cam 3400-6800 rpm

That's a pretty nasty cam there. Unless your heads have screw in studs and guide plates and cut down guide tops (talking stock heads here)plus springs to match, you'll need a smaller cam. If you have aftermarket heads with all the above items it'll work. It will idle right around 1000 rpms, give or take 100. Your motor will also need to have about a 10 to 1 comp ratio as well. With a single plane intake like a Vic Jr, the power won't "come on" till around 3000-3500. This isn't what you'd call a street friendly cam it's more like a weekend warrior cam. Expect the fuel mileage to suck also. The power will come on sooner with a dual plane intake, but that will be around 1500-2000 rpms. Either of the two above it will work with stock heads and valvetrains and be easy to live with in a street car.

I used a cam like that cam in the 80's. It did not seem that radical, but I was a teen then. It will need a looser converter. It looks identical to a Crane cam no longer listed. I went high 12's with it, a TorkerII, 4.11 gears and 351 heads in a Mustang II. I used these studs http://store.summitracing.com/partd...924497+4294867153+4294867142+115&autoview=sku I pulled the press in studs and used a starter tap. Starter taps don't cut as much at first to help keep straight. I used a regular tap to get theads all the way down.

when building an engine you need to take systems approach, and select parts that compliment each other. you want a cam that works from 3400-6800 rpm, then you need heads, intake, headers, torque converter, gears, etc all to fit that cam. when you do that, you no longer really have a streetable car. can it be driven on the street? yes, but are you willing to put up with the eccentricities of the car when it is done? high rpms on the freeway, poor fuel economy, lopey idle, rich fuel mixture, etc.

since you want a street engine, select parts that work in the 1000-5500 rpm range. that way you can use a longer gear for better fuel economy, and wont have to live with monster rpms driving down the freeway.

I have driven and built engines for other cars that used WILD cams on the street.
The key is to match the compression ratio to the cam. Too little compression makes any cam perform poorly at low rpms, lumpy idle and loss of power. Give it enough CR and it will run like a champ, pulling from idle without hiccups etc... Not to mention itr would make the power it was supposed to, instead of losing a good chunk of it in bleed off.

I ran a 345deg custom race cam on the street in a small 1600 4-banger.. it was a bit weak until it hit 3000, but fully streetable and comfortable to drive. This with 2 carb throats for 4 cyls.

Same and wilder (!) cams in all out race engines pull like mad from 1500 and idle all day long at 800... in a 4 cyl. 2 throats and 4 cyls.

Both would have been even better with 1 throat per cylinder. Race rules... argh.



Jan

Checkout www.flowtechinduction.com . Talk to Ed and have him design a cam for you combination. I have used off the shelf cams before, but have since purchased a couple of cams from him and will not go back. He can also help with your setup.

pazur said:

I wanted to use this cam with stock heads, valve, rockers and compression, upgrade only valvetrain parts (rods, springs) and headers, two-plane intake and 600 cfm double pumper. Summit person or catalog never said it needs complete aftermarket heads or increased compression otherwise will perform poor (i.e. worse than ones with rpm 0-5000). Late mustangs with EFI nicely go to 6-7,000s rpm with stock compression, as well as many street cars with sporty engines (yet electronic engines are more driver friendly). So i am asking again whether to trust summit saying that this cam will perform well in stock early 302 or not?

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The Summit tech was not truthful and the catalog doesn't tell the whole story. You'd need both upgraded compression and valvetrain mods with that cam and stock heads. The pressed in studs will be pulled out by the increased lift and spring pressure. You'll need new springs to handle those lift numbers. That will also require work on the valve guide tops (otherwise the new retainers will contact the guide tops at or before max lift) The cam's overlap will need more compression to offset the bleed-off at lower rpms. The EFI Stangs do not rev to 7000 without mods either. For starters they need stiffer springs (the valve guide top mods were done by Ford in the production of the E7 heads the late Stangs had) And then they need better roller lifters, the stockers start bouncing off the cam lobes at about 6 grand. The stock heads are done breathing by that point anyway, yours included. They'll support more with port work. If you want more cam that works with what you have, without all the mods, go with the middle grind.

pazur said:

Can you also tell what's the cam's maximum lift where you can safely use stock compression, pressed-in studs, valve guide tops and stock rockers? And about the flat-tapped lifters: this cam is sold as a kit with flat lifters, not rollers. What do you mean that they start bouncing off? If this happens cam lobes' durability or performance worsens? Thanks for advice

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Ok, unless your motor has a roller cam block, you have to stick with a flat tappet cam. It is possible to go with a roller cam, but the cost will scare you (talking about $600 to convert to roller in a non roller block) Any cam with less than a .500 max lift will be OK with your heads (assuming you have pre 80's small block heads that have not been modified per the previously listed mods I mentioned before) The stock Ford hydraulic roller lifters used in 85-2001 5.0's are too heavy and are not designed to follow the cam lobes above about 6000 rpms. Usually the only thing that results is the valves "float" (engine sounds like it's misfiring once a certain rpm is reached) Worst case, a valve will drop. Same thing happens once the valve springs reach a certain rpm level, they cannot keep up with the valve's motions. This is also called "float" . If you want to use the cam you posted originally, you must remove the heads and have screw in studs, guide plates( these are only necessary with the small block heads cast after March 1966, the earlier heads had pushrod guide slots in the heads themselves) The stock rockers may be good for more lift, depends on the rockers and the stud slot length in their centers. There are "Bandaid" fixes that will allow bigger cams, but judging from your questions, you need a professional machinist to do the work. The two smaller Summit brand cams shoudl work fine with your heads as is, but there will still be a remote possibility of the studs pulling out. You will still need new and slightly stiffer springs to go with either to get the maximum potential from the cam swap. Weak and/or old springs will result in the likely hood of the valves floating at a lower rpm level than you'll get with new springs. The spring swap can be done after the cam swap and break-in period, their softer rates will be easier on the new cam lobes and lifters. Springs that work with either cam should work also with the stock retainers and valve guides.