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So we decieded to pull the original 300 HP stock motor and swaped in a 383 full roller. We could have just purchased a blueprint engine, but I wanted to teach my son how it all goes together and build one. He did all the assembly work, from gapping and filing all the rings to measuring all tolerances. With the headgasket we choose it's right a 10.5:1 this put us north of 475 hp. (hopefully) ? Who really knows.
If you click on the link at the bottom you can view it.
Specs:
ARP main studs
Late model 1989 roller 350 bored .30 over
Eagle rotating assembly with -5cc flat tops, 383 cubic inches
Sportsman II 64cc heads with some pocket porting
Edelbrock Rolling thunder 2204 cam
LS7 roller lifters
Crane old school roller rockers
Edelbrock performer intake port matched to heads
Holley avenger 770 CFM carb
Dougs ceramic coated sidepipes
Last edited by malicatasr; May 14, 2026 at 02:20 PM.
all seems nice.
seems 2204 has a right hefty slice of intake duration (234) and, is ground on a cast iron core (not billet steel).
How thick-wide are pistons' rings ?
FWIW, later GEN 1 sbc roller motors' Right & Left front oil galley plugs have OE holes 0.025" drilled thru centers; aides any air to purge and helps quieten valvetrain upon each startup.
Betting this project pays dividends to both father & son; well into future. I resolved the piston P/N from photo.
silvolite UEM claimer piston, Hypereutectic Casting w/ metric ringpak 1.5, 1.5, 3mm.
Cast Iron crank, EXTERNAL balance both ends: journal radii small enough for OE type inserts.
Eagle SIR 5.7 rods w/ smaller capscrews.
Last edited by Rebelyell; May 17, 2026 at 12:37 PM.
Reason: moinfo
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
I agree, nice to spend some time with your son, he will never forget it. I like the Sportsman II heads, more people sholud use them but don't because the aren't aluminum. I see a small choke point with Performer intake, an Air Gap would have been better. I had a 406ci with the same heads ( they flow 250+cfm), also had the Classic 4779 Holey 750cfm carb, with a Proform main body and a Vic Jr. single plane intake. Also had a COMP Cams XR274R that is an aggressive, street-friendly mechanical roller camshaft.The engine made well over 500HP on an engine dyno, I would have to look it up in my files but I believe it was 550HP which obviously maxed out the head flow.
I believe with some chassis dyno tuning you would be close to what you expected in HP. Good job.
All the side by side testing ive seen done on the dyno shows performer rpm and air gap performance are identical once you cut a divider or use a 1/2" open spacer.... ymmv the flow vary a bit unit per unit due to casting. The airgap does have a an advantage while the engine is still cold or if you stick a bag of ice inder the plenum at the strip.
Last edited by augiedoggy; May 17, 2026 at 02:59 PM.
New engine installed finally
