Is my 347 cranking cylinder pressure too high

[fasterdamitt]

I have a 347 EFI I just checked compression on and was thinking this may be a little high for 91 octain. What's you opinions?

190-200 psi??

347 stroker
Flat Top SRS
AFR 185's 72cc
XE270HR hyd roller
Mass Flow Efi system

 

[CDQICKGT]

That seems high than I remember the norm to be. What's your compression ratio? With cylinder pressure that high I doubt it will be boost friendly.

 

[fasterdamitt]

C/R is supposed to be 9.3:1 but looks like it may be higher with the cam.

 

[Rick 91GT]

I get about 9.42:1 assuming that the SRS is the -4 cc version. I have run much higher on pump gas, mos I build to 11:1 but I am doing custom cams for ths motors so I can control it somewhat.

Your numbers look fine to me

 

[347HO]

It's possible your valvetrain is too loose.
What have you done on the top-end?

Installing the camshaft retarded will give the same results.

Who built the engine?

 

[fasterdamitt]

I used a DSS Racing 347 block, rotating kit from Coast HP, sent to local shop for balance and piston to bore sizing, then assembled myself. I did set the ring gap on the tighter end of the allowance.
Heads where cleaned up but I cc'd them at 71 cc when done. Not sure what the deck hight was.

 

[347HO]

I used a DSS Racing 347 block, rotating kit from Coast HP, sent to local shop for balance and piston to bore sizing, then assembled myself. I did set the ring gap on the tighter end of the allowance.
Heads where cleaned up but I cc'd them at 71 cc when done. Not sure what the deck hight was.

For the issue you have, all the above information doesn't really apply.

I would not suggest you go with a tighter ring gap than the manufacturer suggests.

Chances are you have too much lash in your valvetrain and even a camshaft installed a few points retarded.

You probablly should triple check your lash and degree your camshaft in with someone who's done it a few times.

 

[fasterdamitt]

The ring end gap is still within Hastings specs. What are you thinking on lifter preload? I have built about 20 engines but I am ready to drop this one off at Walker Racing for a second opinion.

 

[347HO]

The ring end gap is still within Hastings specs. What are you thinking on lifter preload? I have built about 20 engines but I am ready to drop this one off at Walker Racing for a second opinion.

I suggest you check your lifter pre-load. You may find you don't have any.
A loose rocker will not open on time and close too soon... thus increasing your cranking compression.