20/21 cams on a 3.5

[greyes59]

would appreciate your oipinion on:

3,5 engine twin plugged:

3,2 crank
JE pistons 100mm 11.5 CR
20/21 cams
bosch motrocinic
3,2 standard exhaust

[Henry Schmidt]

Great choice for all around fun. They accelerate like a freight train.
I built almost the same engine 12 years ago.

[greyes59]

wow thanks for your expert information.

I hope to use 91 gas on it with a knock detector

[greyes59]

Hi Henry,

My cam is a DC 20 and not DC 20/21
can I still use it in the above motor I described?
what valve overlap do you suggest?

will it run on 91 pump gas?

thanks,
George

[camgrinder]

Originally Posted by greyes59

Hi Henry,

My cam is a DC 20 and not DC 20/21
can I still use it in the above motor I described?
what valve overlap do you suggest?

will it run on 91 pump gas?

thanks,
George

The 20/21 is made by Web cams not me.
The DC20 is a little bigger compared to the web 20/21, the closest grind I have is the DC19. I would not recommend either with 11.5-1 compression and 91 octane.
Even if you went with twin plugs the tune up window would be narrow.
Something a little bigger like the Dc24 would work well (with twin plugs).

[Henry Schmidt]

Originally Posted by camgrinder

The 20/21 is made by Web cams not me.
The DC20 is a little bigger compared to the web 20/21, the closest grind I have is the DC19. I would not recommend either with 11.5-1 compression and 91 octane.
Even if you went with twin plugs the tune up window would be narrow.
Something a little bigger like the Dc24 would work well (with twin plugs).

I was thinking a little less compression as opposed to a little more cam. It's a street car after all with street exhaust after all.....

[camgrinder]

Originally Posted by Henry Schmidt

I was thinking a little less compression as opposed to a little more cam. It's a street car after all with street exhaust after all.....

I agree. 10.5-1 is better.

[greyes59]

I thank the experts!

[Jcslocum]

I would like to ask an Octane question and not hijack the thread.

We are building a 3.4 based on a 3.2. We have JE 10.5:1 pistons, twin plug heads and 20/21 cams to install. This will be a street car DD and would like know what static compression ratio would have to be to use 89 Octane fuel is possible. With current heads chamber at 92.5cc and a deck height of 1mm this calculates to 10.1:1.

[camgrinder]

Originally Posted by Jcslocum

I would like to ask an Octane question and not hijack the thread.

We are building a 3.4 based on a 3.2. We have JE 10.5:1 pistons, twin plug heads and 20/21 cams to install. This will be a street car DD and would like know what static compression ratio would have to be to use 89 Octane fuel is possible. With current heads chamber at 92.5cc and a deck height of 1mm this calculates to 10.1:1.

You can make it work at 10.1-1 with twin plugs. Put the cams in at 1.8mm instead of the 2.2mm setting. About 114 or 114.5 degree intake centerline.

[Jcslocum]

John, Thanks for the info!!

[Jcslocum]

John,

Would be considered advancing the cam slightly?

[camgrinder]

Originally Posted by Jcslocum

John,

Would be considered advancing the cam slightly?

The 1.8mm setting is about 2 degrees retarded from the 2.2mm setting. Close the valve a little later on the compression stroke will help with your combo on 89 octane.

[Jcslocum]

Ahhh ok. I understand that! I had a 50/50 chance of getting it right, whether advanced or retarded and of course I guessed wrong...just like when plugging something in, I always have to flip the plug.

911 Cam timing to those of us that has spent their time around american V8's or other less sophisticated engines is enough to give you a stroke! I appreciate your help very much.

[camgrinder]

Originally Posted by Jcslocum

Ahhh ok. I understand that! I had a 50/50 chance of getting it right, whether advanced or retarded and of course I guessed wrong...just like when plugging something in, I always have to flip the plug.

911 Cam timing to those of us that has spent their time around american V8's or other less sophisticated engines is enough to give you a stroke! I appreciate your help very much.

Your welcome Jon. I use the Porsche lift at overlap method when I build a Chevy engine too. With an adjustable timing set I find it easier to hit the lift number and then check the opening and closing. Having a "cam doctor" makes it easy to have the right numbers etc. My pick up has a "Chevy" 400 cu in engine in it.. just no GM parts are used. LOL 20130928_204359.mp4 - YouTube

[Jcslocum]

John, That's a sweet pickup!! Quick too. Are you running an early 70's 400 small block??

[camgrinder]

Originally Posted by Jcslocum

John, That's a sweet pickup!! Quick too. Are you running an early 70's 400 small block??

Thanks. Its an early sbc type engine using a Dart little M block. Makes about 650hp n/a and I have about 500hp of nitrous to add when the situation requires it