[Johnny99]

I've been fighting with this for a week now and running out of ideas.

I bought a 65 Lemans with a 455/th350 a few months ago that had been used for bracket racing but parked about 10 years ago. I had been cleaning up the car over the winter/spring in hopes for having it summer ready. That's not working so well.

drive train config when I got the car:

• 455
• flat top TRW pistons
• older Edelbrock round port heads 87cc
• Torker 2
• Lunati solid cam 292/302 duration 550/571 lift
• QF 850 dp carb
• MSD billet with 6A
• TCI 241001 Streetfighter. 3800 stall
• 4:11 rear
• 2" headers
• 3" exhaust

currently the car is set up with:

• 455
• flat top TRW pistons
• older Edelbrock round port heads 87cc
• Performer RPM
• Summit 2802 cam
• Street Demon 750 carb
• Points distributor
• stock 13" convertor
• 4:11 rear
• 1 /8" headers
• 2.5" exhaust

When I got the car there were holes in the headers as well. It was loud and didn't really move till it hit 4k. I didn't hear/feel any detonation. Only drove the car a few times locally.


Now that the car is together I get nasty detonation at 2500rpm. The timing is set at 12btc (had it as low as 8 btc) no vacuum advance hooked up yet . Mechanical looks to be in by 2500 for a total of 32.

93 octane is in the tank. I added a t of VP booster which should bring it to about 95 knock is still there.

The distributor I was using was a new not rebuilt Cardone with Blue Streak Points rotor and cap. Thought there might be issue with the distributor so I rebuilt the stock cast iron unit from a 66 GTO 389 that I have. No difference.

I checked the fuel pressure (Holley 110 gph). The pump is older but the pressure is consistent between 6.5 and 6.75. When turning the car off the pressure goes down to 0 pretty quickly and when I remove the gauge "T" from the fuel line the line seems to be empty. Nothing spills out. Not sure if this is normal.

I think a 750 Street Demon should be enough carb for the car. Seems people run them out of the box on big block Chevys and Mopars regularly. I'm sure it can use some tweaking but I wouldn't think it would be small enough to cause this type of issue.

My next thought is float level being too low.

Car idles great at 650 in drive and cruises ok till just over 2k accelerating. Past that and hitting 2500 I have to back right off.

I can't really read the plugs because I used the Octane booster so they are brown. They are Champion 9YC's .

I'm open to all suggestions and any help. Thanks

[tom s]

Do a compression test to see what it pumps.For me I have found if they pump over 180 it can be a detonation issue.Cant hurt to check.Tom

[Half-Inch Stud]

Time for Total Advance, no vac adv hose, not initial.
Total with iron head is 34 deg. i dunno about 87 cc E-heads.

[Johnny99]

Thanks. I had run the compression test previously. They all ranged from 160 to 170.

Thinking about it that was with the previous cam. I'll recheck with the new cam. The figures would have changed wouldn't they?

I've got to recheck the total advance. at least to 2500. It was under 32 I remember it being low so I didn't pay much mind to it. I didn't write down the figure

[TAQuest]

Originally Posted by Johnny99

Thanks. I had run the compression test previously. They all ranged from 160 to 170.

Thinking about it that was with the previous cam. I'll recheck with the new cam. The figures would have changed wouldn't they?

I've got to recheck the total advance. at least to 2500. It was under 32 I remember it being low so I didn't pay much mind to it. I didn't write down the figure

Ever get around to checking the compression again? It's key.

[steve25]

The first thing I would try out is one step colder plugs.

Does your timing stay steady at rpms above 2000, or does it slap around?

Also what is the general range of the motors coolant temp?

Once the coolant gets to 160 after a cold start does the motor ping and or knock even at that low of a coolant temp?

Most motors with no vacuum leaks when tuned right will only need 93 Oactane once cranking pressures get to 180 psi.

[Johnny99]

Wow. I go away for a minute and now it's all this.

The wife saw how frustrated I'd become and suggested I take a few days off from the car.

I'll get the compression test done tomorrow. I've also got a set of colder plugs (BKR7E/4644) to try. I'll check out the timing curve at the same time.

The vacuum advance isn't hooked up and there are factory springs in the distributor. Can you get heavier springs? I ordered a Moroso set to see if they offer any more resistance. I'm not sure how else to slow the curve down Though I'm going to bring the initial back down again to test.

The only reason I haven't purchased the wideband gauge yet is I didn't get bungs installed when I had the exhaust done. I should have. I'm going to call and see what's involved in adding them. I'm thinking that in the collectors would be the way to go

Consensus is pretty much it's the wrong cam so that's probably the case. I am going to test everything suggested here first though before pulling the cam again. Thanks

[72LuxuryLeMansLa.]

Originally Posted by Johnny99

Wow. I go away for a minute and now it's all this.

The wife saw how frustrated I'd become and suggested I take a few days off from the car.

I'll get the compression test done tomorrow. I've also got a set of colder plugs (BKR7E/4644) to try. I'll check out the timing curve at the same time.

The vacuum advance isn't hooked up and there are factory springs in the distributor. Can you get heavier springs? I ordered a Moroso set to see if they offer any more resistance. I'm not sure how else to slow the curve down Though I'm going to bring the initial back down again to test.

The only reason I haven't purchased the wideband gauge yet is I didn't get bungs installed when I had the exhaust done. I should have. I'm going to call and see what's involved in adding them. I'm thinking that in the collectors would be the way to go

Consensus is pretty much it's the wrong cam so that's probably the case. I am going to test everything suggested here first though before pulling the cam again. Thanks

http://www.arkansaspontiacs.org/tech...s/recurve.html

[moontower69]

If its pinging at 2500 and above and distributor timing/curve doesn't help, then CLIFF is right, it's the camshaft.

