What not to do when you buy an engine built by someone else

Or, could it be that the brand of high strength push rods, are too thick?

 

I'm more inclined to think that this is just a simple matter of choosing the right rocker/pushrod combo to fix, if you say the rocker geometry looked OK. With a cam lift that high, lots more things can go wrong. I've never had experience with cams that big, but this is a valuable lesson to remember if I ever do.

 

Baddad457,

Yes, going with a 1.5 may solve part of the issue, but I'm not sure how the reduced ramp speeds would effect the motor.
When the motor goes back together we will see what the issue is, and you are right it could be as simple as the roller rockers..........which I think I will deep six in favor of something else.............or the long pushrods.
This will be a first for me also as I've never gone over 680 lift, so a good lesson to cut my teeth on in my twilight years.................

Dave Boyer,

The pushrods are only 5/16, so I don't think the thickness is the issue. I have never liked the Scorpion design but I guess we will find out when I put her back together. I will be talking with Crower's Tech Line about the spring height and coil bind height when I get the heads apart. Also verifiing the gargantuan 617 lbs they spec for these Vasco Jet Max double springs.........................we will see.

 

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with 617# of pressure those 5/16 push rods are probally flexing and touching rockers . 3/8s would be better most likely with that much pressure. imho. you did say they had a lot of run out but not bent.but ive never had a 700 plus cam either 680 about all for me. please let us know what ya find out .

 

i would guess that the rockers were not desgined for that much lift. there may be a perfect storm of events causing this problem. the push rods being too long, maybe the trickflow heads move the valves and the studs inboard alittle. i really dont know but im sure you will figure it all out and let us know. im looking forward to your discoverys.

 

Maverickmadness,

The pushrods are actually .320 diameter (kind of strange dimension) and are one piece and a little on the heavy side, but I don't have a baseline to go from. When I first got the car and set the valves they were on the loose side, but I never really thought about it until now. The cam card says hot they should be .026 intake and .028 exhaust................I have been setting them cold at .028 and .030.............This needs a little more detective work............and we will see what the guides and valves look like.


Bryant,

These heads are kind of mystery to TF as they have a single casting number but do not say TF. They have a serial number which isn't TF's and
were supposed to come of one of Roush/Yates Cup Cars back in the late 90's.....................as I said the exhaust ports look like the TransAm Boss 302's........round and big.................and the exhaust ports are raised/high ports and almost as large as a Boss 302/351.
The car really starts to pull after 5500RPM and continues to pull hard through the traps......................In this car unlike some of the cars I've had in the past..............I would prefer to chase someone down rather than have them chase me.................the front end really never settles down completely until you let off the throttle.........................so we will continue to chase this issue and let you know.

 

Ok, I thought I would post some pictures of the motor as it is taken apart.
When I lifted off the first head I got a surprise............the block is O ringed..................and now I know what 15:1 compression domes look like. I also posted a picture of the 4 piece headers that were made by Dawson in SoCal some years ago. I will have them cleaned and put them back on after cutting the flange off....................if I decide to go with mufflers again I will use a clamp type mount which is much easier to remove than bolts.

 

Here is a close of two of the chambers in the TF-R heads. They don't look too bad for being built in 1998/99.
Will take them apart to see what the valve guides and seats look like.

 

Just thought I would update the head portion of this thread.
The heads are almost finished and short block should be in the shop shortly.
Took the heads apart and found some interesting information that was not totally evident when I bought the car.
First, the springs were on the weak side, they should have been 200lbs at the seat, and the strongest one was 180lbs. The springs could have been shimmed, but I really don't want to chance anything going wrong while spinning the motor at 6500 so I got new ones. The keepers were starting to gall and the retainers were your run of the mill alloy steel and I believe the galling was form the excessive spring pressures initally, so new forged steel keepers are going back on. The retainers were also steel and are being replaced with Titanium. The valves look good and the intake seats are good......................the exhaust seats are Beryillium Copper and really look good also. I will try and get some pictures if anyone is interested.
When I get the short block finished I'll take some pictures and then we will work on the rocker geometry. I just bought some new Comp Cams
Ultra Pro steel roller rockers which should easily clear the large springs and the rollers are rebuildable. I would love to change over to shaft mounted rockers but the $1500 price tag is a little steep for this go-around.
More to follow.

 

Forgot to post the pictures of the modifications that SPD did to the Dawson headers. They replaced the standard collectors with 12 degree merge type collectors and reverse cone transition since I will no longer be running mufflers. The merge collectors and transition are now 321 SS so I shouldn't have such a problem taking them off when the time comes.
The We will see how well they work when I hit the strip later this year.

 

Headers look great! I think even the guys with mild set ups can benefit from a collector upgrade. The collectors on the cheap headers look like crap.....

I've been thinking of making Jig so i can make my own merge collectors.

Those heads look behemoth compared to mine