3.0 to 3.5

[jeffery dalcour]

Good morning, I am fairly new to this forum but Iam amazed but the wealth of knowledge available and the community spirit displayed by the users.
I have recently purchased a 3.0 engine that has 110,000 miles on it. I am planning to rebuild and have questions as to which direction to go.
I want to use the car on the street and occasionally at track events.
I'm not sure weather to go 3.2ss or to go to 3.5
If someone can give me an idea of what would be involved in going in the 3.5 direction I'd appreciate it
Also a comparison of the two would help
Many thanks
Jeff

[jpnovak]

The 3.5 gets very expensive considering you must replace the crank (increase stroke from current 70.4mm to 74.4mm) from a Carrera or 3.3T. Then you must machine the case to accept the 100mm cylinders.

Nothing difficult and easily done. The 3.2SS is a bolt on.

Assuming each has identical builds and flow characteristics I would expect more low-end torque from the 3.5. What is your target application?

[TRE Cup]

I went with the LN Engineering 3.3 10.5:1 slip in kit for my 3 liter twin plug. Very happy with it

[jeffery dalcour]

Thanks guys, I like the idea of having low end torque. I'm 55 going on sixteen, so power is king. I also am not looking for a high revving engine. I've seen the results of valve float and want to avoid that possibility.
What kind of power does the 3.3 achive? Can you give me some idea of the rpm range ect.
Thanks Jeff

[Steve@Rennsport]

Hi Jeff,

The power range of any engine really depends on choice of camshafts,....

One chooses cams based upon what operating RPM range you want.

[jeffery dalcour]

Thanks Steve, I would like the top rpm to be 6,800 to 7,000 and power to start at 3,500 to 4,000 but I don't want it to be a dog in traffic. I will also be driving on the hyway at 65 to 70 most of the time so I'd like it to be as efficent as possible at that speed.
It,s going to be mainly a street hyway car. My reaction time is not what it used to be so a full race car, though coveted , is not for me.
Jeff

[Steve@Rennsport]

Originally Posted by jeffery dalcour

Thanks Steve, I would like the top rpm to be 6,800 to 7,000 and power to start at 3,500 to 4,000 but I don't want it to be a dog in traffic. I will also be driving on the hyway at 65 to 70 most of the time so I'd like it to be as efficent as possible at that speed.
It,s going to be mainly a street hyway car. My reaction time is not what it used to be so a full race car, though coveted , is not for me.
Jeff

I think a Mod-S cam would be just perfect to meet your stated objectives. Make sure you match your CR with the available octane and twin-ignition is STRONGLY recommended with that bore size.

[jeffery dalcour]

Thanks , what CR do you recommend. Fuel hear above 91 octane is harder to get get 94 octane is available but harder to come by.
I am going to dual plug and was thinking 10.5 for compression. I also would like to use the pmo or othrt throttel bodys and EFI from megasquirt.
Jeff

[JP911]

As jpnovak mentions, a 3.5 is an expensive engine to build (especially from a 3.0). I went through a 3.5 build this spring-summer and my wallet is still smoking. If I were to do it all over again, I would give serious consideration to a 3.2SS or a 3.3 as TRE suggests. Good luck!

[Steve@Rennsport]

Originally Posted by jeffery dalcour

Thanks , what CR do you recommend. Fuel hear above 91 octane is harder to get get 94 octane is available but harder to come by.
I am going to dual plug and was thinking 10.5 for compression. I also would like to use the pmo or othrt throttel bodys and EFI from megasquirt.
Jeff

I can't tell you what to do, however 91 octane fuel and 10.5:1 CR are mutually exclusive unless you use very little timing. That saps the throttle response and acceleration so its far from ideal.

I'd rather have less compression and more timing,......

[brads911sc]

Do a 3.2 SS.

Seriously... With a recurved Dizzy, PMO EFI, good cam choice, 9:5.1 compression, ported/machined large heads.. you will see NO advantage or difference in a 3.5 in a street car. You will be well over the speed limit at 5k RPM anyway... so Id shoot for torque from 3-6k. My car was a different car with just the recurved Dizzy... Do your homework.. But for your application, there is no reason for a 3.5, 10.5:1, or Twin Plug.

[jeffery dalcour]

What kind of RWHP would the 3.2SS achive. Built as you suggest?

[jeffery dalcour]

Also what porting to you recommend?

[brads911sc]

CNC Machined the heads so that will match 40 mm PMO's. they are basically large port (like the 78-79) but tweaked for better flow... use a trusted shop like Steve Weiner or Henry at Supertec for this. once I am done with my current build I will dyno it and report back.. but I will tell you.. even without the extra displacement, more aggressive cam, machined heads, or extra compression that I am adding at this time.. just adding the recurved dizzy, pmo's and ssi's on an otherwise stock 3.0.. this was an entirely different car.. pulling hard through the powerband.. there are several on here like Lindy who have basically built my configuration and you should read their post before investing $$$ in the 3.5.. another thought... at 110 k unless you have a problem.. Id send my distributor to Barry for a rebuild/recurve, add SSI's, and add some 40 mm PMO ITB's and get it tuned.. and you may be 100% happy with the feel... its not money wasted since you can do all this with the engine in the car and youll do it anyway if you decide to rebuild...

[jeffery dalcour]

Thanks Brad, I was considering not doing a total rebuild. The engine has been sitting in a garage for ten years, it was removed from a car with a front end collition. The owner shut the engine off after the accident and when the insurance company paid him for the car he bought the wreck and has slowly parted it out. He bought a neser car with a 3.2 engine and is now rebuilding that engine.

I have no way of knowing what real mileage is on this engine. I trust the seller t
ought, he wasn't the original owner of the car. So, it may be prudent (I love that word) to do a complete tear down so I can check the internals . I have been told that it,s a good idea to replace the Dilavar studs. So , I was planning to tear it down to that point, so, I figure that going the rest of the way while the engine is out (not yet installed in my 1974) might be worth the additional cost, if only for the peace of mind knowing that would would give me.
Jeff

[Mark Henry]

Doing a total tear down is expensive but is the only way you'll know you have a 100% solid engine.

I'm also doing a 3.0 rebuild for my 914, I'm semi-close to you in Port Hope.