Thread: For Tech, Denny, and the other engine guru's

Tweet

Ok guys, how's about helping out a chassis guy?? I'm at the point on parts for the 425 Nailhead that I need to start finding the CORRECT cam for the bugger. The Coupe, when finished will cross the scales at around 2100 pounds. I'm going to run a quick change rear end. I allready have the 6 deuce intake and will be running big Rochester 2bbl in the middle, and the small Rochester 2bbl on the ends with progressive linkage. I have the MSD Distributor for it. Pistons are ordered, cast with 10.5 :1 compression. I will be running Lakester headers with 1 3/4" primaries into a 4" megaphone (yup, I know it's not the best performance choice for the exhaust, but I'll make the comprimise to have "the look") I will be running a manual valve body 400 Hydro, vintage '64 Riv.....

My questions concern cam and torque converter. I want the car to be streetable and build gobs of torque at low and mid range, doubt the engine will ever rev beyond 6000. Where do I want to be on the cam (going to get one custom ground) and is 2500 stall ok on a light car????? Thanks for the help.

Dave,

You might find this interesting:

http://www.rodandcustommagazine.com/howto/4907/

http://www.rodandcustommagazine.com/...05/index1.html

http://www.buickstreet.com/build-a-b...ead-page1.html

As I remember, nailhead cams are a bear to find.

Denny, sintered bronze guides, 1.94 and 1.60 chebbie valves. Tires will be 28.5 to 29.5. Rear gear will be a Hallmark, got a gear for any occasion!!! I have a whole box full of quick change gears left over from the circle burner days. Probably about 3.50's for cruisin', for play time I can go all the way to 6.70's!!

I don't have a clue what the stock cam is, the original motor was a 64 Riviera with 10.5 to 1 compression. I'm using the same dome, but a much lighter (the original pistons are full skirted) cast piston that Northwest Speed makes. Also clueless on what the stock rocker ratio is, it's a shaft system and the roller rockers will be the same ratio when they finally become available, probably 2 or 3 more months. They are still in the prototype stage now, or that's the last word I got from the company that will be making them. The only thing I did find is the GS cam was on a 110 center and a 264 duration.

Just found more info, rocker ratio is 1.6

Dave, I don't know if I'll be much help, I've never built a Buick so I don't know what they like. I'm a little surprised that you're using 10.5 pistons with iron heads on pump gas. Are you sure that's gonna work o.k.? Like I said, I don't know anything about the knock characteristics of Buick heads/pistons. You know, in '64 we had good gas.

I think it will be ok Tech. They are a very large chamber head with a centrally located spark plug. I'm not a "drive it everywhere" kind of guy anyway, so the best premium at the pump with a bit of octane booster is allright with me. I may chicken out and put the pistons in th piston vice and spend some time on the mill massaging the tops a bit. I'm building the car light, so there won't be a lot of mass to get moving. One of the things I've learned on the Nailhead allready is that you don't have a lot of selection on which "good" parts you use. These are the best pistons I've come up with and not have to go to the 200 apiece custom built route.

The stock bore is 4.312 and stroke is 3.640, should build huge torque without having to put a lot of timing at it. My biggest concern is to get the cam specs to work in the motor and compliment the hi torque at low RPM charachteristics of the motor. Stock it built 465 foot pounds of torque and 360 horse and had it all in by 4500 RPM, so if I can cam it to improve the torque number, it should fly.

Not to budge in where im not invited, but theres a few things that dont seems to add up here. First of all, why the 6pack? If your not planning to wind it past 6K, you probably wont ever use all 3 carbs at full cfm. 2nd, if you are running the stock dome and havent shaved the heads, you should be running 10.25:1 compression. Assuming it diddnt change sometime in 64. Finally, why the worry on the convertor? I may just be ignorant here(probably in fact), but it seems to me that a low stall convertor would be better for a light car so that your not lighting the tires due to revs. In case you diddnt notice, 64 riverias diddnt weight 2100 lbs

Oh, according to the book, there is .439 lift on the intake valve and .441 on the exhaust. Not much help without the rockers, but something to go by

Drg, I gotta admit the 6 deuce setup is probably not the right way to do it, I'm actually doing it for just "the look". If I was going to get real serious on the performance it would probably be something else. Stock converter would also seem correct to me, but this will be one of the few cars I've ever built for myself that wasn't a stick....and the jury is still out on it being an automatic for sure. There is a bellhousing and flywheel available that would allow the GM 6 speed to be put in the car.....

Been busy on so much other stuff Denny, the head work has been put on the back burner for it bit. If everyone leaves me alone this weekend hopefully I can get back on the heads and do some better quality pics.

The whole car is being done just the way I want it, little thought given to what is practical. Just a geezer building the car I wanted when I was a kid.

Dave, being pretty much clueless, I called Comp Cams tech line and talked with Buggy, as much for my own future information as to help you with your combination. There might be a Buick in my future

With pretty much stock heads and stock rocker ratio, he recommended part number 91-000-5 @ $194.48 for the cam only. This cam will make power from 2,000 to 6,000 and with a little ignition timing adjustment, should run on pump premium with a decent squish (0.045" - 0/.050").

Intake duration 224 @ 0.050"
Intake lift 0.485"
Exhaust duration 230 @ 0.050"
Exhaust lift 0.490"
Lobe displacement angle 110 degrees
Operating range 2,000 to 6,000 rpm's
Recommended converter 2,400 to 2,500 rpm's stall.

Thanks Tech. Is that where I would want to be on the converter on the street with a light car??? I would like the converter to be "loose" at a light, then really come on after a bit of a rollout??? Maybe I should just go the 6 Speed route and stick to something I know more about???? Thanks for the help guys.

Dave, in my experience, you don't want a real loose converter with a light car. It becomes like an on-off switch instead of a smooth transition of power. All the stall you need in your case is enough to get you up on the cam at its low end of power (2,000).

Ok, Thanks Tech. That's what I needed to know on a converter. Like I said, I usually (and still might in the coupe too) run a stick.

Hi Dave, I keep looking at your intake and reading"......will be running big Rochester 2bbl in the middle....."

I really think you might be happier running small carbs all the way across. I haven't really played with my 6 duece set-up for the HEMI yet, but have set up a lot of tri-powers so take this with a grain of salt.

Total potential CFM with SMALL BASE carbs will be in the 1800-2000 CFM area, so I don't think you will need to worry about starving the nailhead for fuel.

IF it were a tri-power intake on that motor, I would recommend the BIGGEST 2BBL possible in the center position, however with the 6 duece, you'll be running 2 of these instead of just one. The Small base carbs are rated at around 300-335 CFM each. Just my opinion, but I think you'll find can get a lot better Idle and throttle responce with the smaller carbs than the larger ones especially with the lack of runner legnth the intake has.

As far as the convertor (if you go auto) I'd go with Techs general recommendation, the beauty of your quick change is that you can play with that to help dial the car in.

Neat project Dave, keep us posted.

Good point, Mike thanks. My concern and the reason for the big carb in the middle was that the manifold is actually two separate "logs" that are only tied together with two small hoses I would imagine to smooth out cylinder pulsations. The carbs will be set up with progressive linkage, and my concern with the small carbs would be whether or not a small center carb would be enough to "carry" the engine till I get into the end carbs. I do have (someplace in the shop) the tap left over from the circle burner days with Super Mods on carbs to convert from Rochester jets to Holley jets, so dialing in the end carbs will be much easier. If a small carb in the centers equalling roughly 600 CFM would carry the fuel needs til the end carbs are in, then tuning would be much easier..... Back to the desk top dyno, I guess. Thanks for the input.