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Comp . 650 flat tappet cam and 1.7 rockers? #3063798
07/30/22 07:24 AM
07/30/22 07:24 AM
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Frostbitefalls MN (Rocky&Bullw...
gregsdart Offline OP
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I have a potential engine combo that could use a lot of cam duration, and a possible combo comes to mind. Big block 604 cubic inch, indy 440-1 heads ported, jesel 1.7 rockers, PAC beehive springs with 150 lbs seat pressure, Comp 290 @ .050 .650 lift flat tappet cam. Rpm would be limited to 6400? The idea being i have a lot of used parts that could be used to build this, but budget is a big consideration. My question is, by limiting rpm, will that allow the use of 1.7 rockers on the flat tappet cam and still live a decent life as a pumpgas bracket motor?
The spring i am looking at is a PAC, BEEHIVE, 2.00 INSTALLED, 150 seat, 385 open, 313 lbs per inch rate.
The net lift would be . 710, allowing a higher installed hieght to lower pressure to 140 seat if need be.

Last edited by gregsdart; 07/30/22 07:33 AM.

8.77 153 mph best, 3055 lbs 528 indy 440-1 alky
Re: Comp . 650 flat tappet cam and 1.7 rockers? [Re: gregsdart] #3063815
07/30/22 09:50 AM
07/30/22 09:50 AM
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Windsor, ON, Canada
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Diplomat360 Offline
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Regardless whether that spring is right for those cam lobes, the first thing I would check is the coil bind measurement. Are you going to have enough room there to support the increased lift?

Following that, even if the spring checks out OK, what about the rest of the valvetrain? So we are talking the distance between the bottom of the retainer to the top of the guide at that max lift (oh, don't forget to leave room for the valve seal in there)...will things physically fit with your existing parts in as-is shape?

You need to assemble at least one INTAKE and one EXHAUST valve and measure things.

Re: Comp . 650 flat tappet cam and 1.7 rockers? [Re: Diplomat360] #3063842
07/30/22 11:32 AM
07/30/22 11:32 AM
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Frostbitefalls MN (Rocky&Bullw...
gregsdart Offline OP
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Originally Posted by Diplomat360
Regardless whether that spring is right for those cam lobes, the first thing I would check is the coil bind measurement. Are you going to have enough room there to support the increased lift?

Following that, even if the spring checks out OK, what about the rest of the valvetrain? So we are talking the distance between the bottom of the retainer to the top of the guide at that max lift (oh, don't forget to leave room for the valve seal in there)...will things physically fit with your existing parts in as-is shape?

You need to assemble at least one INTAKE and one EXHAUST valve and measure things.

The heads and rockers were used with an .868 lift roller, so no problems with heads, guides, installed height, etc . The coil bind height of the spring i looked up was 1.180, 2.00 installed height. So everything will fit. It is just a question of whether the combo of that cam and 1.7 rockers would play well, given stainless steel valves. The cam can be nitrided, and oil feed holes in the Comp lifters would be run. With 200 degrees at .200 lobe lift and a narrow LSA, i felt the Comp 650 might offer pretty solid performance for a big stroker with smallish heads.


8.77 153 mph best, 3055 lbs 528 indy 440-1 alky
Re: Comp . 650 flat tappet cam and 1.7 rockers? [Re: gregsdart] #3063855
07/30/22 12:33 PM
07/30/22 12:33 PM
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Not a combo of parts I would try myself....... but there is only one way to know for sure how it would play out.


68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
Re: Comp . 650 flat tappet cam and 1.7 rockers? [Re: gregsdart] #3063861
07/30/22 12:50 PM
07/30/22 12:50 PM
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Why go backwards now?
I would wait until I could get the proper valve springs and solid roller camshaft for those heads to make max power twocents work


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Comp . 650 flat tappet cam and 1.7 rockers? [Re: Cab_Burge] #3063869
07/30/22 01:29 PM
07/30/22 01:29 PM
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Cab and Fast, this idea is for a potential low rpm big motor to use up all the leftovers from the megablock motor. The goal would be maybe 700 hp, but at 6000 rpm. I have a lot of good parts that aren't going into the 580 inch 572-13 motor i am building .


8.77 153 mph best, 3055 lbs 528 indy 440-1 alky
Re: Comp . 650 flat tappet cam and 1.7 rockers? [Re: gregsdart] #3063979
07/30/22 11:14 PM
07/30/22 11:14 PM
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LA360 Offline
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Back in the days of running flat tappets in Nascar, they'd run 2.2-2.4:1 ratio rockers. It was the only means of getting the valve velocity to where they wanted it. Check with Comp as to what you can run with those lobes.

