Cam shaft - Pontiac GTO Forum
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post #1 of 6 (permalink) Old 08-13-2019, 10:05 PM Thread Starter
 
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Cam shaft

Has anyone tried comp cams pn. 51-224-4? Preliminary research tells me I may need to machine spring pockets but doesn't say whether it's a diameter or depth issue. It's going into a 67' GTO with the original 72cc combustion chamber, casting # 670 heads with ARP screw in rocker studs.
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post #2 of 6 (permalink) Old 08-14-2019, 09:15 AM
 
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IMO, that is NOT a good cam choice, for a high compression pump gas 400 engine.

Please post all your engine specs, gear ratio, & expected driving details.

Example: Cubic inch, compression ratio, rear gear ratio, what trans, all street driving, street/strip, lots of high speed highway cruising, etc.

Unless you're looking to make max hp, I don't see needing more cam than a Summit 2802, for a high CR 400.

In fact, a 2801 is probably enuff cam for most daily street duty 400's. But, there are quite a few decent cams, between the 2801 & the cam you listed.
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post #3 of 6 (permalink) Old 08-14-2019, 12:04 PM Thread Starter
 
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From the top - the carb is factory Qjet 680 advertised cfm and rejetted. Factory intake. Casting 670 heads. 400cid bored 0.030 over to 406cid. Factory rods and crank with advertised 10.5 Wiseco forged pistons. Exhausts through Hedmen full lenth headers and Flowmaster 50s
Tranny is Ford 3 spd toploader, also factory installed. Rear end is 3.55 gears. Will not see the track. She's a daily driver from late spring to early fall, and she's not babied. Running Shell 91 with STP octane boost. The cam currently in is comp cams pn 51-223-4 and in 10 yrs I've not heard any pinging or detonation.
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post #4 of 6 (permalink) Old 08-14-2019, 03:32 PM
 
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Looks like you just wanna move up 1 step, but stay with a CC XE series cam. CC recommends 995-16 springs for both cams. Those springs are rated for 1.70 installed height. Most stock length valves are said to have aprox a 1.60 installed height. That's probably why spring seat machining is recommended.

COMP Cams Catalog - Pontiac 265-455 8 cyl 1955 - 1981

https://www.amazon.com/Competition-C...11874189&psc=1

I don't like the idea of a steep ramp cam, like the XE series, in a high CR pump gas street engine. But, if you want aprox 230° @ .050 lift, there are a couple of slower ramp cams that I'd prefer.

The Howards 410051-14 is one of 'em.

https://www.summitracing.com/parts/h...w/make/pontiac

And, an 041 clone, such as a Melling SPC-8, is another.

https://www.ebay.com/itm/Engine-Cams...UAAOSwtAtboHby

If I ran an 041 clone, I'd definitely run Rhoads lifters. They'll provide a smoother idle, more vac, & more low rpm torque, below 3000 rpm. Most 400 street guys don't like a cam this big in a street driven 400.

https://www.summitracing.com/parts/r...w/make/pontiac

https://www.summitracing.com/parts/r...w/make/pontiac

Here are a couple of slightly smaller cams that might be a little more streetable than the 041 clone types.

https://www.summitracing.com/parts/c...IaAusEEALw_wcB

Crower seems to be real proud of their products.

https://www.summitracing.com/parts/c...0aAuxzEALw_wcB

If I did go with a steep ramp cam, it would be a Lunati Voodoo. They're similar to the CC XE cams, but close the valves more gently, where as the XE cams are said to slam the valves shut, in many cases enuff to produce a very noticeable ticking sound, which many don't like. Many also don't like the ticking sound Rhoads lifters produce.

https://www.lunatipower.com/voodoo-h...8-268-276.html

Most consider cams with 230° or more dur @ .050 lift, much better suited for a 455 than a 400.

Last edited by bigD; 08-14-2019 at 04:56 PM.
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post #5 of 6 (permalink) Old 08-14-2019, 10:06 PM
 
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Im a fan of XE cams. I have an XE288hr-10 in my 10.5:1 zz4 stock headed 355 chevelle motor over 10 years, thousands of street miles and hundreds of track passes. Yeah its slightly different as its a roller but it screams and has a ton of torque with less cubes. (236/244).

Just put an XE268h cam in a 69’ 351w. Has a mild lope, a ton of vacuum and idles great (224/230)

I dont see any reason why a 10.5:1 400 motor wouldnt run great with an XE274h cam (230/236). Yes they have more aggressive ramp rates but properly setup they will last forever. The faster ramp rates allows the motor to have more vacuum then a similar spec cam with a slower ramp rate hence you can get away with more duration. This cam should have enough vacuum for power breaks, should idle with a great sound and good lope, and have tons of mid range power. Plus you’ve got 3:55’s... If you’re only gonna go 1 size bigger than your current cam then why bother. Go with something like this or equivalent, have some fun and make some noise.

Now this cam in a high compression 455 would not be a good choice. Also remember you’ll need a mild converter. In terms of machining the heads they make note of... I did a little research real quick and found something along the lines of using a behive spring will eliminate the need for machining the heads based off another forum thread. If you are really thinking about this cam, call comp and ask them. Also Lunati does make great cams similar to XE line.

Just dont short yourself if you’re a driver and like to beat on it. A 10.5:1 400 can take some cam.

2006 GTO M6

Motor - Stock with Vararam
Bunch of suspension
Bunch of brakes
Stock tune

365/368 std
12.81 @ 110.6 2.03 60'
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post #6 of 6 (permalink) Old 08-15-2019, 02:36 AM Thread Starter
 
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Thank you very much for your time and effort. My engine builder has ordered the CC 51-234-4. I will definitely run our conversation by him. What especially interested me is the valves basically slamming shut with the CC 51-224-4. Obviously not keen on that. Did talk with CC by phone and email and was told the 234 would work fine. Regarding vacuum, I have standard drums all way round so not really a big deal I think. Only external power robbers are water pump and alternator. Learned, not the hard way, last year about lifter differences in Pontiacs. All in all not so much a learning curve as a steep incline this last year.
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, LeMans & GTO Engine Tuning and High Performance

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