Ive got a 1994 lt1 and doing a full top end rebuild and cam swap this winter. Had some questions for the experts. So far the heads and intake manifold have been ported, new bronze valve guides installed, seats enlarged for 2.00/1.56 manley race flo valves, 3 angle valve job. A bottom end build (forged internals with high rpm use in mind) and trans upgrade will come next year, so id like to build these heads to handle more than I need currently. From there my questions are about springs, cams, pushrods, and rocker arms/studs.
Im interested in:

-SUM-8803 cam: 224/232 duration 112 LSA lift with 1.5 is .550/.540 1.6 is .587/.576 1.7 is .624/.612.

-BTR dual spring kit .650 max lift, 170lb seat, 450lb open, 1.8in installed height, comes with stem seals, locks, retainers, and locators

-7/16in rocker studs

-Full roller rocker arms

Spoke with summit they said the cam will work just fine in a 94 LT1 and is still very useable with stock bottom end +stock stall + 3.08 gears. Spoke with btr they said the springs will work well with all 3 rocker ratios. My questions are:

1. What rocker ratio would you reccomend so I dont run into any P to V clearance issues?
2. Self aligning or not? Options for self aligning 7/16th sbc rockers are slim. If non self aligning what pushrod guide will I need?
3. What brand rocker stud? I like ARP but they say to only use their polylock...is that crap or should I go with comp or another brand? What effective length will I need?
4. Is there any parts im missing/you'd reccomend I add while I've got the heads off?

Thanks in advance yall. Any and all advice for any of my questions would be greatly appreciated. Race on!

 

bump

 

Now I'm not certain if the lifter bores are different on LT1 blocks vs a traditional SBC, but you are going to be close to max lift on general factory SBC lifters. A cam of that size is just about the limit before shrinking the base circle and the lifter can drop out of the dogbone and rotate which will eat the cam. Alternatively if its standard base circle the cam may lift enough to bring the lifter oil band out of the bore and you will lose oil pressure. If you do go with this cam, do your diligence to prime the oil system while turning the motor by hand and ensure you aren't seeping oil and that the lifters are secure. Aftermarket lifters probably wouldn't be bad if you are spending all this money on a complete build IMO. Personally, I would ask a cam shop what they recommend considering your engine package and goals rather than picking a part out of a catalogue. From there, pick a spring based on the cam lift you are going for, and make sure your valves are the correct length to reach the install height you need.

1. Run whatever the camshaft is designed for or is recommended by a competent cam grinder or engine shop. Changing rocker ratios gives lift and changes duration which may improve or decrease the performance of the cam choice. P/V clearance is more determined by cam advance than actual lift. The valves follow the piston open/closed and as long as the events are properly timed you shouldn't run into issues, especially with an OEM style chamber. 1.7RR for SBC are VERY VERY aggressive and almost never used. Ratios that high are typically only found on shaft mount rockers which can handle the added stress. Look around at high end race motors and you'd be surprised at how many are running 1.5 rockers because that is the geometry that works and what it was designed for, even on a .650 lift solid roller.

2. They make adjustable guideplates that can be run on whatever width is needed, or just measure the width you need, it should be pretty standard. Also you may have to clearance the guideplates for the valvecover bolts. I would opt for guideplates/hardened pushrods, one less thing to worry about with parts compatibility plus the rocker has one less way to fail.

3. Putting 1.6RR on my L98 I used the 1.895" to ensure I had plenty of thread on the polylock and that was with factory install height. Just measure the factory stud length and move up to the next height ARP makes, extra thread wont hurt you. I see no issue running ARP with a reputable rocker manufacturer's polylocks.

 

So shouldve also mentioned ill be using comp pro magnum lifters. The stock lt1 cam has a base circle diameter of IN - 1.2445" EX - 1.231". The sum-8803 has a base circle diameter of 1.160 in./1.168 so slightly smaller and it has a fairly quick ramp rate. The top dog of lt1 custom cams seems to be lloyd elliot and he offers a 226/234 .584/.584 (using 1.6's)110 LSA cam. Fairly similiar but ill call him and see what base circle he uses and if the sum-8803 with the pro magnum lifters will run nicely. The reason id prefer off the shelf is this cam is temporary. Full build will be next winter, this winters plan is all head work,.but id like a beefier cam to take advantage of all that head work for track days this season. As for rockers, i really wont need them until the spring, when the heads are ready to go back on, so those will be held off on for now. Most guys reccomend going up 1/4 inch up for rocker studs which come out to exactly the size you mention. Ill go with arp studs since i plan on using scorpion rocker arms and their polylocks seem to be made very well. When it comes to pushrods should i just go to 3/8th diamater and guideplates to match? Not really seeing any downsides to that but again id rather ask than assume and be wrong. If theres anything else im missing, parts youd reccomend, measurements to check etc dont hesitate to let me know! Thank you man

