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Discussion Starter · #1 ·
So i came across this deal for a thousand bucks. Its from a trust worthy local engine builder. he said before i can take it from the shop he would tear it down with me and go through all the clearances to make sure everything was good. The specs on the pistons are dome, forged aluminum and 4.030 bore. The number under the piston said 400-SL. The connecting rods are aluminum and look like top fuel rods. Very big. The are 6" and the number on the cap was brc62. The crank is a bryant forged steel crank and has a 3" stroke. Can anyone tell me more about these rods and pistons? Thanks
 

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The only reason I might be interested in a 306 cubic inch motor with aluminum rods is if I had to use that displacement to make a racing class where class is determined by car weight divided by cubic inches and it would put me in at the top of the class. And if I planned to tear the motor down periodically to Zyglo the rods.....or toss 'em after a couple hundred passes.....or whatever....

The rods were manufactured by Brooks Racing Components.
 

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Discussion Starter · #3 · (Edited)
I had a feeling the small displacement would be a downfall. And of coarse if i swapped the crank i would have to change pistons so not really worth it in the end i guess. My plan is to build a nitrous motor good for 650hp. This setup is still cheaper then buying new crank rods and pistons. Are these BRC rods any good?
 

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zildjian4life218 said:
Can anyone tell me more about these rods? I have never used aluminum rods before and never heard of Brooks racing components.
Good rods if you had bought them new, but I would NEVER buy an engine with aluminum rods or even a set of aluminum rods without knowing EXACTLY how many racing laps or 1/4 mile passes were on them. They have a definite lifespan, usually 100 passes or 200 at the most before they are changed out because they work harden in use leading to fatigue(blowing up). The Bryant crank is a premium piece, if that and the block seem reasonably priced to you then OK, but the rods would be unusable in anything I put together, they are wall decorations/Ebay pieces/scrap IMO.

Aluminum rods are like hydraulic cam and lifters or gaskets - NEVER buy them used!!
 

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Discussion Starter · #8 ·
Thank you ericnova for the reply. My machinist said the engine had 26 1/4mi runs on it then the guy who was running the motor switched classes and was not allowed to run aluminum rods. It was putting out high 600hp. The way i am looking at it is in order for me to build an engine that will hold that much power will be about $2500 for the short block alone, so if this block gets me through the summer i would be happy. Any other input on this? plans r 200shot of spray, high 600hp, 2800lb truck. I want to be in the low 10second range(cage is only good to 9.99 i believe).
 

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I would definitely take the deal if I was looking now that you know the history. Brooks is a quality rod, known more to hardcore racers than the public. The Bryant crank alone was nearly twice the price of the whole deal when new and pretty much the best crank you can buy. I would not be afraid to spray 350 hp on it if everything checks out.

This rotating assembly and engine size will make best power near 8800-9000 rpm. Do you have heads and valvetrain good for that?, or just fit what you have and live with what you can get at a lower rpm?? Just curious now.
 

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Discussion Starter · #10 ·
He also told me it was balanced to 10,000rpm. The block is a 4 bolt main 3970010 chevy casting. Do u think i would be safe at 700hp? I cant afford aftermarket heads so im thinking of porting some vortec heads, maybe 1.6 exhaust valve and machining them for higher lift.
 

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zildjian4life218 said:
He also told me it was balanced to 10,000rpm. The block is a 4 bolt main 3970010 chevy casting. Do u think i would be safe at 700hp?
With the short stroke, ...probably, likely, yes. There is just always that chance of failure due to the fact it is a factory block, nothing you can do about that. For the price, I wouldn't even be worried about it, just run the he11 out of it and if it blows just laugh, wink, smile and move on. :thumbup:
 

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zildjian4life218 said:
He also told me it was balanced to 10,000rpm. The block is a 4 bolt main 3970010 chevy casting. Do u think i would be safe at 700hp? I cant afford aftermarket heads so im thinking of porting some vortec heads, maybe 1.6 exhaust valve and machining them for higher lift.
You added the Vortec head after I posted, it won't even come close to being enough head and cost you more to get into shape than just using a Sportsman or RHS vortec casting and equipping it with good valves and springs. If you aren't thinking solid lifter at a minimum and better yet solid roller you are just wasting your time, anything hydraulic will be bitter disappointment. You are going to need 5000 stall mimimum and 4.88 or deeper gears for this engine to shine.
 

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zildjian4life218 said:
Can anyone tell me more about the pistons. I would like to know the specs on them like compression distance, and dome cc.
Just like every other part of life, if you want to know the correct answer, do it yourself.

Compression height can be measured with a dial caliper. Hook one tip of the caliper into the top of the wrist pin bore and the other tip onto the crown. Write down the measurement. Add the radius of the wrist pin bore (0.464" on a stock pin diameter SBC).

To find the dome displacement, first, get a cc kit like this....
http://www.summitracing.com/parts/SUM-911581/
While others may recommend a drug store flask or some other second-class, fosdick arrangement, this is the way to get a first-class measuring kit that will become part of your tool assortment and used with confidence for years to come. To recoup the cost of the tool, offer to cc heads for other racers or amateur builders. $35 for a set of V8 heads and the tool is paid for after doing 3 sets. $20 for a 4-banger head, $28 for a 6-banger.

