[grparen]

I am going with a solid mechanical cam in my 421. Compression is about 10.75 on #62 heads (no porting). Running a 3.42 gear, headers, and dual quad offenhauser with two 400 AFBs. I'm thinking of going with the Comp Cams 51-246-4. Has 248 @.050, .525 lift, and 294 Adv Duration. 110 Lsa or the Isky 901500 which has 254 @ .050, .525 lift, Adv Duration of 288, and 108 lsa. These are single pattern cams but I have heard that Pontiac engines do better with dual pattern cams. If that's true, I am thinking of the Crower 60311 which is a dual pattern with 247/252 @ .050, .505/.517 lift and Adv Duration of 292/302, Lsa 112.

I'd appreciate any guidance from anyone running a solid lifter cam on what is the better cam or if you have a better recommendation. Will be a street car and a once in a while track car.

[61-63]

Gary I have two new Lunati 07703 single pattern cams with numbers close to what the cams you are considering have, but they are hydraulics and not solid lifters. The #s on them are 108 lobe sep., 245/245 @ 50, lift at cam .356/.356, .534 lift at valves with 1.5 rockers and .587 with 1.65s. I will sell you one of them cheap if you think it would work for you.

[tom s]

FYI,you dont have near enough carbs for a 2-4 421.Tom

[tom s]

With that rear end gear I would get your duration at 50 down in the 236-242 range and 112-113.Tom

[grparen]

61-63,
Can you comment on this post regarding my 2 X 4 Carter AFB 400s. In this post it was suggested they were not large enough for my 421 engine profile.

[tom s]

FYI,factory 421s came with a pair of 625 AFBs.Tom

[grparen]

Tom, Sorry, but the SD 421 cars came with two 500 CFM AFBs, not 625s.

[huddie]

I think Tom is right here,http://www.thecarburetorshop.com/PontiacAFB.htm

[61-63]

Originally Posted by grparen

61-63,
Can you comment on this post regarding my 2 X 4 Carter AFB 400s. In this post it was suggested they were not large enough for my 421 engine profile.

Tom is correct; you are leaving power on the table with 400cfm carbs on a 421.

Regarding cfm on the original SD carbs by my estimation they are about 580 cfm each.
I arrived at this by comparing the size of the venturis and throttle bores against an original Carter factory chart. You will see 500 cfm, 625 cfm, 600 cfm, etc. in various books and magazines but they were actually about 580 cfm IMO.

[Hillard]

Without a doubt you need more carb. I also agree you need a little less duration. I'd go dual pattern 236/242 @ .050 on a 112lsa. I have used a 242/248 on a 112 that worked great. Is it stick or auto? If auto, what converter?

[tom s]

As what john says might be right but Carter rated them at 625 and if that is incorrect most likely so are the rest of the factory ratings.I will tell you EVERY 2-4 pontiac engine I have run on the dyno liked more carb.I drive my 63 421 SD engine on the street a lot and it has a factory bathtub with a pair of 750 CFM AFBs.On a 2-4 application two 400s is not the same as a 800 single carb application.Tom

[61-63]

Carter did not rate their carbs by cfm back then. You have to look at the original spec sheets, or measure the venturis and bores, and compare them to one of the later charts
to determine cfm. A fellow named Emanuel wrote a book some years ago on AFB/AVS carbs and included a chart in it, and there are others out there. Not every combination of venturi/bore is on the chart and you thus have to extrapolate to come up with an estimate of CFM for some of those old carbs.

[grparen]

Hilliard, the car has a Muncie 4 speed. Did you go solid or hydraulic on the cam you used? Would appreciate thoughts from everyone on solid vs hydraulic. I like the solid because the original SD cars had solid and have a unique sound. But I realize there is less maintenance with the hydraulic cam. I gotta have a nice mean lope but also don't want to do a lot of wrenching either. Thoughts?

[tom s]

FYI,I have a hyd roller in my 421 tempest with solids on it.Ordering a set of hyd roller lifters today to replace them.I have found the hyd roller lifters have no disadvantage to the solids in my last 3 engine builds.Tom

[Hillard]

Originally Posted by grparen

Hilliard, the car has a Muncie 4 speed. Did you go solid or hydraulic on the cam you used? Would appreciate thoughts from everyone on solid vs hydraulic. I like the solid because the original SD cars had solid and have a unique sound. But I realize there is less maintenance with the hydraulic cam. I gotta have a nice mean lope but also don't want to do a lot of wrenching either. Thoughts?

If you don't mind spending the dough, I'd definitely go hyd roller. You can run solid roller lifters on them and set the lash very tight (.006"). Hydraulic roller lifters are ok too, I just haven't found an advantage to paying the extra $$ for the lifters. I've also found that iron heads are less maintenance than aluminum, so you don't need to check the lash as often. With the 4 spd, I'd run the 242/248 @ .050", somewhere between .500" and .550" lift. A tighter lsa (like 110 or 108) is going to give you more sound, but the 112 will work better with the 3.42 gears...faster and slightly better driveability.

[grparen]

Okay. I think I have my cam choice down to a Lunati VooDoo Hydraulic Flat Tappet. Either the 10510704 or the 10510705. I would appreciate your suggestions based on my engine build.

10510704 has 233/241 @050, .504/.527 lift, 276/284 Adv Duration, 110 LSA, 2000-6000 RPM, need 9.5:1 or better compression, 3.42-3.73 gear

10510705 has 241/249 @ 050, .527/.548 lift, 284/292 Adv Duration, 110 LSA,
2400-6200 RPM, 10:1 or better compression, 3.73-4.11 gear

I know it has been suggested that I go with a wider LSA (112-113) but I want a real lopey sound and will sacrifice some performance for that so considering the 110 LSA. I think the 241/249 @050 may be doable for my car because I will have 10.1+ compression but I am concerned about the 3.73-4.11 gear (my car has a 3.42 gear). Anyway, I want the biggest cam that gives the best performance. I would appreciate your suggestions on the above cams and thank you for all of your input in this post.

[lust4speed]

Originally Posted by grparen

...Compression is about 10.75 on #62 heads...

I've been waiting for someone to comment on the compression, but no one has. Unless you are planning on mixing in race gas, it would make much more sense to drop the compression down to an actual 9.3:1 or so. Having to retard timing is going to cost a lot more horsepower than the drop in compression. The 112° will make more usable power on the street than the 110° for the same duration, and you can also get away with a little more duration going to the wider LSA while having the same idle characteristics. Larger duration moves the power up the RPM range, and with the 4-speed, you don't have the luxury of keeping in the sweet portion of the power curve as you can with an automatic and higher stall converter. Tighter LSA, larger duration, and too much compression in a 4-speed car can make for a lousy experience on the street.

I'd vote for either a solid or hydraulic roller with a modern profile and lift in at least the .580"+ range with dished pistons to go along with those 62 iron heads.

[61-63]

I would get the 10510705 and have them grind it on a 108 lsa. It would really thump.

[grparen]

Anybody else have any recommendations on the two Voodoo cam choices I mentioned previously? Appreciate your input.

[grparen]

I talked to Lunati about getting the 0705 hydraulic cam custom ground on a 108 lsa rather than the standard 110. They do the 110 grind with 4 degrees advanced and were asking what I would want for the 108. Any ideas? Do I go 4 degrees advanced or no advance? I am not knowledgeable enough to make that decision and appreciate any guidance the forum members can give me. Thanks.