 

I know they said it would work but I wouldn't run the stock converter with that cam. It's going to feel like the car is pushing you through stop lights. Also it's going to be a dog off the line. I would invest in a good converter. They are a better mod than the cam is in a street car anyway. I would go with something around 2800 to 3000 rpm stall with that cam and heads. Don't spend the money on a triple disk lockup unless you need the converter to be locked at WOT. That will save you some money.

Call a good reputable converter company and have them make you a converter with a custom stall. Off the shelf converters are ok for drag cars but on the street they are hard to drive sometimes. I always had really good experiences with both FTI and Circle D.

 

I can vouch for the customer service with Circle D. I reached out so I can plan and budget and got a quick response.

 

If this cam isn't staying in after you do the full rebuild next year, then I would do less cam than this. I agree with Phobos that this isn't going to be amazing with a stock TC. This is more cam than most people realize, and you aren't going to extend your redline and therefor you're going to miss part of the increase this cam would give you. This is even more true if your heads are now really flowing well, as that will raise the powerband RPM all by itself. As a reference, my 396 LT4 had heads that flowed 308 on intake, and it had a smaller cam than this (218/224 I believe and .565/.570 o a 110deg LSA). It pulled hard to above 6000rpm even with the extra 46cid. And that was with 3.45 gears (but a ZF6). Given your stock displacement and TC, I think even that cam would be quite a bit. That was a Comp Cams custom grind with XFI lobes from the catalog. They make an off-the-shelf XFI268 that is similar but with more LSA (112 I think) that would probably a good option. You can get the kit with springs, too. IT would be cheaper, and I think you'd like it better.

Do you know what your heads are flowing? IME, most port jobs don't add as much flow as people think, including those from LE. It sounds like they've already been done, but these days I tend to encourage people to consider just getting the AFR 195 heads with Competition porting. They flow almost as well as my ported LT4 heads did (which were done by Greg Good and were amazing).

 

So after speaking with LE it looks like ill be going down to the sum 8802. 218/227 with 525/.520 1.5 ratio or .560/.555 1.6 ratio on 112 LSA. He says thats the max hed go with the stock TC. Again unsure if i should go with 1.5s or 1.6s id love people to chime in on that.

As for lifters he said stay away from comp so went with Morel 7717 lifters. Thats lloyds "Cadillac" at that pricepoint.

I wouldve gone with AFR heads but their foundry is moving and nothing is available on the market and hasnt been for quite some time. Nobody is really sure when theyll be back up and its highly unlikely the lt1 heads will be first (or hell even 10th) off the line when they do open back up.

The heads will be flow tested next monday when my valve job is done. Lloyd highly reccomended the 2.00/1.56 manley race flo valves so i went with those and am having the seats done for those valves. Ill report back with flow numbers. My heads were in good shape but my god was there so much carbon build up, casting flash, and areas needing to be touched up. I dont expect 300+cfm numbers by any means, but a definite improvement over stock for sure.

Trans wise im working with a builder out of north carolina and weve got a very special plan coming next fall. He built my 10pt roll cage this spring, and the plan is to build the first (to my knowledge) 6l80 swapped c4 corvette with paddle shifting. Itll be one hell of a project and ill be sure to post about it when the time comes, but im trying to avoid spending on the 4l60e if i dont have to. If that means a slightly smaller cam for this season so be it.

 

Can I ask why you want to stick with the stock converter? It sounds like you're putting a lot of money into this build and trying to save some money on arguably the most important part. I higher stall converter and a gear change will equate to more usable power in a street car than a cam or heads ever could. I would argue that the stock converter has too low of a stall for even the stock cam. So even though LE says you "can" run that smaller cam with a stock converter that doesn't mean it's a good idea. It just means you could. You would get WAY more usable power out of the car with a higher stall converter. Even if you do swap in a 6L80 later you can always sell the aftermarket converter. Building a motor with heads and a larger cam and then using the stock converter seems like a waste of time. I would keep it stock and swap in the 6L80 first. Or save your money and do it all at the same time. Also I wouldn't be afraid of that larger cam. I run a 226/238 .600/.600 113 LSA on the street all the time. It chops a bit more than I like but it's not horrible. Now that is in an LS but drivability between an LS and a SBC with a given cam are similar.

