1968 Checks under valve covers

[Mosesatm]

The 289 from 1968 has large combustion chambers and a compression ratio of around 8.7. The 302 has much smaller chambers and higher compression of around 10.

 

[p51]

The 289 from 1968 has large combustion chambers and a compression ratio of around 8.7. The 302 has much smaller chambers and higher compression of around 10.

Given the discussion above, one of the concerns I would have about dropping in a roller cam into my J-code 302 engine (53cc heads, 10:1 static compression) is that with the smaller overlap and the longer allowed durations (per Rob's note) that the dynamic compression would be too high to run on pump gas without detonation...

 

[Mosesatm]

Sorry, I forgot we were discussing a 302 instead of a 289.

 

[p51]

Sorry, I forgot we were discussing a 302 instead of a 289.

No problem... I actually think we've gotten to the point where we're discussing both in general terms.

 

[robert campbell]

Given the discussion above, one of the concerns I would have about dropping in a roller cam into my J-code 302 engine (53cc heads, 10:1 static compression) is that with the smaller overlap and the longer allowed durations (per Rob's note) that the dynamic compression would be too high to run on pump gas without detonation...

You could select a roller cam that would have similar overlap to the 302 cam but far more duration and lift. You are correct in your concern of dynamic compression in your engine. Overlap bleeds off this compression at low rpm's allowing for better manners for detonation. The 53 CC chambers do require fine tuning, but I have found that with proper reduction of the vacuum advance curve solves almost all of this. But that assumes you at using a stock dizzy. If not, without vacuum advance it even becomes easier.

The real question is whether all of this is worth it? In my mind if you are not moving to higher flowing heads, long tube headers, and bigger carbs, then it is not worth it. Keep it stock and enjoy it as it is.

At one time I thought of porting the exhaust side of a stock set of J code 4V heads and install 1.94 and 1.60 valves. A sleeper motor on the outside, but again it would require headers and a big cam and increased carb to really get your bucks worth. But it could be done in my mind and make great power. I had a set of 351 C9OE casting that this was done too on my Hipo. They flowed better than a set of Edelbrock Performer RPM heads, with basic stock intake porting, but a huge amount of pocket porting in the combustion chambers and massive exhaust porting. These heads with a stock 302 J code intake and a 600 or 650 double pumper Holley would have made great power under 6,000 RPM and with a stock bottom end. The same could be done to 302 4V heads.

Rob

 

[p51]

...The real question is whether all of this is worth it? In my mind if you are not moving to higher flowing heads, long tube headers, and bigger carbs, then it is not worth it. Keep it stock and enjoy it as it is...

Yeah, keeping my J-code stock is the way to go.

I'd like to (eventually) build an engine - just something that gets 300+hp at the wheels, nothing major. Good quality but on a budget (just for the challenge, mainly). Using the 80/20 rule - 80% of the fun for 20% of the price. The one setup I saw a few times on the web is:

Roller stock 5.0L short block bored no more than 0.030 over (if a rebuild)
Hypereutectic (or forged?) pistons
GT40 heads (good-n-cheap) or AFR 165 heads (more expensive but lighter and allow higher compression because aluminum thermals)
Weiand Stealth intake or equivalent
Tri-y headers
An "appropriate" cam for a zippy "stoplight to stoplight" street car
~9.5 static compression, ~<185psi cranking compression (as a proxy for dynamic compression)
T-5 transmission (which should handle the 300rwhp ok)
3.5 rear gear
TBI (FiTech or Sniper EFI)

One site that I found with lots of "calculators" for doing what-ifs...
http://www.wallaceracing.com/Calculators.htm

For example dynamic compression...
http://www.wallaceracing.com/dynamic-cr.php

And "Eric the car guy" is now into his engine rebuild on his Fairmont project (end of playlist)... fun to watch...
https://www.youtube.com/watch?v=L22GsHQi7tU&list=PLSzhQ6St-ov2nxWVKCeU14Vt7JJ_QSZvs

 

[robert campbell]

Hypereutectic is just fine for your build. If it was me, I would not drop below 10 to 1 on the compression. Especially with the use of an aluminum head. Size the roller to bleed some of the low speed compression off and you will run just fine on 92 crap gas we have today.

Hard to beat Ford Powertrain Applications headers for this build. They tuck up nice a tight and will work with either vintage or Borgeson power steering. I would go to the Modern Driveline hydraulic clutch system. Nice easy pedal and no worries about a cable clutch or a modified Z bar.

Here is a pic or two of the FPA headers.

 

[CougarCJ]

Rob, from the pictures I can't see how your power steering would work. :grin:

 

[p51]

Rob

Thanks for all the info.

James

 

[robert campbell]

Rob, from the pictures I can't see how your power steering would work. :grin:

Scott
I did not have PS on the car at the time, but I took the pic to show that the ram connection on the frame will clear the header without utilizing the ram drop bracket that other header companies use. It clears all the hoses and the normal PS/Steering box.

rob