My engine was just rebuilt with Edelbrock RPM Performer heads and a Comp XE268H cam in a 327, I am probably in the 10:1 to 10.5:1 comp range per edelbrock tech service. Anyway I am geeting some surge at cruising speed and a little bit of stumbling on takeoff. I have been running a mix of VP fuel (I think its 103 octane ) and 97. Is the surge just some carb tuning or is the surge caused by too much compression and not high enough octane.

TIA

:beers: sounds like timing not advanced enough.or dead spot in carb.

To me it sounds like your lean (lean surge)

Your compression ratio could handle pump gas. I run my 412 SBC 11.38:1 CR on 93 oct, at 37* total timing.
It sounds like you have a carb issue, or a fuel pressure fluctuation or both. Another possibility is sticky advance springs, but I wouldn't expect that to come ina nd out.

What is your timing set at?

To me it sounds like your lean (lean surge)

So this means jetting up ? Its a Holley 650 vac. Sec

also low float setting, clogged filter, etc. What is your fuel pressure?

Your compression ratio could handle pump gas. I run my 412 SBC 11.38:1 CR on 93 oct, at 37* total timing.
It sounds like you have a carb issue, or a fuel pressure fluctuation or both. Another possibility is sticky advance springs, but I wouldn't expect that to come ina nd out.

What is your timing set at?

My engine guy set the timing so Im not sure but I am thinking 36, also as far as the fuel pressure goes I took off my electric pump and put on a Holley mechanical pump when I changed over the heads and cam. The electric was on the car when I got it and I never liked electric fuel pumps , I dont have a fuel pressure gage so I dont know what that is.

also low float setting, clogged filter, etc. What is your fuel pressure?


I havent messed with the float level, it was fine before the change over, I did put on a new filter.

Did the problem start when you changed to the mechanical fuel pump?

From my experience, if your running a Standard Tranny, run Mechanical Advance Distributor - sure saves a lot of problems.

Did the problem start when you changed to the mechanical fuel pump?

The heads, cam and fuel pump were all changed at the same thime.

I vote carb tuning. Check float level. Jet it up.

The heads, cam and fuel pump were all changed at the same thime.

If that is also when the problem began, you really need to know if you are maintaining fuel pressure before you do anything else.

You did heads cam and pump at the same time. How about this carb, did it run the engine before, or is it new too?

Carb was on engine before change and worked great.

If you ever suspect you're having detonation problems, take a close look at your plugs. If you magnify the insullator you'll see tiny balls of melted metal stuck to the insullator. A small 25X pencil scope works well.

If you ever suspect you're having detonation problems, take a close look at your plugs. If you magnify the insullator you'll see tiny balls of melted metal stuck to the insullator. A small 25X pencil scope works well.


If I have surge does this normally mean I have detonation also ?

Carb was on engine before change and worked great.

Don't mess with carb until after we figure out the surge at cruising speed. Cruising speed the carb is not in transition, just flowing and mixing. If it mixes well for 5 seconds and then changes, and then goes back to mixing correctly, you either aren't supplying it with fuel, the float is sticking, or there's trash in the bowl.

Check fuel pressure. You are intermittently starving for fuel, on the same engine that was previously fed adequately by the same carb. Heads and cams don't alter flow capabilities intrinsic to the carb. But changing the fuel pump, and not knowing your fuel pressure....

No, surge and detonation are not synonymous, nor are they necessarily interrelated. This doesn't mean that they can't happen at the same time, they just don't have to happen together. A surge is caused by load or power changing and affecting speed. Detonation is the uncontrolled collision of 2 wavefronts in the combustion chamber and it is caused by heat, compression ratio versus fuel volatility, load, air temperature, and advanced ignition timing, engine speed and a few more things.