Blackdog36

iTrader: (3)

I am a ways off from upgrading my engine and drivetrain but had a few questions for planning out my build. I'm going for a repaint first but engine build keeps floating around in my head. Just wondering what your thoughts would be.

I currently have an auto 5.7 with 43,000 miles. I like the idea of making a very strong 350 engine. Car would be mainly a street cruiser with occasional time at 1/8 track. Below are upgrades I am thinking about for engine that would yield around 420 HP at around 5,600-5,800 rpm. I am not sure if my stock bottom end would be able to withstand the increased power. After reviewing a lot online, it seems that stock bottom end should be ok since auto and moderate rpm use. However it appears that upgrading bottom end, especially rod bolts would be a wise decision. If I have to tear down bottom end for ARP bolts, rod resizing and crank balancing, it would make sense to get a 383 storker assembly. I have no objections of going stroker route other than it is going away from my goal of strong 350 build. A couple years down the road I may want to go stroker which at that point I can tear down engine and get a kit.

-stock 350 roller block, 2 bolt main
-reuse stock crank, rods and 7 cc flat top pistons
-FIRST TPI intake
-Comp Cam XFI 268 or similar
-AFR 180 with 65 cc chambers
-upgrade 700r transmission
-most likely will replace rear end with 8.5, Dana S60 or moser

With the above, I have some questions about CR's. Using Pat Kelley's CR calculator, I get static CR of 9.9:1 and dynamic CR of 8.03:1 assuming piston to deck clearance of 0.025" and 0.015" head gasket thickness. Is this CR too low? I thought that you should go up to around 11:1 static while keeing dynamic under 8.5:1 for aluminum heads. Milling heads to 62 cc's increases static to 10.25:1 and dynamic to 8.3:1. This would help CR for 350 build but would probably be too much CR if I wanted to used milled heads for a 383 build. Only other option to raise CR would be to change piston deck clearance or piston relief. Both options would involve tearing down engine for which 383 makes sense.

What do you think?

Blackdog36

iTrader: (3)

bump

bluegrassz

iTrader: (3)

My mods are in my sig and I have a stock bottom end.

bjankuski

Stock bottom end is fine to 6000 RPM.

The compression ratio of 8.0 dynamic is fine. If you mill the heads for a little more those same heads will work fine on a 383 since you can order the correct pistons at that time to give your desired compression ratio.

Blackdog36

iTrader: (3)

Thank you for the responses. I have seen other people here with stock bottom ends on built 350's but was looking for some more feedback. Now I just need to figure out AFR 180 or 195

Bluegrassz, your engine takes quite a bit of power with higher stall and more aggressive cam than I am contemplating. I like to mash the throttle but its hard to get over 4,500 rpm on the street. Stock bottom end will be ok for what i'm planning.

I think that static CR of 10 vs 11 will reduce max power by 16 hp. I will probably have heads milled a few cc's. I may never go 383 but nice to know I could. I haven't had fast cars before and even stock my car feels powerful.

bluegrassz

iTrader: (3)

Ive had no problems with my stock bottom end. I did replace the stock timing chain when I did the cam swap. Im still running the stock oil pump.

I shift out at 6100-6300 rpm, but I have ran it to 6500 without a problem.

We figure my static CR is 10.3-1. We milled my AFR 190's from 64cc to 60cc. This with the .028 head gasket from GM helped raise the compression.
Here is the part number for the gasket: 10105117

Oh yeah, I added ARP head bolts and rocker arm studs.

Blackdog36

iTrader: (3)

Thanks for the info, good to know. ARP head bolts are a good idea too.

I've done some more research on CR and 10:1 seems pretty typical for aluminum heads. Many engine dyno tests use this CR and make good numbers. I found some info that raising CR from 10:1 to 11:1 would theoretically increase power by 2.5% or 10 hp for a 400 hp engine. Not a huge difference as I was thinking. Plus detonation would be lees of problem with lower cr.

I've read that AFR charges $260 for milling heads. Probably just would keep stock port size of 65 cc's and live with 9.9:1 cr. AFR just released vortec style 190 heads that look tempting.

bluegrassz

iTrader: (3)

You can flat mill 0.006 per cc or angle mill 0.008 per cc.
We flat milled mine 0.030, so when we did a buret cc test on them, it added up to 60cc. Watch how much you mill the heads, you can get into intake/head angle sealing problems. We used a thick felpro gasket and everything sealed fine. It was either a 1256 or 1205 gasket.

Oh yeah, I got my heads milled at a local machine shop for around $60 not $260.