Need engine build guidance

[SilvrPegasus47]

Thanks for the replies guys! I'll let him know the info y'all gave me, and we'll go from there and see what happens. He was looking for a 350 originally, but couldn't find one for a decent price that didn't need excessive or obscene amounts of machine work. That's kinda why he was thinking of just doing the stroker kit in his 305. We are still in the planning stages of this build, so there is still time to change things and not screw everything up.

Again, thanks for the help. It really is appreciated.

 

[Clone TIE Pilot]

I would suggest higher compression like 9.5, with the right quench it will still take 87 okay and be more efficient. Seems like too many people overlook their quench.

 

[Intragration]

What's your suggestion for addressing quench? 9.5 CR with iron heads and 87 octane seems pretty optimistic, and even if you could get it to run without detonation, wouldn't you be better off running 93 and bumping up timing? This is, assuming power is the goal.

 

[Clone TIE Pilot]

With the correct quench you would not need as much timing advance which is often used as a bandaid for poorly built motors. Proper quench causes the fuel to burn faster so not as much timing is needed for optimum power. Besides improving power, quench also improves engine efficiency, fuel mileage, and driveability which is what the OP's friend wants.


Quench is the distance of the compressed thickness of the head gasket plus the deck clearance which should be no more than .050. This means you will need to measure the deck height and add the compressed thickness of the head gasket to see if the quench is were it should be. The proper quench will introduce additional turbulence that creates a more homogenous “soup” in the chamber, reducing the harmful effects of lean air/fuel ratio pockets. With all other variables being equal, this contributes to creating an engine that is less prone to detonation. One advantage of the 305's smaller bore is that it can mix up it's charge more evenly than a 350 (since a smaller charge is easier to mix) so it can run a higher CR to help make up for the shortcomings of having a smaller bore.

 

[SilvrPegasus47]

Thanks for that nugget of info TIE. I think you just fulfilled my daily requirement to learn something new! :lol: So compressed gasket thickness plus deck clearance equals quench. Got it. Now can you explain to me what deck clearance is? That is a term I'm unfamiliar with. I'm still kinda wet behind the ears on building engines. I've read several books about how to do it, and helped rebuild a couple of different motors with other friends, but that was mostly just new gaskets. Never got into much besides new gaskets and 1 cam & lifter change. Most of what I did was scrape old gasket material and other dirty work. Although I did do most of the assembly on the motor we changed the cam on. Hasn't blown up yet. So I figure if I managed to accomplish that much with no problem, as long as we both follow the instructions and pay attention, the motor should assemble fairly easily. We're gonna have all the machine work done at a reputable shop, and assemble it ourselves. I've got 95% of the tools to do all of the assembly, just need the plasti-gauge and a couple other tools. Plus I have access to several people who have worked on cars for a living with a combined amount of experience of over 200 years. So if something doesn't look right or add up right, I can always make a quick phone call and get the right advice.

And as always, thanks for sharing y'all's wisdom with someone new to actually doing a full build.

 

[Clone TIE Pilot]

Here is a picture that explains everything including deck height.

 

[Intragration]

With the correct quench you would not need as much timing advance which is often used as a bandaid for poorly built motors. Proper quench causes the fuel to burn faster so not as much timing is needed for optimum power. Besides improving power, quench also improves engine efficiency, fuel mileage, and driveability which is what the OP's friend wants.


Quench is the distance of the compressed thickness of the head gasket plus the deck clearance which should be no more than .050. This means you will need to measure the deck height and add the compressed thickness of the head gasket to see if the quench is were it should be. The proper quench will introduce additional turbulence that creates a more homogenous “soup” in the chamber, reducing the harmful effects of lean air/fuel ratio pockets. With all other variables being equal, this contributes to creating an engine that is less prone to detonation. One advantage of the 305's smaller bore is that it can mix up it's charge more evenly than a 350 (since a smaller charge is easier to mix) so it can run a higher CR to help make up for the shortcomings of having a smaller bore.

Here's the rest of the article TIE is referring to:

http://www.chevyhiperformance.com/tech/ ... ewall.html

I would contend that while quench is certainly something you can pay attention to, if you're throwing a budget engine together in your garage, quench is going to be more of an outgrowth of the rest of your package, and not something that you should be losing sleep over. Personally, I just bump timing and run 93 octane. 😉

 

[Clone TIE Pilot]

While I agree you should not lose sleep over it, you shouldn't ignore quench either. What I would do is this, before you bolt the heads on use a dial gauge to meause the deck clearance of all the cylinders. Use the highest reading to determine what thickness head gasket you should use. Let's say your deck clearance is .040, then you should use a thinner head gasket like .015 for a quench of .055 which isn't bad. It's really not that hard, it's free octane.