[Super-G]

I'm looking for some info/advice.

I've got a 70 Lemans Sport with a factory 4 speed (M-21) and a 3:23 posi rear. The engine is bone stock out of a 68 Bonneville. Most likely a 250 HP motor. The motor has been rebuilt and has a mild cam in it but I don't know any specs, I can't find any markings on the heads at all so I'll assume that they are the originals. The car pulls nicely through all the gears but it doesn't pull like my 67 GTO did.

I just got lucky and scored a finished set of 77 or 78 6X heads for $200.00. They have a 3 angle valve job and new guides and seals.

Here's what I'm looking to do, re-do the top half of my motor. I'm looking to replace the original heads with the 6X's and do a new cam and a quality performance timing chain.

Any suggestions for a nice street cam for my set up?? I am NOT looking to race this car. It's a weekend cruiser only. I have my CDL so funny business on the street is just not happening. Most of my driving is on weekends going to car shows and cruise nights. But like all car guys more power is a good thing.

Any suggestions on a good cam??

[Ken -Ace- Brewer]

Cubic Inch??


Ace

[Super-G]

Sorry it's a 400.

[guccieng]

stamping on the 6x heads? if it's a -8, then it's going to be very low compression, depending on your pistons.

[Z Code 400]

Agreed,

Heads must be properly identified first. All D-Port heads flow about the same, providing they have the same valve sizies, so you will need to identify your current heads and the ones you intend to use first. You may gain nothing or even take a step backwards with the 6X's, depending on what you have on the motor right now.

I would send a PM to 1967Tempest, as he is running 6X-4's on a 400 with about 8.17:1 SCR and a 3.23:1 axle. He is very happy with the Isky 256/262 Hydraulic...Robert

[Super-G]

I haven't picked up the 6-X's yet. I saw them last week and told the guy I'd pick them up this week.

I can't for the life of me find any ID #'s on my current heads. I know to normally look right over top of the center exhaust ports. There's nothing there. Any other ideas where I can look?

["QUICK-SILVER"]

You see alot of older heads with those numbers rusted away. Date codes usually stay intact. So see how close the head dates are to the block casting date. If it's real close chances are the heads came on the block. Then use the block casting number and stamped code to see what the heads were or should have been.

IF?? your engine is a 68, 265 HP, 2BBL 400. It would have been rated 8.6:1 CR with head casting number 14.

Need all the casting numbers and date codes. Not just the XA you posted in one of your earlier threads. Reason being the stamped letters were used on different engines over the years.

Try looking down through the oil cap and see if you can tell if the rocker studs are press in or screw in. A small dentist mirror and flash light might help with that.

Some pics would help a little just to see slight casting differences between older and later model heads.

If worse comes to worse, the real deal would be pulling them off and checking combustion chamber size and valve sizes. That will also let you see piston type and where they are in the hole. That info will help for picking out the right CC head or if you even need to change from what you've already got.

[madokie]

for thoses who dont know how to id a 6x head go to pontiac street performance , they have pictures in tech section.loder heads had rounded casting at center exahust ports at bolt hole where casting number should be,mid to late 70's heads more square and blocky casting.did early heads have all accessory bolt holes in end of head??summit cams are good and cheap.2800(350),2801(400),2802(455).spend your money on good lifters!!!