[takid455]

I will be rebuilding my 74 SD engien shortly and am looking for suggestions and input on what simple 'mods' largely benefit these engines. this will be street driven so all out race stuff is out. I would prefer not to port anything if avoidable. my intentions are flat top pistons & RA 4 style cam. I have a set of 1.65 rockers laying around if they would help. may put a pertronix style ingintion in it to remove the points. car is a stick with 3.42 or 3.23 rears. am I on the right path? just looking to see what works and what doesn't.

[old66tiger]

If memory serves me correctly, the 74 had ultra low compression. Why not a set of dome pistons?

[takid455]

compresion is low and the heads are 110 cc +/-. doens may be an option. 9.5-10:1 compression is the goal.

[Lefty]

I would have the heads professionally flowed on a bench. Then I'd take this data to one of the big cam companies. Talk to their custom cam department, give them the flow data, weight of the car, gearing, transmission info etc, and finally INTENDED USE. They can design a hydraulic roller that should play the best attributes of the total combination. (HR cam for a street driven car.)

I suggest this especially due to your desire not modify the heads. They can also advise best compression ratio too. In the grand scheme of things, the extra cost of a custom cam is minor in rebuilding an SD.

[Larry Navarro]

FWI.....
I built a service replacement SD455 years ago with all stock parts. The only aftermarket part I used was the old H-O racing cam HC-63 which is the enhanced version of the RA4cam.
The engine retained stock bore, pistons, SD intake, ex. manifolds 750 Q-jet and heads.
Ports were untouched, compression at the stock 8.4:1.
The car was a Y code '73 t/a, 4-speed 3.42 gear rear. The car was a beast and ran high 12's @ 108mph.

TAkid455 you're on the right track.
I wouldn't go through the trouble of domed pistons or ported heads for your intended purpose. I'll be happy to go into further detail if you like.

[shaker455]

Takid,
I too have an SD 455.

I would try to increase the CR without going to the extreme of a domed pistion as it will hurt flame travel.

A set of .025" Cometic head gaskets woulld work well and a well choosen piston with a zero deck height will close you in closer to 9:1.

As far as a cam I like the HO cam Larry mentioned but I would lean towards an efficent modern Hyd roller with atleast 112 lobe sep.

Also another benefit of a roller is you don't have to worry about the zinc content in todays oil.

I'm not big on the Pertronics stuff and I would rather see you get the Crane XR-i conversion module kit with an adjustable built in rev limiter then curve the dist with an MSD spring & bushing kit.
Jeff

[Larry Navarro]

Yeah that HO cam is no longer available. The specs on it were 242/250@.050", 113/119 LSA with .501" lift on both sides.
A roller would be my choice too.

[1qikta]

I like the roller to..but keep in mind the lifter bars are going to hit the bottom of your EGR style pan. Just stash your original and get one for just this build. A ball pin hammer is all it takes to make a little room.

I found that out the hard way.

[fiedlerh]

With the price and quality of gas not getting any better, I don't think there is anything wrong with building an engine to run on the 87 octane junk. Especially if it's not going to be used for racing.

[J GLASGO]

Do not port the heads! My SD runs 113 mph quarter mile with virgin heads. It is totally unnecessary,and would ruin a great set of heads.

[steve25]

The stock heads flow enough with a .480" lift cam to make 460 HP, but even with a some where around a RA4 type cam and stock compression 425 HP will still make for a stout street car that can be used on long drives.

[FloridaFirebird]

DUI (Davis Unified Ignition) makes a HEI distributor for the larger diameter distributor hole. They will dial it in for your combo. The HEI is a lot less headache than the points if you're not going for a totaly original look.

FF

[x-bird2]

while i haven't run my latest "final" combo on the strip, i know it's good for high 11s/low 12s. best ET to date is a 12.20 on 20 psi drag radials with nice street manners. (latest change since that run was the exhaust system and a few other tuning tweaks) the basics now are original heads with a touch of porting to lessen the sharpness of the short turn radius, decked to 8.9:1 CR, orig rods, replacement TRW pistons- .040-over, single pattern solid cam 246 duration 110 lsa .495 lift., 1.5 roller rockers, street dominator intake--stock form, holley 850- dp, stock fuel system and hooker 2-in. supercomps to a 2.25 in exhaust with no x-over. Prior to that config, stock intake and q-jet along with 240 duration cam same lift and 1.5 roller tips netted a best ET of 12.84. mph has stayed the same around 107/8, 3.42 gears, ATI 10-in 2600/2800 treemaster convertor.

[takid455]

seems these SD engines run well even w/ low compression. i was thinking I was going have to mill the heads or get dome pistons to get a good CR that would yeild good power. maybe pontiac engineers did their homework. I know the deal w/ flat tappet and zinc, but what are good cams in both FT and HR. seems 0.500" lift and 230-240 dur. @ 50 is ballpark for most of the suggested cams.

if mr. navarrow would car to go into detail, by all means. you can PM me if you want.

is teh SD carb any different than regular Q-jet other than different metering rods?

[Larry Navarro]

Originally Posted by FloridaFirebird

DUI (Davis Unified Ignition) makes a HEI distributor for the larger diameter distributor hole.

I would think that they offer a sleeve to fit in the block rather than offer a larger distributor housing, right?

[takid455]

took engine apart last night. looks preety good. some rod bearings are work. minimal to no ridge on cylnder walls which is good. sould be an easy rebuild. Did super dutys come stock with flat top pistons?

[FloridaFirebird]

Don't mean to steal this thread but to respond to Larry. The DUI distributor for the SD has a larger shaft, no sleeve. Their website is www.performancedistributors.com I believe. Look under street/strip GM distributors on the right hand application side.

I think they cost about $300, they will custom curve them for your application and they come in several colors, including black cap, stealth/stock appearing.

FF

FF

[Tim john]

Pete McCarthy wrote a book on building the SD to run as they were designed and it is a nut by bolt reference, everything you can imagine to build this engine right. I have the book and it is very detailed,with part numbers too for bearings,ect...things to check and watch for such as a certain set of rods that were considered "soft" It would be well worth your time and money to get a copy. PM me if you want additional details.

Tim john---

[Tom Vaught]

Just a question on the modded vallve pan?

Why all of the extra holes in the pan?

The pan is designed to shed the oil from the oil vapor on a normal valley pan before entering the PCV Valve.

Kind of defeating the purpose of the baffleing, don't you think?

Tom V.

[Larry Navarro]

Originally Posted by takid455

Did super dutys come stock with flat top pistons?

Yes. Also have a single valve relief or trough.