On your rocker arm ratios, they don't really effect drivability or ease of tuning but they do add a little power because of increased lift. I always pick the rocker arms that give me the maximum lift that my heads and springs can support with the given cam. So more than likely with that 218/227 cam I would definetly go with the 1.6 rockers.

 

Since the OP is with a whole different trans setup next year, I can certainly understand not wanting to buy TC for the stock trans right now. This makes even more sense if he's also going to get a different cam at that point (presumably he's increasing displacement with a stroker crank and/or increasing the redline?).

I'm no expert, but I know what my own car was like. At 396 CID, and the CC custom cam I mentioned above, it would have been lovely with a stall speed in the range of 2200-250. But for a 350, I think it would have needed 3000rpm stall. Based on that and your stock TC with 3.08s, I think that 8802 is a good bet. With the lower duration and LSA of 112 (so a good bit less overlap than my cam had), I think this will work well enough on your 350. It is also ground +1 degree advanced, which will also help. It actually has sportier lift numbers than the 8803, so the ramps are fairly aggressive (which I like).

On the rockers, I guess I would suggest that if you plan to keep these lifters with the next cam, then go ahead and get your 1.6s now. I'm not sure I see a penalty for using them. Even if your heads don't take advantage of the extra peak lift, the bigger ratio will mean your valves are at the ideal lift for longer.

For the heads, I didn't realize AFR is off the table right now. That's unfortunate. Now that I'm posting from home, I found the flow specs for my LT4 heads. These were done by Greg Good in Houston, and he's really renowned for his port work. He tends to stay with smaller port volumes and works really hard at keeping velocities high. As a result, his heads flow well at low lift values. These were done back in the early 2000s when there weren't lots of options for 2nd-gen SBCs. I don't know if Greg would even work on Gen-2 heads anymore: he's way into the LS and new-LT scene these days (and Vipers, and other stuff). Anyway, here are the flow numbers they got:

• .1 84/56
• .2 157/120
• .3 220/171
• .4 267/199
• .5 297/218
• .6 308/223

This was on 2.055"/1.625" valves, which I also think help at low lift values.They compare favorably to the AFR 195 Comps, especially in the low-lift range. I don't know how much different the LT1 heads are, so I'm not sure if those numbers are even theoretically possible with them. This set of heads is pretty special, and I told the guy who now owns the car that if he ever ditches the 396 or scraps the car or whatever, I want dibs on getting the heads back. Anyway, I'm not saying those are realistic goals for your heads, but it gives some idea of what is possible with stock castings.

 

The motor and trans build next year will definitely feature a higher redline and much higher stall. Id absolutely love to throw in a higher stall converter for the 4l60e its just financially a lot to spend for something only being used for a few months. Knowing myself too i couldnt help myself but throw in a shift kit and do a bunch of other modifications adding to the waste. Id rather save that cash for long term mods next year and deal with the performance loss of the stock trans.

Glad that cam gets the seal of approval, its looking like a great choice. Very interested to see what power marks ill make with it doesnt seem like theres many using it.

Heads wise yeah im not expecting numbers close to that high. Im really no expert but my porting looks pretty good and ill be going up to 2.00/1.56 manley race flo valves so flow numbers should be solid. Ive been really meticulous with the porting. Taking many measurements and ensuring consistincy, cleaning up every little area i can. A pro would hands down do this better and faster, but for a rookie id say not half bad. Ill post pics when theyre all finished up.

As for rockers i think 1.6 are the way to go for sure since ill be using them for the future build. Scorpion full rollers seem to be the way to go but keeping an eye out for deals on comp gold or similiar. Gonna go with 7/16th studs as well i see no downside.

 

trust me if i was keeping the 4l60e id slap a 3k stall and much rowdier cam in there no doubt in my mind. Its just spending the time and money for something ill use for only a few months. Youre 100% right, id just rather save the grand n change for the swap next fall. The cam im using this season is just temporary to take advantage of all the head work...not in need of going all out just yet...but once the 6l80 goes in shell get a custom stall and a much, much rowdier cam