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326 donor for 421 build

03/04/2019 12:23
FIRSTLAST
What parts can I correctly swap over to a 421 block, to build a pretty correct 1963 421 HO engine with correct heads for that production. My donor engine is intact, 100% there, so I could take oil pan, timing chain cover, brackets, etc... I don't know what is equivalent or different. Closest I would have to compare is a 1965 421 engine complete. Is a guide like Pete McCarthy's book helpful in comparing the sub-parts on the engine? Key internals, like Crower 068 or rods, crank will be procured, not carrried over (of course). This engine is design phase, select the build parameters, find the various pieces I don't have. I am open to options. I am building for 11s in stock form, but I would welcome your comments on stroking or not stroking? The heads will be ported, and my rear ratio is way too high, so I either need to match this to a overdrive unit or a Keisler OD automatic transmission, so I am not spinning at 3500 going down the road. I do expect to reduce the rear diff to around 3.9. Stroking is basically getting you the same result as gear reduction at the crank shaft. It all needs factored into the plan. I am not an engineer and you won't insult me by telling me how little I know. Thanks.
03/04/2019 16:45
ASHLEY P
What is the end goal? (A certain ET, a certain MPH, a certain look, ect.)
03/05/2019 19:45
FIRSTLAST
Fast streetable car I can do light track and road work with. Need a manageable highway RPM, and right now have a super high 4.55 rear. So putting a stroker with that high rear, even if I drop it to a 3.9 makes this somewhat challenging. I would need a Keisler, or overdrive, and I haven't seen anyone fabricate a over drive back in the absent tunnel space ( flattest floors of any Pontiac until we hit FWD drive trains). This car will wind up being more and more tracked but for initial plans, need it to be less track and more street. Rear suspension will be fitted into the factory wells, which still give me a good 10.5 to 11" footprint. Suspension is solid axle posi, with conventional trailing custom links you see in a quantity of these converted cars for track. I think the build is capable of upper 400 hp given the factory intake and dual carter quads. It will not be equivalent power wise to a super duty but is absolutely a tribute car to that design. Heads being ported, and 455 Pontiac crank stroker is a likely option, but no plans firmed.
03/05/2019 21:33
ASHLEY P
Respectfully, "fast" is not a number. If you give a MPH or ET and the race weight of the car, we can work backward to design an engine to make that happen. My 455 moved about 3600 lbs of 78 Trans Am to 12.1/111 using an iron intake with Q-jet, 041 cam, self ported heads with 2.11/1.77 valves. It was plenty street driveable in my opinion. Popped miniature wheelie (both front tires about 1.5") with a clutch dump, 3.50 rear gears, 9" wide/27 tall tires.
03/05/2019 21:38
ASHLEY P
Good flowing heads (descent porting is a must) and a mild roller cam is the way to make great power. Cam and lifters are not cheap, but well worth it in the power dept. I helped a friend build a 455 just after I built mine. He used a mild roller cam and I was impressed with the engine's throttle response and overall manners. The roller offers more cam with better street manners.
03/05/2019 23:02
FIRSTLAST
The engine uses all 63 components, except for cam, crank, rods, and pistons of course. Heads will flow 235 to 245 after porting. It would be nice to use 455 crank for stroke if I can not over do the fact that rear is very high, and these two things multiply wheel torque. 4.55 rear now, and would be better switched to a 3.9 IMO. Since this car is about 2800 versus your much heavier car and bigger overall displacement, I should think my challenge will be not spinning too much, and not turning way too high for a week of cruise like power tour, or possibly a race week if I really get into the track side. My life is too hectic to make a lot of racing possible, so I am building to enjoy, show and cruise week on the road a week at a time.
03/06/2019 09:26
ASHLEY P
My Trans Am ran low 8s in the eight with 2.41 gears and the 4 speed. It was a dog for the first 40 feet. The 455 allows a BROAD torque curve which in turn allows a broad selection of rear gearing. Of course, racing will have a particular optimal ratio, but if your main concern is the street, use something at or between 3.23 and 3.55.
03/06/2019 15:28
ASHLEY P
You estimate race weight to be 2800 lbs? That's with fuel and driver? And using an iron headed Pontiac block? That's pretty light...so light that my engine would move that car to mid to high 11s very easily. Build as much CID as possible, with mildly ported heads, mild roller cam, and that light car will be in the 11s easily all while being fairly easy to drive on the street.
03/07/2019 23:11
FIRSTLAST
your car with the low gearing had little spin off the line. Yeah, slow 60 foot times but sure beats spinning and losing race instead of gaining acceleration. What RPM did you launch at?
03/08/2019 09:18
ASHLEY P
Let's clarify. There are low and high gear ratios. High gear ratios are 2.41. Low gear ratios are 4.56. "Low gear" in a 4 speed is the same way.
03/08/2019 08:58
ASHLEY P
With 2.41 gears I once put 27x9 slicks on it, over inflated them (maybe running 20 psi), and launched at 5500. The Jerico didn't mind, I was only trying for 7s with those gears. Before that I had a th400 and stock converter, launch was <2000 rpm.
03/12/2019 16:35
FIRSTLAST
I looked up the high low flippy flop subject. Could NOT have made that more illogical in their explanation. Anyhoo, what can I pull off my 326 block to use on the 389/421 block? Timing chain cover? Pulley's? Distributor? etc...?
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