Anyone running a weber 38 on a 200? Cam selection?

Hello all, I was curious as to if anyone had experience running a weber 38 2bbl conversion. Mostly interested in what cam you are using. I have recently bought a 66 200 with a small log head, which was cut down 60 thousands and had the block 0 decked. Oversized valves were also installed. It seems as my cam is lacking the proper amount of overlap (clifford 270 .214@.050 .478 Lift) told it was installed with the dots lined up (no degreeing but built in 4 degrees advance) I read the tech section on classic inlines and it describes how cams with more overlap prefer higher static compression. Because they reduce dynamic compression right? I say this because ive been having an on going problem with detonation/pinging no matter which way i spin the distributor and no matter what i set the timing curve to. Too retarded its spits out the intake. Too advanced it pings. Ive tried jetting up with little luck. I posted about this before. Just curious if anyone else has experience with a 2bbl conversion and high compression any more help is greatly appreciated. I know this is kind of a repost but i am truly stumped.

HOwdy BB:

What distributor/ignition system are you using? Have you figured the static compression on this engine? What spark plug heat range are you using? What do the spark plugs look like? Have you checked to verify the accuracy of the timing mark?

What transmission? What is the rear end gear ratio?

Is the Weber carb direct mounted or are you using an adapter?

Keep it coming.

Adios, David

CZLN6":3dy8g70w said:

HOwdy BB:

What distributor/ignition system are you using? Have you figured the static compression on this engine? What spark plug heat range are you using? What do the spark plugs look like? Have you checked to verify the accuracy of the timing mark?

What transmission? What is the rear end gear ratio?

Is the Weber carb direct mounted or are you using an adapter?

Keep it coming.

Adios, David

Click to expand...

Mallory electronic, previous owner said about 10 to 1, a colder motocraft plug (cant remember the # but colder than stock), they look good according to some plug charts i looked at. I dont really think the timing mark matters. I can literally turn the distributor as im going down the road (econoline van) so i really can fine tune the timing and feel how the motor responds in real time. Ford 3.03 3 spd manual with the low econoline 1st and 2nd gears, 3.50 rear, direct mount to the intake log -prev owner had a plate brazed on (a true 2bbl no restrictions).

10:1?!! No wonder you're having problems. I think you're going to have to pull the head and verify the compression ratio, then unfortunately you're likely going to have to find a new head, late model head, with 62cc chambers and then calculate and have it milled to bring the c/r to an acceptable level. Or go to an aluminum head, but that will require a custom intake in an econoline. Or run racing fuel all the time. What elevation are you at? I don't think you're going to want a bigger cam than the one you already have. The good news is the head you have is valuable b/c of all the work that was done to it for someone who hasn't zero decked their block., So that would offset the cost of having a new head done up.

In an Econoline you'll probably want to swap to a smaller cam actually and get more power down low where you need it, imo. Something like a 256H or 262H from Schneider. Which will raise the likelihood of pinging unless the c/r problem is addressed.

Any guesstimates on my actual comp ratio? So stock is like 9 something to 1. the mill cut of 60 equals aprox 1 more point of compression (falcon handbook) and then a composite gasket drops it a bit. But... I have my block zero decked.

My first thought is i really would like to keep the head as it has a bunch of work done to it. To add im running 30 over pistons with the little dish in them.... Just a thought. Maybe far fetched but i have heard about doubling head gaskets?

Before you do anything, it would be good to know where the cam timing is at.

With the rocker arms off put a dial indictor on the end of the #1 intake pushrod.
When the pushrod has moved up .050" as the crank is rotated clockwise, the timing mark at the harmonic balancer should be 1 degree before TDC if the cam is installed 4* degrees advanced.

You have the option of retarding the cam but it will cost you some low end torque.

With 10-1 compression you need to use the cam you have to bleed off some cylinder pressure. Do a cranking compression test & if between 180-195 you will need 91-93 octane fuel.
Your distributor also needs to be curved for your combination.

Hey Bill, where can a guy get his distributor recurved?

I would have to look at his distributor.
I can curve a real HEI or go to one of my DS11's .
What octane fuel is he using???
Once i put his Mallory on the sun tester i can get a better idea.
With the small log head he is loosing 30+ HP.

