crank. In that case look for a stock steel crank, should be plenty strong for your engine, and even a good cast core balanced well would be good to.

The x rods with good bolts would be fine. Otherwise you could get a decent set of SCat i beam rods for less than 250 i am sure.

Pistons its kind of a toss up, the forged are stonger yet heavier, wheras the hypers arent as strong. if your not planning on really wingin this thing either one would be fine, the hypers might be easier on the rods though since they are lighter. I know guys turning the hyper pistons close 7000 regularly and havnt had any trouble with them, That is prob about the limit though, at least to me. Best would prob be a set of SRP or JE forged flat tops, light weight and strong at the same time. If you have some that are only 2 valve releif they will have a higer compression than 4 releif pistons I would go with them.

Definetly use moly rings, even if they arent file fit rings the moly is definetly the way to go. Will hold up better longer.

If there is no compression rule I would look into the DArt 49cc heads, that would help get your compression up. Otherwise a good set of iron eagles would be my next choice. I think it would be hard to get 11:1 compression with standard flat top pistons and 64cc heads. More compression means more power, so anything you can do there will help.

If there is no claim and you dont have to worry about losing it then you could spend a littl emore on some of it if you wanted. It might be overkill but you wouldnt have to worry about failure as much. If you are limited then be choosier about what you do and if anythign put a little more into the bottom end now and upgrade the top end as you can. That way you have a good base to start with.

spray004
Dirt Full Roller

Total posts: 29
posted May 19, 2005 05:23 PM  
With a 49CC head I can get around 13:1 compression at most (zero deck), which I think will be too much for hypo pistons.

Elmo
Dirt Forum Racer

Total posts: 79
posted May 19, 2005 10:54 PM  
If the forged pistons mic out ok, build with them, use scat cap screw rods and get it balanced using a good cast crank, or forged chevy if it's available. my opinion, if you balance it you'll never notice the difference in rotating weight. Also the forged pistons are much more forgiving.

spray004
Dirt Full Roller

Total posts: 29
posted May 20, 2005 06:42 AM  
The GM X-Rods are reconditioned w/ new Pioneer bolts. Only have $80 in them so pretty good deal I think. I'd like to find a GM steel crank for cheap. I've been searching Ebay and being patient to look for any deals. I found one steel crank but its already been turned .040 so I'm a little leary of it.

tin cup
Dirt Full Roller

Total posts: 40
posted June 11, 2005 01:52 PM  
Dump the X-rods, they are junk. My engine builder cut's them up and tosses them. The only thing that's make's them X's lite weight, is that they are thin. If your buying high dollar piston's and crank, spend a little more for a set of good rod's. Eagle I beam's are better and stronger than X's. Remember, you get what you pay for and rod's take the abuse more than anything else.

    

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