Hello.

Ruminating over my project that is coming. Since I will totally restore the car, it seems prudent to not do what I originally thought I would and freshen easily done things on the engine, and instead do the whole thing including valve seats to avoid lead additive and such.

A 67 400 in the 442 specs sits at 10.5 to 1 CR. Goal for this engine will be to exceed stock numbers by *some* and that some will be determined by other factors. Stock heads, manifolds, pan, water and oil pumps, distributor, carb, etc. The original cam in there is something wild which we've talked about before on here, and I'll probably source one close to the w-30 style to accompany this track pack setup I have for it, but perhaps a little better manners for the vacuum needing accessories.

Anyhow, I'd like to maintain as much CR as I can. I can source 93 ethanol free around here, and could do 91 and octane booster on the roadtrips. Is that a feasible method for holding 10.5 to 1 or should I back it off and depend on a more radical cam to recover what is lost from compression?

 

Don't use a more radical cam to counter lost compression. Unless you want your car to have all the accelerative capabilities of a bowl of soggy Raisin Bran. An engine needs a lot of cylinder pressure to support a big cam.


If you curve your distributor VERY carefully, you should be able to get by with 93 octane plus octane booster. Also, keep in mind that if you're doing any kind of overbore, then that will lower your effective compression slightly. In any case, I'd doubt you're going to be anywhere near the advertised compression.


My guess? Built to factory specs other than an 0.030 overbore and a slightly hairier than stock cam ... you should be all right.

 

Overbores raise CR. More cubes are squeezed into the same combustion chamber.
10:1 is considered the max CR useable with iron heads. You might consider dished 350 pistons. Pin height is the same. A lower compression engine with a good advance curve will feel better than a high CR engine with a retarded spark advance curve. If you are still squeezing it tight then run a wide LSA cam like 114 or better and zero deck it to as close to .030 as you can get. Tighter and you might kiss the head at high RPM; less and it loses effectiveness against detonation.

 

With my 400 build I did it stock, clean up mill on heads but not on deck. Went with the Egge flat top cast pistons .030 and cast rings. I used the repop 67 W30 cam and have 390 gears. It runs just fine on premium gas no pinging with a little more than stock timing. I have no power anything so I dont care about vacuum....

 

run premium in my 65 400 stock no problems, we also run premium in sons race car with a 68 455 motor it runs 12.30 in quarter no octane booster and it gets raced every weekend

 

Take a look at the Comp Cams 274 XE and install it about 4 deg. advanced. I can get Rockett 110 at the pump here, so don't know about ordinary premium gas. You could mix gas if you have pinging. Unless you deck the block, etc. you probably won't have a real 10.5 to 1 with your rebuild.

 

Not sure about some of these responses. But here's what I do know.
Don't assume you have 10.5:1. Chances are you don't. Take a cranking compression reading, 190 is a good number. Over 200 and you're going to get into trouble with pump gas.
And if you do have more compression that you want, a Comp XE 274 will only make it worse, especially if you advance it as per r to r's recomendation. Those are fast ramp cams with minimal off the seat time to build cylinder pressure. You most likely already have enough. The last thing you need is more.

Jmo

 

You have to look at comp ratio and pump gas as not one single item that you have to get right.
But a complete system.
comp ratio
quench
cam events
timing
cooling

There will be sub categorizes to research in each of the category
Such as coatings,water type injection,combustion chamber polishing,piston head design,
ignition retard set ups,type of engine oil that you will use,cold air intake,heat riser blocking,cool fuel.

I'm not saying to use the above tech but it is always better know what others have used to control detonation and why.
Good luck

 

Thanks for advice. Like most seem to suggest, it will be as close to stock as I can get it minus certain modernizations like hardened valve seats. I don't know about the state of the cylinders yet, but I doubt I'll get away with just a hone.

I'm not going to make a race engine, Bernhard, though I appreciate the advice. With stock heads and hopefully stock pistons, I am thinking quench will remain unchanged other than how it is affected by head height. Cam, you are right on on there. Timing will be stock distributor but I can play with that. Cooling will probably be a stock 3 core redone.

Hopefully I can avoid the tech you listed, though it's good to ponder it. I've worked with other engines before both as hobby and profession, but this is the first Olds.

The theme I am going after with this car is if someone had bought the track pack and put it on an AC car, which I think was possible, just not wise. The cam in there now is not original, and it's tuned badly, so it does accelerate like soggy raisin bran. Previous owner had it in bad shape when I got it. It MAY have been a dog with this cam and was sold to get rid of it. My plans are an appropriate cam to get street and highway fun with more than stock performance, yet remain somewhat mannered and run the power brakes. Fuel economy can kiss my ***, but I will want to run pump gas, 93 when I can get it.

