: 383 stroker or not? Dual or single pattern cam?
Apr 27th, 00, 05:04 PM
I was thinking of going with a 383 stroker for my 68, I talked to a performance shop with a real good reputation from some local and not so local hotrodders. The people their tell me that they don't really care for the strokers that their can be some problems that they don't hold up well, spinning bearings and such. He has a 10 sec. small block 67, converting to a big block. Anyone else have any info on the 383? The shop says I can get an easy 400-450hp without using the stroker, which set up would be better suited for street with some strip the stroker or not? They also recommend a dual pattern cam over the single pattern comp cam that I was thinking of using, any input on that one?
Apr 27th, 00, 06:53 PM
The 383 (a combination of a 350 block overbored 0.030" and a 400 crankshaft) is perhaps one of the best small block combinations to build for a street/strip application. I'm confident that many people at this site have had positive experiences with this engine...including myself.
When built and used properly, I don't understand why this engine configuration would compromise reliability. When building a 383, the 400 main crankshaft journals are machined to the same diameter as a 350 crank to fit in the 350 block (with thick bearings), so the rotational speed of the journals has not changed. The connecting rod journals are also the same diameter as a 350, so, generally speaking, increased bearing wear should not be more of an issue than with a 350 (again, assuming proper lubrication.)
Although the crankshaft of a 400 is cast, it is perfectly happy with 500 horsepower. Some will argue that forged is a better way to go, however I believe that, assuming proper (external!) balancing and a quality vibration dampener, this is not a concern. The connecting rods are at least the same length as in a 350 (5.700"), but some grinding of the inside of the block is required to clear the longer throw of the rods. Also, in some cases, some of the rods have to be ground to avoid contact with the cam.
For the street, torque is key, because you're not (I hope) going to be revving to 8,000 rpm from stoplight to stoplight, and you want something that idles halfway decently. The 383 delivers gobs of torque, and if built properly, can also peg the rev limiter at the strip.
It is much easier to build an engine with 1.17 hp/cid (383 with 450hp) as opposed to 1.29 hp/cid (350 with 450hp). The higher this number gets, the less broad the powerband is (assuming a normally aspirated engine.)
With respect to dual vs. single pattern cams, this really depends on how the engine will be used. It is my opinion that, in higher performance applications, the optimal intake valve duration/lift may be much different than the optimal exhaust valve duration/lift. Hence, a dual pattern may be best.
Apr 27th, 00, 08:49 PM
racerx said it very well.
I'd like to add a couple of thoughts.
You need to use a crank that has 350 mains, 350 rod journals. Not the 400 size.
You SHOULD run the 5.7" or better yet, 6" long sb rods, not the shorter 400 rods. The 400 rods will rattle the pistons at idle, the longer rods will aid breathing and octane tolerance too.
The 5.7" rods will hit the cam unless ground on the bolt heads for clearance.
Get HOW TO BUILD HORSEPOWER VOL I by David Vizard, It's all in there.
Use a piston with a dish in the combustion chamber only, or completely flat. The part that comes near the "squish" area of the head needs to be flat.
Use a new aftermarket crank. My engine wound up with a reground stock cast crank that had been welded! Cracked the crank in just over a year.
Cast or forged? You decide.
Dual pattern? Usually the dual pattern is better. Chevy heads don't flow as well on the exhaust side so the exhaust timing is different. If your heads are extremely good on exhaust flow, maybe the single is OK.
It costs more to grind the dual pattern. At least it used to. Nowadays with computerised grinders, maybe not so.
Anyway, in my opinion, the single pattern cams are promoted to sell cheap, and compete with the low buck buyer. The dual pattern is a step up from that, at least from a cost standpoint.
Get the best heads you can find, and undercam it, don't go wild.
The older I get, the faster I was!
Apr 28th, 00, 05:22 AM
Thanks everyone, I really like the idea of the stroker and it was what I planned on, this guy almost talked me out of it but I think I'm still headed there. This rod clearance stuff I had no idea about so now I know what to ask the machine shop to see if they know what there doing.
Apr 28th, 00, 05:45 AM
Best small block street package starts either with a 327, for mild engine, or 400 (406). 350 is useless, 383 is compromise.
Dual pattern cams have more exhaust timing to cover problems with weak exhaust ports/system, using one depends on just what kind of racing/performance useage the engine is designed for, head efficiency and exhaust flow, and other factors.
Good example of dual pattern cam use is Ford small block 302, very poor exhaust port design. Needs more exhaust event to make the flow work. GM engines usually don't need dual pattern, but careful selection may add power in certain setups with weak head flow numbers.
Apr 28th, 00, 08:42 AM
Iman - Welcome to the camaro side of life. Could you elaborate on the 350? Is it a hp per cubic in thing? or? I know they are the most common block around these days. Does availibility make them more popular over performance? I have seen (more on the chevelle page) guys asking for advice on their 327 and everyone tells them to swap it for a 350.
I have read many posts that you have taken part in and have respect for your experience and expertise and would like to hear more on the 350...
Apr 28th, 00, 09:33 PM
According to my Lingenfelter SBC book it says that 1,2,5,6 rods need the tops of the rod bolt shaved for cam clearance. You guys are talking about dual pattern cams and he mentioned that his car will be used on the street with occasional strip use. I have to knod towards the Xtreme energy cams. I plan on using the XE274 in a 385 (bored .040" over) and that will be my daily driver. It is a dual pattern cam and will still have good vacuum ... and that oh so sweet racy lopy idle. Gotta make the BMW and Lexus owners roll up their windows while sitting at the stop light. http://www.camaros.net/forum/smile.gif!! Just my .02 cents!!