Grumpy and all othes I Need Advice on New Engine Build

[Guest Anonymous]

I orginally asked a similar question on another board. Never had my question answered. So I came back home.

 

I will be building a new 350 or 383 to go in a 91 Z/28. The engine will be mounted to a close ratio T-10 and 3.73 -4.10 gears. It will be used for road racing and an occasional drag strip and runs to the grocery story. It will not be my primary transportation, but, will have heat air, radio, full leather interior, etc. Weight should be around 3600 lbs.

 

I desire a 10.25 CR 6 inch rod combo regardless of the 383 or 350. The bottom end will not be junk.

 

Now Heads. I have read various build up all of which use 350 10:1 CR, 190/195 AFR heads, Vic Jr., 850DP Thease are summerised below.

 

CAM

HP/RPM TQ/RMP Dur Lft Dur Lft LSA ILC

506/6500 436/5500 248/.562 254/.580 110 ?

522/6600 454/5200 242/.578 248/.584 110 107

527/6400 459/5600 254/.583 260/.589 110 ?

 

Peak power around 6500 peak torque around 5500. Is this due to the heads?

 

I have read various build up all of which use 406 10:1 CR, 210 AFR heads, Vic Jr., 750DP, 1 3/4 headers. These are summerised below.

CAM

HP/RPM TQ/RMP Dur Lft Dur Lft LSA ILC

487/5500 494/5000 236/.525 244/.543 112 ?

521/5700 510/4900 233/.582 240/.586 112 109

 

This one is a 400 with AFR 195, RMP Air Gap, 750DP, 1 3/4 headers.

CAM

HP/RPM TQ/RMP Dur Lft Dur Lft LSA ILC

554/5900 538/4500 236/.555 242/.540 112 108

 

My conclusion. The 210 AFR do not offer significant improvements over the 195s. The larger engines do not offer significant power over the 350 only torque and the torque is at a lower RPM.

 

Based on my intended use... What type of motor should I build, and where in the RMP range do I want to have peak power and torque.

 

This is very opern ended and I hope to get many responses.

[grumpyvette]

read this first;yes it is important to read and not skip over the link

 

http://www.vettenet.org/torquehp.html

 

NOW I POSTED THIS BEFORE BUT IT MIGHT HELP HERE TOO

the formula for hp is (torque x rpm / 5252= hp) that basically reflects the that torque is cylinder pressure during the power stroke times the number of strokes per minute times the leverage(stroke) now if we take a 4000fps max piston speed and 1000psi cylinder pressure for both engines we find tha the 383 has a 6400rpm max piston speed a 12.7sq inch piston area and a 1.875" leverage arm we find 76200000. psi of cylinder pressure available to do work spread over each min.(3200 power strokes)(yes Im aware that the cylinders don,t really fill 100% at top rpm)

now with the 377 we find a 6896rpm max piston speed, a 13.5 square inches of piston area and a 1.74" lever for 80676405. of max cylinder pressure available,over each min thats a 4476405. psi of cylinder pressure available (spread over 1 minute and 3448 power strokes) that the 377 has for an advantage(thats about 5.5% advantage in work force available for the 377 over the 383 (or about 191 extra power strokes per minute if your useing the 383 power strokes as a base measure)) , thats WHY the 377 is used more than the 383 as a racing engine now its very likely that if you don,t take advantage of that extra higher rpm torque range of the 377 that a 383 geared more to ITS IDEAL TORQUE RANGE will run with or beat the 377. if you take a 3600 lb car with a 3.08 rear gears the 383 is likely to win, but put 4.88 gears in a 2600 lb nova and theres no contest the 377 will win.

BTW you can have some of the advantages of both combos by building a 406 sbc(4.155 bore x 3.75stroke)(3200 x 13.5 x 1000psi 1.875=8100000psi of cylinder pressure spread over 1 minute (3200 power strokes)thats the torque of the 383 and the power of the 377 + 1% because of the larger displacement

[Guest Russ240z]

Great topic, I too am weighing my options with the 406 or 350. I have both engines but neither one is running with a good combination of parts. Cylinder heads are the weak link in my case (need to buy a new set). I am leaning towards the 406, Canfield 195's, comp xe284, performer RPM, 750 DP, 1 3/4 headers T56 trans, 3.54 200r, all in a '72 240z.