rdtreur

Just got my 1971 Cutlass supreme and need to plan my engine build. I need some advice from you guys. I live in the Netherlands so to get the parts here it cost me a lot shipping and tax... Luckily I got a lot of parts with the car..
Here is a list with parts that come with the car:
-1 x 1971 compleet motor with the #7 heads, 2v intake, needs rebuild.
-1 x 1969 compleet motor with #5 heads, broken valve, cilinder damage, bend connecting rod. 4 v intake.
-Used comp cams XE268 H cam
EDIT: IT IS A MARINE high energie OL 268h 10 cam (marine app)
-brand new set Speedpro flattop pistons, W31 std bore
-Hei
-Headers and dual 2,5 inch exhaust
-Stock TH350, 3.23 gears (I think)

My goal:
approx. 350 HP, 10.5 or 11 compression ( no problem on dutch LPG/propane with 105-108 octane), fast daily driver with some punch.

I hope I can use the new pistons, that would save me some money.
Is the XE 268 H a good cam for this or should I get a other (roller) cam?

Please advise me what I need to do to get the 350 HP.

I'm not planning to get aluminium heads.

Many thanks!

olds 307 and 403

Propane, interesting, used to see a few around, now they are rarely seen here. I would get the 2.07"/1.625" valves and open the bowls up and porting done to your #7 heads. Get the Performer RPM intake. That Comp cam should work fine with your build. If chambers cc at 64 you will be around 10 to 1, which should be plenty. Hopefully your cylinders with clean up enough with hone for those pistons which need .0045" clearance.

rdtreur

Thanks for your input . Propane is very common here in the Netherlands, So no problems on that end. it saves a lot of money at the gas station;-).
About the #7 heads, I have heard that the #5 run flow better, so why not putting big valves in the #5 heads?
What about the piston rings, what should I chose?
Thanks again.

cutlassefi

5, 6, and 7's are all about the same.
The bowl work is more important than the valve size, spend your money there.
If you're going to run propane all the time then shoot for at least 10.5:1, it'll run strong, done a couple of propane builds.
But that fuel is very dry, make sure your clearances are just a tad looser and you use very good oil.
And any good moly ring will work as long as it's honed correctly.

rdtreur

@ Cutlassefi: Thanks for your response. I will look into the bowl work part. Never did any porting... As you being a "cam specialist" can you advise me in picking the right cam? I read in the Franz Hofmann propane bool that Propane needs a different cam profile. Will the XE268H be any good?
And is the performer RPM not to high RPM for my purpose? Many thanks, Ramon

olds 307 and 403

I didn't realize Propane had such high octane. I know power is lost converting, apples to apples. Your motor will run a ton of miles due to the dryness of the fuel, which is a bonus.

rdtreur

Thanks for your response guys. @ cutlassefi: I will look into the bowl work. Never did any porting before... About the cam, do you think this cam would work for my purpose, running on lpg/propane?
Is the rpm performer not to high rpm for my purpose?
Many thanks, Ramon

olds 307 and 403

The Performer RPM works fine from idle to where that cam will run out of steam. If you have stock 4 bbl intake that will OK as well. The RPM intake is dual plane with much longer runners than the Performer or the stock intake. Bowl work is important otherwise bigger valves especially are a waste of dollars.

rdtreur

Well it seems that I was mis-informed about the cam that comes with the car. It seems to be a marine aplication high energy OL 268h-10...... Please inform me about this cam for my setup. This is the cam card:

TripDeuces

That's a very mild cam. It has 4 degrees of advance built in so putting it in 'straight up' would actually be 4* advanced.
I doubt that cam would get you to your goal of 350hp in a SBO.

rdtreur

Today I went to the machine shop to get my block inspected. It seems that with some good honing, I stil can use the brand new speedpro flat top pistons.
All the cilinders are good and all the bearings are like new. So more money for the rest of the build.
Back to the cam options:
The cam that came with the motor, a Comp cams OL 268h 10 , is like new but a bit to tame I think.
So I 'm thinking XE 268h or Crower power beast #56903. Any input from you guys??
Also i'm going with a rpm performer intake.

cutlassefi

Wrong cam for your goals and comp ratio.
If you're trying to buy a Comp cams over there then do the bigger Dual Energy cam. should work well with 10.5-11.0:1.

67 Cutlass Freak

Mark is right about the bowl work. I don't think you will need much more in porting for your goals. My friend Don recently did a set of #7 heads with 2.07" intake valves, and a good valve job. He hogged out the bowl with a cutter, then blended it with a carbide. He told me he spent a total of 6 hours smoothing the transition of the cutter into the bowl. He gained 30 CFM over what the stock port flowed. I'm intrigued with your use of propane. I work on forklifts. What type of carb and vaporizor will you be using? Deffinitely be careful with the valve guide clearences, and don't use the Viton type seals, or you will not get enough lube on the valve stem. The good old umbrella seals is what you will need.

rdtreur

Thank for the input guys. I'm going for the compcams xtreme energy 268h and need to check about the porting with my machine shop.
About the propane. I'm going with a impco vaporizer and impco 425 mixer (propane only) or a 300a mixer (dual fuel). Advance the timing a few degrees and put lighter springs in the ignition. Propane also bennefits from a cold air intake so a W31 filter housing would be nice;-)
I did a 396 BBC with a 2x impco 425 mixer, with the bird catcher above the hood, that BBC ran great:-)

rdtreur

I got al the Parts from the machine shop. After putting the pistons in the top of the pistons is flat with the block. Very happy so far:-)





I found a nice moroso oil pan and pick up local for a nice price, overkill but looks good :-)

olds 307 and 403

Looks awesome, even with untouched heads, your compression would be 10.3 to 1. With 64 CC heads, 10.8 to 1.

distributorguy

Looks great. Set the intake centerline around 111 and you'll get all the torque you want, probably come up short on hp. Or leave it as spec'd at 106 and you'll get a little more hp.
(DynoSim5 software results)

cutlassefi

Not necessarily. An earlier Icl will build more peak power/tq, sooner.