Hi guys! My dad bought me a 1990 Vette because I always wanted to restore a car. Now I read the 800 some odd page book almost down to each word, so I think I know most of the car. This baby needed alot of body work (clear coat was screwed up, along with a lot of other things) a hard cleaning of the interior, and a new motor. I yanked the old L98 out (my dad's a mechanic and its nice to have a lift) in about a half a day. Found it wasn't the heads as I and my dad had thought, but rather the piston turned and threw the rod into the block. Here comes the questions:

1.) I bought a Jasper short block. The pistons, I found out, are H423NP .040. I assume this means .040 overbore. But the problem is the stock motor has flat top pistons. This motor from Jasper has dished pistons. I'm worried about compression. The tech guy told me they mill the deck surface for imperfections and then put in the disked pistons to maintain the OEM compression ratio. Wouldn't the piston come above the deck surface and hit the head in that case? Jasper usually never screwed us over, but now they're thowing out alot of crap. Would the compression ratio be the same?

2.) I want to install a 160-180 degree t-stat. How would I go about changing the temperature engagement on the fan controls?

3.)How strong are hypereutectic pistons. I thought they weren' supposed to be strong? I have the 4 bolt main. I am going to put new heads/intake/cam on it down the road, and want to get around 400 hp but want to make sure those pistons will handle it.

4.) Any cheap (under 200 dollars right now (this car is depleting my bank account)) mods? I have the cut filter, K&N air filter, TB bypass, and am going to do the 160-180 t-stat mods. What other cheap upgrades do you guys recommend for now? It came with Flowmasters, so I don't want to do any exhaust work.

5.) Any advice on nose bras?

Thanks for the help guys!

 

You can buy a relay from Ecklers or MAD to control this. BTW welcome to the forum! :cheers:

 

Congrats on your new Vette and welcome to the Forum.

1) Turn over the motor and measure the distance between top of a piston and deck; I believe it's something like .020" and you will have .030"-.040" of compressed head gasket thickness. Remember that reducing this quench volume raises CR and decreases octane sensitivity.

My '88 has dished top pistons and about 9.5:1 CR; your '90 came with flat top pistons that gave a 5chp gain over my '88.

2) Since the engine is out this job is easy. Remove the square plug in the block below #1 & #3 spark plugs and install a 160deg aux fan switch. Then simply connect this switch to the grn/wht wire at each fan relay.

3) I think those pistons will handle 400chp NA, but don't try juice of forced induction.

4) Remove the "frisbee" (explanation on my site, link in sig. below) from the water pump pulley for 10chp. Install cut-back AC Delco spark plugs for 8-10chp gain, details on my site. Either replace the front Y with a mandrel-bent unit or gut those two pre-cats, unless you plan on doing FL headers. Meanwhile, port those stock shortie headers. Advance base timing till just below ping, maybe around 8-10deg BTDC. Since the stock #113 casting heads are off, have them pocket proted with larger valves, etc; you can wait till later to do the valve train unless you are going to take advantage of the block being out to do a nice cam now.

5) No advice on bras... :bb...nah, let it ride.

Though it seems like a money pit now, this is a great opportunity to take some time and do the internals (cam & heads) before the motor goes back in. Check out results of L98 mods data on my site to see what these two mods will do for your Vette.

 

Would you recommend removing the frisbee from a 90 as well?

 

While your at it maybe someone here can tell you if flipping the pistons would work. I don't know about small block chevys but on BB mopars an old trick was to reverse the pistons on the rod. Seems that chrysler had a certain amount of offset in the pin location to reduce slapping while the engine was cold. You could reverse (i.e. put them on backwards) the pistons and pickup a free 20+HP due to eliminating the friction losses.

 

OK, thnaks for the replies guys! I don't think I'm going to d any port work, as my parents don't want me to. I will remove the 'frisbee' and do the cut back plugs. I also dn't knowabout the pre-cats. I don't think my parents want me to do any exhaust work since it already has a cat-back system.

 

Maybe you can sell them on the idea of a 2 1/2" mandrel-bent front Y as it also increases gas mileage. ;)

 

I wish, maybe I could. But I also drive a 1997 Ford Explorer, so I don't think they would think I cared all that much.

The reason I am asking about nose bras is because on the front of the hood there is like a 5 inch run spot where the guy must have spilled acid or some on it. It's actually eaten into the fiberglass, and I want t cover it up.