Cam for 340 with 2.97 gears

[RustyRatRod]

I would like to clear a few things, I respect Jim at Racer Browns. He had a number of ideas for the right cam profile for my car. I need to confirm the 340's actual compression ratio. Once I have that I going to contact him and go from there. I have researched this issue with the rear gear ratio/ tire diameter since I bought the car years ago. I am finally building the car, and the cam choice is tough since it not the most common application. I have gained a lot of information on FABO. I started this tread to find out if anyone else has experience with this problem and what worked for them. The more informative you gather the more you know. Which is why I contacted techs from different cam manufacturers. My goal is to know more so I can talk to Jim some what intelligently, at least I hope.

Not a bad idea. I would listen to Jim ultimately though. He is perhaps one of if not the best camshaft mind on the planet.

 

[AJ/FormS]

OP,Food for thought:
Many decades ago I put a complete 318 top end and cam, into a very early 340, yes with a 2bbl. And dropped it into a 65 Valiant station wagon with a A904 from a 273. This,essentially, made it a high-compression big-bore teener. The only performance nod was the Hooker fenderwell headers. That was my second-favorite all-time combo. and I would build it again, if I had a nice long-roof. I have no idea what the compression was, but man did that car bark..... and flew pretty good too.
That mightabin 1976.
If somebody out there wants to donate the body, I will get right on it; I still have that engine.

 

[bbab3]

RustyRatRod your posts along with others is why I called him. Things you learn on FABO.

 

[1Fast340]

I would like to clear up a few things, I respect Jim at Racer Browns. He had a number of ideas for the right cam profile for my car. I need to confirm the 340's actual compression ratio. Once I have that I going to contact him and go from there. I have researched this issue with the rear gear ratio/tire diameter since I bought the car years ago. I am finally building the car, and the cam choice is tough since it is not the most common application. I have gained a lot of information on FABO. I started this thread to find out if anyone else has experience with this problem and what worked for them. The more informative you gather the more you know. Which is why I contacted techs from different cam manufacturers. My goal is to know more so I can talk to Jim some what intelligently, at least I hope.

Research and learning from a bunch of different sources is almost always a good thing !

 

[Bighead440]

Shelf cams that will do the job cheaply and reliably include the 272 Crane (formerly Energizer Cam Dynamics) 216@.050", 110LSA hydraulic, or if you have 273 (adjustable) rocker gear, the 270S Comp Cams 224@.050", 110LSA stick would be nice. Both are under .500" lift (.454 and .468" respectively), so they could work with 340HP red valvesprings or my drop-in favorite, the Comp #901.

 

[dibbons]

Will the Comp #901 spring tolerate 6000 RPM with a hydraulic camshaft?

 

[Bighead440]

Will the Comp #901 spring tolerate 6000 RPM with a hydraulic camshaft?

Most certainly. Accurate preload will help, if you use adjustable rockers or pushrods.

 

[MopaR&D]

Jim is very easy to talk to and doesn't mind answering questions about cam tech. Very humble and doesn't have any kind of "you should know better before asking dumb questions" or "I'm the cam grinder I know everything, you don't" type attitude you get sometimes with experts in the field. Just be respectful and have as much information about your engine, drivetrain, and car setup on hand as you can. He will pick cam profiles based on your needs and then explain why he chose those specs.

 

[nm9stheham]

The trans has 1:1 fourth gear, headers are 1 5/8". The compression I need to confirm. The pistons sit .0014" above the deck and have four vale reliefs. I just ordered the stuff i need so I can figure out actual compression ratio.

If they are Sealed Power 428P pistons, they sit somewhere around .007" above the deck, not .014" above deck, unless the block has been decked lower. Or perhaps the Silvolite 1267 pistons, which should only sit about .002" above an undecked block.

For some CR numbers:

• If they are the 428's and an uncut deck, then using a Felpro 1008 head gasket will be close to the margin of safety for piston-to-head clearance, and any piston that sticks up, say, .010" above deck due to an uneven deck will have a piston to head clearance of < .030" which is too close in my view for long term street use. So for that piston, a standard Felpro 8553PT head gasket would be safer until you make very thorough checks of the pistons distance above deck on each cylinder. With that head gasket and piston and heads, your Static CR should be around 9.4-9.5 with a .030" overbore.
• For the Silvolite 1267 pistons and an uncut deck, then the Felpro 1008 head gasket would be a good choice, and in that case, the SCR should be in the range of 9.5-9.6.
• If you have mocked this up and the pistons indeed sit .014" above deck due some milling work, then SCR with the standard Felpro 8553PT head gasket will be around 9.6.

So there is not any real difference between the 2 pistons with suitable head gasket selections, if I have guessed your PN's and set-up correctly.... I think you can safely take 9.5 SCR to Racer Brown.

As you can see above, be cautious with the head and pistons above deck and the head gasket selection so you keep adequate piston-to-head clearance across all cylinders. Check ALL cylinders so you can catch any slope on the decks or things like connecting rods that are oddly long.

The good side is that you will have a good quench gap and AL heads. Since I think this application will end up being a shorter duration cam and the engine will operated in the lower RPM ranges, that is important. Make sure you mention these 2 things to Racer Brown, as they will very likely be factors in his view on what cam can be used. (His website notes make this pretty clear.)

 

[Wyrmrider]

dibbons
6000 rpm
depends on the lift and how radical the cam is
compare a cheater low lift cam {a "square" cam} with lots of acceleration with a race hydraulic with a lot of acceleration and a lot of lift and a street hyd
you can have better results with a MOPAR master than a Chevy Master (however Isky Mega Cams rev like crazy but they are not radical)

Thanks for the Thanks
Anytime I'm around 6000 I'm thinking dual springs even if the seat pressures are low Had a Jones chevy hyd cam rock steady at 6500 on the dyno with Isky 6005 duals power was still going up but we chickened out
in a boat so runs hard all the time
have to have a margin of error in case the prop comes out of the water
rev limiter would be a good idea

 

[yellow rose]

Jim is very easy to talk to and doesn't mind answering questions about cam tech. Very humble and doesn't have any kind of "you should know better before asking dumb questions" or "I'm the cam grinder I know everything, you don't" type attitude you get sometimes with experts in the field. Just be respectful and have as much information about your engine, drivetrain, and car setup on hand as you can. He will pick cam profiles based on your needs and then explain why he chose those specs.

Very true. It's pretty easy to talk to Jim and figure out he's not a bullshitter. And he doesn't make snap decisions. It took him awhile to come up with my cam, and he had to make sure I wasn't bullshitting him.