Once I get the car down here, there will be epic build thread.

 

That's the spirit!

 

A lot of the tech I listed is very basic like blocking off the heat riser and ram air. keeping the intake charge cool is always worth the effort as it pays on two fronts, hp and detention control.

 

Ok. Do you mean the heat chamber across/through the intake manifold that goes under the carb, or the heat pipe coming up from the manifold to an air cleaner snout like found on later years? I guess another heat thing is the valve on the exhaust crossover, but I don't think you mean that. 67s had no exhaust manifold to air cleaner heat pipe.

Ram air, got you covered, stock OAI style. My cleaner needs rechroming, but it's a nice piece as is.

Thanks for advice.

 

Under the intake manifold, you can block it of at the head to intake seal.
Some vendors make block off plates, some machine a recess in to the head on intake side.
Ram air 67 OAI very cool.

 

XE series cams have a 4 degree advance already built in

 

The XE cam recommendation is to maximize performance. I use Rockett 110 because I don't drive enough miles to care that it costs more than pump gas. It also has lead to protect the valve seats. If you want a slow ramp cam, just get the early W30 (=W31) camshaft. The XE will give more vacuum, which you expressed interest in getting. The engine will start quickly and have good mid range with the XE, compared to the slow ramp cams. Depends on what compromises you want to make. For that matter, Comp can make you a custom cam that is even better than the XE274 with those .921" lifters, and nitride it for durability. Again, it depends on what compromises you want to make. I don't want to use pressed in valve seats on early heads with little meat around there, so I could run unleaded gas. I also run stock rocker arms.

 

Max performance is nice, but I doubt it will ever go down a drag track more than five times total, so there's no need to wring every bit out of it to sacrifice reliability or using commonly available gas. I don't have a problem with putting in lead substitute, but I do want to be able to use normally available gas and go on road trips (not many, like 1 or 2 a year). I may do some internal upgrades on the rotating assembly and valvetrain, but they will be small and keep the engine looking stock.

That intake block off port may be a good idea. I drive my other old car very little in cold weather, it basically hibernates from Dec to March.

 

I would also run a piston with a modern ring pack, and make sure the cooling system is 100% effective.

 

Please explain how you can make this assumption? You're way off base here.
If anything it would crank easier with a "slower" ramped cam due to the lower cranking compression. And actually starting is a whole other issue.
I guess you work for Comp cuz that's all you ever say. How many different cams from different companies have you installed, checked or had first hand inpressions of? Based on your posts I'm guessing only a couple.
By the way I'm a Comp dealer as well and the first two cams I got from them weren't what I asked for, I had to send them back.

Op, imo you need to verify a few things before you move forward.

Thanks.

 

http://highperformanceolds.com/phpbb...php?f=1&t=4315


modern piston and rod.

 

I don't work for Comp or for Erson; I am not a cam dealer like you are, efi. I have used Comp since the 1970s and far more than a couple of them, and from different companies. I am not trying to cut into your business, just provide information and my personal experiences.

 

Comp has been a major cam company for a long time, I remember when comp was coming out with smaller duration and dual pattern cams in the 80's and guys were running a lot quicker than there big duration cams. Other manufactures were still promoting large duration single pattern cams. At that time comp was bring a lot of new tech to the market along with great customer support with there tech line.
I don't know what there rep is today but they sure brought a lot to the racer in the 80's and 90's.

 

I never thought for a minute that you were trying to "cut into my business".
But quite simply your claim is unfounded. You're telling him it'll start quickly with an XE cam? Really? That's bull crap and you know it. There's no way ANYONE can make that claim on a cam, waaay too many variables in that equation.

That's my point. Thank you.

 

I have found that my 9.3 compression 400 starts much quicker with the relatively small XE type cam, around 230 deg. at .050" lift, and advanced as I posted above, compared to slower ramp cams of similar "size" like the w31 grind, and/or bigger cams. Not any size XE, nor any combination one might imagine for the rest of the engine.


Why not come to the OCA Nationals this year, race with us, and let us benefit from your knowledge and experience with various Olds combinations?

 

Sure, still way too many variables. Maybe the idle circuit on your carb is better suited to your combination? Maybe it was that your old cam just wasn't right for your combo.
I could go on but again too many variables imo.
And thanks but I'm not a drag racer, I'm more of a road course guy, sorry.