All Small Six Highest...Safest compression ratio?
- Thread starter wakjob
- Start date
This relates to all small sixes
Comression limits are determined by what fuel grade do you plan to use as well as locale weather, air temps, altitude, and terrain? A stock 1980 Granda 200 will have a dished piston
Always 90-91 NON-ETHANOL... and I'm not adverse to putting in some Lucas Octane Booster if needed.
I only drive my car in the summer months... so 70F-90F.
I live in a valley at 800' and climb the hills to 1400' max.
Paved roads only.
I plan on machine shopping the engine as mentioned... "zero decked" & "flat top pistons"
Large LOG ported, largest valves possible, and machined to take a 2 barrel without the need for an adapter through the small hole.
I'm warming up to my current Clay Smith cam of 264/264 110... but I'm open to options.
I only drive my car in the summer months... so 70F-90F.
I live in a valley at 800' and climb the hills to 1400' max.
Paved roads only.
I plan on machine shopping the engine as mentioned... "zero decked" & "flat top pistons"
Large LOG ported, largest valves possible, and machined to take a 2 barrel without the need for an adapter through the small hole.
I'm warming up to my current Clay Smith cam of 264/264 110... but I'm open to options.
I have a lead on a smashed up 1980 Granada with 12,000 miles
Unless you've confirmed it's a 200, in this DSO most Granadas' are 250's encountered.
... anecdotally, the anvil strong 7 main bearing 200 and stroked 250 can support higher than stock compression ratios with a little help. 'Modern' ignition and fuel management upgrades are generally needed.
... I run a later Maverick 170 with a Granada 250 head milled .070" with a steel shim gasket for @ 15 years. With the cut head and thin shim gasket static CR with stock cam is @ 9.5:1. May not be fast but sure is faster and fun on 93 octane ...
'74 Maverick had a Buick derived Turbo on it's 250 until a little extra enthusiasm (boost) had the piston ring lands crack off leading to an oily mist across windshield and loss of any power. 250 pistons yielded at @ 15-20 lbs of boost which is a static CR of @ 15:1...
Unless you've confirmed it's a 200, in this DSO most Granadas' are 250's encountered.
Highest...Safest compression ratio?
... many factors of fuel and ignition and whether static or dynamic CR.... anecdotally, the anvil strong 7 main bearing 200 and stroked 250 can support higher than stock compression ratios with a little help. 'Modern' ignition and fuel management upgrades are generally needed.
... I run a later Maverick 170 with a Granada 250 head milled .070" with a steel shim gasket for @ 15 years. With the cut head and thin shim gasket static CR with stock cam is @ 9.5:1. May not be fast but sure is faster and fun on 93 octane ...
'74 Maverick had a Buick derived Turbo on it's 250 until a little extra enthusiasm (boost) had the piston ring lands crack off leading to an oily mist across windshield and loss of any power. 250 pistons yielded at @ 15-20 lbs of boost which is a static CR of @ 15:1...
With 90 - 91 fuel a 200 six could reasonably go to 9.5 or maybe 9.7 static with stock spec cam, yes even 10.1 or more with a cam of the right specs. X3 as pmuller9 and powerband stated in their above posts, with your Flattop Pistons, Zero decked or more (depending on head gasket you use) to get a good quench distance with the short block and large log head (this can be an excellent 200 short block combo). Next with your cam selection you can then calculate out its dynamic compression ratio to see if it works out for the fuel you want to use. Best of luck
Best to stick with 5:1 rocker ratio on something like this?
Stock...or 302 valve springs?
I'd obviously check it with clay for piston to valve clearance during the build.
I'm just basing everything off of my current new build, and looking to improve on things.
I've been on the aluminum head list for 2 years like most other people.
But I think a modified large LOG would be fun too.
Stock...or 302 valve springs?
I'd obviously check it with clay for piston to valve clearance during the build.
I'm just basing everything off of my current new build, and looking to improve on things.
I've been on the aluminum head list for 2 years like most other people.
But I think a modified large LOG would be fun too.
The stock valve springs are ok with a stock cam but if you add the hypo 289 / 302 valve spring you can get about 400 to 500 More RPM before valve float. If your going with an aftermarket cam then use springs that match their recommendations. On your large log mod's there is lots that can be done to improve it intake valves up to about 1.82 to a max of 1.88 and a 1.5 exhaust valve. Pocket porting the valve bowls, center exhaust port divider, direct mounted Carb or Carb's, full exhaust porting. Best of luck
