Quick camshaft question!

funkytrunk92 · Nov 22, 2006

Just looking into cams and had a few questions.

1) What are the advantages/disadvantages of having more exhaust lift than intake lift. I noticed this on some of the cam specs.

2) What are the advantages/disadvantages of more or less lobe seperation. Does more lobe seperation make it less computer friendly?

I am just trying to learn some more about the details of engine building other than "throw a cam in it."

Thanks.(I'm sure I'll be posting soon----Which cam should I get---but I will spare you guys for now! )

LEE93COBRA · Nov 22, 2006

more lift or duration on the exhaust side allows more time for the spent gases to get out (remember the exhaust valve is a good bit smaller than the intake valve)

less lobe separation affects how EEC friendly it is and also make the cam more 'vocal'

funkytrunk92 · Nov 22, 2006

so more exhaust lift would be more benificial than say a Ford Racing cam with even lift on both valves? or is it application specific?

65ShelbyClone · Nov 22, 2006

Many times the extra exhaust lift and/or duration is to compensate somewhat for the low-flowing stock exhaust ports. It's less important the better the heads are. My Crane 2031 has more lift and duration on the hot side because I bought it when I still had my '89 GT and planned on GT-40 heads. However, I went with Edelbrocks instead. Worked fine with the stock EEC, BTW, but it's not too radical.

funkytrunk92 · Nov 22, 2006

I am running stock GT-40 heads with ferrea 1.55 exhaust valves(14 degree) not sure if that matters, but It is a stock cobra motor with stock 1.7 rockers. No porting or anything. Oh yeah its a 306 now with aod and stall converter
=
I am running an E cam now and really just want to try something new. Its just a street car and was maybe hoping for something with a little more bottom end. I guess I am going for more driveability rather than raw power. I was thinking of the B cam or something along those lines.

65ShelbyClone · Nov 22, 2006

I wouldn't use the feature of split duration or lift as a determining factor in which cam to buy. The 2031 I have is actually made for 1.7 rockers and to a degree is aimed at Cobra engines. As long as you have gears steeper than ~3.27, it will be a pretty street friendly cam. I'm running an aluminum flywheel, single plane intake, and 3.0 gears in my '68 and it has a surprising amount of low-end. I'm not saying to go out and buy one right now, just that it might be an option.

funkytrunk92 · Nov 22, 2006

65ShelbyClone said:
I wouldn't use the feature of split duration or lift as a determining factor in which cam to buy. The 2031 I have is actually made for 1.7 rockers and to a degree is aimed at Cobra engines. As long as you have gears steeper than ~3.27, it will be a pretty street friendly cam. I'm running an aluminum flywheel, single plane intake, and 3.0 gears in my '68 and it has a surprising amount of low-end. I'm not saying to go out and buy one right now, just that it might be an option.

Thanks for the input! Every little bit helps.

65ShelbyClone · Nov 22, 2006

Glad to help. I think I still have a sound clip of my old '89 GT if you like. It had Flowtech 1 5/8" shortes, Flowtech offroad true x-pipe, and an American Thunder catback. I also have one of my '68 with that same engine and old-style true dual Shelby side-exits with 24" glasspacks. It doesn't sound like the same engine.

LEE93COBRA · Nov 22, 2006

funkytrunk92 said:
=
I am running an E cam now and really just want to try something new. Its just a street car and was maybe hoping for something with a little more bottom end. I guess I am going for more driveability rather than raw power. I was thinking of the B cam or something along those lines.

What gear ratio are you running? This is something to look at instead of a cam change. You should be running at least a 3.73 since you have an AOD with a stall

thumper460 · Nov 23, 2006

There are two cheap thing that will help you ALOT!! advance the E303 4* !! the lowend will increase and the sound will become more raspy and aggressive !! Or the B303 installed advanced 4* also!! We have found the FMS cams when installed in at 103/104 ICL ( advanced 4*) work extremly well !! Cost ?? a new timing chain assy and a few gaskets!! Sure is a lot cheaper than a 250.00 camshaft!!

Split duration /lift cams have been out since the 60s, the need is there in the early heads... as the heads got better ( gt40s ect) the split has become less.. they are good cams!! unless you are RACING.. the cheaper cams are fine.. look into the TFS1 or 2 cams.. just a thought.
Just me..............................

Thumper

funkytrunk92 · Nov 23, 2006

LEE93COBRA said:
What gear ratio are you running? This is something to look at instead of a cam change. You should be running at least a 3.73 since you have an AOD with a stall

I am running 3.73 gears, forgot to mention that!

--
When you say advance the timing 4* which way would I turn the timing gear, clockwise, counter clockwise , I have a double roller timing chain, would I need something else to do this?

65ShelbyClone · Nov 23, 2006

You need one of the timing sets or at least the crankshaft sprocket that has multiple keyways in it. Most are labeled as to what timing change each key will make. You would just put the lower sprocket on the 4* advance keyway and line up the cam to the dots on both sprockets.

Quick camshaft question!

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