383 Rotating assembly question
Thread Starter
Drifting
Joined: Aug 2009
Posts: 1,635
Likes: 8
From: Enid Oklahoma
When I started reading the thread, I was questioning your running with flat-top pistons without even considering the top end. Oversize valves or a large cam could lead to your wanting a little more clearance. Easy to accomodate now...tougher to accomodate after you've made the investment.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
You could get by with I beams no problem unless youre stuck on the heavier rod
5140 cast crank
Youll need smaller than 70cc to get 10:1
I think the avg FT piston with 3cc(??) relief with 64cc and .005 in the hole might get you 10, 10.3 depending on head gasket. Off top of my head figures so they wont be exactly accurate but in the ballpark
5140 cast crank
Youll need smaller than 70cc to get 10:1
I think the avg FT piston with 3cc(??) relief with 64cc and .005 in the hole might get you 10, 10.3 depending on head gasket. Off top of my head figures so they wont be exactly accurate but in the ballpark
Thread Starter
Drifting
Joined: Aug 2009
Posts: 1,635
Likes: 8
From: Enid Oklahoma
One of the Scat balanced kits is the best buy if you're going with a cast crank. IMHO, a cast crank -> hypereutectic pistons; I don't see the value in forged pistons with a cast crank - if you need forged pistons from a power-adder or HP perspective...then you need a forged crank. It can also make balancing interesting, as the bobweight is a fair bit different. Avoid Eagle cast cranks, period.
As for design, it all has to work together - so just start fitting together all aspects of the design...just don't BUY anything until the design is DONE.
I sometimes end up with guys having expen$ive "leftover" stuff because they get excited and buy parts before the design is frozen...even when I tell them specifically and with emphasis not to. It's a sure way to end up spending more $$$.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
The short answer, and I'm sure there will be many perspectives, is that you're looking for the smallest intake runner size that will deliver the flow needed to hit your power targets. This is where the quality of a head will really show - AFR for example will deliver more flow from a 180cc runner than other companies can make with 220cc runner. Port cross-section has a major impact on low- to mid-range throttle response - so you do get what you pay for.
Happy to share more detail via PM, but I don't enter into the huge pizzing matches on this stuff in the public forum any more
Drifting
Joined: Mar 2009
Posts: 1,253
Likes: 4
From: East Wenatchee (2hours from n e where) WA
Looks good; An aluminum head will help at the track, 40# of hight nose weight is significant. For a little more comin out of the turns you may ask Comp about grinding you a 268 on 108 lca vs the 110 it will improve mid tork but cost a little vacume and top end. +5hp early in the straight will beat +40hp at the end every time.
Burning Brakes
Joined: Sep 2012
Posts: 818
Likes: 0
From: coon rapids mn
aluminum heads allow you to run a higher static compression.the runner sized you want is some what determined by engine size and where you want to make the power.the smallest runner will great low end power but limit all out HP with your 383.the 220 runner I feel is best suited for street and strip .the biggest 235 runner would be nice for big cubes and high rpm HP.have you considered a 3.875 crank ?
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
Good info on port sizing.
http://forums.corvetteforum.com/c3-t...ce-builds.html
http://www.dartheads.com/tech-articles/port-volumes/
http://forums.corvetteforum.com/c3-t...ce-builds.html
http://www.dartheads.com/tech-articles/port-volumes/
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
As for port sizing the huge increase at low RPM with a small (180) port is overblown. Look at the back to back dyno testing in the Dart article above. It is back to back testing on a similar 383 to the one your planning. AFR 195 is the best head for your application. If not AFR 195 look at a different 195-200 port size. A lot of the drop off in low RPM and throttle response noted with large port heads can be attributed to the lack of available dual plane intakes with the large intake port. With the recent increase in building large CI SBC engines (427-434) requiring a larger port head the need for a Dual plane with 215-245 cc port sizes will soon move intake manufacturers to designing new intakes geared toward that market.
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Drifting
Joined: Mar 2009
Posts: 1,253
Likes: 4
From: East Wenatchee (2hours from n e where) WA
Good info on port sizing.
http://forums.corvetteforum.com/c3-t...ce-builds.html
http://www.dartheads.com/tech-articles/port-volumes/
http://forums.corvetteforum.com/c3-t...ce-builds.html
http://www.dartheads.com/tech-articles/port-volumes/
Le Mans Master
Joined: May 2008
Posts: 9,063
Likes: 2,736
2022 C3 of the Year Finalist - Modified
compression
What I have so far(on paper)....12CC Dished pistons, 70CC heads with a .015 gasket(fel pro 10094 steel embossed gasket) and a .020 deck, thats keeps me from needing the block decked. I will need to use 6 inch rods and short skirt pistons. But that should get me at 9.78:1( I wanted it a tad lower than my initial after more research and how I want to drive it)
And using a Comp cams 268H Cam I can get by with my stock rear end for now and stock converter, but I plan a new converter while the engine is out, may go 2200 stall. And eventually a new rear gear, but I can recam at that point if I need to. This cam will make the power where I want it and the intake will work well with it.
The heads I am looking at are RHS aluminum 70CC and I will put 202-160 SS valves in them with springs that will handle lift up to .525 lift if I ever decide too in the future. I already have the valves and associated parts. Probably will go with roller tipped rockers. All of that should net about 450 HP if I calculated right, but it should be a fun driver and run easily on pump gas. I will use I beam rods, and a cast stroker clearanced crank internally balanced. Performer RPM Intake, with my recently rebuilt Qjet on top. That with my headers and 2.5 true duals I already have should flow well and run good. If anyone sees an issue with this setup please let me know. Thanks!
And using a Comp cams 268H Cam I can get by with my stock rear end for now and stock converter, but I plan a new converter while the engine is out, may go 2200 stall. And eventually a new rear gear, but I can recam at that point if I need to. This cam will make the power where I want it and the intake will work well with it.
The heads I am looking at are RHS aluminum 70CC and I will put 202-160 SS valves in them with springs that will handle lift up to .525 lift if I ever decide too in the future. I already have the valves and associated parts. Probably will go with roller tipped rockers. All of that should net about 450 HP if I calculated right, but it should be a fun driver and run easily on pump gas. I will use I beam rods, and a cast stroker clearanced crank internally balanced. Performer RPM Intake, with my recently rebuilt Qjet on top. That with my headers and 2.5 true duals I already have should flow well and run good. If anyone sees an issue with this setup please let me know. Thanks!
