SBC 355 Cam selection
Im ready to buy a cam and need a little help make the best choise for my setup.
First off I cannot afford a roller cam and so would like to go with a Flat tappet cam. Currently i have a Comp cams 268H hydraulic Flat tappet camand would like to retial the lifters if possible. But am not oppose to moving to soild lifters and cam if i can get a justifiable gain out of it.
The car is a Datsun 240z weighing in at around 2400lbs. Coilover suspension and lots of monocoque bracing for stiffness. I would like to be bale to run power brakes but am willing to run a vacuum reservoir canister if needed. The car is going to be 80% street and 20% autocross. Very little if any strip. Like anyone lese building a hot rod i would like to make the most power possible and have a aggressive idle sound; while makeing it a fun driving street car.
The motor is a:
SBC 350 bored 40 over.
Aluminum Patriot freedom heads 185cc runner 2.02 intake, 1.60 exhaust.
Fel pro 1010 head gasket
Edelbrock RPM airgap intake
Holley 700cfm double pumper
flat top pistons
9.75:1 compression ratio
MSD billet distributor
Summit racing mutli spark ignition box with 7000rpm rev limiter.
Manual 5 speed borgwarner transmission with the following gears:
1st – 3.35
2nd – 1.99
3rd – 1.33
5th – 0.68
R200 4.11 gears
I called Comp cams and they recommended the XE274H cam.
XE274H-10, Camshaft Part#12-246-3 Dyno Sheet
I called Summit racing and they recommended XE284H cam.
XE284H-10, Camshaft Part#12-250-3 Dyno Sheet
If it was my car I would change at least 3 items
If your carb is a 4778 that would be first,the 4779 works better
you should have a newer HP design with removable air bleeds
2) I would use an open plenum intake
CL110102-06DL (3) 275 281 240 246 .505 .520 106 102 .022 .022 1,3
something like this
I would not use a hydraulic flat tappet in a sports car
with 4.11 gears and 3.35 first gear I see first gear as useless in a sports car
your top speed(making power) is 35 mph with a flat tappet hydraulic
the solid would get you to 42 mph,,26 1/2 tire
If you road race,not many corners have you slow to 30 mph even in a hairpin so first gear has no use in your application
my first gear allows me to go 55 mph in first,as an example
If you drag race,the solid lifter cam will get you by the tree in 1st gear
BTW having your lifters reground is almost the same cost as buying a new set.
Down the road I would also get the 3.54 gear set for the R200. 4.11 is a little steep for your weight and first gear ratio, also a 3.54 will lower your highway RPM some- nice for long cruises.
ap72,there are 3 variations of that shelf cam. I started at the lowest icl because of the low CR. A smaller cam might not breathe well at higher RPM and thats where this engine needs to be with the 4.11s. If the 3.54s are used then it would be more usable as a road race car as 1st gear would be good for hair pin turns.
some where in this area of cams.I would not use a hydraulic unless I had to.
To be honest I have 3 different diff's for my car. I have a 3.36, 3.54 and a 4.11. It only takes about 2 hours from start to finish to replace the diff in these car and i can swap it out at any time.
Ive used 600/650/700/750/800/830/850 and currently 950 CFM
the 700s and 800s were both dog carbs compared to the others
The dual plane is wrong for your car,you should blow through the low end drive ability too fast to notice it,because the gears you have keep the rpm up and the car is light
with the single plane,better carb and far better cam,you would find that off idle is slower,but from 10 MPH the car would rev so fast and pull so hard that you would shift about 500 RPM past your redline with out even realising what just happened
If you were here I would lend you a manifold and bet you lunch and beer that you would be shocked at the difference in accelleration
Im betting 6/10s in the 1/4
Vacuum canister for road racing / AutoX is a bad idea!
It will be good for one, maybe two cycles of the brake before needing to "recharge". You will have a false sense of confidence until you have to negotiate a couple quick turns and run out of brakes. Not the same as street driving and stopping at a light with a big cam. Higher idle rpm and initial timing would help more than a canister.
For AutoX your carb will need a few mods to perform well. I tried to get a nice Proform 750 carb to work with road racing and AutoX for a year and finally just switched to fuel injection.
what are direct lube lifters?
Also i take it that the reason you are recommending howard cams is beucase comp cams is junk?
Pn 30121101 from lunati with face oiling lifters or grooved lifter bores.
60140 would be a hair better for street use but they're pretty close
look what I posted
"something like" I just use howards for quotes as their catalogue is easy to see where comp is stupid.My car has a comp cam in the engine.
If I pick random cam specs out of the air then people say things like "no such thing"or other comments like that
The low ICL was to work with the CR you have and the small heads.The solid cam would rev cleanly to 6500 with room.Im still quoting road racing type tuning.
what is the car used for,road racing?street?drag?
anyways the 3 parts I mentioned to replace are based on personal experiences of used cars Ive bought and fixed
If you like the shifting through the gears and not covering much ground but having fun,you have exactly what you need.
look at a few of Landsharks videos to see what you "could" have
Quick question- are you sure that trans will work? That looks like the ratios for the V6 T5 from a Camaro. I could be wrong though.
If it is then the trans needs a near impossible to find factory bellhousing from an AMC or an aftermarket one.
The trans bellhousing mount pattern is the same as the Ford T5-s but the bellhousing has a 60 degree V6 pattern.
Well from what i can see the cam you suggested and the one Vinnie suggested are about the same and gives me a good idea as to what im looking for.
They are pretty close with only a few subtle differences-
a hair less duration (better for lower RPM power)
a hair wider LSA (better for your heads and application)
a hair tighter lash (quieter and usually more durable)
Overall there's probably not even a 15hp difference between the two.
EFI is also something to consider, it really makes a hell of a difference on power, economy, and durability. You can cobble together a system with a bunch of used parts for a few hundred bucks, even a basic TBI system would be a good starting point.
You dont have to pick that exact cam,its just a guideline,what I would use.The dual plane will eventually come off and you will remember this thread.Your car is so light that the low end boost is really wasted on your car.Good luck with the car,hope to see a video of it soon.
There is a 240 in my area with a Toyota 6,probably makes 500 hp and sounds great.
|All times are GMT -6. The time now is 07:04 PM.|
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2015, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.