You could try it and see, the valvetrain might eat itself though


Alan Jones
Re: Comp . 650 flat tappet cam and 1.7 rockers? [Re: LA360] #3063991
07/30/22 11:51 PM
07/30/22 11:51 PM
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Originally Posted by LA360
Back in the days of running flat tappets in Nascar, they'd run 2.2-2.4:1 ratio rockers. It was the only means of getting the valve velocity to where they wanted it. Check with Comp as to what you can run with those lobes.

You could try it and see, the valvetrain might eat itself though


Was that not tool steel core/dlc lifter?

Sounds expensive smile


69 Charger. 438ci Gen2 hemi. Flex fuel. Holley HP efi. 595rwhp 475rwtq.
Re: Comp . 650 flat tappet cam and 1.7 rockers? [Re: INTMD8] #3064162
07/31/22 08:01 PM
07/31/22 08:01 PM
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LA360 Offline
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Originally Posted by INTMD8

Originally Posted by LA360
Back in the days of running flat tappets in Nascar, they'd run 2.2-2.4:1 ratio rockers. It was the only means of getting the valve velocity to where they wanted it. Check with Comp as to what you can run with those lobes.

You could try it and see, the valvetrain might eat itself though


Was that not tool steel core/dlc lifter?

Sounds expensive smile


Yes they are, was more so pointing out that high ratio rockers can be used with lobes designed for them


Alan Jones
Re: Comp . 650 flat tappet cam and 1.7 rockers? [Re: LA360] #3064884
08/03/22 11:36 AM
08/03/22 11:36 AM
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HardcoreB Offline
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As some have replied use a NASCAR flat tappet profile at a minimum if you're going to try this. But a getting the core nitride wouldn't hurt.

Re: Comp . 650 flat tappet cam and 1.7 rockers? [Re: HardcoreB] #3064955
08/03/22 03:18 PM
08/03/22 03:18 PM
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fast68plymouth Offline
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As I understand Greg’s post...... he already has the 650 cam and the 1.7 rockers....... hence the inquiry.

It will obviously work...... up to some rpm.
Whether that rpm is high enough to work satisfactorily for what he’s doing is the question....... with only one real way to answer it.

If buying new, a nitrided SFT cam isn’t enough of a cost savings over a roller to make the gamble worthwhile IMO.

There are plenty of higher RR friendly lower lift roller lobes that would ultimately be a much better option........ but that requires spending extra $$$.


68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
Re: Comp . 650 flat tappet cam and 1.7 rockers? [Re: fast68plymouth] #3064964
08/03/22 04:03 PM
08/03/22 04:03 PM
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Originally Posted by fast68plymouth
As I understand Greg’s post...... he already has the 650 cam and the 1.7 rockers....... hence the inquiry.

It will obviously work...... up to some rpm.
Whether that rpm is high enough to work satisfactorily for what he’s doing is the question....... with only one real way to answer it.

If buying new, a nitrided SFT cam isn’t enough of a cost savings over a roller to make the gamble worthwhile IMO.

There are plenty of higher RR friendly lower lift lobes that would ultimately be a much better option........ but that requires spending extra $$$.

Right, I read that too but then "The cam can be nitrided, and oil feed holes in the Comp lifters would be run. With 200 degrees at .200 lobe lift and a narrow LSA, i felt the Comp 650 might offer pretty solid performance for a big stroker with smallish heads." kinda read to me like he was considering ordering that cam. If i had an incomplete engine with some mismatched parts, the last thing I'd do is piece something together. twocents I'm just saying I THINK you'd do better selling pieces individually. Especially if something goes wrong in the build.

Re: Comp . 650 flat tappet cam and 1.7 rockers? [Re: HardcoreB] #3064984
08/03/22 05:04 PM
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You may be right.
I guess he’d have to clarify.

If one wanted the cam nitrided, it would have to be new.
You can’t nitride a cam that’s already been parkerized.


68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
Re: Comp . 650 flat tappet cam and 1.7 rockers? [Re: fast68plymouth] #3065038
08/03/22 10:21 PM
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Frostbitefalls MN (Rocky&Bullw...
gregsdart Offline OP
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Originally Posted by fast68plymouth
You may be right.
I guess he’d have to clarify.

If one wanted the cam nitrided, it would have to be new.
You can’t nitride a cam that’s already been parkerized.

I was looking over what i have on hand, a block, full ready to run shortblock in pieces, a set of very good flowing 440-1heads and Jesel valvetrain that need to retire to a lower compression environment, and a lot of used rollerlifters ( some might be rebuildable) pushrods, etc. I posted this to see if the 650 cam might work. But, i think it would be better to custom order a cam if i chose to do this. Comp does give specs for running the 650 lobes 2ith 1.7 rockers, but as Dwayne pointed out, at what rpm would it run to? So maybe better to get a professionally selected kit.


8.77 153 mph best, 3055 lbs 528 indy 440-1 alky






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