With the motor sitting oil pan-down, choose any cylinder and turn the crank so that the highest part of the piston dome is just below the deck surface (like maybe 1/16"). Using the slide function of your dial caliper, measure from the deck to the main part of the piston crown right next to the bore, not on any part of the dome. Write it down. Just for example, let's say it is 0.371".
Use a heavy grease such as Vaseline to seal the perimeter of the piston crown to the cylinder bore, so that none of the liquid you are going to pour into the bore can get past the piston/bore interface all the way around the piston.
Alcohol will be "wetter" than water for this operation, so go to the grocery store and buy a quart of rubbing alcohol (doesn't matter if isopropyl or ethanol) and a small bottle of food coloring. Red, green, blue, doesn't matter, this is just to make it easier to see the fluid level in the burette. Pour a little of the coloring at a time into the quart of alcohol until you get an easy to see color saturation.
Grease the perimeter of the cylinder bore with Vaseline to seal your clear plastic to the bore. Position the feed/vent hole in the plastic at the very top of the bore, right next to the edge. If the plastic isn't drilled for a feed/vent, drill a 3/16" hole close to the edge of it. Leave enough plate between the hole and the edge of the plate so that you can seal the plate to the block deck.
Position the burette so that just the very tip end of the spout sticks into the hole, not enough to block the hole entirely, because this is also a vent hole, but enough so that the fluid will travel into the void you are measuring and not flow out onto the outside of the plate. Depending on the O.D. of the spout on the burette, you may have to make the feed/vent hole a little bigger, but I have never had to with a good quality burette.
Using a small funnel, fill the burette to the fill line with the colored alcohol. Turn the spigot and begin filling the void. Depending on the height of the dome, you should be able to fill the void on one filling, without having to stop at zero and re-fill the burette.
Now for the math:
Let's say that you positioned the piston down in the bore by the previously mentioned 0.371". If the piston had no dome at all and no valve notches, with the volume above the piston crown looking more or less like a hockey puck, then the volume above the flat crown to the block deck would be 77.548cc's. (.7854 x 4.03 x 4.03 x .371 x 16.387 = 77.548cc's).
Let's further say that you used 49.6 cc's to fill the void. Subtracting 49.6 from 77.548 would reveal a dome displacement of 27.948 cc's.
There, see how easy this stuff is? You just go through the steps and there's the correct answer!! You know it's correct because you did it yourself without relying on possibly bogus information from some fosdick guy like me. :thumbup:

Now, going further to figure the static compression ratio:
First, you want to cc all the chambers in the heads. Position a head on the bench with one edge slightly higher than the other so that your fill port in the plate will be the highest point. Seal the valve perimeters and spark plug threads with Vaseline. Pour as instructed above, with your plate sealed to the perimeter of the chamber with Vaseline.

Punching a number on the end of each head and detailing the volumes on a sheet of paper will provide you with good information for later. For instance, if you punched "1" on the end of one head and "2" on the end of the other head, then you could list the chamber volumes a 1/64.3/64.0/63.9/64.2 and the other head as 2/64.1/64.3/64.0/64.2 reading back from the number punched on each head.

We'll say that you determine an average volume would be 64.2. The easiest way is to deduct the dome volume from the chamber volume and go ahead and figure the c.r. from there as per usual. The kicker will be the piston deck height of the main flat part of the piston crown to the block deck. If the piston is down in the bore 0.012" for instance, you can't just figure that as a flat hockey puck type of volume, because the dome sticking up renders that invalid. It would actually look more like an o-ring seal, with the hole representing the dome. You can guestimate this volume by determining the average width of the ring around the dome or you can disregard it altogether if the piston deck is small enough. Let's say that taken on average, the width of this ring is 0.500". That would make it 4.03" on the O.D. and 3.53" on the I.D. If the piston deck is 0.012", then this would calculate to 0.58cc's. Call it a half cc or disregard it altogether.

To figure s.c.r. in this motor, we will need the cylinder cc's (627.08), chamber cc's (64.2 average), piston deck cc's (0.5), gasket cc's (8.64 on a 4.100" x 0.040" gasket) and dome volume cc's (27.95).

Deducting the dome volume from the combustion chamber volume, we will eliminate the dome and figure our calculations with a 36.25cc chamber.

627.08 + 36.25 + 0.5 + 8.64 = 672.47cc's filled with the intake valve open.
36.25 + 0.5 + 8.64 = 45.39cc's with the piston at TDC.
Dividing 672.47 by 45.39 = 14.81:1 s.c.r.
 

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Discussion Starter · #17 ·
wow....... thank you so much for the explanation inspector. It makes so much sense. And like you said i know its right, and not just assume i got the correct info from someone else. i will post a picture of the setup when i get it. I sat down and really tried to figure out what i want to do with this motor and i think i might go down the turbo route. I wouldn't consider n/a due to the small displacement and require big buck aftermarket heads. A nitrous build will require a big shot200-300, aftermarket heads, and bottle fill ups. It will be cheaper in the long run because i won't be having to fill nitrous bottles every other week and i already have a garrett turbo with a T6 flange, I believe the AR is coldside-.55 hotside-.84. I know the turbo would do better on a bigger displacement motor but It will just come in later in the rpm range. I should be able to get 2 summers of drag racing out of this short block so i guess i will deal with the small displacement for now. Any criticism?
 

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zildjian4life218 said:
If i ran race gas could i run dome pistons with 64cc heads?
If this is with a turbo you are looking at race gas that will cost you $20+ per gallon along with a Boost Retard timing controller and probably water injection to keep it out of detonation.

If you are looking to just use this short block for a couple of summers Nitrous is your best bet and cheapest option, even over the long run. Turbocharging is never cheap by the time you get everything you need to get it running.

Port the best head you can afford, on a tight budget I'd use the RHS S/R or RHS Vortec or Dart S/R Torquer type as they will already be machined for screw-in studs and bigger springs, get springs matched to the cam you choose and a decent set of valves (I go here for parts- www.competitionproducts.com). Do whatever porting you can do yourself and feel comfortable with, live with what you get, and just spray the pants off of it.
 
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