'88 350 TBI Compression Question

[trukman1]

Can anybody tell me what the compression ratio is for a stock TBI 1988 engine? Wondering, also, if they had dished pistons. I know it's 99% probability they did run dished pistons but I can't find this information anywhere to be sure.

While I'm asking, does anyone know if the stock rollers can be used with an aftermarket camshaft? I know most people don't run used lifters with a new cam, just wondering if it is a bad idea or no big deal.

Thanks for all responses,
trukman1

 

[84 M1008]

The cam and lifters should be replaced as a set.

 

[bucket]

If they are roller lifters, you can reuse them as long as they are in good condition. But they are probably not roller lifters.

Iirc, my '88 TBI 350 that pulled apart has flat tops.

 

[4WDKC]

When I pulled mine tbi apart it only have valve reliefs, but the 76cc heads keep the compression low like 8:1 upgrading to 64cc heads is rumored to make a stock engine 9:1...I know it sure made my engine sound alot stronger when I swapped the vortecs on it. Dont have it tuned yet to know for sure.

 

[trukman1]

Well, darn! I was hoping they were rollers! Oh well, makes the decision to replace them easier. This part of the project is still a long way off so I just thought I'd start planning now.
Found a post on another forum that says compression ratio is 9.3...just ran across it by accident. Also ran across an episode of Engine Masters doing a Vortec head swap and they said that raised compression to just over 10:1. With a good cam that should wake up the pathetic power of the current engine. Thanks!

 

[4WDKC]

Well, darn! I was hoping they were rollers! Oh well, makes the decision to replace them easier. This part of the project is still a long way off so I just thought I'd start planning now.
Found a post on another forum that says compression ratio is 9.3...just ran across it by accident. Also ran across an episode of Engine Masters doing a Vortec head swap and they said that raised compression to just over 10:1. With a good cam that should wake up the pathetic power of the current engine. Thanks!

here is what pace says about their crate engien with 64cc heads
DESCRIPTION
For 1987-1995 Chevy/GMC trucks with 350 vin code "K" engine up to 7200 GVRW
Specs on this engine are as follows:

• 1986 and up 2 bolt main 1 piece crankshaft seal block(no mechanical fuel pump provision)
• Nodular iron crankshaft
• Powdered metal connection rods
• Dished hypereutectic pistons
• 9.25:1 Compression ratio
• High volume oil pump
• Morse link type timing chain

Camshaft specs as follows:

• Flat tappet hydraulic camshaft
  • Intake lift .382"
  • Exhaust lift .402"
  • Intake duration @.050-165.9
  • Exhaust duration @.050-174.8
  • Lobe center separation - 111.9
• Camshaft mechanical specs
  • Intake valve opens @ -30.2 BTDC * Intake valve closes @ 16.1ATDC * Intake lobe centerline - 111.8
  • Exhaust valve opens @ 18.1BBDC * Exhaust valve closes @ -23.3 ATDC * Exhaust lobe centerline - 111.8

Cylinder Head Specs:

• Casting number 14102193
• Swirl port intake port design
• 64cc Combustion chamber
• 1.94" Intake valve 1.50" Exhaust valve
• Valve spring part number is 3911068 (same spring used with the old 300hp 350 crate engine)
• Installed height 1.70" Pressure @ Installed height is 80 LBS * Pressure with valve open is 267 lbs.
• These springs are good for .550" lift but clearance between guide and retainer must be double checked before attempting.
• 7 Bolt exhaust flange
• Center bolt valve cover flange
• 1987-1995 Intake manifold bolt pattern with center intake bolts canted @ 72 angle

 

[4WDKC]

when you take those duration numbers and look them up here, you see why those engines were so down on power.. 350/8 is 43.75 CID per cyl.

You must be registered for see images attach

 

[trukman1]

4WDKC, Thanks for the information!