Fred's 2375 Rebuild Thread Options

[friethmiller]

[A softball question for the Ninja and/or others]

This is the cam card that came with my 2357 engine, which was originally built by Rimco/Fat (long block) a few years ago. Can someone explain why with an intake/exhaust of 448, the lift was only set to 327 degrees? I'm about to rebuild my motor and a lot of focus will be directed at piston "deck clearance" and the valve train geometry that wasn't set correctly. Thanks.

[VaccaRabite]

I've got some opinions here.

Remember that this is an aircooled engine, and compression = heat.
9.7:1 - 10:1 is going to be REALLY hard to keep cool, even with coatings. This is water cooled compression land, and that's a totally different ballgame. To run that kind of compression, you are going to need to spend money for the Nikkis pistons and cylinders, ARP studs, etc. At that point, you will be using only the case, crank and rods and pretty much replacing everything else including your heads.

KB pistons are good pistons. And you can absolutely build an engine using them and rehoning your cast iron cylinders that will easily make 150+ hp, and run cool doing it. But you are going to be looking for compression in the 8.6:1 - 9:1 range to do that (and 9:1 is going to be pushing it). COATING WILL HELP! Ceramic is damn near magic, and will go a long way to push heat out of your heads and into your exhaust. And the coating itself will give you a slight compression bump.

No matter what you build, you are going to require aux oil cooling to keep oil temps in line and protecting your bearings. With my 2258 I'm learning that the passive extra oil cooling isn't enough and will be adding fan packs to my aux cooler. I'm going to caveat this saying that I believe head temps are mor important then oil temps, and I'm comfortable driving with 250* oil temps in an air cooled engine. I'm not comfortable driving with 375* head temps. On very hot humid days and 4+ hour drives my oil temps were creeping towards where I was uncomfortable (260+) with only passive aux cooling, though my heads were fine.

Cams - I'd look at the LN9520 which is the cam that Jake designed for stroker engines running carbs or modern EFI. I'd note here that they recommend a 9.5:1 CR for this cam - which they get safely through use of Nikkies P&C, purpose built heads, ARP studs etc. The 9520 (IIRC - its been a while) was based on the 86 cam.
The 9530 is the web494 with extra exhaust duration. I have a lot of experience with this cam (and the 494 it was derived from) - and its a gem IMO. It performs WELL even at the more moderate compression required by steel P&C sets.

My advice (for a street/touring car) is ALWAYS to build an engine that favors drivability over peak HP. A wide powerband and a cool running engine are going to be more pleasurable in the long run then a peaky hot running motor that makes 15 more HP.

Zach