I'm about to take my block to the machinist so I'll have to give him all the required clearances. I've done some research and there are a lot of different clearances used.

So, I'd like to hear your opinion on what clearances to look for.
Here is what I'll be using in this short block:
- stock block - 0.020" overbore
- stock crank - micro polished
- SCAT forged 5.7" rods with ARP bolts
- SRP 4032 forged flat top pistons #138084
- Clevite bearings

So what would you recommend for:

1. piston to cyl. wall clearance
2. main bearings clearance
3. rod bearings clearance
4. piston rings clearance

This engine will be used mostly on street but also for some road racing.

Also, while asking, does anybody know at what point on pistons should measures be taken? SRP page says at 0.5" from the bottom of the skirt usually. But what does usually mean. I don't have pistons spec sheet as I bougt them used.

Thanks for any input.

Quote:

Every engine builder likes to run their clearance differently, espc on the rods and mains which correlate directly to the type of oil, oil pan and oil pump they like to run.

1. .0035 - .004
2. .003
3. .002 - .0025
4. Top .018
Second .020-.022

4032 is a very forgiving piston alloy. It is low expansion and a good choice for street cars and part time DP cars. I personally think SRP's recommendations on piston to wall is a bit tight, espc for something that is going to get run on a road course or used in a drift competiton where it's hung on the rev limiter for a while. Thats why I'm recommending and extra .0005 of clearance over what they say.

Keep in mind - this is how I like to set up most of my DP SBC engines. I prefer to run 15W40 oil, I use a good Road Racing 7qt oil pan (Competition Componets or Champ) and lately I've been using the Milodon PN 18750 oil pump which gives me 70psi sustained oil pressure at RPM and 55-60psi idling (both hot).

Quote:

It means you place the mic, to measure for the piston's dia, .500 up from the bottom of the skirt. They have a diagram on the spec sheets - which you can download and print from here:

http://www.jepistons.com/dept/tech/dl/piston_instrc4032.pdf

It is identical to the paperwork they send with the pistons new.
Will

Thank you for a very nice reply. That spec sheet is exactly what I was looking for.

Thanks again.

One more question. Instructions say that spiro locks shouldn't be reused. Is that really so?

Quote:

Yep, probably because they get stretched when they get removed. It's hard to pull them out and not stretch them.
Besides, they are inexpensive.

Spiro locks do normally get screwed up pretty bad when removed. People tend to pick the outer edge of them up and then take needle nose pliers or something smiliar and just pull them out of the pin bore groove. This streches them all out and makes them completely unsuitable for use again.

While I have very careful removed them so I could re-used them occasionally in the past - I won't recommend anyone else follow that practice.

They are pretty inexpensive and most people only remove 1 side when changing pistons/rods (no one wants to fight with them more than they absolutely have to) - so you should only have to buy 8 new ones.
Will

I would really like to get new ones (I need 16 because there are 2 on each side) but problem is that I can't find anything on e-bay and I can't be sure what size to get.
They should be specific for SRP #138084 pistons and I can't find it anywhere on internet sale. And since I live in Croatia it's a problem.

Does anyone know where could I find new spiral locks online?

Competition Products sells them sperately.

http://www.competitionproducts.com/products.asp?dept=560

You can call their tech line and give them the measurements off your old ones so they can sell the right ones. A dial caliper will get you close enough. Their tech line is actually staffed with coherent car persons unlike Summit/Jegs.

http://www.competitionproducts.com/products.asp?dept=560

If you want to buy from the technically inept ones.

http://www.jegs.com/p/JE-Pistons/JE-P ... iro-Locks/753431/10002/-1

http://www.summitracing.com/search/?keyword=spiro%20locks&dds=1

Will

Thanks Will!

I'll try to contact competition products and see if they'll ship Croatia. I tried with JEG's and they ask
$102 for shipping


Thanks again,

Bruno

Just as update. I've bought and allready received new spirolocks.

Bought them at Competition products, as Will suggested.
Nice people to deal with.