Thread: gas and valve questions 327/ 350 HP

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I've torn down my 327/ 350 HP out of my 68 vette. Ran poorly before teardown. Engine has 109,000 miles.

First question is regading the valves. There is no evidence of valve stem seals. Engine was smoking and burning oil. Did someone leave them out when a valve job was done, or could they have disintegrated? Only have a small O ring seal on valve stem near top of valve.

Second question regards running pump gas. Had been running premium plus Octane booster plus lead substitue. Last tank last fall contained ethanol.

I'm replacing rings and bearings along with new valves, seats and cam.

Anybody have recommendations for what Gas is available for 11:1 compression engine?

Thanks for your help

Or get the Victor umbrella seals made for Napa. Designed to fit inside the small spring. The o-ring was only to control oil drip from the tip of the rocker and keep it from flowing down the stem and into the guide

Thanks for the help.

Do you have a comment on the question about recommendations for gas for this engine?

93 oct or higher. Additives are across the board pretty equal. Cleaning agents are the biggest difference in these products.There will be a political storm now that I've stated that. Don't pull back on fuel ratios Carburation specs) to save gas. It creates havoc with pre detonation and unstable combustion. If you wish to get a jug of av gas or race fuel mix it in to your gas with small amounts. Maybe 5:1 ratio (5 gas :1 race). You mind it is a bit much to start but as you play you'll find your solution.

I ran a 400 hp 350 on the street in the 80's with 11.5:1 CR. Ran unleaded premium. At first it pinged a little, then I indexed the spark plugs so that the gap pointed up between or towards the intake valve, and the pinging stopped completely. I ran a Mallory Unilite back then with a 40 kV coil; point being you'll want a good spark ignition IMO.

An alternative to race gas is a water injector. I did the race gas bit with my 68 427 Vette running 11.7:1 CR. IMO this would be less of a PITA.

You might consider some aftermarket aluminum heads as well.

Regards, Kitz

The real fix for a high compression motor on pump gas would be minimizing the squish at 0.035" to 0.045" with a large flat area on the piston to mate up with the flat portion of the underside of the head ajacent to the chamber and maybe Singh grooves in addition.

Short of re-engineering the motor, I would have to agree with Kitz about the water injection. I've used it before and it works well to eliminate detonation. Here are a couple of links to explore:
http://www.snowperformance.net/
http://www.coolingmist.com/
http://www.aquamist.co.uk/

I have been using 89 octane in a 350 with 11:1 forged pistons, 041-64cc heads,
after market HEI distributer and a Crane Hi 6 ignition. It has never pinged. Tried 87 octane, doesn't run so good. 91 or 92 octane made no noticable difference except to my wallet. Might be I just got lucky with the combination. Engines about 5-6 years old now.

Food for thought REJ. Which cam? anything can be done if the resaearch is accomplished. Thanks.

Cam is Wolverine Blueracer .480/.480 lift

I've run that same cam in my big van. With the 305 heads, I only pushed 10:1. It was a bit touchy in the summer months with a slight ping. That's when I would have to spring for bigger octane. It doesn't help That we have winter blend fuel and then summer blend from the pump. I don't dare play with the add packs I work with. Since I'm not the only who drives it, I don't dare trust anyone else to put the stuff in. I just drive it for what it is and keep it running.