QuestionHey Dan,
Hope you can help, if not maybe steer me in the right direction.
I own an 80 Z-28 Camaro. I bought the car from a drag racer and am in the process of fabrications to convert the "Z" to a pro-touring sometimes auto-cross racer. My question concerns the conflicting info that I'm reading in regard to combination of aftermarket parts I should use to rebuild my existing 350 cu.in. sbc. I have 4.10 gears in the rear, a Tremec TKO 600 over-drive 5 speed trannie. The car's been on a diet to get under 3200 lbs. Suspension mod's........ Now back to the question. With a modestly heavy car, the theme is a broad torque curve; 1500 - 7000 rpm. The existing motor is a .030 over, 1970 350/350 block with a stock spec forged crank with 9.5/1 compression ratio piston. Don't know the rod length but 5.7" is a good guess. Early model, World, cast iron heads w/ 2.05 int. and 1.60 ext., 1.5 rockers. Comp Cam Extreme Energy flat tappet hydraulic cam with 507/510 gross lift and 240/246 duration at .050 lift, with 110 degrees of separation @ 106 intake center line. Ignition is controlled by a MSD billet distributor, with a 6-AL control box and built in rev limiter. Holley Commander dual plane intake topped w/ a ported, Holley 4150, 650 double pumper. Existing headers are Super Comp 1.75" long tubes.
Definite changes are; true equal length tuned headers, aluminum heads and new intake. My wish list is to stroke the motor to a 383cu.in.
The headers are a no-brainer, with design help, I'll be building them myself. Now! Here comes the dilemma. I like the Dart Pro-1 with 200cc intake runners and 64cc chambers. Plan is to port match, blend, polish the exhaust runner and take out some ceiling area from the intake runner to increase cc. and velocity. Are the Pro-1's the most efficient design for my application and dollar spent? I'll be moving to a 1.6 rocker for additional lift with out affecting duration to widen the power band. Is that faulty thinking? I also want to get the compression up to around 10.5 to 1. Hmmmm... pistons or mill the heads? Pistons will have to be installed and since the bottom end is internally balanced will the whole thing need to be re-balanced after new pistons? If we mill the heads I'll check for valve shrouding, but will likely be the case and cause extra work and guessing how much to mill for final compression ratio. Due to the existing rod to stroke ratio of 1.64 of the stock specs on the existing bottom end would it pay to go to a 6.0" rod and a lite piston (that would take the ratio to about perfect, at 1.74 and cure my compression problem at the same time)? That's if I decided to keep the existing forged crank? When it comes to the intake all the magazines are singing the praises of the "All new, AIR GAP RPM Dual Plane intake from Edelbrock". They have dyno numbers to back there claims. They had me leaning that way, but still their claims were met with skepticism since their income is dependant on marketing dollars. After discussing the intake with a custom header builder, we agreed that the h.p. increase that is purportedly from the "dense cold air" being ingested by the carb, was actually being cooled after the entering the intake since the "air gap" is "under" the dual plane plenum, cooling the air/fuel mix, effectively causing poor atomization. (thus the poor performance numbers coming from engine builders and not the dyno operators of the magazine's) After further Internet investigation, I also discovered that the design has been manufactured under different names for years, then abandoned to be picked back up and marketed as an all new product. Great Marketing! Since we want a wide curve; Good dual plane with a spacer? Are there open plenum intakes with good mid-range numbers, with the cam and heads I'll be using? I want to stick with the ported, Holley 650. My thinking is the smaller cfm with a 1.74 rod to stroke ratio will offer the right amount of velocity for mid range torque and can be tuned for off idle and high end R's. Your thoughts? Last but not least, if I buy the stroker kit I'll get a Scat, pro lite 3.75" knife edged 43# crank and 6.125" rods (1.63 rod/stroke ratio) and lite weight forged pistons (if I do it, it'll be once and right).Is that best for my dollar to horse power ratio? In other words, the existing bottom end has only about 3000 miles of run time, i.e. are there better heads that will realize the, about 30 pure horses that I'll get from the increase of about 30 cu.in. (with price shopping for parts and machine work, just under $3000), for less money since I'm changing the heads anyway? When all is said and done, I'd like to be over a realistic 450 h.p. to the ground. Is that possible with what I describe?
Oh yea, what are your experiences with crank scrapers and windage trays?
I want G's coming from all directions!
Thanks In advance for your time and consideration on this matter.
Sincerely,
Blaine Bowling
AnswerHi Blaine:
My short answer is , go with new forged pistons, and the long rods. the difference is worth the extra cash. If you decide in favor of J&E, Mike Partwell can help you with calculating your compression ratio and the balance issues. My answer is yes, you will have to re-balance the crank assembly.
I think you may be thinking of too much port volume for good low end, the bigger the port, the weaker the bottom end torque. The stroking to 383 may be a good idea but take that up with the guys I mention below.
As for all the rest, I start to get nosebleed when there are more than 6 spark plugs involved. You need to write to my friend and
V-8 Guru, Randy Cooper , a pro engine builder in Ariz. someplace. Try
<< coopster62@cehighperformance.com >>
He's a super guy and very willing to share his knowledge.
Another source of good info would be
<< www.summitracing.com >> look for the phone number of their Tech department. those guys really know their stuff too.
I apologize for not being able to help more. but in my group, when they can afford to race the big V-8s they send their engine work out to the tune of a $30K motor each year !! For that they get about 700 HP , and BOY are they fun to drive !!
Good luck !
Dan Liddy
Sarasota, Florida