EITHER (1) the cam is too small or (2) cam is not installed correctly and the cam timing needs to be retarded. Possible the timing chain is mismarked or defective (seen that before).

Just my 2 cents.

[pastry_chef]

Yes, the cam is small and not ideal.

Yet, in the last year there have been two different members with this issue. Both swapped to a larger cam/112 LSA as the board prescribed and the issues persisted.
Then it was,, your compression is too high, or your gas is crap..

[Cliff R]

Simple problem and solution. The cam is WAY to small for that set-up, replace it with one having about 10 more degrees seat timing. Cylinder pressure (dynamic) too high, and peak torque happening too early. It's made worse by the good flowing heads and with their excellent cylinder filling abilities you aren't able to manage pump fuel in it.

I've never used that cam in a 455 and wouldn't recommend it. The smallest cam I'll put in any 455 build with have 230 @ .050". The 2802 is better suited for a 400 build with 9.5 or so compression, not a 455 with over 10 to 1 compression.

Look at the attached dyno chart. The first cam pinged and the engine is only 9.3 to 1 compression. It used #96 iron heads that were professionally ported to 250cfm (not even as good as what your using) and it pounded so hard on the dyno it required rod bearing replacement! It got nothing but a cam change, idled better, no detonation at all and made quite a bit more power..........Cliff

[77 TRASHCAN]

I went to SD Performance website yesterday, they have a calculator for several engine and other spec's. Your 455 is 10:1 or very close.....

[Johnny99]

Based on what I'd read I was assuming compression would be around 10:1.

With a 180 stat in it it runs at about 210 at idle. Right now it's just putting along a 2k locally and wasn't getting any hotter. I'll have to check exactly what it's running at. When the car came to me it was running only a restrictor, center of the stat clipped out, and running pretty solid 180s .



According to what Cliff is saying a big part of my problem is the heads flow to well something I had wondered about. Unlike most I'm not looking to wring out peak numbers which is why I thought this cam would be a good choice. It looked similar to a 744 and with the wide LSA I thought it would help with static compression

• Duration: 298 int./303 exh. 224 int./234 exh @50
  
• Lift : 0.466 int./0.488 exh.
  
• LSA: 114

Right now I'll check out the cranking compression total compression and temp tooling around at 2k just to have the numbers.

[shaker455]

Originally Posted by Johnny99

Based on what I'd read I was assuming compression would be around 10:1.

With a 180 stat in it it runs at about 210 at idle. Right now it's just putting along a 2k locally and wasn't getting any hotter. I'll have to check exactly what it's running at. When the car came to me it was running only a restrictor, center of the stat clipped out, and running pretty solid 180s .



According to what Cliff is saying a big part of my problem is the heads flow to well something I had wondered about. Unlike most I'm not looking to wring out peak numbers which is why I thought this cam would be a good choice. It looked similar to a 744 and with the wide LSA I thought it would help with static compression

• Duration: 298 int./303 exh. 224 int./234 exh @50
  
• Lift : 0.466 int./0.488 exh.
  
• LSA: 114

Right now I'll check out the cranking compression total compression and temp tooling around at 2k just to have the numbers.

Car is running too hot.
Got to get temps down under 190 as the gas boils there.

[Cliff R]

Decent cam for a 400 build around 10 to 1 compression, WAY too small for what you are doing, which is obvious as it woln't effectively manage pump fuel at 10 to 1 or so compression and the heads are aluminum.

Years ago I built a 455 with Edelbrock round port heads (early design) and 87cc chambers. It made 505hp/551tq, with a 231/240/113 Crower (RAIV clone) cam in it. It was DONE making power at 5200rpms, clearly showing those heads wanted more camshaft. The Crower cam also has 304/316 seat timing, considerably more than your 2802 cam. So not only are you pinging, you're leaving a butt-load of power on the table with that cam.....IMHO.....Cliff

[Formulas]

Another troubleshooting thing you can do is near empty gas tank put some race or AV. gas in it to get the right octane fuel that would work with the combo
Also how many times did you check the timing chain? at cam install degree it? Or dots?

Then figure out next step with the results

.

[jamaca85]

i agree put some racing gas in it. no mix just straight. i think even if you change the cam its safer to go with a higher octane gas. you dont want pieces of your pistons flying out your exhaust.

[Johnny99]

The timing gears were set by the dots. Verified a few times while adjusting the lifters.

Cliff is your recomendation the Crower 60919 cam? How would that work with a stock convertor and highway gears?

I'll check a few things and when done pick up some racing fuel to test. If that works I'll just run the high octane for the rest of the season. After that I'll need to close the garage door and rethink the combination.

I understand a bigger cam looks to be the answer but it's not an engine combination I think I'm interested in. I don't want a street/strip car. Running out of steam at 5200 would probably be fine. My goal is a cruiser. I think a factory style 455 might suit me just fine.

I had reservations with the EDL heads thinking they would flow too well for my needs and wasn't sure I could put something together to work around them but that doesn't seem to be the case.

Initial thought is find a set of large chamber iron heads to bring the compression ratio down or maybe dished pistons and chose a cam from there. then again that could just be frustration talking : )

[steve25]

Since you say the motor was built before you got the car for bracket racing, and since you say it still knocks with 95 octane or so fuel , I might question if those heads are not the 72 CC heads and not the 87s you where told they where, or they have been milled some.

[PunchT37]

Originally Posted by steve25

Since you say the motor was built before you got the car for bracket racing, and since you say it still knocks with 95 octane or so fuel , I might question if those heads are not the 72 CC heads and not the 87s you where told they where, or they have been milled some.

Could be. The heads have the same casting number under the valve cover. One could pull the intake to see if they have the exhaust crossover or not.