Ah yes the small log... I knew it wasn't optimal for the 2bbl conversion... But it had the oversize valves. I realize the plenum (is that the right word?) is smaller than the large logs and more restrictive. Still should be better than a stock large log though right?

The Blue Box":o9felqu5 said:

Any guesstimates on my actual comp ratio? So stock is like 9 something to 1. the mill cut of 60 equals aprox 1 more point of compression (falcon handbook) and then a composite gasket drops it a bit. But... I have my block zero decked.

Click to expand...

Using my Falcon handbook I will assume that a .060" will eat at least 8cc's from the volume of the combustion chamber of an early head and maybe 10 or more. Using my trusty DCR calculator from Pat Kelly and making up the cam details, b/c I don't have them I've done the math.

With that cam advanced 4 degrees I come up with:

Intake opens @ 29
Intake closes @ 61
Exhaust opens @ 69
Exhaust closes @ 21
Overlap = 50 degrees
This assumes advertised duration of 270/270 w/ a 110 lobe seperation and intake centerline @ 106.

This yields an effective stroke of 2.523"

Assuming a best case scenario of 53cc chambers reduced to 45cc's, zero deck, .050" gasket, .030" overbore and 6cc dished pistons =

SCR @ 10.1:1
DCR @ 8.4:1

If he used a Victor gasket and you lost 10cc's in the head @ a 52cc early head:

SCR = 10.85:1
DCR = 8.95:1

Putting a huge(r) cam in hopes it fixes this in a truck is a waste of time imo. If you replaced the head with a victor gasket and 53cc chambers with that cam you'd be golden @ 9.3 scr and 7.75 dcr but still pushing it. Otoh put in a smaller cam and have punch and grunt down low where you want it and need it and mill a late head to 58 or whatever it takes once you know the real #'s.

jmo

Econoline":235met6z said:

The Blue Box":235met6z said:

Any guesstimates on my actual comp ratio? So stock is like 9 something to 1. the mill cut of 60 equals aprox 1 more point of compression (falcon handbook) and then a composite gasket drops it a bit. But... I have my block zero decked.

Click to expand...

Using my Falcon handbook I will assume that a .060" will eat at least 8cc's from the volume of the combustion chamber of an early head and maybe 10 or more. Using my trusty DCR calculator from Pat Kelly and making up the cam details, b/c I don't have them I've done the math.

With that cam advanced 4 degrees I come up with:

Intake opens @ 29
Intake closes @ 61
Exhaust opens @ 69
Exhaust closes @ 21
Overlap = 50 degrees
This assumes advertised duration of 270/270 w/ a 110 lobe seperation and intake centerline @ 106.

This yields an effective stroke of 2.523"

Assuming a best case scenario of 53cc chambers reduced to 45cc's, zero deck, .050" gasket, .030" overbore and 6cc dished pistons =

SCR @ 10.1:1
DCR @ 8.4:1

If he used a Victor gasket

Click to expand...

Man thats high. Thanks for doing the math seth. I am using a felpro gasket with the little dish pistons

Is it possible to grind out combustion chambers enough to make a difference? I know just smoothing them will help with detonation according to the handbook

Also i have a dumb question. When preforming a cranking compression test is the needle supposed hold and build pressure or bounce around from zero? I think my harbor freight compression tester might of crapped out

It should build pressure and hold.
Is the valve stuck open?

That might be what it is. The instructions said 3 cranks of the engine. And thats your reading.. But it doesn't hold. Just goes up and down

Sometimes the one way valve is in the extension line.

"...Assuming a best case..."
too much assuming to this point.
Things have to be measured now to really know where you're at...
then, knowing 'what's here' - comparing that to what you really want the vehicle for / to do / application.
Finally, IDing what components need change out if any.

Seems like PO might have decked the block w/o doing the work to CC the head?
I'd look 2 C if the block IS decked, CC (if U don't have the figures), etc...

thanks guys for all the answers, i found some useful stuff here now while sitting home doing nothing but searching for meds reviews and that's awesome. but i was wondering if i may ask you something else ? i'm new here and i just don't know the rules, may I pm you? thanks!!