Engine performance question

[david bench]

Hello been following the post about cylinder head and cam selection lots of great info so thought i would get thoughts on my engine package. I have a 66 383 bored .30 over with stock pistons and 906 heads bought a Summit 6401 cam and timing chain and gears with 9 different keys have the Wieand 8008 duel plane intake with a Edelbrock 1406 carb. 600 cfm with Hedman headers and 410 gears in rear so the summit cat says at least 9.5 to 1 compression and gears and stall converter.....i don't have converter how will this affect the performance and what key way would you think best to install cam with and is this package going to be the best it can be with out spending more cash on different items thanks in advance.

 

[Qbrozen]

Just a point of clarification for me: how can you have stock pistons in a 030 over bore? Sounds like a mistake to me.

 

[david bench]

Sorry stock compression no hypo pistons..thanks

 

[Lionized]

I have approximately the same build; 906 heads, Performer RPM, 1406, stock exhaust and Comp Cams 21-670-4 (280/287 x 474/474).
I'm running a TCI 2400 converter with a Trans Go stage 2 kit. The car is an animal when I manually shift but docile enough to daily if gas was cheaper.

 

[dvw]

Do you know your true measured compression ratio? If not let's at least get an idea by measuring how far the piston is in the hole. Have the heads been milled heavy, just touched up, or nothing at all? If they are untouched I'd use 89cc as a close guess. If it's 9-1/9.5-1 I'd put it in at 110, maybe even 108 if it's below 9-1. A stock 10 3/4 converter (340, 383 HP, etc) won't be to bad. A stock 11 3/4 won't be as good.
Doug

 

[lewtot184]

that cam doesn't need a looser than stock converter (10 3/4 4bbl converter). doesn't need 4.10 gears either. would like something bigger than a 600 edelbrock.

 

[Yatzee]

Hello been following the post about cylinder head and cam selection lots of great info so thought i would get thoughts on my engine package. I have a 66 383 bored .30 over with stock pistons and 906 heads bought a Summit 6401 cam and timing chain and gears with 9 different keys have the Wieand 8008 duel plane intake with a Edelbrock 1406 carb. 600 cfm with Hedman headers and 410 gears in rear so the summit cat says at least 9.5 to 1 compression and gears and stall converter.....i don't have converter how will this affect the performance and what key way would you think best to install cam with and is this package going to be the best it can be with out spending more cash on different items thanks in advance.

Use the stock key position with initial advance 15-16 degrees. A 2400 convertor has quite a bit of slippage and you can easily go to 32 - 3400 with no detriment. Actually you'll not only get better performance in the higher range, you'll also get better mileage. It is adviseable to use a separate tranny cooler, not just the rad loop.

 

[rlem1977]

Here are a couple of links to a Hot Rod test of 383 intake manifolds. I do think the 600 cfm is too small.

http://www.hotrod.com/articles/hrdp-0712-mopar-intake-manifold-comparo/
http://www.hotrod.com/articles/hrdp-0801-mopar-intake-manifolds/

Also, here is a stall speed chart from the 1970 shop manual that was posted by Photon440 in another thread:

Hope this helps.

 

[wyrmrider]

That's a long seat duration cam for a stock compression 383
however depending on the replacement piston they could be "compensated' or have less compression height than the originals so what piston and what compression height or how far down are your pistons at tdc?
and you are most likely running a thicker gasket
and 383's came with several stock compression ratios- all of which were not really as much as advertised
so really no idea where you are
if it's all together drive it and work on ignition curve
then try checking real cam install points as you most likely are at the line up the dots- if you are installed to spec then advance it 4 degrees, reset the timing and give it a try
do a compression check before and after

 

[david bench]

Engine is apart but pistons and crank in block still, was not going to mess with it fairly new but not by me bought it this way cam chain was on the stock dots but sloppy so i bought the chain and gears with 9 different keys. I remember way back i bought a purple cam from direct connection and said to use 4 degree adv key when install in another motor it ran great so i bought gears so i could change cam degree on this engine. So i should put engine on tdc and measure from top of piston to top of block?

 

[david bench]

Also everyone seems to think 600cfm too small?

 

[david bench]

On a very tight budget so was tryin to work with what i have 410 gears in car when i bought it

 

[lewtot184]

the real difference between a magnum cam and the 6401 is area under the curve. the 6401 will have 10 degrees more duration at .050" and .200" lift. seat timing is close between the two. LSA is 115 on the magnum and is installed at 113CL. the 6401 has 114LSA and 112CL installed. advancing the 6401 to a 110CL installed wouldn't hurt nothing. the 6401 will need a better spring then any of the stock wedge springs. the 6401 is a better performance cam than the magnum. the 6401 makes more torque and doesn't require a lot of rpm.

 

[Lionized]

Also everyone seems to think 600cfm too small?

Not me.

 

[mopar 3 B]

Not me.

Why a bigger cam and then starve it to death?

 

[wyrmrider]

yes please measure how far down the pistons are and try and cc the heads, even with a syringe or whatever- just get close- does not have to be perfect
re=read what lewton had to say
The summit is the same as the Edelbrock cam- at least you did not pay Edelbrock prices for it
it will work with stock HP springs- the ones with a dampner- it was designed back in the day when bad springs were the rule.
I've never seen any improvement over a magnum cam
That said advance it once you get the ignition dialed in
just one thing at a time
and run a compression check- cranking compression should improve. Seat timing is greater than the magnum cam which is not saying much as the magnum cam is also really lazy- which is why both are reliable and can work with not much spring, lift is near stock so no stem to guide work is needed- drop in and go
let's get you compression approximated B$ any more cam comments

 

[Lionized]

Why a bigger cam and then starve it to death?

To be honest I have yet to try a larger carb with my set-up but I'm happy with how it performs.
I think this set-up WOULD benefit from more cfm due to the fact that he's running headers.

 

[SlinktRR]

just build it with the parts you have and then upgrade as you drive it. The intake could be better, the carb could be bigger, but it's fine for a base line and these parts are easy to swap. To have fun with a 383 it needs to be able to rev clean past 6000rpm. If you run out of air you will hit a wall somewhere in the 5k range. First limiting factor is usually carb or intake. I would go performer rpm intake and a 750 street demon carburetor at some point.

 

[BSB67]

Engine is apart but pistons and crank in block still, was not going to mess with it fairly new but not by me bought it this way cam chain was on the stock dots but sloppy so i bought the chain and gears with 9 different keys. I remember way back i bought a purple cam from direct connection and said to use 4 degree adv key when install in another motor it ran great so i bought gears so i could change cam degree on this engine. So i should put engine on tdc and measure from top of piston to top of block?

Just measure how far down the pistons are at tdc. report back

 

[wyrmrider]

lots of different purple cams- any numbers on it most obsolete now